Friday 17 June 2016

The Nuclear Spear: Casaba Howitzer

When a nuclear technology has been kept classified since the 60s, you know that it is worth looking into. The Casaba Howitzer is one configuration for a nuclear shaped charge, that can concentrate the power of an atom bomb into a narrow cone.
In this post, we'll look at its potential configurations, its advantages and limits, and how it can be applied to both propulsion and warfare.


Visualization by Rhys Taylor
Before the Casaba Howitzer, there was Project Orion.

Project Orion was the nuclear upgrade to the idea of explosive pulse propulsion, first proposed in the late 19th century by the Russian Nikolai Kibalchich (1881), by German Hermann Ganswindt (1891). Instead of chemical explosives, an Orion spaceship would use the awesome power of nuclear bombs.

As you may already know, the original Orion involved a thick plate of steel, called a 'pusher plate', mounted on suspension arms, that would be struck by a nuclear explosion. The plate would endure the heat and radiation, while the suspension transferred the plate's momentum to the spaceship.

Orion 10m Propulsion Module
Even if the pusher plate only captured a fraction of the energy of the nuclear bombs being used, it would still be a more effective than any chemical rocket. Theoretical calculations and empirical testing gave engineers an idea of the largest explosion the pusher plate could handle (67000°C and 340MPa), and suspension cycling gave them the maximum frequency at which the individual bombs could be detonated (0.86 seconds in the initial design). Used together, we could design an Orion spaceship...

But it would end up being wasteful and nearly impossible to operate in an atmosphere without generating devastating EMPs.

Like all explosions, an atomic detonation is spherical.
The angle AฤˆB is very important
The original proposal (USAF 10m Orion) detonated bombs 25m away from the pusher plate. The pusher plate has a radius of 5m, so with tan, we can calculate a half-angle of 11.25 degrees. 

In other words, the pusher plate captures at most 10% of the energy delivered by the nuclear pulse unit.

This is wasteful, as most of the expensive fissile material does not get used properly. It would also require very large individual pulse units to produce sufficient acceleration, likely in the megaton range. Megaton-level nuclear detonations produce a lot of fallout, produce enough thermal radiation to damage the spaceship, and most importantly, generate electromagnetic pulses in the upper atmosphere that would disrupt electronic devices.

The Nuclear Shaped Charge

The solution was to create a device that directed the energy of a nuclear explosion into a one narrow enough for the pusher plate to capture almost all of it. 

With a higher percentage of the energy captured, the nuclear pulse units could be made much smaller, cheaper and unlikely to produce harmful EMP.
A simplified representation of a nuclear shaped charge. Note the lack of explosive lenses. 
A nuclear shaped charge, which became the Orion pulse units, worked in three steps.

-The nuclear device detonated, producing 80% of its energy as X-rays, released in all directions. They are blocked by the non-fissionable uranium, except for a hole on top.

-The channel filler (Beryllium Oxide) absorbs the x-rays coming through the hole, and re-radiates them as heat (infrared). It is the most important part of the design.

-The tungsten propellant absorbs the infrared emissions and vaporizes, becoming a fast travelling stream of plasma headed towards the Orion's pusher plate. The tungsten is plate-shaped so that the plasma produced expands into a thin column.

In effect, the tungsten plasma becomes the Orion's propellant. Exhaust velocities of up to 120km/s have been proposed for the original Orion designs. 

The full deltaV equation for an Orion spaceship is given by:
  • DeltaV: Collimation factor * Plasma Velocity * ln(Mass Full/Mass Empty)
The collimation factor (between 0 and 1) is how much of the tungsten plasma reaches the pusher plate. In the original proposal, collimation was 0.85. It can be improved by using a wider pusher plate, detonating the pulse units closer or using a thinner and wider tungsten plate. Plasma velocity is the velocity the tungsten travels at.

Other Propulsion
Through the use of nuclear shaped charges, other nuclear pulse propulsion types have been designed.

The simplest of these are larger Orion spaceships. One space battleship proposal gave a mass of 4000 tons, another interstellar concept masses a thousand times that figure. 

Medusa nuclear pulse propulsion concept.

There are designs that reverse the pusher plate configuration, detonating instead the pulse units between the spaceship and a retractable sail. 

More advanced designs include the Mag-Orion, that replace the Orion's physical pusher-plate with a magnetic field. A Nuclear Shaped charge allows the use of a smaller field and lighter magnets.

Variants and variables

The original Nuclear Shaped charge design is not the only possible configuration.

The design can be modified to achieve more desirable characteristics.

One such modification is the shape of the tungsten propellant. The thinner and wider it is, the more focused the cone of particles produced. 

The choice of tungsten itself is not definite. The propellant contained in each nuclear pulse can be replaced by other materials. Lighter materials, such as water, will reach higher exhaust velocities, but need to be thicker to absorb the thermal radiation from the beryllium oxide. This hinders their ability to be spread into a thin plate to achieve a narrow cone.

A simplified configuration for water-propellant nuclear pulse units.
For mass savings, it is possible to use beryllium oxide itself as the propellant.

For a Mag-Orion drive, a material that produces a plasma more readily affected by magnetic fields might be more suitable than tungsten. 

In a setting where tungsten might not be readily available, iron could be used instead. It will have about three times higher exhaust velocity, and proportionally lower thrust, with the risk of hot Fe+ ions chemically reacting with the the pusher plate.

A further development of the Orion is the Mini-Mag Orion. This design centers around externally starting a fission reaction in the pulse units. This is done by compressing the fissile fuel (uranium) using a Z-pinch device. The main advantages are lighter units, lower minimum yields, increased safety (the pulse units are not self-contained bombs in the wrong hands) as well as all the efficiency and mass savings of electromagnetic capture of the particles produced.

Externally-ignited nuclear reactions brings fusion to mind. Using fusion fuels instead of fission fuels in the nuclear pulse units has several advantages. In terms of propulsion, fusion products can achieve much better velocities and power densities than with fission: exhaust velocity of the particles is proportional to the square root of their temperature.

ICF pellet design, ignited by lasers
Fusion pulse propulsion allows for the use of much smaller individual units. This is important, as it means the impulse from each detonation is lower, leading to lower structural requirements and suspension mass. The storage of non-fissile elements is better than handing over several tons of uranium along with their triggers to a captain heading off to deep space... However, the spaceship has to carry along its own power source to trigger each nuclear pulse, and carry protection against neutrons emitted by neutronic fusion. The latter would normally be the job of a physical pusher plate.

Tellar-Ulam design.
The advantages of fusion can still be obtained without external power by using a Teller-Ulam device: it uses a fission reaction to trigger a subsequent fusion reaction. However, the individual pulse units will be larger than either pure fission or fusion devices, and more complex, with the disadvantages of both systems. Considering that propellant is cheap in outer space, and that more than 100km/s is wasteful in our Solar System, there should be no reason to ever use these. 

The ultimate nuclear pulse unit uses antimatter. Small quantities can be used to ignite fusion pulses in Antimatter-Catalyzed Fusion, large quantities can be used in pure Antimatter-Matter Annihilation. They would allow the use of very small individual pulse units, with corresponding low structural and suspension requirements, and extreme exhaust velocities that are perfectly suited to an interstellar mission. The main challenges though are actually producing useful quantities of antimatter, storing it safely until it is used, and finding an efficient way to convert gamma rays into infrared radiation.

The Casaba Howitzer

The Casaba Howitzer is the result of research into reducing the spread of the particles produced by a nuclear pulse unit. Make the cone narrow enough and it becomes a destructive beam.

Concept design by Scott Lowther
The original nuclear shaped charge design called for the use of a tungsten plate. The particles that resulted from the detonation of a pulse unit would fit inside a cone with a spread of 22.5°. The particles would be relatively slow (between 10 and 100km/s depending on thrust requirements) and rather cool (14000°C in transit, 67000°C after hitting the plate).

As noted before, using lighter elements, such as plastics or even hydrogen, in a thick and narrow instead of wide and flat shape, you can achieve a very narrow cone and very high particle velocities. A Science & Global Security report from 1990 used polystyrene as the propellant material to produce a particle beam with a spread of 5.7° and a velocity of 1000km/s.   

Particle velocity is derived from the Root Mean Square equation. It can be written as such:

  • Particle velocity = (24939 * Temp / Mass) ^ 0.5
24939 is a constant equal to Boltzmann's constant (1.38*10^-23) divided by unitary molar mass in kg (1.66*10^-27) times the degrees of freedom of motion (3). Temp is the nuclear detonation's temperature in Kelvin, and Mass is the mass of the propellant used in g/mol.

For an atom bomb (10^8 K), uranium (238 g/mol) will be ejected at 102km/s.

In a fusion reaction (10^9 K), deuterium (2 g/mol) will be ejected at 3530km/s.

The difficulty is in transmitting this thermal energy to the propellant, and keeping the particle cone focused.

In a propulsion pulse unit, it is not known how efficiently a nuclear shaped charge is able to heat the propellant. Most sources cite a 85% of the device's energy being sent in the desired direction. It is unknown also whether this is before or after some of the propellant is accelerated in the wrong direction, and whether larger pulse units are more efficient (higher propellant mass fraction). This is important as it would allow a thermodynamic estimation of the particle velocity.

It would be reasonable to use a lower figure when calculating the amount of energy delivered to the propellant. Scott Lowther gave a 50% figure for small fission charges. An SDI nuclear weapons study, project Prometheus, experimentally tested Casaba Howitzer weapons using plastic propellants. It achieved 10% efficiency. A Princeton University study from 1990 on third-generation nuclear weapons cited 5% instead, but for fusion devices with ten times better beam focus. 


Despite the reduction in cone spread, the stream of particles produced by by Casaba Howitzer dissipates much more quickly than an electro-magnetically accelerated particle beam or a laser.

It is possible to reduce the beam angle to 0.006 degrees in width, as reported by the third-generation nuclear weapons study. 0.057 degrees has been experimentally achieved by project Prometheus. The trade-off is much lower efficiency than propulsive units (5-10% vs 80-85%).

The theoretical maximal performance of a thermonuclear device is 25TJ/kg. Modern weapons are able to achieve 2.5TJ/kg, but this figure is for large weapons that have better scaling. Smaller warheads such as those tested for project Prometheus are likely to be in the kiloton range, and mass about 100kg. Better understanding of fission ignition has reduced the nuclear material requirement down to a kilogram or less.

A nuclear detonation only lasts a microseconds, so we can assume that the entire energy of the unit is delivered to the target in a single pulse of duration 10^-6 seconds.  As the particles produced expand in a cone with an angle ๐›‰, we can use the following equation to calculate the destructive potential at various distances:

  • Intensity = (Yield * Efficiency * 10^6) / (3.14 * (tan(๐›‰) * Distance) ^2)
  • Irradiance = (Yield * Efficiency) / (3.14 * (tan(๐›‰) * Distance) ^2)
Intensity is measured in watts per square meter. Irradiance is joules per square meter. Yield is how much energy the nuclear charge delivers, converted to joules. Efficiency ranges from the 0.85 of a propulsion unit to the 0.05 of a Casaba Howitzer. ๐›‰ is the cone angle. Distance is between the nuclear detonation and the target, in meters.

Let us calculate some examples:

Small Casaba Howitzer (50kg)

0.01 radian directivity (0.057 degrees)
5kt yield, 10% efficiency: 2.09TJ
Distance 1km: Irradiance = 673GJ/m^2
Distance 10km: Irradiance = 6.7GJ/m^2
Distance 100km: Irradiance = 67.2MJ/m^2
Distance 1000km: Irradiance = 672kJ/m^2

Large Casaba Howitzer (1000kg)

0.001 radian directivity (0.0057 degrees)
1Mt yield, 5% efficiency: 209TJ
Distance 1km: Irradiance = 6728TJ/m^2
Distance 10km: Irradiance = 67.3GJ/m^2
Distance 100km: Irradiance = 672MJ/m^2
Distance 1000km: Irradiance = 6.7MJ/m^2

Futuristic Megaton Nuclear lance

0.0001 radian directivity (0.00057 degrees)
1Mt yield, 20% efficiency: 836TJ
Distance 1000km: Irradiance = 2691GJ/m^2
Distance 100000 km: Irradiance = 269MJ/m^2

To determine destructive capability, we can model the Casaba Howitzer as a direct energy weapon. We can recreate the particle strike as a laser weapon firing a single pulse with equal properties.

We will describe the strike as a laser pulse of duration 1 microsecond, containing X energy and with Y spot radius. A 1.63 micrometer wavelength laser focused by a 2cm diameter mirror consistently produces the same spot sizes as a 0.01 radian beam. A 20cm mirror is used for 0.001 radian beams, and 200cm for 0.0001. We test penetration against Aluminium. 

Small Casaba Howitzer:

X = 2.09TJ
1km, Y = 0.994m: 734mm penetration
10km, Y = 9.94m: 0.73mm penetration

Large Casaba Howitzer:

X = 209TJ
50km, Y = 4.97m: 586mm penetration
500km, Y = 49.7m: 0.59mm penetration

Futuristic Megaton Nuclear lance:

X = 836TJ
1000km, Y = 9.94m: 293mm penetration
5000km, Y = 49.7m: 2.35mm penetration

The results reveal that the Casaba Howitzer is an extremely destructive weapon, with the larger models able to strike at distances usually reserved for lasers. Even a small Casaba Howitzer is effective at up to several kilometers, using technology tested in the 80s. Larger, more modern devices can strike at greater distances. Futuristic devices will reach particle velocities of about 10000km/s, so time to target is negligible.

However, these distances are lower than those of powerful lasers, so the Casaba Howitzer will need a delivery system such as missile, or be used in defensive roles. 

Making use of the Casaba Howitzer

The Casaba Howitzer's advantages are numerous, and can be exploited in four ways:

-Terminal warhead:

A MIRV's warheads.
Hard science fiction with a military focus usually boil down to where the author has placed their marker on the sliding scale between missile and laser dominance. Make lasers too powerful, and they make mass missile attacks uneconomical. Make missiles cheap and fast enough, and you can overwhelm any laser defense. 

Missiles are hindered by the requirement to track the target and follow until impact. Lasers are increasingly effective as missiles close the distance to their target. Past a certain point, any missile touched by a laser is quickly destroyed. So quickly, that a laser defense's primary limitation is the time it takes to switch targets. In other words, a laser defense sets up a 'death zone' around itself, within which any wave of missiles will quickly be annihilated. 

A combination of efficient lasers, multiple turrets and competent target handling can cut through hundreds of missiles.
The counter to this, on the missile side, is to perform randomized high-acceleration maneuvers called 'jinks'. This tactic is already used today by sea-skimming missiles once they enter the range of CIWS defenses. The problem is, in space this requires the missile to have powerful thrusters, lots of propellant and active, autonomous sensors that survive to the terminal stage of its attack. This means that missiles will end up being heavy, hard to bring up to speed, large (easy to track and hit) and expensive due to on-board electronics. These are all characteristics you want to avoid when trying to make massive waves of missiles economical, or if jinking through the death zone.
Using a Casaba Howitzer warhead solves this conundrum. 

It allows missiles to deal damage from outside the death zone. It also removes the requirement of saving propellant for the terminal stage, or even the necessity of accelerating up to a high velocity intercept. At allows missiles to be lighter and smaller. Depending on the price of the nuclear technology, a few Casaba-Howitzer missiles may be cheaper than multitudes of kinetic impactors.

-Point defense

The usefulness of a nuclear shaped charge extends further than just being a warhead. As calculated in the Effectiveness section of this post, the particle cones spread quickly, but remain effective at short ranges. 

In a defensive role, a Casaba Howitzer will have to be lightweight and efficient in its use of fissile material. This is because it must be deployed in numbers comparable to the incoming projectiles. Optimizing for efficiency has the consequence of producing a wider cone.
This cone can be used to sweep away missiles in the terminal phase. Close enough, it will outright vaporize kinetics. Further away, it can still damage sensors and shatter propellant tanks through impulse shock. The large angle of the cone is advantageous, as it would reduce prevision requirements against jinking missiles, and might even catch several missiles at once. 

Other advantages of using Casaba Howitzers as a point defense is that it can easily be aimed, does not consume power and has infinite firing rate. If you detect missiles coming in, dump your entire payload of defensive drones and have them point at targets. Once they come within range, all can detonate simultaneously. 

This might actually be the preferred tactic, to prevent previous nuclear detonations from interfering with the detonation of subsequent charges. This is a concern if the Casaba Howitzers use fusion fuels that are sensitive to external sources of neutron radiation. 

Example defensive Casaba Howitzer:
100kg, 10kt yield
85% efficiency: 35.56TJ beam
Beam velocity 1000km/s 
Beam angle: 10 degrees
Effective range (penetrates 5mm of aluminium): 16km 

This warhead can destroy anything within a 6.15km^2 circle up to 16km away. It reaches targets in less than 16 milliseconds, and unlike a pin-point laser, it affects the entire surface of the target at once. 


The awesome power of a nuclear shaped charge does not have to be used directly to damage targets. It can be used in innovative ways.

Instead of being used to generate high velocity particles in a narrow cone, a Casaba Howitzer can be used as a nuclear version of modern shaped charges. A metal cone is put in the way of a nuclear-heated beryllium filler. It is accelerated by the blast, like in an Explosively Formed Projectile. The only requirement is that the energy deposited into the metal lining is not sufficient to vaporize it.

-Particle beam weapon

The ionized particles produced by a Casaba Howitzer can be used to feed a particle accelerator. Unlike a traditional accelerator, its main role is not to accelerate particles closer to the speed of light, but to use magnetic lens to focus the ions into a tightly collimated beam. At the muzzle, the ions are neutralized to reduce bloom using a co-axial electron beam. 

The greatest point of concern is pushing the particles into the accelerator without reducing their velocity. A magnetic 'funnel', much like that of a mass spectrometer, can perform this role.
A shaped-charge-pumped particle beam looks like this, in reverse.
The second point of concern is preventing the particles from damaging the particle accelerator. This can be remedied by building the accelerator as a series of widely spaced loops of wire acting as electromagnets. The particle beam is focused in stages, narrowing after each loop. 

The optimal Casaba Howitzer configuration for this weapon is a fusion device that is built to maximize particle velocity. 10000km/s (3% of the speed of light) may be achieved. This is much slower than an electromagnetically-accelerated particle beam weapon, but it has the advantage of requiring little to no external power (the electromagnets can be fed by the heat they receive from the nuclear detonation), massing much less than a regular particle accelerator and able to extend the range of small nuclear pulse weapons to useful distances (in the thousands of kilometers).   

Integrating the Nuclear Lance into your setting

The Casaba Howitzer is best used as an 'early technology' science fiction setting. When space exploration is still new, and opponents start out in the same orbit, the short-ranged but powerful nuclear shaped charges available are extremely effective. 

It can be mounted on modern-technology missiles to allow them to be effective regardless of the impact velocity, alternatively, missiles will accelerate to low velocities then expend the majority of their dV in evasive maneuvers. It will more likely be used by the most technologically advanced nation to greater effectiveness, as the technology is far from well understood even 58 years after its conception. 

When the technology becomes widespread, such as following its development in nuclear pulse propulsion, it will still be the favorite of nations with greater access to fissile materials. While a fusion device allows greater yields, and would be better for propulsion, a Casaba Howitzer weapon does not benefit from the 1000km/s particle velocities. Easy to detonate fission charges are easier to handle and use.

They will however fall out of favor as lasers extend the range of combat beyond even their reach, into the tens of thousands of kilometers. More efficient missile propulsion, or the development of cold stealth technology, might change the battlefield even further.

However, as developments in propulsion continue, newer, simpler methods of detonating thermonuclear devices might become commonplace. Antimatter-catalyzed fusion or supercapacitors powering Z-pinch devices might allow Casaba Howitzers to return to the battlefield as cheap anti-missile defenses, free from the requirement of fissile materials.

Throughout history, however popular or effective they are, Casaba Howitzers will force states to carefully watch who and where to fissile materials are sold. Just 2 kilograms of uranium can be converted into a several kiloton-yield weapon, easily hidden in a civilian cargo-bay or remote satellite, and used to destroy an expensive warship in an instant.


  1. Correction: the half angle should be 11.31°, not 11.25°, for a pusher plate interception of 0.97%, not 10%.

  2. Really good article, great work here...

  3. I realize that the casaba howitzer in your particle beam form resembles a toned down yamato cannon from StarCraft. This got me wondering if such a weapon could be viable in a turret form, or would it be restricted to a spinal mount for very large warships or an unmoving space fortress? If this form of casaba is able to be made into a turret, then wouldn't this solve an issue with kinetic weapons you mentioned in an earlier post? You said that it could be possible for it to use little to no power from the ship, thus giving the ship an advantage in situations where the ship has little power to spare over kinetic weapons (low velocity).

    1. Sorry for the late reply!

      The casaba howitzer is a nuclear explosion. Yes, it ejects its energy mostly in one direction instead of a sphere, but the remaining percentage is enough to carve out several tons of material from anything near it.

      If the Casaba Howitzer design being used is 85% efficient, it would require that a turret contain the remaining 15%. When the yield is in the terajoules, 15% is no laughing matter.

      In the near future, you will definitely have to build the spaceship around the weapon. The magnetic focusing loops will be enormous, to the point where it might be easier to make each loop an autonomous drone with its own engines and fuel.

      As technology progresses, you'll be able to detonate smaller and smaller thermonuclear charges, meaning you can use them closer and closer to your spaceship.

      In an advanced technology setting, you might use 'micro-fusion' Casaba Howitzers inside a magnetic shell with a small opening for high velocity particles to rush out of. Enclose the whole thing in armor, make it rotate and you're got your nuclear turrets.

    2. I've visualized a sort of bazooka arrangement for such turrets- the "gun" is carried flush with the hull until needed, then it extends from the hull like the warp nacelles on Cochrane's ship did, plus has a swivel mount in azimuth and elevation once extended. They's have a limited angle of elevation from the hull surface because you want the backblast as far from it as possible.

    3. The Casaba howitzer would send up to 15% of it's energy in ALL directions. Even if you held it inside a bazooka-like tube that is open from both ends, you'd need to contain a nuclear blast within the walls of the tube. This might amount to 10% of the blasts's energy, which is still too much to handle without incredibly thick walls (once), huge ablative shielding (a few times) or incredibly strong magnetic fields...

  4. This has always been an intriguing weapon for me, and I'm glad to actually have some idea of range and application now.
    A question that comes to mind is what would performance be like in atmosphere, either fired in atmosphere or fired into the atmosphere from orbit?

    1. Imagine you dive into a swimming pool. You drag along a garden hose with you. With a twist, you switch on the nose, and water jets out underwater.

      How far does the water keep moving? 30cm? 10 cm? Less?

      That's how effective a Casaba Howitzer is within an atmosphere. The kinetic energy of the particles is very quickly absorbed by collision with atmospheric particles, until it becomes nothing better than a cloud of hot air. A Casaba Howitzer in an atmosphere is a plasma weapon of the sort hard scifi commentors love to explain why they won't work to soft scifi fans.

  5. 1 megaton yield equals 4.5 PJ not 45 PJ therefore with %20 efficiency energy of the nuclear spear is 0.9 PJ not 8.56 PJ. other yield to energy conversions are also off by a factor of 10. Great article by the way.


  7. Hi Matt. Thank you for this resource (am big fan also of Winchell's Atomic Rockets website). Am I the only one here who thinks that 70 METERS of aluminum armor penetration by a 1 MT Casaba Howitzer across over an 200 meter-wide area at a range of 10,000 KM is kind of a serious game-changer? That's some serious reach and area of effect! I'm writing a sci-fi novel (Winchell has mentioned it in his Atomic Novels section), and one of the first problems I ran into was how difficult it is to economically engineer a long-range laser without needing seriously large mirrors and ginormous power generators (to say nothing of the heat radiator system). Thoughts?

    1. It is!

      Casaba Howitzers have the potential to do what guided missiles did to the naval gun: make them utterly obsolete!

      Imagine your 1000 ton laser-firing behemoth with a kilometer squared of radiators and a multi-gigawatt power station onboard, taken out by a single missile.

      The practicality of the devices is where you, as an author, can choose to make or break them.

      If you want Casaba Howitzers to be the supreme weapon, you have to provide very large quantities of rather rare materials. This supposes a large military-industrial complex. Explosive lenses which trigger the nuclear detonations are some of the most advanced technologies right now. The large amounts of high-grade fissile material consumed per warhead has to come from an even larger supply shared with power stations and nuclear rockets.

      With a few advances in beam tightness, the Casaba Howitzers can reach 10000km+. The warhead will mass a lot, but if it can take out a much more expensive warship, it will be worth it.

      The consequences, however, have to be dealt with. With a vast supply of nuclear material, it makes more and more sense to use some of it for creating electricity where sunlight is unavailable. Mars, for example, would built its colonies anywhere it wanted, without worrying about the football fields of solar panels required per home. Mercury would be a less attractive destination, as sunlight can be replaced with nuclear power.

      Nuclear rockets would open up the solar system like never before, meaning it is possibly cheaper to get your nitrogen from Neptune's moon Triton than excising it from Earth's biosphere.

      Warfare will change is possibly unexpected ways. Nothing can survive the beams, so armor is cast off the wayside. Mobility, stealth and first strikes are paramount, much like modern jet combat. Spaceships are likely to be small, each packing only a dozen warheads, but operating in swarms.

      Non-government actors become disproportionately powerful. Any commercial ship can pack ship-killing weaponry in a closed cargo crate. Nuclear bombs can be made easily from the effusion of nuclear material available. Useless in space, but devastating on the ground. Just the explosives required for triggering the nuclear devices can be scavenged and turned into lethal weapons in pressurised environments.

      If you want you traditional capital-ship navy that slugs it out at close ranges, then there are many ways to stop Casaba Howitzers from interfering.

      The easiest way is to limit the supply of fissile material. Its already rare on Earth, and hard to extract from other planets, and unless Asteroid Uranium flies by, we won't have much more.

      You can also put mechanical restrictions on the beam tightness, reducing Casaba Howitzers to devastating but short-ranged defensive weapons. Alternatively, push the laser effectiveness even further, so much so that 10000km range is insufficient.

      Political restrictions, such as the modern day chemical weapons ban, is a cheesy way to do it, and is the most vulnerable to people just not caring, but it removes you from having to go into technical details about why such or such is not trouncing everyone on the battlefield.

    2. I mean, there's recently been some pretty major advances in laser technology.

  8. First off, thank you for an excellent article! As a writer aiming to portray at least reasonably realistic space combat, this is a very thought-provoking and detailed resource.

    Second, I had a question/hypothetical: I see above that you answered a comment saying that a weaponized nuclear shaped charge would be effectively worthless in an atmosphere, but was wondering if the potential might exist to use the weapon instead as a bunker-busting munition against ground targets. Specifically, the potential application of detonating a large yield weapon upon contact with the ground above a deeply buried hardened structure, using the focused plasma jet to drill through rock and concrete, or applying it directly to a HEAT-style explosively formed pennetrator.

    Thanks very much for your excellent work, it's a wonderful resource and a great read!

    1. Hello and welcome! Sorry,t he blog is in a bit of a down period for now, but I'll keep answering comments.

      A Casaba Howitzer is actually a particle beam weapon, but instead of magnets accelerating a small number of atoms, a nuclear weapon blasts away a large amount of plasma.

      In an atmosphere, this plasma will slam against slow, cold gas molecules and transfer their energy. This rapidly disperses the beam and heats up the surrounding air. The range will be terrible, with an effectiveness of a few hundred meters at most.

      However, within that distance, it is more effective than a nuclear bomb in trying to take out bunkers or buildings.

      Better than the Casaba Howitzer is the Nuclear Explosive Formed Projectile. Like modern anti-tank weapons, a disk of metal is is explosively accelerated into a thin stream of high velocity ejecta. Half molten, it remains dense enough to punch through any amount of armor. The NEFP is the nuclear version of this, utilizing a very thick slab of tungsten instead of a copper plate, and drilling through dozens of meters of concrete instead of a few centimeters. It won't be very effective in creating huge craters like regular nuclear bombs, but it will get through bunkers undergrounds and set anything inside on fire.

    2. Thanks for your reply!

      Is there any existing equation or resource to calculate the effective penetration of a NEFP? I would be very interested to know what sort of RHAE penetration values could be attained by such a weapon, especially in terms of using it in the context of a spacecraft firing on deeply buried anti-orbital weapons positions.

    3. The equation's I've got allow us to calculate the velocity of the EFP. They're detailed in the post under the title 'Gurney equations'.

      For a very small 1 kiloton yield device and a 0.85 efficiency, we must use a very high mass ratio to achieve acceptable velocities. The Casaba Howitzer used for propulsion purposes had a mass ratio of 0.2 and reached over 2600km/s... unless capped by a tungsten plate. This is essentially a particle beam! It will blow through just about any vehicle, but cannot travel beyond a few meters in air or a few centimetres in rock.

      However, the equations fail when we use nuclear weapons, as they basically become a ball of hard x-rays in microseconds, instead of the relatively gradual pressure building up a 600 degrees Celsius in milliseconds.

      If we want deep penetration of a target, we must use a very thick plate that can take the energy and carry it through the medium without losing velocity. This is done by increasing the mass ratio to about 20 or more (1 part uranium for 20 parts plate).

      An even more efficient method is to use a beryllium filler between the nuclear device and the plate. It absorbs the x-rays more efficiently and becomes a high-pressure gas the pushes instead of vaporizes the metal plate.

      All in all, I came out with a 1kiloton device using 2kg of uranium pushing a 100 ton plate of steel to about 20km/s at the tip of the stream. It is 10cm thick and 13m wide, and can penetrate about 26000mm RHAe. Total device mass is about 111 tons.... and I don't know how to make it smaller without wasting the vast majority of the uranium's energy.

  9. so you're talking about firing the equivalent of two main battle tanks at 20,000 metres per second and that would take out 26 metres of armour? the numbers are astonishing

    1. Sometimes, I worry that they're too good. If casaba howitzers are so good, what's the point of lasers and missiles and railguns?

    2. I think the good news here is that casaba howitzers fall into the (large!) class of techs that are permissible, so to speak, in a hard-ish SF setting, but are not required.

      On the one hand, the basic concept has been demonstrated. On the other hand, it has not been demonstrated that extremely narrow streams can be achieved in practice. Precision sculpting with exploding nuclear weapons is not easy!

    3. I've tried modelling space warface where casaba howitzers are widespread weapons... and I've concluded that they are something to avoid.

      Even using laboratory results from two to three decades ago (Project Prometheus), they would have the range and destructive capability to render lasers seem wimpy and kinetics pointless. Missiles could be defeated by wide-cone nuclear blasts, so combat would devolve into missile swarm slugfests.

      Each side launches a swarm of missiles with various low- and wide-angle casaba howitzers. The low-angle missiles fire from fire away at spaceships. The wide-angle missiles attempt to fry the opposing wave of missiles. This is an environment that is very hostile towards equipping spaceships with anything above a bare-minimum missile-bus design. Human crews have no place in the middle of waves of radiation and kiloton plasma spears.

    4. mainly? the howitzers are too expensive to throw around like you can all those other things

    5. That might be true today, bob, but it might not be the case in a setting where both sides agree that they are very effective.

      If, for example, a handful of nuclear warheads can take out a spaceship reliably, while saving you the cost of a massive nuclear reactor, electric generator, radiators, laser beam generator and focusing array, and costing much less than their target... then they will be deployed.

      This 'cheaper than the target' logic applies to very expensive missiles such as million-dollar cruise missiles and 10-million-dollar anti-carrier ballistic missiles.

      Also consider that dominant weapons receive inordinate amounts of funding towards their research and development. Casaba Howitzers will certainly become cheaper over time. The biggest factor is the cost of nuclear material. However, there is news of uranium being extracted from seawater, and some asteroid containing large amounts of rare and heavy elements...

  10. The Small Casaba Howitzer has a irradiance of 2kJ/m² at 1 Mm. Still it's capable of penetrating 734 mm of Aluminum. How is that possible? Besides that awesome post, always loves to see something from Project Rho.

    1. I spent an hour re-doing every calculation, and the maths holds up.
      At 1000km, the beam diverges onto an area with a radius of 99.43m. The surface area is 31058m^2.
      Dividing 2.09TJ by 31058m^2 gives us a very good 67MJ/m^2.

      Use this link for the laser weapon calculator:

      Input the following figures in each box:

      Select aluminium and hit 'Fire Lasers' to generate a table.

      The first numbers simulate a laser with equal divergence to a 0.01 radian beam. The 2.09e18 and the 0.000001 simulate the pulse energy delivered over 1 millisecond. You should find the first entry for 1000km gicing a penetration of 734mm, as stated in the blog.

      So... still very impressive.

    2. Thanks, glad that my "Gamma Ray Burst in a Box" are somewhat plausible.
      I've always inserted 2.09e12 MW instead of 2.09e18 MW. 2,090,000 MJ divided by 0.000001 seconds.
      But why does there still stands 2kj/m² Irradiance at 1000 km if the real number in 67 MJ/m²? And the Laser calculator says 6.729GJ/cm² = 67.29TJ/m²?
      Sincerely yours.

    3. PS: reduced wattage to 2.09e12 MW, the result were 0.0067MJ/cm² = 67 MJ/m² like you said in the upper part.
      but it resulted in pathetic 734ยตm penetration of Aluminium.

    4. I seem to have made a mistake. I always thought the laser calculator was in Watts, not MegaWatts. I'll redo the calculations...

    5. Great, now I ruined my one of my favourite weapons in Hard Sci-Fi, and it has little to no advantage against CIWS systems anymore. I was too good to be true...

    6. Based on the B41 bomb's yield-to-weight ratio, a megaton weapon would mass about 200kg.

      A weapon system only 200kg in mass yet with the ranges of lasers massing thousands of tons of a very good thing: 10000km+

      If you use a warhead the mass of a Brahmos missile, you can get ranges of 150000km+.

      The only thing that's changed is that instead of casaba howitzers being nuclear shells, they're something closer to nuclear cruise missiles in size and practicality

    7. You still have to add the very heavy depleted uranium case, and some channel filler and propellant. Let's say 350kg. Add a little prize of handwavium to increase efficiency and better focus. 12,5 megameter for slightly/unarmored ships, 7,5 Mm Light/Medium Armored, 5 Mm for Dreadnoughts. Assuming they are using Composites with spacing. The weight matches the W88 Warhead, which means 12 (or more because of zero G environment) can be mounted on a Trident II size missile. Still pretty awesome. PS: How old is this post on Atomic Rocket? I'm wondering why no one ever noticed it

    8. No need for a depleted uranium case, a megaton yield weapon in the sub-ton range is usually a fusion-boosted fission warhead. This means it is coated with much lighter Lithium-6.

      The B41 yield-to-mass ratio is calculated from the complete package, so I wouldn't worry about unknown masses.

      The channel filler is very lightweight plastic to achieve the narrowest cone and the highest particle velocity possible. Its mass is negligible (a couple of kg).

      The total is closer to 220-250kg.

      The efficiency figures I'm using are on the conservative side: un-optimized lab figures from 3 decades ago. A more realistic level of efficiency would double the ranges listed, so a 3-ton cruise-missile-sized 'futuristic' package is going to be carving 30cm deep plates out of its targets at 240000km+ ranges.

      And that's just the penetration rate. The armor material is vaporized so quickly that it causes impulse shock - spallation, fracturing, fissuring - closer to the effects of a grenade going off next to a tin can. There are also secondary damage mechanisms. Particles suddenly slowed down by impact release Bremsstrahlung X-rays that can penetrate deep into the target's spaceship.

      It's much more destructive than an equivalent-penetration laser.

      The original Atomic Rockets post on Casaba Howitzers is older than the Internet. My section was added in response to this post, so about 10 months.

    9. Isn't Lithium-6 Only good for Neutron Shielding? X-ray and Gamma-ray shields usually use high Z materials like Tantalum, Tungsten, DU etc. I agree on the Laser part. Problem is there is no weapon calculator for particle beams, one could do it without one, but nor me or most other people have the patience/time for that. What is use of the Casing anyway? the DU case would only partially reflect the X-ray. and the rest radiation is wasted in a ordinary nuclear explosion anyway. Also a 30 cm Plate? Wasn't it somewhere stated that thinner plates results in narrower cones? But also obviously in lower efficiency hence to lower mass of such plates. As mentioned before armored vehicles will use Spacing which removes most dangers of spallation, just like Squash Heads nowadays are ineffective against tanks. CoaDE taught me to never underestimate spacing, Spall-liners, and Whipple shields (if you have tons of Diamonds, Spider Silk and boron of course)

    10. I remember now, Lithium-6 is used in Many Nuclear Weapons as a way of storage for Tritium, Lithium-6 when under Neutron Flux turn into the hydrogen isotope Tritium.
      Correct me if I am wrong.

    11. As far as I know, the uranium casing bounces the x-rays produced by the fission primary back into the fusion secondary. It is necessary for the Teller-Ulam design to prevent the X-rays from being wasted, but you can use lead instead, as you said.

      The B41 bomb I keep referencing is a triple-stage thermonuclear warhead. Fission-fusion-fusion. The third stage is the largest and contributes the most to the yield, and that does not need any casing.

      The 30cm plate is in reference to the shape of the hole carved by a 15 megaton yield 'futuristic' casaba howitzer warhead (massing 3000kg) at a range of 240000km: about 290mm deep and nearly 20m wide.

      The spallation effect I mentioned is not about killing the crew with shrapnel, but to indicate that there is a supersonic shockwave travelling through the armor material, causing destruction and overall failure of that segment of armor beyond what the penetration numbers indicate.

      For example, if I had 1000mmm thick slab of aluminium, I cannot count on it to survive 3x300mm penetration Casaba Howitzer blasts. The first blast's secondary effects would fracture and crack the slab all the way through.

    12. Depleted Uranium Casings are used as the Third-stage in Thermonuclear devices, DT Fusion releases 14.1 MeV Neutrons which can induce fission in U-238 (DU). Fission Neutrons which only have 2 MeV are only able to induce Fission in supercritical fissile material. So Three-staged Nuclear weapons are Fission -> Fusion -> Fission. A examples for this is the B41, and also the Original Tsar bomba which was supposed to have a U-238 Case with a whopping 100 Mt yield. Which was never realised in the fear of creating immense fallout (It would have created 25% of all Fallout caused by every nuclear detonation.)

      Increasing the amount of spacing significantly reduces dangers and total damage of spallation and other Kinetic and Thermal mechanical effects.
      Example: 10X 100mm Aluminium Plates
      Particle beam vaporizes 3 Plates and induce spallation which hits the fourth plate, which acts as a kind of whipple shield. The Fifth plate only receives minor damage.
      Reality: the 291mm only counts for vaporization, it's likely that the rest of the armor would liquified. And the Bremsstrahlung will be deadly more organic matter.

      One Should also consider that armour will also be highly advanced at that point, materials like e.g Graphene could be mass produced at that point. Advanced Alloys and Composites may offer increased protection against such strikes.

      Also, the Nukes ain't cheap. Enriching Uranium/ Breed Plutonium-238 is very expensive. Which may decrease in the future but a Megaton Casaba Howitzer under 1 million $ (2017) would be very hard to produce.

    13. PS: Checked some numbers again, The Large Casab Howitzer uses 0.0001 radians beam of the Megaton Lance

      As the Described in your text
      1000km: 70.2 ยตm
      1000km: 70.2 mm
      (= 0.0001 radians)
      Megaton Lance
      As Descripted:
      1000km: 291.3 mm
      10,000km: 291.3 ยตm
      10,000km: 291.3mm

    14. @OMG its WTF:

      -Casing: It seems you're right. X-ray reflectors are needed even in the third stage.
      -Armor: Testing revealed that even super-materials would only reduce the penetration ability of a Casaba Howitzer (or any direct energy weapon, really) by about 3-4x. There is a limit to how much chemical bonds can survive, after all, even the strongest carbon-carbon ones.

      Spacing the armor seems to prevent the secondary damage effects I mentioned from being transmitted through the entire armor's thickness, but I'm unsure as to how the front plate acts after receiving enough energy to vaporize it several times over.

      I'm guessing it turns into a big plasma explosion, but how powerful would it be? Would the concussive force of the front plate exploding into plasma contain half the energy the armor absorbed? 90%? More, less? Most importantly, how does the 'excess' energy get transmitted into the lower layers?

      -Price: modern missiles cost several millions, sometimes more for the larger ones. If you only need a couple of missiles to take out a multi-billion target, then it is worthwhile.

      New figures: You keep writing '163e-9', when it should be '1630e-9'. Might that be the source of the discrepancy? Also, it should be '2.09e12' for the small casaba howitzer figures I gave you, and '0.83e15' for the megaton casaba howitzer. Also, the mirror radius figures at 0.01/0.1/1 for the small/megaton/futuristic warheads.

    15. Re New figures: What is the question mark for? You're right. it perfectly matches the discrepancy. 10x smaller wavelength and a resulting 10x beam angle decrease.
      Re Armor: That is even more than i expected. those Super materials (Let's say Graphene) can with advanced nanomanufacturing be produces in masses, and the resources for it are cheap as dirt.
      Re Price- Well, this is a tricky one. Getting clear results would require a lot of Economics, and Excel charts. But if it holds true what you said,
      then it fits my rule of Cost effectiveness, Being able to kill an enemy which is 1000x More expensive than the Weapons and ammo i used.
      Re Plasma Explosion: In the "Fourth Generation Nuclear Weapons" it was mentioned that a 10t Fusion Bomb detonated 1m away from its target would deposit 5kJ/cm² in the first 10cm of the material. Effectively turning the armor plate with high explosives . Because the beam is made out of Carbon or other low atomic mass particles they would behave very similar to Neutrons in form of penetration. Instead of vaporization only happening the outest particles a 10cm plate would be heating "equally". I gonna do some research at the weekend, how to get numbers. I already have a idea how to calculate it.
      Post scriptum:
      "it should be '2.09e12' for the small casaba howitzer figures I gave you," Uhm, didn't I gave you the that numbers in the first place? Nevermind, seems like the circle is closed now

    16. Post Post scriptum: About Futuristic Lance, I replaced the Heat of vaporization with the Heat of Fusion too see how much would be "melted".
      1 Mt Lance: Vaporization (as a safety check) 291.3mm at 10 Mm
      And 7920 mm Liquefied. But Heat of Fusion doesn't mean that it would be as liquid as water but instead like Lava/Magma. maybe 5000 mm is turned into a puddle of molten Aluminium.

      Re Casing: The Third Stage doesn't need a X-ray reflector, it's a x-ray on itself. Third-stages only work if you have a Fusion reaction as the second stage. Due its purpose being to create Fast neutrons which induce further fission in the First-stage and due it's being 14 Mev instead 2 Mev Neutrons being able to induce fission in non fissionable depleted uranium. X-ray don't take any part in it besides triggering fusion in the second stage and turning the foam inside the device into plasma which expend to the fireball and heats and implodes the second stage.

    17. Plasma Explosion Verdict: If we say a 10cm thick aluminium plate absorbs 24% (200TJ) from a Futuristic Megaton Lance with a spot radius of 9.943m
      (the plate weights around 83.7 tons (pi x r² x h x 2,7g/cm³)the Specific heat of the plate is 75MJ. (83700 kg x 837J (kg * K)) this results in a final temperature of 2,663,864 Kelvins. The Energy density is 2387 MJ per kilogram (TNT = 4.184 MJ/kg) and 6.45 MJ/cm³. I tried using Thermal expansion calculation to find out the final volume but it only resulted in 5563m³ from initial 31m². A fireball with 10m radius

  11. New figures: Just trying to confirm. You seem to have compensated for the 10x discrepancy three times, in the wavelength, pulse energy and mirror radius. The '2.09e12' does indeed come from your first comment.

    Casing: Well, that's something I've learned!

    Plasma explosion: I was trying to mentally visualize the effects of a Casaba Howitzer impact, and I realized that the low velocity particles from the nuclear explosion, likely to be less than 1% of the speed of light, would travel only a few millimeters through solid metal before they deposit all of their energy.

    After all, the particle penetration of relativistic particles is barely better.

    So what happens when gigajoules of energy is deposited into a very thin layer of material? It explodes, as you predicted.

    But such a thin sheet's expansion would be nearly 3 dimensional. The pressures mean that it expands into the solid face quite easily.

    A 3D expansion of a small amount of material efficiently converts thermal energy into kinetic energy.

    The flashed material's kinetic energy would pretty much equal the energy it received.

    A very fast moving gas cloud behind a plate of mostly solid material... does that not sound like a rocket engine? More specifically, how a Explosively-Formed Penetrator is formed?

    It is entirely possible that Casaba Howitzers punch through armor not by directly melting and vaporizing the material, but by acting like a HESH round that punches through the target with its own armor material.

    Because the armor plate is being propelled to a few km/s at most, hydrodynamic models of penetration can be used. This is good for penetration because the material does not shatter into a million pieces like hypersonic rounds up against whipple shielding.

    Imagine it: a Casaba Howitzer blast flashing the outermost millimeters into plasma, rocketing the remaining plate back into the target like a spear of hot metal.

    I'll do some math on this effect tomorrow morning.

    1. A few millions degree hot plasma is launching solid material... kinda sounds like a caseless Casaba Howitzer to me. Problem with the HESH equivalent,
      in modern anti-tank warfare HESH warheads has gone extinct due to the incorporation of spacing. But if you're distributing the force of 200 kilotons over 310m² it might change the situation. For the particles I don't think that the penetration is that low.
      For example: A beta particle (electron) is casually moving 75% the speed of light. but it can be stopped by a few layers tin foil, fast Neutrons moving at 17.3% of c are able to penetrate centimeters and still be mechanical lethal or meters and being able to be Biochemically lethal. This might be explained by the Energy difference: 1.6 Mev beta and 14.1 Mev for Neutrons.
      So it is possible that momentum and KE is more important than shear velocity.

    2. I read up on the HESH warheads more closely and you're correct - the 'Misznay–Schardin effect' is easily defeated and not similar to what is happening here. It is closer to the Monroe effect used by HEAT warheads: a half-molten plate of metal accelerated inwards.

      The majority of the particles in a Casaba Howitzer's particle beam are hydrogen ions and low molecular weight particles such as carbon and oxygen. This is the case if a plastic propellant is used. They are generally much more massive and much slower than alpha particles - alpha radiation is said to be stopped by a sheet of paper.

      Let's consider the Futuristic Megaton lance at 10000km. 830TJ of energy deposited over a circle nearly 20m wide. Most of it is halted and absorbed by the first millimeter (or less!) of the target material.

      Suppose an advanced carbon-based armor material like Diamond-Like Carbon is being used, of thickness 100mm. The first millimeter of a 20m circle of carbon masses 714kg. A kinetic energy analysis tells me this 714kg will act like a propellant that pushes the remaining 99mm to a maximum of 153.3km/s. A thermodynamic analysis says that the 714kg will be heated to a maximum of 2.3 billion K, which then expands at 2179km/s. Using momentum, the 99mm plate is pushed to 22km/s.

      It's hard to estimate which is the correct model, before inefficiencies and losses are considered.

    3. 430J kg x K for Diamond like carbon. 2.3 giga kelvin. 989 GJ per Kilogram.
      714kg. ~700TJ. Thanks obeying the laws of thermodynamics. It's unrealistic that 100% of the momentum is imparted into the plate. 50% is lost in the backward and only forward plasma does the job. And wouldn't a lot plasma just be bounced back without imparting much momentum? Taking the path of least resistance. I would take the lower number. otherwise you have more momentum than the plasma had breaking the first law of Thermodynamics.

    4. Also why is the post on Atomic Rockets still the old one? I remember that it was updated. But it's the "perpetuum mobile" version of the Casaba Howitzer again.

    5. In meters
      Radius: 9.943
      Height (Thickness): 0.1
      9.934 squared is roughly 340. 340m² times 0.1 = 31m³. Diamond density 3.5g/cm³. 3.5kg/L.... 108,705kg.
      Formula used:V =ฯ€ x R² x h

  12. I was using a 0.83PJ figure. Using wikipedia's entry for diamond's heat capacity (509J/kg/K), I found the temperature to be 0.83PJ/(714*509) Kelvin.

    Atomic Rockets updates every week.

    Your volume calculation is wrong because 1mm = 0.001m and not '0.1'Also, diamond-like carbon is closer to graphite in density than diamond.

    1. Hm... Wikipedia entries says
      G: 709J/kg
      D: 427J/kg
      Probably because I used the german wiki site for both density and heat capacity because i couldn't find the heat capacity for kilograms instead of moles.
      I've thought that Diamond-like carbon will have the heat capacity and density due to the crystal like construction instead of Graphite which is basically crude layered graphene.
      Misread the text. Thought you meant the 714kg were for the 99mm plate and not for the "propellant" layer. 649-692kg. or 656-700.57kg for 20m diameter.
      For the upper part: Just checked if it has more energy than the beam itself had.

    2. Actually now i am wondering, when 1 millimeter weight 714kg then the hole 10cm plate weights 71,400kg alone excluding other layers or whipple shields. And thats only for 20m diameter circle. Covering a hole ship with that stuff? You were better of using a iron asteroid as a station. When even the strongest materials only reduce the required armor thickness by 3-4x one would still require many centimeters of armor resulting in kilotons of armor on spaceship bigger than a spaceshuttle. It creates a small conundrum in my head: If Casaba Howitzers make every armor nearly obsolete why even use Armor? And If no one uses armor. Why use expensive Casba Howitzers? Besides their CIWS Advantage they are just very expensive if you don't use exotic ways of Creating an Casaba Howitzer [1]. Otherwise they are just completely Overkill.

      [1] Antimatter-catalyzed-staged-fusion: A handful documents mentioned that one microgram antimatter can ignite fusion in for example 100g LiH. Creating an 1kT pure fusion explosion. the radiation of that explosion could be used to ignite a bigger megaton stage. It would create even smaller Casaba Howitzer warhead due the lack of the bulky fission core and its explosive lenses. And it's probably even less costly, if 1 gram antimatter cost 250 billion-1 trillion. then 1 microgram cost 250k-1M. less than the Plutonium requires for a fission stage which has to be able to get supercritical requiring at least a few kilograms.

    3. There are ways to mitigate the armor mass required. One method would be to deploy strong magnetic fields to deflect charged particles. Another is to shoot beam interceptors into the path of the beam. A fission Casaba Howitzer fired at 10000km takes between 0.3 and 1 seconds to reach its target. A polystyrene plate launched at 1km/s at the moment of firing can clear the hull by as much as 1000m. It can absorb some of the beam's energy and dissipate as harmless wisps of plasma.

      Personally, I see near-future casaba howitzers as being used in Nuclear Explosive-Formed Penetrators. These are able to deliver 100% of the nuclear energy without dissipating, across arbitrary distances. Warships of any size and armoring would be terrified of multi-ton lumps of metal containing terajoules of energy, arriving out of nowhere with only a couple of seconds or warning, and mostly oblivious to conventional defenses such as lasers, small projectiles and reactive armor!

      More discussion on armor:

      Antimatter: a truly fearsome technology indeed. Cheap megaton weapons could completely change the battlefield. More importantly, they allow for rapid space travel by allowing fusion engines to ignite their fuel with only a few nanograms of AM per pulse, and allow for small missiles to reach the performance of the fastest spaceships...

    4. This comment has been removed by the author.

    5. I've always considered that they would use some kind of particle accelerator on top of the larger models. To get more bang for your buck and also make magnetic shields less useful. And even without them you'll need crazy strong fields for such forces. On normal Particle beam weapons it could work but no so much on Casba Howitzers. Like overwhelming point defense, If you have enough missiles (particles) you can overwhelm any defenses.

      There are a few Problems with your Reactive armor (Sounds interesting for Missile-armor.) It isn't launched instantly. Sensors-(Cables)-> computing-----> igniting the explosives. Even modern processors need a few micro-milliseconds for such a task. And even a Attack Helicopter has dozens of kilometers of wire.
      Next is if your ships cross-section is rounded you have the problem that you have blind spots. If you don't rotate your plate in the beam direction they may miss. And you would need 20m diameter plates to cover the hole beam. And you can't cover your entire ship with them or otherwise you can't have weapon turrets.

      Third Problem. A few centimeter thick reactive armor plate would disperse the beam if it absorbed all energy but the beam is in the form of a cigarette. Meaning that a few percent will be absorbed and then the plate explodes microseconds later and the rest of the beam just travel through the plasma debris. Like a long rod penetrator, they are able to pierce modern reactive armor without destroying a significant amout of the projectile same with long stretched plasma cones
      Yes, NEFP have a few good advantages:
      -Infinite range
      -"Stealthier" (You don't really know for sure where it exactly will hit when you the giant flash.)
      -More Energy per square meter
      -They basically behave like nukes at their velocities.
      But they also have disadvantages:
      -Lower efficiency (
      -Often higher propellant weight (as you said "multi ton lumps")
      -Slower (It doesn't really make that big of a difference though)

    6. Particle accelerator: You have to input the energy to accelerate the particles to relativistic speeds from another source. Focusing them is fine, accelerating them costs petajoules of electrical power.

      Particle beams defeat magnetic shielding through sheer momentum. The shields cannot deflect them in time.

      The NEFP will emerge from the casab howitzer glowing red-hot and becoming *brighter* in the targets screens over time, as the glowing hot rear face transmits its heat to the front face.
      The high mass allows for the NEFP plate to distribute the energy of the blast and prevent too much of it from vaporizing.

    7. This comment has been removed by the author.

    8. Yes, I do know that Particle Accelerate aren't magic, I used particle "accelerator" your Magnetic 'funnel, the one mentioned in your post. It has a few Coils to focus the beam and a electron beam to de-ionize a few particles. Making them neutral and thereby unaffected by magnetic fields.

      You shouldn't forget that behind your NEFP is a Megaton bomb. And as you said "both sides agree to use Casaba Howitzers" (some older reply) You'll know what it means when you see nuclear flash from few thousand kilometers. And a casaba beam is multiple times faster thus decreasing the time to hit the target. Thereby making it harder so protect yourself.

    9. What about the deceleration force of a 10,000km/s beam being slown down to 0 in a millimeter of armor? And I've wondered when there is some amount of pressure and billions of kelvin on the Armor. Could it happen that the carbon in the armor undergoes fusion, Or otherwise the hydrogen from the polyethylene molecules.

    10. Well, let's see...

      The report I linked to ( uses 32kg for the mass of the pellets. These pellets are meant to survive as solid particles up to impact, so I guess this range of plate mass is above what a 'particle beam' casaba howitzer would use.

      Let's stick with 10kg for 1Mt.

      The 10kg would be spread out over a 20m wide circle. That's roughly 33 gram/m^2. If it is polystyrene, it is a distribution 32 micrometers thick.

      Stopping this material from 10000km/s to 0 in 1mm distance implies an acceleration of 5e16 m/s^2. That's a force of 1.65TN! However, much higher pressures are reached in fusion experiments where a relativistic velocity particle beam of protons strikes a plate of Boron-11... and there is not much success. I doubt that fusion ignition will play a major role here.

      But this reminds me to further develop the concept of 'fusion bullets' based on the kinetic-impact ignited fusion post.

    11. Thank you very much,
      -I got similar numbers but i feared they were waaay to high, which they are. 10e9 mm/s beam velocity. 1e-10 seconds from 10,000km/s to 0. But forget this part.
      -1.65 tera newton over 310m² (9,943m^2 x 3,14159....) This gave me a pressure of 5 MPa or 725 psi. Sounds kinda alright, but it isn't that high.
      -Yes, but i didn't say that the pressure alone will do the job. 2.4 Gigakelvin should lower the coulomb force quite a bit, plus a few megapascals. But I guess you're right. Carbon burning requires 5e8 Kelvins with 3e9kg/m³. 2.4e9 Kelvins and "some" density might not be enough. But we still have hydrogen in our ionized beam of death. So proton-proton fusion could occur. Whether it happens or not isn't really relevant. Just wanted to state the immense forces of these weapons. A truly terrifying weapon

  13. Greetings!

    Just discovered your blog! I'm nearing completion on my first novel, a hard-science fiction space opera/military thriller I'm calling "Captives of the Singularity". I really appreciate the discussion here on Casaba-Howitzers as I'm using them in the book. My big, big, big question that I apologize in advance if I've missed the answer to is ... how accurately can these things be fired? We know that the effective lancing range is on the order of thousands of kilometers. I noticed, as someone pointed out, that the lance is essentially a particle beam, which probably suffers from deflection inaccuracies due to ambient magnetic fields in space or around massive planets. It also seems that there are unknowns as to how finely we can shape the charge itself so that it blasts in the direction we want it too. Bottom line, the weapon's effectiveness is degraded if we can't aim accurately across, say, 10,000 km. Any comments on this? I'm very eager for an insights on how accurately we can actually aim a Casaba Howitzer in space. Thanks!


    1. Hi, so what do you mean exactly?
      Mechanical manufacturing accuracy or the ability of modern computer systems to hit a target from that afar?
      For the later: First off there "Ain't no stealth in space" that means even with a small sensor which can fit in your hand you are able to spot everything hotter than the boiling point of nitrogen from hundreds of thousand kilometers. And you won't miss a Spaceship which has radiators which are literally glowing hot.
      Even your smartphone has enough calculating power to estimate its final position using some dedicated software and formulas, Quadruple the power add multiple tracking systems, sensors and laser and you are good to go.
      On Mechanical errors: If you see how modern high tech satellites (e.g Hubble (not so modern anymore)) are build you'll see that there wasn't any room for error. The mirror for example couldn't be any millimeter off or you satellite is for the garbage can.

      For your story: Vast amounts of crude Lances: Spray and pray vs. Few perfected Lances: the rare One-hit weapon,
      Yours sincerely.

    2. @Brian:
      Hello and welcome!

      Never fear asking questions here. Even I learn things and make frequent corrections.

      The divergence of a particle beam produced by a Casaba Howitzer is much greater than that of a particle beam produced by a particle accelerator, like in CERN. This is why its divergence is measured in whole milliRadians!

      In fact, considering that the Casaba Howitzer is a relatively lightweight, non-vibrating inert object, it is very easy to aim it in the right direction. It will be quite *accurate*, meaning it will point straight at the enemy, but it will be quite *imprecise*, meaning it spreads its energy like a shotgun instead of like a rifle.

      For example, if we use the Large Casaba Howitzer warhead, we will have a beam spread of 9.94m at 1000km. This means it will deposit its energy across a circle nearly 20m wide. Most spaceships aren't even 10m wide (depending on the setting)! It is easy to rather vaguely point at the spaceship's area and smother it all in nuclear fire.

      If ranges are lower, you can intentionally spread your beam more than necessary and still do a lot of damage. This allows you to cover a large area of the sky.

      The Futuristic Megaton Lance can shoot down the ISS end-to-end from 50000km.

    3. @OMG its WTF: Have you visited the rest of the blog, specifically the Stealth in Space is Possible posts?

    4. Could you explain it to me, please?
      I though in this scenario the Casaba is already locked in the rough direction of its target and will be soon in firing range, and then it could use LIDAR if the enemy uses heat sinks or anything else to make it stealthier.

    5. @OMG its WTF:

      It is in response to your 'no stealth in space' comment. :)
      I wanted to direct you to my take on that topic, and maybe get you to comment on other parts of the blog!

    6. This comment has been removed by the author.

    7. Ah, I see. Well thanks!
      "other parts of the blog?" could you be a bit more specific with "of the blog"?
      I really should continue reading the Bible of Nuclear Physics and Relativistic kitty litter again.

    8. Stealth in Space:

      Space Warship design:

      Laser Weapon Web:

      Some of my best stuff.

    9. Ahhh, the other parts of YOUR blogs.

    10. @OMG its WTF and @Matter Beam

      Thanks for the welcome and quick reply!

      Wasn't thinking of stealth in space or in pointing accurately (I understand that we can get pretty darn accurate on the pointing, with limitations being mainly due to things like jitter). As Matter Beam pointed out, the CH should be a fairly stable platform.

      My concerns are 2-fold.

      1) Will the particle stream from the CH be bent significantly off target by the magnetic fields in the areas. My specific wargame scenario calls for a battle above the 1.8 Mass of Jupiter world at Mu Arae (I believe its current designation is Mu Arae d). The battle's altitude is similar to Calisto's, so the field strength of the planet is present, but not especially strong. I doubt that a magnetic field around the ship used for defense against solar storms would be able to deflect much of a CH's shot.

      2) Manufacturing tolerances in the bomb itself. Analog of the problem is manufacturing bores for cannons. Do we have any idea of how precisely we can build the bomb so that it will indeed fire in the exact direction we want?

      Thanks again!

    11. @Brian Mansur:

      1) The particle stream is a neutral plasma, so it shouldn't be excessively affected by electrostatic forces. It will respond to magnetic fields... but this is not some lightweight electron beam. Its a very heavy bunch of atoms and even molecules (C-C, CO-, NO). These are not easily deflected, especially over the half-second or less it takes to cross the distance between the firing point and the target. If it is, you still have a 20m margin or more to hit the target.
      Basically, the beam will ignore most planetary fields and 'natural' effects, but might be affected by strong 'shields'.

      The magnetic field in a sunspot is only 0.1 Tesla.

      2) These are impossible to guess until we start building them en masse. However, from a worldbuilding standpoint, they are an excellent way of balancing forces without having to mathematically justify one way or the other.

      For example, how can I make a larger force seem weaker than a smaller force? Maybe I can write that their stock of Casaba Howitzers is old and degrading, making then prone to producing bent beams or even failing to detonate at all! How do they compensate? They increase the beam spread to allow wonky beams to still hit the target...

      ... the consequence is that they end up having shorter ranges than the smaller force. This leads to tactical decisions and better story-telling.

    12. @Matter Beam
      Thanks for the analysis! This is very helpful!

    13. If the particle stream is of Neutral plasma, can they be deflected by strong shields completely?
      large force: crude old lances
      smaller force: well-made modern lances
      Sounds familiar, have a nice day/night whatever timezone you in.

    14. @OMG its WTF:
      Absolutely. Charged particles moving through a magnetic field do feel a force, even if the plasma is overall neutral.

      Strong shields can be quite effective. You only need to cover your spaceships's cross section, at long ranges this can be a few grams of matter.

    15. But what if the particles are incomming at a 90° Angle relative to the magnetic field lines? They had to stop nearly-relativistic particles nearly instantly. I know that at for example CERN they are able to catch high-relativistic particles but its a completly other story there.

    16. The amount of energy contained in the CERN beams is measured in individual joules. Its nor really comparable to the energies and beam momentum of these warheads, so I can't definitively answer this question.

    17. That wasn't a question it was statement. Just want to answer a hypothetical argument that CERN is able to catch particles with hundred times the energy per particle and that a shield "should" do that too. No, my question was that if the beams comes in a 90° angle relative to the magnetic field lines. The field has to stop forward vector of the beam. So if the magnetic field catches all particles they have to be decelerated extremely fast. Thus probably creating Bremsstrahlung (or not?)

  14. Hi Matter Beam, Winchell Chung advised me to get in touch with you directly about a calculation question I had concerning Casaba Howitzers that you completed for him on the Atomic Rockets website (and which is also part of this blog post).

    I reproduced the calculations for a small casaba at the link below using 1630 nm and .01 m radius mirror. AR says on the Conventional Weapons page that you used 1 microsecond to simulate the damage a 5 kt nuke with a .01 radian beam would do to aluminum armor. The thing is, I could only reproduce the AR table's numbers if I plugged in 1 full second. Have I misunderstood something?

    Thanks for your assistance. - Laser Weapons Calculator

    1. How many MW have you plugged in? If the beam duration is 1 microsecond you have to multiply the beam output by one million.
      Here you go, 733mm at 10km.

    2. @Brian Mansur:
      A megawatt in a microsecond contains as the same energy as a watt for a second.
      So just input the total beam energy (2.09e12) as the laser power.

    3. @OTM its WTF and Matter Beam

      Thanks for verifying this for me. Yes, I used 2.09e12. Sorry, I didn't get that input into my first post (I was a bit rushed at the time I wrote it). I think I understand now how you got the figures you did.

      I always like to give credit where it is due. Unless you'd prefer otherwise, I am mentioning the ToughSF blog in the acknowledgements section of my book (there's a disclaimer that inclusion does not imply endorsement). Also, anyone who wants to is more than welcome to screen the pre-publication drafts. I'm up to a 91,300 polished word count with a budget of 115,000 words for book 1, so I expect to be finished, God-willing, on or about the end of the year. Some folks like to get the chapter by chapter updates. Most want to wait for the finished pre-publication draft (no I don't have a publisher yet ;) It's an open invitation until I sign a contact. Just let me know.

    4. @Brain Mansur

      What can you tell me about your book "Captives of the singularity". More specific, I am interested in knowing your setting.

    5. @Brian Mansur:

      Since you have a hard SF setting and you are taking time to research and at least get an estimate of the numbers for the technologies being used, it might be useful to direct readers towards the same resources you used in a 'find out more' section at the end. This might be a more interesting replacement of the traditional acknowledgements section.

      The best example I have of this is the back of the 'Blindsight' book by Peter Watts. Just those few page along are pure, peer-reviewed research gold.

      While at this stage I think it is too late to start re-writing the setting, it might still be a good time to go through some designs you've made or concepts you've used. Correcting any sort of mistake should only take a few lines in these cases.

      If you don't want a public discussion, contact me through private message on Google Plus, or through my email.

      @OMG its WTF: yup, this is the sort of story that has an audience already carved out for it.

  15. Hi MatterBeam, Why does the NEFP have a yield of 100 tons when its called "1kT NEFP" ? And secondly, What is that velocity for? Is it 800 grams channel-filler and a 200 propellant gram moving at 2619 km/s(around 686 GJ/16% of 1kT) or is it the detonation velocity of the working fluid?
    I got the impression CH are the most effective with high megaton yield and NEFP with low kilotons yield, Would you agree on this statement or do you have your personal view on these two Weapon systems?

    1. Sorry, I used a 10% nuclear-to-kinetic conversion rate, then another 85% going in the right direction. I'll change it to clear this up.

      The velocity is that for the metal plate. It depends on the mass ratio between the filler and the plate. The Monroe effect allows for a plate with a faster tip velocity than the average velocity of the explosive...

      I personally think Casaba Howitzers are short ranged weapons, and NEFP are long ranged. The Casaba Howitzers are devastating spears of energy that disperse too quickly to be effective without losing their mass advantage over conventional direct energy weapons. NEFP are much less efficient, but they're the equivalent of sniper bullets.

    2. Huh, doesn't that mean the Casaba has a 100% nuclear-thermal&kinetic ratio and then 20% in right direction?

      I still don't entirely understand this ratio, does that i mean i could use kiloton bomb and 800kg Channel-filler to launch 200kg to 2619km/s?

      8,5% efficiency is still quite horrifying, having a NEFP the size to fit on a AIM-9 missile shooting something with the energy 85 tons of TNT at infinite range? Is that efficiency really that useful?
      Shouldn't higher masses have higher efficiencies because they can absorb the energy better?

    3. The second part with "800kg channel-filler to launch 200kg to 2619km/s?" is a rhetorical question.

    4. I'm working on very sparse data for the Nuclear-Explosive-Formed Penetrators. Some older reports cite 10% nuclear-to-kinetic energy before any directionality is considered, others simply use 100% of the energy.

      Considering that there is 20 years' difference between the two, better testing might have taken place and 100% is the correct figure. I've amended the results to reflect this.

      I think one factor not being considered here (unmentioned in any report) is that the Monroe effect only really takes place between an explosive filler and a metal place that physically interact with each other. If they are turned into plasma by the explosion temperatures, then they don't receive any 'boost'. This might impose a maximum yield-per-kg ratio on the weapon.

    5. I have my one theory, The monroe equation is made for a explosive/propellant ratio. Example 800kg TNT = 3688MJ/200kg = 6072m/s
      8kg =36,88MJ/2kg = 6072m/s, Utilising the monroe equation for this is quite tricky because the power of "explosive" in this case channel-filler isn't always the same e.g TNT but depends how much energy every kilogram absorbs from the detonation. So the we can calculate the energy the channel-filler receives, for a specific Energy/mass ratio, and then we can calculate the velocity. If we have 1 kiloton nuke. And we say the channel-filler absorbs 10% of the energy that means the 800kg has the energy of 0,125T/kg if we take 400g instead we get 250T/kg.
      TL;DR The NEFP working fluid energy density depends on external sources (Thermonuclear device) while normal EFP energy density stays the same.

    6. I'll do some more research.

    7. Also two little things, Did you want to describe a megaton or one kiloton NEFP in your post? the Energy quantity is 1kT. Also, the "1MT NEFP" has ten times the energy but also ten times the velocity/ hundred times the kinetic? That means two things, either you have a perpetuum mobile or the mass ratio is now 40g Channel-filler 10g Liner (Propellant). I don't think that it will stay solid/molten.

    8. The small NEFP is 0.1kt. The big one is 1Mt. The difference is x100.
      The speed increases from about 2600 to 26000km/s, x10, so that's a square ratio, which fits with the kinetic energy equation E=0.5mv^2

    9. But why does there stand 4.2TJ on the megaton NEFP if the actual number is 4.2PJ. The difference is 10,000x Energy, square root of that is 100x. My numbers were based on the "4.2TJ" not on a actual yield energy of a megaton. 1Mt = 1000kT and 1kT = (10x 0.1kT) = 1Mt = 10,000x 0.1kT.

    10. @OMG its WTF:
      The whole matter is quite complex. A true 1 megaton yield converted into kinetic energy as in the Gurney equations gives faster-than-light velocities...

      I don't personally know all the maths behind the concept, and researching the matter is quite difficult as most sources are classified.

      What I do know is that a shaped charge can push a metal plate to velocities up to 10 times greater than the detonation velocity of an explosive. A nuclear explosive's detonation velocity can be estimated using the Root Mean Square law for perfect gasses, or the Gurney equations.

      The equation on the blog comes from here:

      Look at the top of page 7.

    11. So, can't we just leave the velocity at a certain value and then just change the mass of the NEFP? like, the 0.1kT gives the NEFP a energy of 0.085kT, using the annoying sqrt{2*E/M} We get 2666km/s for a 100g projectile and 60km/s for 200kg.
      So a megaton bomb should propel a 1000kg projectile to 2666km/s.
      And to use my theory again, we divide the yield (in joules) of the nuke by the kilograms of the channel-filler. Which we will then use in the Gurney equation as a Thermal explosive. A 1kT 800/200kg Mass-ratio NEFP will have the same energy as a 0.4/0.1kg NEFP, but much lower velocity.

    12. Yeah, the problem is that the channel filler, past a certain temperature, is just an expanding gas. The velocity of the gas is determined by the root of its temperature. It gets even more complicated when it start heating up to 3000K temperatures and molecules dissociate, like hydrocarbons into carbon and hydrogen...

    13. "Yeah, the problem is that the channel filler, past a certain temperature, is just an expanding gas. " Where is there the problem? That's how any explosive works, extremely fast expanding gasses often multiple kilometers per second. And isn't beryllium used as the channel filler?

    14. The consequence of this is that the behaviour is non-linear. You cannot directly extrapolate from the kj/kg contained in the filler the velocity of the explosion. It doesn't even follow a square function, due to the changing nature of the gasses.

      I'll look into the matter further, as promised.

    15. Alright, It was said in the blog that the NEFP can achieve higher velocity when its vaporized.... But now the 1kT NEFP has more velocity (8.9% c) than the Thermonuclear Casaba Howitzer (3% c). I will ignore the hole gurney equation thing until you have come back with some information, So now i just use the energy amount, 3556,4GJ (85% of 1kT) which is enough energy to accelerate 10g to 26,669km/s (exactly 8,9% of c) With the mass ratio we need 40g of Beryllium, Let's say the beryllium absorb the 85% of the the yield.
      Specific Heat: 1825J/kg K
      Mass: 0.04kg
      Energy: 3,5564e12 J
      =48,717 million kelvin for the 10g Liner. For 2666km/s / 1kg s the temperature is 487 million kelvin. Can the Vaporization of the liner be circumvented to a degree by using some kind of insulator?

    16. A NEFP channels the shockwave from the nuclear heating fo the filler material into a single point. This allows the tip to reach velocities 10 to 40 times higher than the velocity of the particles themselves. For example, this is how modern HEAT weapons generate streams of up to 14km/s out of explosive gasses expanding at only 2km/s.

      The principal driver for this effect is the ratio of densities between the metal plate and the explosive filler. A high ratio (dense metal, lightweight filler) allows for higher velocities. This is why copper is used in HEAT warheads, in addition to its ductility and heat resistance.

      The problem with the 10g design is that the weapon's inefficiency (15%) will distribute heat throughout the warhead. If even a fraction of 15% of the atom bomb's energy reaches this plate, it will vaporize and lose the high density ratio.

      This is why I think NEFP weapons might require several hundred kilo metal plates to survive the heat wave as semi-solids, even for kiloton-sized warheads.

    17. You mix up HEAT rounds with EFP, HEAT rounds create a very high velocity jet, the tip can reach 14km/s that is correct, but the tail for example is most often only traveling at about 2km/s,
      HEAT: Hypervelocity jet
      EFP: The projectile is formed by the explosion and can only travel.

      Modern Weaponry:
      HEAT: Extreme penetration, extreme short range from target max 5m because the jet breaks up immediately because of its superplasticity, so even in a Nuclear HEAT the jet would probably travel around 100km before breaking down.
      EFP: Traveling at 2-3km/s. Solid "heavy" projectile, Infinite range in space.
      If 15% will be absorbed as heat, the liner itself you would need to have the weight of several tons, How do you manage to keep something semi-solid at 627,6GJ of Heat energy?
      Aluminium because of its high heat capacity would be great, at few hundred degrees below the point of vaporization you can have 1.8 MJ per kg, that means the liner has to weight over a hundred tons to stay liquid.

    18. PS: I mentioned the "10g design" because at higher Liner masses the NEFP would have over hundred percent efficiency at thermal to kinetic. Only a 10g liner is able to such velocities, but it is impossible to build such a device.
      Would you consider a EFP velocity of 2666km/ to high? A 1kT device with 1kg Liner can achieve this velocity without breaking the laws of thermodynamics. I believe the gurney equation only gives you the highest possible achievable velocity for a given mass ratio.

    19. Okay, so I've looked at the Gurney equations and this research article:

      The mass of the warhead behind the filler and the plate is important. If it is too small compared to the plate, through momentum exchange, the warhead material will fly backwwards the plate only a little forwards. You need 10x mass ratio to get the most out of your explosive's velocity.

      About 5% of the warhead's explosive energy is converted into kinetic energy, but this might be increased in the future.

      The velocity of a simple flat plate of metal on top of a filler and a warhead is equal to (2E)^0.5 * (M/C + 1/3) ^-0.5
      E is the kinetic energy yield of the warhead.
      M is the mass of the plate
      C if the mass of the filler
      If E is 5% of a kiloton, M is 10kg and C is 10kg, then the velocity is 560km/s. A 10x heavier plate reaches 200km/s.

      Exploiting explosive lensing and high-density metal plates allows for faster-than-explosive-detonation-wave velocities. 10x the simple flat plate's velocity was deemed the practical limit, so 5600km/s instead.

      Does this violate kinetic energy? Watch this:
      Only a small fraction of the liner reaches high velocities. This is the HEAT jet. The majority of the metal plate is just pushed inwards, squeezing out the tip but resulting in near-zero KE. An EFP pushes the whole plate out, but without any velocity gain.

    20. So are your NEFP EFP or HEAT now? 5600km/s is your number if you use a HEAT design, but it wouldn't be that great because only a very small percentage of the Plate mass reaches that speed. HEAT Jets break down because of the stresses in the Jet. So we are left with EFPs, If you don't believe you can search it up. Its a very complex topic though.
      Hope you have nice day.

    21. Can you explain me if I Insert: (2*209.2e9)^0.5*(10/10+1/3)^-0.5
      I get a 10kg traveling at 560km/s right?
      KE of that plate would be 1568GJ, And 5% of 1kT are 209GJ. 5% Efficiency from Thermal to kinetic and then 750% Efficiency in the direction?

    22. The difference between an EFP and a HEAT is simply the angle the metal cone forms. A plat or open angled plate will come out as an EFP. A small, acute angled conical plate will 'pinch' and 'squirt out' a blob of metal at much faster velocity.

      The 560km/s is for a flat EFP design.
      The 5600km/s is for the HEAT design, where I assume only 1% or less of the metal actually reaches that velocity.

      The HEAT jet fragments because it is an inelastic bit of metal being stretched at a rate of several dozen to (in our case) hundreds of kilometers per second. Unlike in an atmosphere, where drag forces spread the fragments apart, a space HEAT warhead will remain quite dangerous over long distances. The accuracy would be horrendous, however.

      The 5% figure doesn't seem right, as you put it. I think it was an experimental value, ie the difference between the nuclear yield and the actual measure kinetic energy of the plate. I personally think the 2E figure is the thermal energy contained in the heated filler, as this is more in line with the 'specific energy' cited for conventional explosives.

      If we go back to our nuclear pulse propulsion design, 85% efficiency is what is measured for the difference between the nuclear yield and how much the beryllium absorbs.

      So, 85% efficiency gives a (2E)^0.5 of 2666983. This is a specific velocity, as it is the maximum possible expansion rate of the explosive - 2667km/s.

      The second part of the equation, I think, measures how effectively this velocity is carried over to the metal plate. A 10kg plate with 10kg filler can be accelerated up to 86.6% of the explosive's specific velocity, so 2309km/s.

      Doing a kinetic energy calculation, we get 26.65TJ in the metal plate and 3.55TJ in the warhead. It doesn't add up... unless only 13.3% of the EFP actually reaches this velocity.

    23. I already mentioned that the these equations don't give you the velocity of a certain projectile but instead the Maximum velocity a shaped charge with these mass ratios can reach. 10kg and 2667km/s? I created a spreadsheet using your efficiencies the yield, and the equation sqrt{2E*M} I got 1kg at 2667km/s as the maximum velocity if 85% of the yield is transferred into the plate. How horrendous would the accuracy be then? No fancy maths, just your estimation. Even with drag forces out of the game the extreme stresses in the jet will "vaporize" pulverize it. I've done some calculation on how destructive a EFP with 850 tons of TNT would be.
      Graphene (130GPa): 1,24m
      Hyper/Nano-Diamonds (310GPa!): 0,93m
      CNT (66-11GPa): 1,58m - 2,83m
      Boron Nitride Nanotubes(33GPa): 1,96m
      Structural Steel (250MPa): 9,986m
      (Tried to send this message through my gmail account, sorry for the late response.)

    24. I think that the energy method, where X amount of yield is transferred into Y amount of plate kinetic energy, is the safest.

      However, I believe less than 85% yield will reach the plate, even if the propulsion unit is rated at 85% efficiency. The 85% is for how much nuclear yield reaches the beryllium filler. It expands like a rocket engine's exhaust. Some particles spread to the sides and don't contribute towards accelerating the plate. Some energy is lost as heat energy, as there is no 'nozzle' that allows the beryllium to fully cool down and expand correctly. More energy is lost as mechanical stresses, and so on.

      The accuracy quote was for the HEAT jet. An exploding warhead, directly in contact with your projectile, is a significant source of vibrations. The metal liner's defects can cause the jet to be diverted more to one side or the other. The jet in flight might still be subjected to residual heating from the warhead's debris and be diverted by ablation. All in all, I expect 100m to be the sort of accuracy to be expected from HEAT jets.

      Could I have the spreadsheet you are using, maybe through google docs? At the energies and velocities in play here, I expect cratering to be the primary damage mechanic.

    25. Could you use your thermodynamic equations you already used to estimate the spalling velocity? We have Filler mass, material and energy. I will have to modify my spreadsheet to be used by google docs. Should be done in maybe 30 min.

    26. Here you go:

    27. Are the equations all right? I used your Electric cannons and Kinetic impactors excavation principle. Sometimes I didn't had yield strength ready, so I used Ultimate tensile strength so for some materials to replace the missing yield strength value. What you mean by "reach" the plate? I think the beryllium will be in a case with a plate on top, the top should create the least resistance, maybe some kind of little gun design? 1-2m of "barrel". It would work very similar to a ordinary chemical gun, hot expanding gas propels a heavy projectile. Or in this plasma.
      So how much do you think a 1kT Plate/Filler will weight? What the lowest possible plate mass for 1kT device which wouldn't vaporize?
      Other than that, If I look at the numbers right now, the NEFPs are looking way superior to Casaba Howitzers.
      -No spread
      -No magnetic shielding
      -Infinite range
      -Harder detection
      -Higher penetration values
      -Slower projectile

    28. I've looked around and around, and tried using everything from hydrodynamic (expanding gasses impart momentum) to thermodynamic (gas particles travel at specific velocities based on temperature and molar mass) models, but I have failed to reach any solution based on concrete data.

      The biggest problem is that the temperature of the filler material does not increase linearly with the energy pumped into it by the nuclear warhead.

      The second is the Gurney equations need the metal plate to remain mostly solid throughout the 'acceleration period', which it will certainly not do when being blasted at the expected million Kelvin temperatures.

      What I can say is this:
      -Energy coupling is strictly lower than 50% in tampered charges, 25% in 'open-face' charges.
      -Nuclear energy densities in the filler on the order of terajoules per kilogram compared to megajoules per kilogram in high explosives will allow velocities about 30 times greater than existing shaped charges. This means 100km/s for EFPs, 420km/s for HEAT.

      If we want to keep the metal plate solid, we want to look how much heat is transferred between the million K filler and the plate over the course of the 10 nanoseconds that the warhead delivers the energy. Conduction is too slow at these timescales. A 10 million K blackbody emits 5.67e20W/m^2. The plate and filler cover the same area, so the plate absorbs a maximum of 5.67TJ. It would completely vaporize, nothing we can do about it.

      Unless, we greatly reduce the energy density to lower the temperatures.

      The closest real world approximation is real NASA studies on nuclear pulse propulsion charges. They produce a 67000K plasma, which is survivable. From the Atomic Rockets page, a 4000 ton ship uses 5kt charges to accelerate by 12m/s per pulse. Using momentum equations, a large thin 10kg plate would be accelerated to 4800km/s. The thin plate would be roughly the size of the 10m bumper plate.

    29. @OMG its WTF:
      I looked at your spreadsheet. It looked okay, but you labelled everything 'steel' so I couldn't tell which yield strengths you were using and the 'needlegun' page's figures were wacky.

      By reach, I meant how much of the filler's energy was absorbed by the metal plate. As noted in the previous comment, this the filler absorbs its energy as 50% heat and 50% kinetic energy in its particles. An open-faced shaped charge, which is a naked filler on top of a single metal plate, will receive at most half of the filler's kinetic energy, so 0.25*0.85: 21.25% of the nuclear yield as kinetic energy.

      In the Project Rho propulsion example, we got a 115TJ plate out of a 21TJ nuclear yield, so maybe this percentage is better than using momentum equations.

      The NEFP and the plate can be detected easily, and the projectiles possibly faster* than the Casaba Howitzer, but your analysis is correct.

      *: A collapsing nuclear HEAT round can produce a jet with tip velocities 10x higher than the detonation wave. The detonation wave velocity is the velocity of the Casaba Howitzer particles, so an inefficient two-stage beryllium-to-hydrogen filler with a thin Mylar film on top can be propelled (potentially) to 30% of the speed of light.

    30. Added the materials names over it, what was wacky about the Needlegun figures? I accidentally send you the prototype for the Coilgun equations part: The efficiency from the projectile section is meaningless it came from the Laser Sail section which I just copied, and set the efficiency to 100% because the ferromagnetic projectile doesn't have a real efficiency here, the Drilling values only says how much material will be excavated in a second/minute non-stop firing. I edited both Needlegun and NEFP section I hope that fixes some problems, when not please give some feedback.

      Using Nuclear Propulsion Units and a bumper plate? That sounds like the Laser Driven Sails I once mentioned on solution to long range combat. Only way more awesome, can the actual plate weight around 1-5kg and the rest be a payload?

      30% of C? That's sounds terrifying, how do you want to protect yourself from something that no matter what, will kill you, Lasers? Have fun with the Plasma clouds that's travelling 10x faster than a casaba howitzer beam.
      With the vaporization part, the heat will be deposited in only the first few micrometers, Is there even time for the heat to deposit all energy into all of the plate before it gonna slingshotted away at 1-2% of c?

      115TJ energy? Kinetic? From a 21TJ Nuclear Yield? 547% Efficiency?

      I didn't said it would be hard to detect, just harder than casaba beam which is multiple million degrees hot compared to maybe one-two thousand of a NEFP.

      Also have a question, at what distance can a Casaba Warhead disable a ship? Not destroy it just cripple it, I just don't get clear answers for that and I'm not sure if the 0,8mm aluminium vaporization + Impulsive shock I gave Brian are enough to disable a spaceship with 2cm Carbon/Aluminium Armor equivalent.
      Have a nice day. I used a 5Mt Large Casba (5%) for the 6,000km range.

    31. PS:
      -Nuclear Energy Densities: Shouldn't the velocity difference be 1000x instead of 30x? I think you mixed tera and gigajoules up, A terajoule is a million megajoules, square root of that is 1000x, Verdict: Nuclear Shaped charges should reach 1000x higher velocities than conventional shaped charges.

    32. Hi OMG.

      The needleguns, based on the crater depth model of penetration, should be doing way more damage. Your new figures are correct.

      I'm currently writing a short post on my findings on Nuclear EFP.

      The 30% C figure is for a maximally focused HEAT jet, like a cone about 5 degrees wide, made out of very thick tungsten and propelled by a pure DT fusion explosive. The fusion explosive, like the fusion casaba howitzer, will have a particle velocity of 3% C. The Monroe effect can create a tip up to 10x faster than the detonation velocity, so 30% C. It will be rather short ranged (10000km before complete fragmentation of the jet?) and deliver a tiny fraction of the nuclear warhead's yield.

      The explosive heats up and pushes the plate out over timescales longer than it takes for the explosive to receive the energy from the nuclear blast. A nuclear blast consumes itself and explodes in about 10 nanoseconds. So, necessarily, the plate will be in contact with the hot explosive filler for longer than 10 nanoseconds.

      This is long enough for million K gasses to radiate away entire terajoules into the plate material.

      Momentum equations are stupid and I hate them.

      The NEFP's rear end is a nuclear blast. If the overall efficiency is 21%, then 79% of the warhead's energy goes into heating stuff up. It will be very visisble!

      Warship damage has several levels, but one thing a Casaba Howitzer does well is scrub away all exposed equipment. This means blackening the windows sensors look through, blasting away antenna, knocking laser mirrors out of alignment and poking holes in radiators. As the equipment is much weaker than solid aluminium, the harmful range of a Casaba Howitzer is much longer than its deadly range. I'd use 0.1mm aluminium penetration for this.

      Velocity increases with the square root of energy. 1000^0.5 = 31.6

    33. But you said Terajoules per kilogram, A terajoule is one million megajoules, 1000000^0.5=1000.
      Huh, how do Laser ablative drives work then? They often are hit with energies which are enough to vaporize the whole propellant but it only vaporizes a very small portion. Wouldn't some kind Leidenfrost effect be created in such short times? You can put your hand in liquid nitrogen for very short times without any effect.
      I don't really know if the "HEAT effect" works with plasma. Why would the needle guns do more damage? Excavating 10L of Boron for 95MJ sounds pretty reallistic for me, for comparison: The same weapon can excavate 127L of steel with the same 95MJ.

    34. Sorry, my mistake.
      Laser ablative drives have very small pulse energies. The resultant gasses also get to fully expand inside a nozzle. A million K explosive filler contains literal terajoules of energy and is confined against the plate to expand in only one direction. It cools down R^3 times slower, with R the radius or length of the gas.

      The HEAT effect happens with any fluid. Squeeze an apple pip between your fingers and it will fly out under the pressure.

      The needlegun's previous figures had velocities much higher than in the new version.

    35. Huh? No, they had lower velocities, I guess the comma as the decimal mark was the problem you meant.
      I am sorry, But I feel like the NEFP still don't have any clarity, the Nuclear Pulse Unit method makes sense in momentum sense but not in the energy. 4kT to 12m/s has only 288MJ but 48MN, 10kg at 4800km/s has 48MN but 115,2TJ. So that the energy/velocity thing is cleared up: The NEFP velocity is now 3Mm/s and the N-HEAT is 14Mm/s? Any ideas to prevent Plate vaporization? And allow velocities up to 3000km/s for NEFPs?
      I got the impression that the thing that limits NEFP velocity isn't the NEFP itself but how much material you need to prevent vaporization.

    36. Back to the Gurney equation, Is it energy density as I predicted or something different? Energy density would explain some of the values: If you have less channel filler you have a faster expansion velocity but less mass.
      Or you have more channel filler with lower expansion velocity, but more momentum. 1kg at 3km/s has 4,5MJ of energy and 3KN, 4kg at 1,5km/s has also 4,5MJ but 6KN. Disadvantage of the later is that the max velocity for NEFPs is 1,5km/s or 15km/s instead of 3-30km/s.

    37. I hope my upcoming post on nuclear shaped charges can clear some things up.

      You were correct about energy density for the gurney equations, but the gurney equations as a whole do not respect conservation of energy... because it was designed to model chemical fillers that supply energy proportionate to their mass, while a nuclear-pumped filler would not have the same restrictions.

    38. I stay tuned.
      Wouldn't dividing the yield through the channel filler mass give you the needed energy density for the gurney equation? Nuclear Thermal Explosive (Channel-filler) has a relative energy density.

      Sometimes I am wondering about on how many list I must be on, after all that research about Nuclear weapons, shaped charges, modern weapon systems etc.

  16. @OMG its WTF, sure thing! Below is the working draft of my back cover blurb.

    Back Cover Teaser

    The long-predicted Technological Singularity has engulfed mankind. Now the remnants of baseline humanity have been relegated by the Transhumans to a far-flung star system called Mu Arae. There the people are forced to live in massive cylindrical space colonies, watched over by brutal machines called the Wardens.

    As before on Earth, the residents of this expansive reservation squabble over their allotted resources. While some try to build homes and dreams, others travel between the colonies to forge empires of conquest and enslavement.

    Standing in the gap, the Mykonian Republic sends an operative, Rafe Hastings, to investigate why one smuggling cartel has suddenly risen to take over the criminal underworld at Lakshmi colony. The secret he discovers promises to shatter the balance of power at Mu Arae.

    Against the backdrop of the ensuing crisis, Lieutenant Sean Merrick tries to recover from the death of his estranged wife. He is completely unprepared, therefore, when an adventurous yet vulnerable young nurse named Sarah Riley arrives and takes a liking to him. While serving together aboard the battleship Tsunami, they little anticipate how their budding romance is about to be eclipsed by the terrifying menace that Rafe has unveiled. As Mu Arae threatens to plunge into a savage fight for survival, will the trio find the courage to stand against the horrors that await them, no matter the cost to themselves or their loved ones?

    1. @Brian Mansur
      Well, the story will escalate quickly if you are searching information for Casaba Howitzers....
      Sounds interesting, have good luck with the book of yours!

    2. Sounds promising.
      Are you attempting to go for a duel plot that ties together all the characters before the end of the book? The Expanse took this approach in Leviathan Wakes.

  17. @ Matter Beam and OMG its WTF

    Below is a dropbox link to the working draft that's open to the public. I periodically update it with the latest work I've done. If you want to be on my mailing list, you can send me your address of choice at ecuasage at gmail dot com. I'm always eager for any constructive feedback. The book was written with readers like you and Winchell Chung in mind. While much of the setting is finalized, I am constantly tweaking details in the book (a sentence here and there as you noted), so I'm sure your input would be very valuable at any stage of the process.

    About providing a list of resources in the back. I like how you think! In fact, I've had an acknowledgements section with links to Atomic Rockets and Rocketpunk Manifesto in there for a while. I recently added ToughSF to it. ;)

    The stories for the three characters do converge as the book progresses. The tech level for the humans has been arbitrarily balanced by the Wardens. The tech exists to make lasers more powerful or missiles more numerous, but the Wardens deliberately keep the capabilities of their charges limited. The reasons are explained in the book (don't want to spoil it).

    Thanks again for your input! Gotta run!

    1. Very nice, I had a quick look through. Can it be that the Singularity limits their technologies to ensure that they can't create the same scenario as with nuclear weapon in the cold war. Give Humanity the chance to destroy its enemies.... And itself.
      How much of your book is roughly done?
      Can It be that Casabas are your McGuffin? ;)

    2. @OMG its WTF

      Don't want to give away too much ;)

      I'm at 92K words with a target of 115K. Expect to be done by end of 2017. Most of what I've written I consider polished. A whole lot of thought has gone into the story at every step.

      Below is the prologue. Enjoy :)


      In the 22nd Century, humanity crossed into the Technological Singularity – the point at which computers grew sufficiently intelligent to run civilization. A handful of people rose to claim lordship over this new order. They transplanted their brains into evolved bodies of flesh and machine, becoming the Transhumans.

      To eliminate any potential rivals to their power, the new masters culled the human population at Earth. Some of the overlords, however, convinced their fellows to set aside the Mu Arae star system as a reservation for mankind. Since the system had no habitable worlds, the Transhumans tasked their robotic minions, artificial intelligences known as Wardens, to build enormous space habitats for the colonists. The Wardens also ensured that the lower species could never evolve to become a threat. Thus, humanity fell captive to the Singularity.

      After centuries of traveling in cryogenic sleep to their new home, the refugees quickly founded settlements in the image of their original, long-defunct Earth nations. This replicated many of the discordant patterns of 22nd Century society, religion and politics. While some colonists worked through their differences, most struggled against the ancient patterns of war, poverty and abuse.

      Thus doomed to repeat history, human civilization at Mu Arae rose and collapsed repeatedly, often edging towards extinction. By the 44th century, the colonies once again teetered on the brink. Despite receiving resource allowances and quotas of manufactured goods from the Wardens, selfish leaders frequently mismanaged these gifts. Then, without warning, the Wardens cut back on what they provided, pushing the colonies into a savage game for survival.

    3. Oh, I've already read that much of your story. Do you plan to make multiple books with a ongoing story? When I look at your Acknowledgements your story seems pretty dark.

    4. @OMG its WTF

      It is definitely dystopian. If you like the Expanse series or Revelation Space, I think you'll like this. Story will probably be 2 books long.

    5. @Brian Mansur:

      I'll give you my real name instead of my online handle.
      Also, note that 'Casaba Howitzer' is a code name, like MARAUDER or EXCALIBUR. It's a very specific term for 80's era SDI. In this setting, they can be called a descriptive 'nuclear lance' or 'nuclear plasma warhead', or a different common name, like 'nuke' or 'a-bomb'.

  18. I'll update your name when you send it. Do you want it paired with the site or listed in the alphabetical roll?

    Good point about Casaba Howitzer being a code name. In my mind, it was simply the name that stuck, kind of like how everyone calls a facial tissue by the brand name Kleenex, because it made the thing popular. Post-it notes. But for clarity, I might tweak the section when it gets introduced. Thanks for the idea!

  19. Wouldn't it be better if you pair all names to the their sites? Like ToughSF... Creator: MatterBeam (John Q. Public) Or MatterBeam / John Q. Public, alias/ real name.

  20. @OMG its WTF. I'll have to think on how whether or not to pair up the names. What I like about the current arrangement is that it reads like a more individualized letter of thanks, rather than another roster. I am, however, seriously thinking about including a dedicated list of useful websites, so maybe I should just do both :) I'll have to play with the idea as I get closer to completion.

    1. Either you do both, or you chose one of the two or you ̶f̶̶l̶̶i̶̶p̶̶ ̶̶a̶̶ ̶̶c̶̶o̶̶i̶̶n̶ Observe a unstable atom, If it decays in its half-life you choose the first option.

      "Any technical errors are purely my own", just a month ago Casaba howitzer were a million times stronger than they really are, besides that all your descriptions of the Lance (CH) are looking accurate.

      I feel honored that you also mentioned me (Why though?). How can I send you my real name? E-mail? A reply?
      Yours sincerely.

  21. @OMG its WTF.

    Anyone who has provided me encouragement or their valuable time to provide feedback, I like to thank. :)

    I'll think the acknowledgements page through at a later date. Probably, I'll keep it in the present format because I like the narrative approach it takes. I might also create a separate bibliography page for useful sites (because I want to promote sites like this one!). You're right that a suggested readings list doesn't fit well in an Acknowledgements section.

    IMPORTANT: What changed on the nuclear lance potency that I missed?!

    1. On 23 April I posted as "Anonymous" that the numbers seemed a bit odd, So I started a veeeery long conversation with MatterBeam. The old small casaba could destroy 733mm at 1000km! Matter Beam confused the Megawatts as watts so he always inserted e.g 2.09e18 watts instead of 2.09e12. You're lucky that you got your Casaba stats after their potency was corrected.
      You'll know what I mean if you scroll up a bit, around in the middle of the right bar. Now the same thing is happening again with NEFP, It's always the simple math errors that you miss.
      It's a miracle to me no one ever checked to numbers of the Casabas in a single year, especially on Atomic Rockets.
      TL;DR: The Casaba in their current form, as you have depicted. Are accurate. Several recalculation should do the same. In short: Nothing, you have missed nothing so don't worry.

    2. @OMG its WTF. Whew! Thanks for catching that then! I've tried to respect "the numbers" and realized that I had to "black box" a lot of things like the fusion drive, laser system and, yeah, well, to be honest, I haven't had the guts to draw up any hard stats on how the warship tonnage is broken down in my book. I have total tonnage and propellant needs figured out for a given thrust value, but there are still just so many unknowns. I need a full blown simulator to do this properly. I purchased Children of a Dead Earth thinking it would help. While it helps get me thinking, it isn't flexible enough.

    3. @OMG its WTF. In answer to your earlier question (Sorry I missed it), you can email me at ecuasage at gmail dot com if you want to provide any information directly. :)

    4. Yes, Children of a Dead Earth is a handy tool, but quite limited, is can be slightly circumvented by using some mods.
      There are always problems in making Hard Sci-Fi stories, in your case don't knowing all physics or in my case: Having no clue how to writte anything interesting. The good thing in the first case, others can help you, in my case it's rather hopeless.
      The positive thing is you don't have to necersairly include that information in your story, Maybe as a seperate site at the end of the book called "How does it work?" explaining all the designs and how they work?

      Can I please help you these unknowns? I would be pleased for a positive response.
      Is your email address: ?

  22. @OMG its WTF, yes, is the email address. Sorry, I've gotten in the habit of spelling emails out because supposedly it reduces the chances of some online trawling bot from picking it up and spamming it. I don't know if it actually helps ;)

    Everyone has a talent. Yours has already contributed by helping sites out like this one and Atomic Rockets. For that, I'm very grateful.

    If you're interested in helping to crunch some of the harder numbers for the ships, I'd be most obliged. I've kind of spent my quota of time to work on the project today, so give me a little time and I'll send you what I've worked out so far. Doing that by email is probably easiest, so drop me a line that way when you're ready.

    I'm thinking of putting the "How does it work" section in an online site. That way I don't have to worry about word count :) I saw John Lumpkin's Human Reach site and was thinking of doing something along those lines.

  23. I just got a weird vibe. These are kind of like space torpedoes. Kind of. Not exactly similar, of course, but nonetheless, a space torpedo boat could even be a chemical rocket and just have one or two of these and deal ridiculous damage to enemy ships. Cheaper, too. Maybe a naval situation like the late 19th century could be carved out.

    1. Like everything else on this blog, the concept shines when you integrate it into your setting and use it as you see fit.

      There are rumours that the US is able to hide 0.1 kiloton yield explosions underground without triggering worldwide sensor nets. These yields are useless for airburst warheads - just too small.

      However, they are perfect for testing nuclear-pumped directed energy weapons and nuclear shaped charges.

      Building upon this, I can forsee a future where advanced casaba howitzers are available as weapons before high-efficiency nuclear propulsion is commonplace. Chemical rockets will boost these warheads to their targets.

  24. The main politico-strategic problem with deployment of casaba howitzers is the first strike implications of a hundred-kiloton spear of nuclear flame that can gut a ship or a city without warning.
    Putting them in orbit, less than three hundred kilometers above enemy cities, and you've got a perfect weapon for decapitation strikes.
    Once everyone has them (and everyone will do their best to get them), you find yourself in a world where hundreds of millions can die instantly at the touch of a button (instead of in 5-30 minutes).

    1. There are practical and political reasons why such a situation is unlikely to arise.

      First of all, nuclear weapons hanging around orbital infrastructure within effective range are either easy to detect or hard to keep undetected. This is mainly due to the sheer density of sensors needed to avoid collisions between spacecraft leaving and passing by the stations.

      If they are detected, then they will have lasers trained on them to shoot the instant hostilities are declared. Casaba Howitzers can be used in defensive configurations to wipe out multitudes of targets above the cities. Some will pass through...

      Which is why politically, putting a nuclear warhead within a zero-reaction-time, no defense possible (once its fired) range of the target is absolutely the same as laying siege on the target. Siege is an active form of warfare even if nothing is happening, because unlike simple blockades you are putting your enemies one button press away from death. The targeted populations cannot rely on your good will to stay alive! They will retaliate once such a threat is present. In practice, this means nuclear warheads are destroyed as soon as they are detected without escalating the current conflict.

      A real world example is India acquiring nuclear weaponry. No-one could argue that Pakistan, one strike away from utter annihilation, should not get nuclear weapons of their own.

      However, even if we do reach a situation where everyone lives with a Sword of Damocles over their heads, it might still not be the case for hundreds of millions.

      The Casaba Howitzer cannot effectively penetrate thick atmospheres and it not a very good bunker-buster (earth penetration) unless it is extremely close to the ground. This means that population centers on Earth and Venus will cannot be threatened by Casaba Howitzers, not will habitats naturally placed underground for radiation protection.

  25. So what exactly would this weapon and it's effects *look* like? I can imagine a giant hulking platform to house the technology required for this and extremely strong, dense, and heavy material to absorb the x% yield from the blast. Also, out of atmosphere, the weapon would not necessarily have a visual effect to the beam as it is a microsecond of particles firing? In atmosphere I can imagine it'd look different albeit much weaker. Very fine work by the way, this was an extremely informative and well written article.

    1. Thanks!

      The Casaba Howitzer plasma-beam version of the weapon will physically resemble an inverted cone. The wide top is the propellant plate. In the middle is a section of x-ray absorbing materials, which can be beryllium. At the narrow tip is the actual nuclear charge.

      In space, the explosion is very brief. A lightbulb lighting up and dying in a flash. The vaporized components of the weapon are visible for slightly longer as a rapidly expanding cloud of white hot gasses and metal droplets. It disappears as it expands and cools down. Faint wisps of plasma might endure as the magnetic fields generated by moving ions makes them atoms coil around in spirals and curves.

      The propellant is bright, fast and you might even see it moving. It will look like an extremely fast 'plasma bolt' from SciFi movies. When it hits something, the propellant compressed upon the target and heats up again, creating a big flash. The molten remains of whatever it hits will continue to glow.

  26. @MatterBeam I thought you would like to know that I finished the novel I was working on. I changed the title a bit to Captive Embers, Book 1 of the Singularity's Legacy Saga. Winchell Chung was kind enough to post a blurb about it on his site at It's geared to fans of hard sci-fi and space opera in that I've thought through the science and situations as deeply as I know how.

    If you'd like a copy to review, please email me at I'm presently hunting for an agent/publisher.

    1. That is excellent news!
      I will be contacting you shortly.

    2. A couple quick comments on this one:
      Magnetic shields won't work for two basic reasons.
      The first is that momentum transfer is still a thing even when you're using a big magnetic field as the interaction area. All the energetic particles that the shield deflects are going to impart momentum on the field coils that generate them, in the case of playing catch with a Casaba, do so very vigorously.
      The Small Casaba at 100km will impart ~67MJ of energy per square meter of shielding, and assuming the particle jet is doing a pokey slow 1000km/sec, that’s about 130 grams of material striking per square meter. That’s about 130,000 N*S of momentum per square meter of shielding, and it’s being deposited in about 1 millisecond. If we assume the shield covers just 10 square meters, you end up with the field coils needed to handle the total load of about 1.3*10^9 Newtons, and dissipate 670MJ of energy, which would be enough to more or less liquefy them regardless of what they were made of, or how they were mounted.

      The second is the Bremsstrahlung X-rays from the very act of diverting the plasma stream are going to be enough to cook to death anything that’s been shielded, in a variety of new and exciting ways. Let’s assume for the sake of nice round numbers that diverting the plasma is going to take 10% of the total incoming kinetic energy and convert it into a variety of soft and hard x-rays that scatter uniformly and deposit 10% of THAT energy into the ship. Only 1% of all that KE is turning to shortest light, which leaves us with only 670kJ per square meter of hard X-rays impacting the craft. A single Joule of ionizing radiation absorbed by 1 KG of mass is one Gray, five such Grays being enough to kill any human being in short order.
      Just for giggles, we assume the ship has shielding that protects the occupants from 99% of the incident radiation, and that a human has roughly 0.5 m^2 frontal area in the sitting position. Using the calculated 670kJ per square meter x-ray luminance, we end up with a 3.35 kJ maximum dose. 7 cm of water will absorb roughly half the energy, so we’ll fudge it and say that half the total maximum dose is carried through to the human pilot. 1700J/50KG human = 34 Gray whole body dose. He real ded.

      Turns out the modeling on the armor impact as a laser strike doesn’t do justice to the incredible amount of mayhem caused by 130 grams of plasma ejecta striking a square meter of target at 1000km/sec. Just the momentum transfer is gonna do real interesting things to anything it hits, with nothing to be said for the huge quantities of x-rays a bare metal ejecta strike would cause.

  27. Hey matt can we use the heat of a fusion torch drive to launce the partical beam and use the magnetic nozzel to concentrate the beam. This might give higher efficiency partical velocity and also a sustained firing. Well it be equal to the reaper cannon from mass effect.

    1. My calculations show that focusing the exhaust of a fusion torch drive down to a small focal point would require massive magnetic fields, and would be impossible to do once the exhaust leaves those magnetic fields.

  28. Ok then what about spaced NEFP,just keep a metal plate in front of the fusion exaust with some spacing. The plasma or gas would push the plate just like in NEFP and you can focuse it just enough that the plasma is straight to the plate. This would give many advantages like lower Weald, high velocity, also cheaper .Only disadvantage would be colateral damage I would launce an encripted message to aware any friendly or civilian ships in the line of fire.

    1. That concept is treated here:

    2. Hey Klalib, i was not taking about a fusion bomb but the exaust of a fusion torch drive. Just imagine you through a metal plat in front of the Epstein drive. The exaust will push the plat at enormous speeds. But you wont need to make a bomb. You have one behind you.

  29. I was just wondering if it would make a difference if you used xeion as the propellent instead of tungsten, and what if you used powerful magnets to further focuse the particle beam for better range

    1. That might be possible, but I haven't done the maths on that yet...

  30. With 285, 10 megatons casaba howitzer 10 000km range, if you detonate them at the same time again't the same target, you could increase the range of the attack to (10000x285^0.5)to 169000km. With 285, 150 megatons casaba howitzer, the range of the attack would be 422000km. So a casaba howitzer ship could detroy the laser star before the laser could engage or detect it.

    How do you defend/win again't such attack ?

    1. You would try to destroy the warheads before they detonate, or at least try to disturb their aiming, using lightspeed weapons like lasers... but in general this cannot be relied upon.

      Your best bet is that even if you lose the fight, you win the war. 285 x 150 megaton weapons is about 7 times the entire yield of the US nuclear arsenal. Having to expend that many nuclear warheads to take out a single (or small number) of laser-equipped warships could be a losing proposition as you might end up spending much more money per kill than your opponents.

      It doesn't scale well either. You have to quadruple your nuclear yield to double your range. A laser-equipped warship can simply use a bigger mirror, which is a cheaper and easier solution.

      In the long term, Casaba Howitzers cannot be used as the main weapon in very long range engagements... unless you help them get closer with missiles!

    2. 285 150 megatons CH would cost less than 500 millions dollars much less than a warship. A big nuke doesn't cost more than a small one because they use the same amount of fissile material. The US had 30 000 nuke in the 60's.

      422 000km range, the laser won't be able to hit you (regardless of the mirror size), because of the light speed lag espacially if you use missiles to close in your CH instead of warship.

    3. I'm not sure how you got that cost figure. The Tsar Bomba only released 50 Mt. Our megaton weapons only release those energies because they use huge volumes of deuterium to boost the fission with fusion energy, and that is not cheap. Modern variants use lithium-6 and an uranium tamper though, which is cheaper but still does not mean a 1kT and 1MT yield weapon have the same cost.

      422,000km range means you'd have to use a 4.22 times bigger on a 100,000km range laser. Light lag can be countered by spreading the beam over the area you can dodge.

      If your ship is accelerating at 1g, then you can cover a distance of 38.8 meters in the 2.8 seconds of light lag between detection and beam arriving. This means that a beam with a radius of 38.8 meters will always hit you if it is centered on your last known location.

  31. This is very interesting, I'm trying to calculate the effectiveness of a 'Small' casaba howitzer with a 15 ton of TNT nuclear charge (Davy Crockett). With your Irradiance formula it shows at 25 meters it outputs 24.5 GJ/m^2, what I can't understand is how penetration against aluminum is calculated. How would this weapon preform used at ground-level at a ground target, specifically creating the smallest possible Casaba Howitzer as an anti-tank weapon. Amazing article.

    1. Hi!

      Very rough calculation:

      It takes about 45 MJ to vaporize 1 kg of aluminium. There's 2700kg in 1m^3 of aluminium so it takes 121 GJ to vaporize that.

      Divide your irradiance by this 121 GJ to get a vaporization depth in metres.

      I get 24.5/121 = 0.2m

      Casaba Howitzers don't work well at ground level because the atmosphere very quickly causes the plasma beam to disperse and lose energy.

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  33. I'm a bit confused about Fenstermacher's comment in regard to a Casaba Howitzer probably not working at higher yields due to the pellets being overtaken by blackbody radiation and in the process destroyed or ionized. Isn't it the point of the weapon to eject a plasma beam? What's the difference between a howitzer using pellets and one using a beam of ionized particles? Does Fenstermacher's point stand?

  34. This is a fantastic post, thanks for making it!
    I have a few questions:
    1. The laser simulator site you linked uses power, rather than energy, as a variable. Would you mind telling me how I would go about translating the terajoule numbers given here into a megawatt approximation?
    2. Would it be possible to counter a casaba-howitzer by putting your propellant tanks on the outside of your ship? I'm thinking that the propellant would sap the kinetic energy of the casaba-howitzer particles, which might not entirely stop them from doing damage, but would shorten the range of such a weapon.

    1. Hi!

      1. You can alter the beam duration. Power x Time = Energy. I recommend this more detailed calculator anyway:

      2. Your propellant would act as an ablative shield. By vaporizing into gas, it absorbs the energy of the Casaba Howitzer before it reaches important equipment inside the spaceship. It's a good option if you have nothing else to protect you. However, it would be very inefficient in terms of how much propellant mass is needed to protect from a hit, compared to dedicated armor panels made of steel or graphite.

    2. Thanks for the calculator! What you say about the propellant shielding makes sense. Would something like active cooling help make armor more effective against casaba-howitzers?