Thursday 18 January 2018

Piracy in Space is Possible Part I: Dastardly DeltaV and Stealth Steamers

Space Piracy is a common science fiction trope. It has been continuously derided in Hard Science Fiction as silly and a holdover of the 'Space is an Ocean' analogy. 
But is it really that unrealistic to have space pirates? Let's find out.
What is piracy?
A chinese Junk, by Wayne Haag
Piracy is a specific type of theft. Goods, crew or the vehicle itself are stolen, ransomed or captured by pirates while in transit.

Piracy functions under the rules which make theft worthwhile:

-The value of the reward is worth the cost and risk of a pirate attack
-The reward can be liquidated reliably
-The pirates are safe from prosecution after an attack
By artist Geoff Hunt.
These are rather straightforward rules. 
Pirates want to gain something from the attack worth their time and the risk they take. Unless the reward is cash, they need to convert their gains into money. They then want to spend and enjoy that money without having to be constantly on the run from police authorities. 

One prominent modern example of how critical these rules are to piracy is the situation off the coast of Somalia between 1986 and 2013. 

In 1986, a devastating civil war started following the brutal crackdown of an aging tyrant on his population. Government institutions ceased to function, rebel and gangs organized themselves into armed groups and the Somalian Navy disbanded.
Fishermen felt the toll of illegal dumping and pollution of their fishing waters and saw their livelihoods at risk of disappearing too.

Together, this situation allowed for numerous men equipped with AK-47s and RPGs to get a hand on fleets of small boats and fishing trawlers and have free reign of the seas... the very same seas that saw a constant, rich stream of ships laden with cargo containers entering or leaving the Indian Ocean through the Suez canal.

These men attacked those ships.

Now pirates, they had practically no opposition either at sea or on land. Shipping companies paid ransoms on their crews and whatever the tiny bounty their boats could carry back was traded with unscrupulous merchants. This money was then shared between the pirate crew, the pirates' patrons, bribes for officials, the cost of fuel and new boats, and with the fishermen and their families. Often the Somalian pirates were seen as benefactors of the fishing villages.

The pirates were earning millions, at little cost and with no real risk. Their rewards arrived directly in bank accounts or in cash from jewellery, mobile phones and other high-value items stolen while on-board the cargo containers: these are easily sold. Finally, there was no real police or government authority to enforce any sort of law on the pirates. All the requirements for piracy were met.

The situation changed by 2011. 

Barkhad Abdi from the Captain Phillips movie.
The pirates had grown to attack thousands of ships a year, and were demanding ransoms measured in the millions per ship. The world's navies were given permission to violate Somalia's waters as needed in the pursuit of pirates. US warships now patrolled the waters, along with contributions from more than twenty nations, including Japan and New Zealand. The cargo ships were equipped with water cannons, safe rooms and armed guards. Somalian anti-piracy initiatives raided pirate hideouts, confiscated weapons and created Maritime Police Forces.     
US Navy destroyers looking for pirates.
The risks increased considerably. Failed attacks now could lead to pirates being shot by US Marines or detained and trialled in foreign countries. These stories scared many and forced the rest to travel further and further in search of unprotected prey, so costs increased too. Shipping companies became less inclined to pay millions to recover their crews and instead called in the warships to handle the situation. Satellites trained on the region could follow even fleeing pirates, to be plucked out of the water by helicopter or to be intercepted upon their return to the shore.
Rates of Piracy.
The requirements for piracy were no longer being met. And thus, there have been no successful attacks on cargo ships off the Horn of Africa since 2012
The end of an era.
Numerous examples throughout history can be analysed in light of these requirements to understand why piracy was prevalent or not. The most famous examples, such as the Pirates of the Caribbean, the Barbary Pirates and the Qing Pirates, were all the result of situations that met these requirements. 
Southeast Asia is the new piracy hotspot.
Piracy... in Space!
One of the most iconic 'Space Pirates'. 
Pirates have attacked horse carriages, trucks, trains, ships and planes. Space is an entirely different environment and presents new challenges for meeting the requirements for piracy.

We will assume for now that we are considering piracy in our Solar System, where most solid bodies are inhabited by permanent populations of various sizes that trade significant volumes of goods across interplanetary distances. 

Travel between the planets is cheap enough for bulk goods to be worthwhile (large quantities of raw material), yet the cost of propellant is not negligible and is an important variable in the profitability of shipping companies. 

Due to the danger a accident a collision poses at interplanetary velocities, either to the spaceships or to space stations, either directly or through the debris created, omnipresent surveillance and tracking of all objects larger than a centimeter is the norm throughout the Solar System. The implication is that all spaceships are weapons of mass destruction while in operation and are treated as such.
The Kronos 1 by MacRebisz
We will consider how changing these assumptions will affect piracy in space, but for now we will work with a realistic, 'near-future' setting. 

Finding a target

This is not a trivial task, and it is a crucial step to making piracy happen at all.

Pirates are parasites on any economy, and so prolific piracy requires a large host. The consequence is that for every pirate operation, there are hundreds, thousands or more, legitimate traders and businesses running transport ships between across the Solar System.

Due to the significant delay between a cargo being ordered and it reaching its destination, measured in weeks, months to years, it is only possible to make a profit upon arrival by correctly predicting the market conditions weeks, months to years ahead: the timing of these deliveries is crucial. This is exacerbated by the fact that the cheapest shipping involves infrequent deliveries of massive quantities of goods all at once, with a significant 'dumping' effect on the markets at the destination. 

The dangers inherent in space travel require that every spaceship declare its flight plan and time of departure ahead of time. This prevents a nasty collision between spaceships that leads to a shower of debris hosing down densely-occupied orbits and littering busy trajectories between planets. 

As merchants are unable to hide their timings, they will insist on privacy on the nature and quantity of good being shipped. A competitor with that sort of information would be able to short sell the markets, undercut prices or place well-timed buy orders that steal profits away from the shipping company.  

By SMPritchard.
A delivery of iron or platinum would look pretty identical from the transport ship's outside, and it becomes impossible to distinguish the goods being transported at long distances, through a telescope for example. 

Pirates would need to glean this information from three sources: the transport authority's inspection reports, spying operations or from the internal communications between the shipping company's agents.  

Piracy cannot happen in space without this sort of detailed information. It is too expensive in terms of time, effort, propellant and simple risk to intercept potential targets blindly. 

Therefore, it is required to make piracy work that there is some possibility of hacking, bribery, infiltration and other information collection methods being both effective and undetectable.

Intercepting the target

The next challenge is to actually get to the target once it is in flight and outside of the safe haven of the port or space-station it departed from. 

The Spitzer space telescope.
The major problem is the ubiquitous tracking of spaceships.

If every ship is under observation, any pirate attack will be witnessed by everyone. Any spaceship deviating from its planned trajectory would be flagged as a potential threat to everyone around them and to anything in their path. This is similar to how aircraft are tracked today when flying over North America or Western Europe.

If the pirates conduct an attack, they will be recorded in the act and watched intensely wherever they go. A military spaceship might be sent after them, or they will be greeted by the police once they dock at a space station or other port.

In space, every increase or decrease in velocity, or change in trajectory, requires propellant. Matching a trajectory with a target usually involves accelerating towards the target, and then slowing down until the relative velocity reaches zero. As a consequence, pirate spaceships must have a higher deltaV capacity than their target in the best of cases.

The target will notice a spaceship speeding towards it due to the previous fact, usually from millions of kilometers away. It will start to accelerate to try and 


For every meter of second gained by the target, the pirates will need 1m/s to catch up and another 1m/s to slow down after the attack. The pirates will need more than twice the deltaV of any target they attempt to run down. 

For example, if a target travelling at 20km/s has a 25km/s deltaV reserve to slow down at its destination and maneuver, and is equipped with a rocket engine that has an exhaust velocity of 30km/s (Isp 3058s), then its mass ratio started off at 4.48 and is now 2.3. For every kilogram of dry mass, the target spaceship is carrying 3.48 to 1.3kg of propellant. 

Expendable propellant tanks helps achieve high mass ratios.
A pirate spaceship attempting to catch this spaceship must first reach the 20km/s the target is travelling at, run down its 25km/s deltaV reserve, then slow down from 45km/s to stop. If it has similar engines as its target, it must start with a mass ratio of 20. For every kilogram of dry mass, it must bring along 19kg of propellant: it is over 95% just a stack of propellant tanks! 
Due to how the Rocket Equation works, doubling the deltaV capacity of a spaceship requires that the mass ratio be SQUARED. 

There might be a slight chance to stage an 'accidental intercept' and catch the target in without having to ride around on propellant balloons, but it will only work once, and for a very short period of time. 

There is a solution to this critical problem with space piracy: Stealth.

Screenshot from The Expanse.
If the watchful eyes of police and military sensors cannot detect the pirate ship, then it is free to do whatever it pleases. It can approach its targets unannounced, attack them in complete secrecy, and return to the base of operations without being tracked or followed.

Stealth in Space was covered in a four-part series earlier in the blog. The gist of it is that detection in space happens when a spaceship reflects sunlight, has a thermal signature or bounces radio waves off its hull. Sensors available even today can track even the smallest amount of reflected light, the lowest temperatures and the faintest radar returns over extreme distances. So, the avoid detection, a spaceship must be perfectly non-reflective, have an undetectable heat signature and have no radar return.

Each requirement is met in turn by a Vantablack non-reflective coating, a system of heat pumps and liquid hydrogen heat sinks that cool down the hull exterior to the cosmic background temperature, and an insulating sheath around any metallic component.

A pirate spaceship that incorporates these elements into its design can achieve 'hard' stealth: it would be physically impossible to detect unless it is on top of its targets.

Spaceship using mass driver for propulsion.
Maneuvering while 'running cold' is accomplished through any sort of thruster that expels very low temperature exhaust. Cold gas thrusters are one example, mass drivers are another. Curved nozzles with extreme expansion ratios can be fitted to a conventional 'hot' thruster to expand the exhaust until it cools down into untraceable gases.   

Stealth has another benefit: if the target does not know that the pirates are coming, they will not know to run away until it is too late. It will not have the opportunity to expend all of its deltaV, and so the pirate ship's deltaV requirements fall to those of typical transport ships. 

This undetectable spaceship design, called the Hydrogen Steamer for its use of boiling liquid hydrogen, does have drawbacks. It requires very large amounts of liquid hydrogen, which is not very dense. This makes even the lowest endurance Hydrogen Steamers very massive. For example, handling 10kW of room-temperature waste heat requires that 2.3 grams per second of liquid hydrogen be boiled off. If the spaceship attempts to hide for six months, it will require a reserve of 36 tons, which has a volume of 517m^3. This is a cylinder 3m wide and 73m long!

Covering this large volume in carbon nanotubes might be a very expensive affair, depending on the level of manufacturing technology the pirates have access to. Cryogenic heat pumps that can operate at 20 Kelvin and lower might not be readily accessible at kilowatt power levels either. Preventing the hydrogen over long periods of time from escaping is no easy task either. 

Furthermore, the low temperature exhaust requirement imposes a performance penalty on the spaceship's propulsion. Covertly matching the trajectory a target spaceship will require boiling away huge amounts of liquid hydrogen to cover the increased waste heat production from using propulsion systems.

The difficulty or ease with which stealth is achieved depends on what the pirates expect to get away with.

If the pirates are under a total surveillance and must evade the concerted efforts of every nation's military forces, they will need complete end-to-end stealth. A dedicated 'Hydrogen Steamer' design is required.

If the pirates operate out of locations with less stringent surveillance, sparse military forces and traffic control that doesn't ask questions about the pirate vessel's suspicious features, they can choose to use stealth only intermittently. Accelerating into a trajectory that takes them somewhere near their target can be done in plain sight, using normal propulsion. Liquid hydrogen is consumed only to hide the pirates as they fine-tune using 'cold' propulsion an intercept with their target to conduct the attack, after which they return to regular traffic as if nothing had happened. 

Port Royal was a pirate haven. 
Depending on how long the pirates need to maintain stealth, the spaceship they need might only need to carry small amounts of liquid hydrogen - small enough that they look like regular propellant tanks. The pirate vessel can then pass off as a merchant ship or fast transport and transit high-surveillance zone without worry. 

Making money - Types of attack

So the pirate ship catches its target. At the intercept, it may still be hundreds to thousands of kilometers distant from its target, and pirates' victims remain completely unaware of the situation.

From Disney's Pirates of the Caribbean.
How does this intercept become a pirate attack?
In fact, it heavily depends on how the pirates hope to make money. 

The easiest way to make money is to ransom a crew.

The vast majority of private entities will feel obligated to pay for the safe return of their employees if they wish to maintain their reputation - those that don't will quickly see themselves out of business. Ransoming a crew in space doesn't require boarding parties: all is required is that the pirates have a means of putting the crew's life at risk. This can be as simply as threatening to punch a few holes in the hull, or shining a laser on the radiators. Pirates might sit a few hundred kilometers away from the target and demonstrate their ability to do damage. They then establish a communication channel with the shipping company and start negotiations. 

A manned spaceship usually means that the goods being transported need human attention or supervision: high-value items, confidential data ect. 
Spanish merchants returning from South America laden with gold were prime targets.
Pirates might have knowledge of these and demand that they be handed over: in addition to a ransom, they commit theft (or take hostages). 

Theft in space is more complicated. The pirates must physically interact with their victims, and need the cooperation of the crew to some degree. Depending on how well the pirates threaten their victims, they can convince the crew that handing over the precious cargo is of less dire consequence than resisting the pirates. 

Release a cargo container or we will shoot!
By Luke Berliner. 
If it is impossible to guarantee the crew's cooperation over the radio, then the pirates might escalate to dealing damage to their target, or even attempting a boarding action. 
Hacking the airlock, by ThDark.
A distinction must be made between 'boarding' that forces a docking, but can be foiled indefinitely with a burst of the maneuvering thrusters, 'boarding' that destructively creates another point of entry into the target's hull, which puts the victims at considerable risk and might convince them to fight back, and non-penetrative 'boarding' that involves latching onto a spaceship's exterior and interacting with it from the outside. The latter method is the safest for both parties involved and of greatest interest if for example the victims' spaceship has a depressurized cargo bay that can be accessed and stolen from without touching the habitation sections. 

Another valuable prize for the pirates is any passengers onboard the target spaceship.

Passengers can be taken hostage and ransomed back to their families or employers. These ransom negotiations can take place along different channels than those for between the spaceship crew and the shipping company. It is in the pirates' interest that they keep their hostages safe and unharmed - this maintains their value during negotiations. 
Luxury space 'yachts' transporting VIPs must be vigilant.
However, pirates might decide to take their hostages onboard their own vessel so that they can escape under stealth before the authorities arrive without having to abandon their prize.

Pirates might try to make money off the target spaceship itself. It might be the only option if the pirates intercept an unmanned transport that does not carry any valuables or passengers. While it is unlikely that the spaceship can be carried away and sold whole (unless it is modular), there are valuable components and parts that can be sold on the black market: rocket engines, nuclear fuel or navigational computers, for example.

Finally, if pirates can intercept and even board a target, it might not be much more difficult to take control of the spaceship. This is hijacking.

Hijacking a spaceship allows pirates to make money even if their target was unmanned, carried no valuables or passengers and was made up of only parts with no re-sale value. 

There are three things that pirates can do with a hijacked spaceship: re-route, disable or turn into a weapon.

Re-routing a spaceship ensures that it arrives at a different destination (such as a dock where corrupt porters will steal its cargo), or takes much longer to arrive at its intention. A delay in shipping can create market movements that financially savvy pirates can exploit: it can reduce a company's stock value, force the payment of non-delivery fines, increase the price of a good due to artificial scarcity or manipulate market options and bets to the pirates' benefit. 

Disabling a spaceship forces the shipping company to spend money (and huge amounts of propellant) to retrieve it before it goes too far or even leaves the Solar System. This is interesting if the pirates are working in conjunction with a corrupt recovery business, or if it is part of a ploy to increase the value of a ransom.  

As mentioned above, any spaceship travelling at interplanetary velocities is a weapon of mass destruction. A hijacked spaceship can be pointed at a space station or colony to cause a huge loss of life and materiel... or the pirates can be paid a huge amount of money proportionate to the 'savings' from having the spaceship returned to its original trajectory. Larger settlements are therefore likely to pay more. They are likely to have defenses to shoot down asteroids and rogue spaceships, but there is little they can do against an unmanned ship hauling thousands of tons of rocks or ices, especially if the pirates hide traces of the hijacking until the last possible moment. 

The Base

Pirates need a base of operations.

Lunar propellant depot by SMPritchard.
It is where the pirates service their vessels, offload their bounties and stage their attacks. This implies that the base is able to provide propellant and fuels, replacement parts and repairs, fresh crew and information gathering services, secure storage, a method of moving stolen goods to black markets (or has its own marketplace), and most important of all, protection from the authorities. The protection for the pirates can be accomplished through stealth (the entire base is undetectable), weaponry (the base is not worth assaulting) or some sort of immunity (the base is located somewhere the authorities are unable to exercise their power).

Whether it takes the form of a pirate haven, a hidden space station or a reliance on their own infrastructure depends on the technological assumptions.

If the pirates cannot repair their own spaceship or obtain their own propellant, they will need a full-scale port that provides these services. If instead they can 3D-print most of the components they need and can scoop up propellant through In-Situ Resource Utilization, then they are much less beholden to any single location. 
Base embedded in a comet.
In practice, most pirates will need access to all three types of bases. Even the most self-sufficient pirates will need a way to sell stolen goods, and even the most dependant pirates can gather more propellant and parts, at the very least by stealing them off their victims' spaceships.  

Alternative pirates

So far, we have assumed that the pirates must travel in a vessel of their own, physically approaching a target and conducting an attack that they must then escape from under stealth. This is only a slight modification to the traditional sci-fi trope of Space Pirates, themselves a version of the romantic notion of Pirates of the High Seas converted to take place in Space. 

By that assumption, pirates are a group of space-going criminals skirting the law with specialized vessels. 

In reality, there are a broader range of options that match the true definition of 'piracy', which is any robbery or violence that targets ships in transit. 

Therefore, it is just as likely that we might have pirates that stay at home and try to remotely hack through the electronic defenses of their victims' spaceship. This sort of pirate is featured in Corsair by James L. Cambias. If they cannot get through these defenses, they can instead remotely control a drone ship to their target. This drone ship doesn't even have to be exciting: it can be a micro-satellite equipped with a radio, hooks and manipulators. 

Drone with manipulators
The drone can use its manipulators to access any exposed electronics, sensors or communications devices to bypass the electronic defenses and hijack the target. If even this is too difficult, the pirates can simply install a bomb on-board the drone and inform the crew that if they do not follow instructions, it will go off. 
This micro-satellite is much easier to hide using stealth than any large manned ship. It can flit around docked spaceships and latch itself onto a target's hull before it has even launched. Intercepting a target in deep space is also easier, as a micro-satellite does not need a big engine or huge amounts of propellant. 

Remotely or through these drone, the pirates can make money through most of the methods mentioned before with no risk to themselves. In fact, it is more realistic that 'pirates' are simply criminals that disperse dozens to hundreds of these miniature drones to multiply their chances of intercepting a rich target.

The other assumption, that the pirates are criminal groups, can be challenged as well.

The pirates might simply be contracted commerce raiders. This is a legitimate method of waging war, and pirates that fall under this definition have been known as privateers throughout history. Privateers act like pirates, but only against the enemies of the nation that is sponsoring them.

Privateering solves most of the complications that pirates in space have: they have a secure base of operations, they do not have to hide themselves in friendly territory and will not be hunted all the way base to their base of operations if caught. Captured spaceships can be diverted to the sponsor nation's ports to be sold whole or in pieces. 
German WWII U-Boats conducted commerce raiding expeditions throughout the war.
However, the number of potential targets is more limited than for true pirates Their sponsorship can be revoked if they do not follow the rules, or if the conflict ends. They will also be actively hunted as a military target and are unlikely to win fights against true warships. 

There is also a type of pirate that is a criminal, but has nothing to fear from the authorities: the corporate raider.

The East India Company practically had its own military, and its rule was law.
Corporation in space will compete at every level for control of the markets. This competition can spill over into illegal activities, such as attacking competitors' spaceships and raiding their commerce to ruin reputations or steal sensitive information. Between the enormity of space and the amount of money corporations have on hand to spend on bribes, a lot of these illegal activities can be hidden.

In short, these corporations can hire off-the-book crews to acts as pirates that attack only the spaceships of their competitors. They will be protected from the consequences if they follow these rules, but left to the authorities if they breach the terms of their contract. 

A competitor might be frustrated by police and military inaction, and might decide to take matters in its own hands by hiring its own pirates and pirate-hunters. There is even less of a chance that military forces intervene in 'red on red' conflict, even if it escalates into corporate warfare.

By Robbert Middelkoop.
The main difference between corporate warfare and true piracy is that the corporate pirates are unlikely to gain any money by ransoming their victims, as the corporations have nothing to lose from writing off their responsibilities, and are unlikely to target major settlements by using spaceships as WMDs, as this will draw in attention from the authorities that cannot be bribed away. 

Up next

So far, we have looked at what is needed in a setting to allow piracy to take place and even prosper. Pirates in space can be glamorous raiders that slip in and out using undetectable spaceships cooled to cryogenic temperatures, or mundane criminals working from home using remote-controlled drones.

Next, we will discuss the countermeasures that will be developed to combat piracy, and what effects this will have in terms of worldbuilding. 


  1. Very interesting analysis. I had mostly thought through the idea of corporate "piracy" and using letters of marque and reprisal. For your amusement, here is part of an answer on Worldbuilding Stack Exchange where I suggest that piracy might actually be an outcome of a particular world building exercise:

    "A much more likely scenario is there are already a few, very small research stations set up around the Solar System, and the survivors on Earth are sending what amount to space barges filled with supplies to keep them going (550 tons of MRE's will last a very long time indeed). Without surviving space infrastructure or an astronaut corps to supervise refuelling in orbit, these things are going to be sent on minimum energy transfer orbits, taking years to arrive. You now have a nice set up for space piracy, privateers hijacking supplies destined for another colony and other scenarios."

    WRT the actual cargo delivery system, I would suggest that in the interests of minimizing costs, the cargo is actually being sent via mass driver in un or minimally powered pods to a receiving mass catcher on the other end. While this makes the job of the pirates somewhat easier (you are essentially just grappling an ISO container floating freely in space, so it won't have any deltaV to speak of, and no crew to threaten or engines to disable), one thing the shipping companies are going to be livid about is the energy costs of stealing a pod. The mass driver can recover a great deal of the pod's energy when used in mass catcher mode, so missing a pod would throw their energy budget out, possibly by a considerable amount (catching pods coming from high up the Solar gravity well would provide a lot of energy to carry out operations). Setting up booby traps is probably a bad idea for the shippers, but some sort of anti tampering system will likely be included if only to prevent the pod from being opened by unauthorized people at the delivery dock.

    1. Thanks for the early reply, Thucydides!
      That is quite an interesting scenario. It is implied that the privateers have spaceships that can match the trajectory of the payloads - so these ships must also be available for the shipping companies to use, albeit at a higher cost. The higher cost leads to the 'emergency' shipping creating greater food costs, which is black market price for food, which in turn reinforced the incentive for piracy.

      Observation can tell if your cargo pods are being intercepted, which allows for a manned 'arming' of anti-tamper systems.

  2. Excellent article, I can't help but be pleasantly surprised that a number of concepts I thought of while writing my upcoming book (in-situ refueling, nanite auto repair and most of all ... pirates!) has been detailed in this very write up.

    One of the ideas I worked on was a sort of pirate called an aphid- who would use a stealth steamer to literally siphon off information from remote interstellar courier drones and sell it on the black market.

    I can't wait for the next part.

    1. Well, my conclusions are only logical. The specific details will depend on how you've built your setting though!

      A data siphon will only be useful if it is trying to intercept narrow-beam (laser) communications. Any random radio will pick up omnidirectional transmissions and will therefore not give you something worth selling.

      Laser transmissions will likely have methods of confirming that they are not intercepted or interrupted. For example, the data will come with a checksum based on the speed of light - attempts to intercept the signal while evading detection by reproducing an identical beam will fail as they reduce the 'pseudo velocity' of the laser.

      One method I can think off is using gas scattering. Lasers travelling through a gas cloud will reflect off some of of the atoms in random directions. This 'leaked' laser light can be picked up without detection.

      So, the data aphid would sit next to a random gas cloud and passively pick up laser signals travelling through the area.

    2. High value information is already sent encrypted, and even secured using VPN and other technologies (some of which won't work with free space laser transmission). "Quantum encryption" has also been proposed, which would cause a collapse of the wave function once it was intercepted.

      While gathering raw data has uses as well (developing link and pattern analysis, for example), it probably isn't as valuable as the data being hidden behind the firewalls and encryption.

  3. A pirate's vantablack net engulfing a pod would make quite a visual (or narrative sequence). A mass of blackness engulfing the pod, and then.... nothing.

    I wonder if there is a place for a kind of Q-Ship here?

    I've been writing some articles on the U-Boat War in the Irish Sea in WW1, and Q-Ships are touched on briefly. Probably not useful (and the articles had to be ruthlessly edited), but if there are some real-world things that inspire you, feel free to have a look.

    1. That would be visually striking, yes.

      I mentioned pirates passing off their craft as regular merchant vessels, so would technically be Q-ships. They would still need a reason for approaching another spaceship without raising alarm, a method of conducting an attack without being seen, and a method of hiding or returning to regular traffic without being traced back to the attack. Despite these measures, it must be expected that the spaceships closest to the victim will be called in for questioning and inspection afterwards, so it might be simpler to just stay under stealth the entire way.

      I'm reading those links now.

    2. I think a great solve for this. Is a mother ship. It poses as an innocent merchant doing a regular trade run that happens to have a route close to the target. Then it releases a steamer from its cargo hold to intercept the target which can be looted hijacked or whatever. This allows the pirates to hide their obvious piratical vessel inside a confidential cargo hold. Whose contents are a secret for reasons you already mentioned.

      Obviously authorities would try to track down these mother ships by seeing who was always near by at the attack, but I am sure their is a work around for that.

      I could imagine pirates would organizations as nests of shell companies and faux spoofed owners and ships constantly mothballed and renamed and modified and purchased. After all the cheap cargo motherships which the authorities only lead are much cheaper than the expensive stealth interception craft.

      Easy enough to play the shell game with them.

    3. Good point. The number of loopholes and shenanigans possible within bureaucratic administration are much greater than when dealing with strict physical reality. There may only be two ways to hide a spaceship from sensors, but two hundred ways to make them invisible to the authorities!

  4. Finally, the pirates.

    I don't think even the most corrupted government simply leaves the warring corporate alone. If the corporate are actually employing gangster, not some undercover security of their own, PMC in disguise or other hired guns, or there are some real collateral damage from corporate warfare, the government may or has to step in, in order to maintain its authority.

    Though some small and carefully controlled corporate warfare may create more business opportunities, let's say Corp A sees Corp B as a new rival, and A found a PMC subsidiary recently. A wants to expand its security business, they employed some criminals through third parties, instructing them to use mass catcher to intercept cargo containers of B, harassing the trajectory of some Corp B-related colonies with drones, racketeering some third-party settlements for distraction etc.

    Then A starts to promote their security packages to third parties.
    If they can cover their tracks good enough and endure the counterattacks from rivals with smaller loss, small scale corp warfare maybe profitable.

    1. This does depend on what kind of relationship the state and the company has.

      If a country is host to dozens of companies that are competing with each other, it must seem fair to keep businesses within its borders and their tax money rolling in.

      If the country is host to a single business or a small set of very influential companies, it must risk breaking its own laws (or modifying them) to submit to these companies demands. Examples today are oil countries where two or three oligarchs practically run the country. In space, it might be the case of a space nation held alive solely by the services of one or two shipping companies.

      There can also be cases where a country is poor and has no economic advantages - it can only attract businesses in return for being very lenient on its application of the laws. A partial example today is tax havens. In space, there can be nations built entirely around the fact that they let companies do whatever they want.

      Finally, as I featured through the case of Somalia in the 90s, there are states in constant crisis, that cannot use their authority to impose the law even if they wanted to.

      When it comes to 'soft' worldbuilding, which does not use physics and numbers but policies and human organization, there is really no limit to what you can create.

    2. Then, non-intervened corporate warfare is much more likely to happen in places that governments are weak, owned by companies de facto or under anarchy.

      Tax havens...
      I can imagine that some remote space colonies or settlements may be some districts exclusively for companies do everything they want, as long as they bring in the money.
      Perhaps a pirate haven can grow in areas like these.

    3. There are perfect real-world analogues for both situations, both present and historical.

  5. In the space environment, someone needs to be in charge, if only to ensure the life support system is functioning. The most devolved polities may become "hydraulic empires" with the power consolidated around whoever is running the technical systems that ensure survival. So unless the life support and other systems are incredibly robust and distributed, I doubt that a state of anarchy can exist for very long on ay spacecraft or space colony.

    In fact, it also changes the completion of things like mutiny or Coup d'état, since you can't *just* occupy the bridge or presidential palace to ensure victory. Even pirate ships had issues if the cruise wasn't being successful, although usually they were smart enough to wait until they were back in port to elect a new Captain and Quartermaster.....

    1. Well, each spaceship must operate independently for months on end, so the 'robust and distributed' is somewhat a feature of life support in space.

  6. Excellent analysis. One thing to mention though, I don't think the pirates will need quite as much of a delta V advantage as you stated earlier when stealth is not available.

    I'll use your example: The target has 45 km/s, 20 for outbound, 20 for braking, 5 in reserve. Suppose the pirates wait until the target starts its coasting phase (thereby ensuring that it is committed to the destination) then burn 20 km/s to match its planned trajectory.

    At this point the target's options are limited. Even if they can safely use their full reserve to evade the pirates and still be on course they'll still need to keep 20 km/s to stop at their destination. In this case the pirates will need a maximum of 10 km/s to outrun the target's reserve. Figure the pirates also need 20 km/s for braking and 5 km/s reserve and we have 55 km/s to run down a target with 45 km/s, mass ratio about 6.3 with a 30 km/s exhaust velocity.

    The tricky part is in escaping on a tight delta V budget. If the pirates don't have to worry about authorities then they might simply proceed to the same planet the target was originally bound for; after all a planet is a big place and whatever cargo was being carried is presumably in demand there. If they do have to worry about authorities then I imagine that their best option would be to pick a destination that requires a relatively small correction from the target's original trajectory (on top of the 20 km/s braking burn). This could be anything from an icy asteroid for ISRU propellant to a heavily defended planetoid run by pirates and mercenaries. Naturally this depends more on the politics of the setting than anything else.

    Alternately if the pirates are feeling particularly crazy they might ride on a bare minimum craft without a delta V advantage; they go in planning to hijack the target or die trying. Of course if the pirate craft is unmanned then this is essentially the same as the drone concept you mentioned, though it is fun to imagine a bunch of space pirates crammed into a tiny ship with "Victory or Death" strictly enforced by orbital mechanics.

    1. Spot on.

      Note that if the pirates manage to close in without being detected until the last moment, they can use an acceleration advantage to reach the interception distance even if their deltaV reserve is lower than their target. A 1g chemical thruster can 'sprint' across 17.6km in less than a minute using 588m/s of deltaV, while an electric thruster with 0.01g of acceleration will only cover 176m in that time despite producing much more deltaV in the end.

      Another factor that I haven't mentioned in Part I because I'm leaving it to the follow-up post is that weapon ranges can greatly simplify intercepts. If you can deliver your threat over 1000km, then you don't need to bother with differences in acceleration and deltaV so long as you get within a 1000km bubble around the target.

      Commercial crews have insurance and can reasonably expect their company to pay for their recover if they have to run from pirates. They can use every last m/s of deltaV to escape. Pirates don't have the same amenities. They must keep enough deltaV to get home on their own: commercial crews can rely on this fact to run away even from pirates with access to much faster ships.

  7. A slightly different take from my own world building notes. We already are aware of my preference for shooting ISO containers into transfer orbits for bulk and non perishable cargos, but high value and time sensitive cargos (read passengers) will be going by fusion powered "Fast Packets". These will be the closest analogues to "torch ships" as can be made with the current understandings of science and technology (tempered by resource and cost constraints), so piracy on the "high seas" isn't going to be an option for anyone less than Captain Morgan (who was essentially running the entire real Pirates of the Caribbean show on behalf of His Majesty's government, as an early example of a PMC. When piracy was no longer needed or desirable, the very same Captain was then hired by HM to clean out the remaining pirate's nests).

    On a more practical note, a Fast Packet can be run down by another, unladen fast packet carrying a Letter of Marque and Reprisal, or the actual Space Navy can dispatch a warship to intercept. More traditional types of piracy will need to revert to how the actual pirates operated in the Spanish Main (and other places), waiting close to shore and sneaking out in small boats to capture unwary merchantmen who were sailing slowly to avoid navigational hazards. The analogue might be some sort of cutter outfitted with the vantablack and hydrogen "stealth" simply lurking in low or medium orbit, ready to intercept a Fast Packet before it lights off the fusion drive. The packet will be moving relatively slowly and wanting to avoid collisions with space debris, while the pirates may only need to latch on and deliver a commando team to download and copy files (the Fast Packets will be elements of a solar system wide "sneaker net"l or possibly kidnap some high value target if they believe they can override the alarms and get in and out before the ships' crew can respond.

    As for the hydrogen "stealth", it is actually going to be somewhat easier since you only have to be showing the temperature of the planet below you for a target in higher orbit, and modifying your emissions to look "cold" for anyone in lower orbit. Even hydrogen leakage is explainable given the amount of traffic (boiling off reaction mass tanks from other ships).

    As a side note, *these* pirates are not going to try to intercept an incoming or outgoing cargo pod. The mass driver is shooting the thing out at 100g acceleration (to keep the sleuth of the mass driver somewhat reasonable, and incoming pods will be moving at interplanetary velocities until the are gathered up in the mass catcher's magnetic fields, so conceptually this would be like trying to catch a modern artillery shell with your bare hands.

    1. I think catching a Fast Packet near the end of its braking burn is a more interesting option for the pirates. They have more... options... for exerting pressure over their victims in that scenario, compared to before the trip, when the Fast Packet is still nearby the departure point and can call for help.

      Spaceships will move slowly near their destinations even without any debris involved, to lessen the consequences of an accident. Space stations, for example, might impose a maximum 'speed limit' set by what velocity fragments its Whipple Shielding can handle.

      Intercepting a cargo pod involves accelerating a spaceship to the pod's velocity, nudging it out of its designated path, then taking all the time in the world to slow it down using high Isp engines into another orbit. You mentioned fusion energy as being available for propulsion. It has the potential to switch between high thrust and %-lightspeed-exhaust velocity modes.

    2. I see fusion drives as the products of a fairly sophisticated supply and logistics chain, so the first issue with that scenario is where are the pirated getting the drive? The other question is how do they plan to hide what they are doing or where they are coming from/going to, since the drive itself will have a very bright signature across the spectrum.

      Even if (say) Mars is willing to turn a blind eye to pirate operations, other nations will not be taking such a relaxed position, and Mars could find itself at the focus of naval, customs and police operations dedicated to rooting out the pirates. Captain Morgan could have the run of Port Royal and command a fairly large and sophisticated pirate fleet essentially because he was a PMC in the employ of the British Crown and supplementing the Royal Navy. Once the Crown had no more use for pirates, they not only withdrew Captain Morgan's letters of Marque and Reprisal, but ended up hiring him clean out remaining pirate nests where pirates refused to lay down arms and cease operations. Future Martian pirates at might be in the same situation if the Uranus Space Navy has hired them to conduct harassing operations against the Imperial Jovian Navy, especially after the conclusion of hostilities.

    3. If the pirates have plenty of time and transporting a mass catcher is somehow relatively invisible, perhaps they can still catch the pods.

      In a solar system that fusion-powered fast packets are widely used, pirates may get them relatively easily.
      For maintaining stealth, I am thinking about the possibility of a design with both cooled nuclear thrusters and regular fusion drives, or simply having a cooled mothership, carrying fusion fast packets.

    4. The fast fusion packet in my mind would be a very large, expensive and sophisticated device, much like the very large passenger liners near the end of the passenger ship era. Think of something like the SS United States ( So the idea of easily getting one is out (you need lots of money or access to a large and sophisticated yard to build one), and a stealth mothership holding a fast packet as a battle rider.....well.......

      Setting up a mass catcher in the orbital path is actually something which makes sense, especially if the pods are part of a "pipeline", such as hydrocarbons being sent to Mars from Titan. The minimum trajectory orbit changes slowly with time, so nudging the mass catcher can be done. After the first two or three have been caught, people will become aware something is happening, so then you'd have to pack up and relocate.

  8. Can a pirate stealth ship hide in a nebula to intercept cargo freighters? :/

    1. I am only considering Space Pirate inside our Solar System for now.

    2. Then, ships must be travelling through the nebula for some reasons.

      Someone living inside nebula?
      Nebula is on the shortest way between two points?

      Without FTL and nebula is not a destination, I don't see the reason to hide in nebula and prey the freighters.
      Spending so much fuel and time for an operation that no one guarantee a success? Maybe preying them inside the destination system is better.

      With FTL, you still have to solve many problems like why freighters must travel there without FTL.

    3. IDK...maybe the freighters were just stopping by the nebula to pick up extra fuel

    4. Then the pirates should know the target's flight plan or they have a mole onboard, though the crew who proposed they should refuel in that nebula would become the biggest suspect, this may lead to the end of the pirate group.

      If the nebula is some kind of popular refuelling site, the pirates have to raid their targets much carefully. Raiding them too frequently may alert others to avoid the nebula or attract groups to hunt down thw pirate.

      While I don't think space piracy is impossible, it is simply a business that is hard to earn real profit.

    5. Hhhhhrrrmmm....maybe instead of using the nebula as an ambush point, then maybe it's just better for it to be used as a hideout.

  9. Yeah, I know. I was just only curious :P

  10. In case you've been busy, Atomic Rockets has posted a new section on General Atomic's ORION nuclear pulse drive being used to design a 1960 era "Space Force" (Since GA's sponsors were the USAF, no Space Navy for that time line....). This is a fairly well thought out force using 1960 era technology (the proposals date to *1965*, 4 years before the moon landing).

    And of course, looking at this real life vision of a space force, it is easy to extrapolate with updated technologies and visualize a series of "FireStars" capable of running down space pirates or rapidly deploying to identified pirate lairs and closing them down with extreme prejudice.

    1. If nothing else, I always keep up with the Atomic Rockets updates through twitter.
      There is a possibility in the future that some sort of incentive which puts pressure on humanity to deliver high performance spacecraft... would force us to dust off these plans.

    2. Scott Lowther has done some amazing work on researching ORION, Casaba Howitzers and so on. He also has been noodling with a story concept of an alt history timeline where the United States does build ORION warships, but hasn't really fleshed out the concept that much. has links to various parts of the project.

      I hope he does more work on this, but lately he has been working on more work on a different project involving Lovecraftian themes. Worth checking out.

    3. Thanks for the link. I'm sure it'll be interesting to read.

      I myself have a setting I am worldbuilding. I will present it first to my Discord chat (link in the top right if you want to join).

    4. Oh, speaking of Project ORION, and Casaba there like a safety feature that prevents nuclear EFPs from causing collateral damage by hitting the wrong target (IDK, a stray passenger ship, or planet)? Cause...I was impressed with a SUPER NUCLEAR-POWERED PROJECTILE that can split a warship in two, but...I was also concerned with collateral damage from a stray shot with this thing O____O

    5. That's an issue that sounds problematic, but in practice won't concern anyone in the heat of the moment.

      For one, stray passenger ships should not be anywhere near the tell-tale flash of nuclear detonations, even if the bright radiator glow of dozens of warships accelerating towards each other didn't tip them off.

      Second, stray projectiles would still take days, weeks or months to travel a significant distance from the battle area. Unless the combat happens right on top of a crowded orbit, the victors have a lot of time to deal with stray rounds.

      The stray rounds can be dealt with in two ways: get an ally in the path of the stray projectiles to intercept the stray rounds with a big asteroid, or shoot them down yourself with lasers if they are still within range.

    6. I based one of my hard sci-fi books after reading up on Project Orion on the Atomic Rockets site. The premise is that once spaceflight becomes routine in the near future, the US military decides to reactivate it and in a matter of a few years has a fleet of Orion nuclear pulse battlecruisers armed with railguns and casaba howitzers stationed at a base located at L-5. Of course the Chinese follow suit...

    7. The idea of riding a series of nuclear explosions using technology we already have access to always sparks the imagination.

    8. I really believe that once space becomes lucrative, there's no doubt in my mind that the military will get involved, and an Orion pulse drive would make an ideal warship since the concept has been tested somewhat and it works. A lot of the material about this remains classified to this day.

  11. What about settings wherein Torchships and least-time trajectories are common? I’d imagine physically rendezvousing with a target without drawing suspicion would be a lot more difficult given the near-constant acceleration. Perhaps cargo ships would be most at risk during the middle of their trajectories, when the main drive is turned off and they’re flipping around for the braking burn? Or would intercepting them closer to port like in the above “fast packet” case be the only viable method?

    1. That's an interesting conundrum, but it is still solvable.
      The solution I see is to reach the velocity that you expect the target to have at the moment of rendezvous. This will require a very high acceleration, or a long acceleration conducted a long time beforehand. After this acceleration, you drift under stealth to the intercept.

      Of course, there are problems with torchships being very visible when under acceleration...

      However, torchships implies access to extreme amounts of power. This power can be converted into electricity, and used to power various 'stealth drives' that do not eject hot exhaust. A coilgun shooting cryogenically cooled projectiles is a form of propulsion. A magnetic loop riding on a cold mass stream launched from a hidden base can accelerate hard without using a drop of on-board propellant.

      There's a lot of room for creativity!

    2. Awesome. If there's one thing I love in my SF, it's room for creativity. I also had a thought that a "hot" ship could accelerate to the point where the difference in velocity between it and its target is low enough that they can deploy a smaller stealth ship (likely a drone) to make it the rest of the way. The larger ship would keep accelerating after deployment to avoid suspicion while the drone attaches to the target's hull and does nasty pirate-y things.
      If the drone's own propulsion system isn't enough to make up the difference without the pirate ship getting suspiciously close, they could always employ an on-board mass driver to launch the drone itself.

    3. The "Dismal Science" suggests that the high speed torch ships will not be used for cargo, unless it is highly valuable, or time sensitive. In the modern world you can see some fairly obvious examples, such as how the Boeing 707 essentially killed passenger liners (people being time sensitive, prefer to cross the Atlantic in 8 hr rather than 3 days to a week). In the modern age, we have Boeing 747 freighters thing off from Colombia to deliver fresh cut flowers to markets in the United States. I also cam across a rather strange example where Mercedes Benz had a plant shutdown in the US because an Icelandic volcano shut down air transport from Europe for a short time. It turned out the transmissions of the vehicles were built in Germany and then flown to the United States.

      But bulk cargos and commodities are not shipped by air freight. Container cargo vessels and tankers churn their way across the oceans at a fraction of the speeds of airfreight, and no one is particularly fussed about the lack of speed, economical transportation is the name of the game.

      In my own world building thinking, I see bulk transport taken to the extreme of removing the "ship" entirely, and using mass drivers or similar devices to fling cargo pods to receiving devices orbiting the target destination. You can picture loaded ISO containers floating across the ocean and drifting into port propelled by the current for a very inexact analogy. Time sensitive cargo and passengers will be going by fusion powered fast packets. since they will be large, expensive and have very bright signatures, running them down under weigh might be a bit of an issue, especially since the only sorts of ships capable of doing so will be other fast packets. If you were sailing across the Atlantic on the RMS Queen Elizabeth and suddenly saw the SS United States bearing down on you, that might suggest something out of the ordinary was going on, and at least make you much more alert.

      Deploying mass catchers in the projected ballistic orbits of bulk cargo pods as suggested upthread by Felix does seem to be a doable project, and Matter Beam pointed out the best times to try to pick off a fast packet is at or near the end of the braking burn, when she has shed most of the velocity and is low on reaction mass.

      I'm thinking that a great many people's views of piracy are based on movies and novels. Age of sail battles on the high seas and pirates swinging from the rigging does make for compelling visuals, certainly far more exciting than the reality of rowing out at night to intercept a slow moving merchantman who is more concerned with avoiding reefs or other navigational hazards (or modern day pirates coming after slow moving container ships in speedboats....). I suggest, me hearties, that we take a page out to the real pirates and see how that translates into proper swashbuckling adventures on the high orbits...

    4. @Trevor Peterson:
      That's actually how real world spacecraft are designed. One vehicle per mission. Separating the designs (torchship, drone) by purpose allows each step of the pirate operation to be conducted in optimal conditions.

      Yes for more realism.

    5. For someone who really can't throw away piracy, like me, restructuring "space pirate" is better than simply seeing it as silly, even the restructured one in space maybe no longer like those in present days or many SF works.

      Crimes always follow business, if trading expands into space, criminals would go after it for sure.

  12. Srry for going off-topic again, but there's something I would like to rly share. So, I have been bored lately, and I was just randomly reading about random military topics for entertainment...but then suddenly I came upon this VERY INTERESTING, AND UNIQUE weapon. The weapon is called a rarefraction wave gun, and it has some desirable characteristics. Now in a regular recoilless gun (for example a bazooka), you can have a near-recoilless effect by ejecting propellant out the back instantly...but this action robs velocity from the projectile fired from a regular recoilless gun, because this instant ejection of propellant apparently causes a wave that catches up with the projectile, and alter its velocity (this is the main reason why recoilless weapons like RPGs, and regular recoilless cannons are limited to a low muzzle velocity of around 50-500 m/s). However, a rarefraction wave gun is different, because instead of ejecting the propellant out the back instantly upon firing the weapon, the rarefraction wave gun instead delays the ejection of propellant (so at this stage it acts like a closed breech gun) until the projectile has travelled 1/4-1/3 (once this occurs, a special type of venting port releases the propellant out the back) of the cannon barrel. This action delays the interferring wave, and prevents it from catching up to the projectile, and rob it of its velocity. So, due to this unique quirk, a rarefraction wave gun has pretty have muzzle velocity (& efficiency since, the wave doesn't "catch" the projectile) of around 1000 m/s, and higher.

    Another unique characteristic of the rarefraction wave gun is that it can reduce A LOT OF RECOIL (values can be high as reducing 75-80% [so that means you can shoot a projectile that is 4-5 times heavier] of the original recoil...but to get those sort of values, you would have to be a bit inefficient, and use more propellant than usual).

    So, basically this thing is a super bazooka that operates like a hybrid of a closed breech gun, and a open breech recoilless gun

    1. Are you sure about this?
      As I understand it, recoilless guns cannot accelerate projectiles to high velocity because they cannot generate high pressures. A lot of the gas energy produced by propellant combustion just escapes and does nothing to push the projectile.

      This rarefaction wave gun is interesting, as it keeps the breech closed while the projectile is in the gun (full pressure) but opens just as the projectile leaves the muzzle, to gain the benefits of recoil reduction of an open-ended gun.

    2. Well...I am not quite sure about it too, since this is also a new topic for me. But there is an explanation detailing the rarefraction wave gun further, according to a PDF document titled "RAREFACTION WAVE GUN TANK MAIN ARMAMENT DEMONSTRATOR" from the authors: Eric Kathe*, Kevin Miner, and Robert Dillon
      US Army, ARDEC, Benét Laboratories
      Watervliet Arsenal, NY 12019. The document states "The tank main armament demonstrator operates on the rarefaction wave gun principle. In such a gun the
      breech is intentionally opened while the projectile is still traveling down the barrel. This causes a dramatic drop in chamber pressure as pressure rapidly bleeds off through the open breech. Although at first it would be anticipated
      projectile acceleration would be compromised, such losses cannot occur until the pressure loss wave (i.e.,rarefaction wave) reaches the bullet. The speed of this
      rarefaction wave is limited by the speed of sound within the propellant gas."

      So basically it's explaining that when the venting occurs after the projectile has travelled some distance (usually 1/4-1/3 of the total length of the barrel), the sudden drop in chamber pressure does not negatively effect (rob it of velocity) the projectile's velocity, because the pressure loss wave (rarefaction wave) hasn't reached the projectile yet [Note: I am rly surprised such a behaviour could happen for gas pressure, but I don't fully understand it yet]

      But for the figure of reducing recoil by 75-80%, I have no idea how it does this (because so far, I THINK that regular guns require their propellant to have the same momentum as their projectile's momentum in order to push the projectile out of the gun tube [But I am rly not certain of this, so plz feel free to correct me on this if I have made a mistake]. So, maybe the rarefraction wave gun is able to reduce recoil by 75-80%, because it uses more propellent than contemprary closed breech guns? IDK]

      As for "Are you sure about this?" IDK. Maybe you should ask the army that researched this thing :P

  13. Just for clarification, current generations of recoils weapons are variations of the "Davis Gun" principle.

    The Davis Gun was a real life WWI weapon designed to provide high powered punch to lightweight platforms, especially airplanes. It used a rather brute force approach to eliminating recoil, being open ended at both ends, the round comes out the muzzle and an equal weight of grease and sand is shot out the rear end.

    German weapons engineers looked at the idea, and realized that a mass half the weight of the shell moving twice as fast in the opposite direction would also cancel the recoil. Taken to the logical extreme, sending a mass of the burning propellant gasses out the back at high speed would cancel out a larger, slower moving shell's recoil.

    Weapons based around that principle generally use about 4/5 the propellant to balance the mass of the exiting projectile, and the true limiting factor for conventional recoils weapons like the 84mm Karl Gustave, or the 106mm Recoiless Rifle is the velocity of the propellant gasses exiting the venturi. Since the gasses are limited as to how fast they can move (even with the assistance of a venturi shaped like a rocket exhaust), there is an absolute limit to the size, weight and velocity of the round coming out the front. If you could somehow use pure hydrogen gas. the lower MW might allow a much greater velocity of the gas, but even then there is an upper limit (and you would need some sort of external energy to accelerate the gas in the first place).

    I have vaguely heard of the rarefaction wave gun (the name is entertainingly close to the "Wave Motion guns" popular in Japanese animation), and will look it up .

    1. That's something I'll have to look up...

    2. Lol. That's what I thought of too when I read about the rarefraction wave gun. The only thing missing was that they need to put in that giant space bazooka on that space battleship Yamato :D

    3. Woah...why is this comment section ssssooooo quiet all of a sudden? Usually there would be a comment/two a day, but now...itz like a ghost town :/

      Super I the last survivor?

    4. Shhhh. The pirates might hear you.....

  14. So I have been reading more about the rarefraction wavegun, and for the life of me, I can't fffing figure out where they got the reduce recoil by 75-80%. Initially, I thought that recoil in a closed gun is equal to momentum of the propellant equal to the projectile's own, plus the projectile's own momentum (so technically what I think is recoil=projectile momentum x2). But the document I have been reading states that gun efficiency (of a closed breech gun) is around I guess this could explain why it can reduce recoil by 67%. And the document states that the gun could achieve 75-80% recoil reduction by allowing for a significant drop in velocity (by very EARLY venting) I guess either sacrificing 25% (having only 75% of the original...I think this seems consistent with the figures I have been reading on the document, it states the normal rarefraction venting produces muzzle velocity of around 1500 m/s. However, very EARLY venting causes muzzle velocity to drop to around 1125 m/s) of the original muzzle velocity, or sacrificing 33.333% (so having 1.333 times more). But I am sure if I am right about the momentum of a gun (at 33.333% efficiency) rly 3 times the momentum of a projectile, or am I just imagining things? o__O

    1. I mean...if the momentum of a gun is 3 times the momentum of a projectile, it could sorta explain the crazy figures I have been seeing on some muzzle breaks (I believe 75% recoil reduction/efficiency is the largest figure I have seen) :/

    2. You must factor in the mass of the propellant, which often is several times greater than the projectile.

    3. But for a normal chemical propelled gun of 33.33% efficiency is the propellant's momentum greater than that of the momentum of the projectile? And is it, because of this 33.33% inefficiency? That's what I don't get :/

    4. The gun, so far as I can tell from the documents I have read, eliminates much of the recoil using the Davis Gun principle of expelling mass in the opposite direction of the round (in this case high speed gasses like most modern recoils rifles).

      The *trick* seems to be a shockwave from the expanding gasses is reflected from the open vent mechanism and moves back up the barrel, either compressing the propellent gasses to maintain pressure and thus velocity of the shot, or directly impinging on the base of the round itself (not entirely following some of the arguments).

      Try looking at this document:

      In terms of space warfare, this is really a non starter, since the rounds will be moving ridiculously slowly compared to electrically driven rounds from a mass driver or railgun, and firing will fill the entire volume around the spacecraft with expended propellant gasses from the muzzle and breach, with negative effects on things like infrared or thermal imaging sensors, antenna and possibly liquid droplet radiators.

      I could see this mounted on vehicles for surface warfare, since self contained chemical energy rounds will be useful on any planet or asteroid against other ground targets, and the Marines will not be carrying separate power packs, generator sets, batteries and so on for electric weapons. Should they need that sort of firepower, they could still be self contained using miniature nuclear EFP's or Casaba Howitzers to shoot at enemy space threats (think of something like the Davy Crockett nuclear launcher: Firing a mini nuke in the direction of the enemy and then watching as they fly into a cloud of 100km/sec pellets or a plasma bolt packing the energy of a heavy ships laser should be entertaining (the rounds will likely be guided and oriented by a second stage rocket motor to point the weapon and get the effect desired).

      To make this conform to the topic, we are obviously speaking of the equipment pirates may use against a base, or the Marines use to clear a pirate nest.....

  15. An excellent discussion on the topic! I'm working on a story that incorporates a number of these techniques (and others) in a rather complicated and sneaky way, and it never even occurred to me you could just sneak a bomb onto the target vessel in a port. I think though, that that would only work a few times before either port security was beefed up, or people simply stopped visiting that port.

    I think a generally much more likely way to involve piracy is to have smugglers. Even with the quality of sensing equipment we have so far and are likely to get going forward, the Oort cloud is going to be mostly unsupervised. It's a truly massive expanse, where even a rocket plume visible from a billion kilometers away is utterly insignificant, as that's less than 300 cubic AU that it's visible in, while the Oort cloud has a volume of hundreds of trillions of cubic AU at the low estimates, going up to tens of quadrillions of cubic AU. It's simply not policeable. So that means there will be smugglers, and smugglers make a perfect target for pirates. They intrinsically *have* to operate in shady areas, away from well regulated ports of call, and will likely be meeting ships in the middle of the darkest nowhere for exchange of illicit goods. Someone at some point is just going to take things by force and just like that - space pirates.

    1. Thanks, WarDaft!

      The port sneaking tactic was simply to show that for every daring pirate attack in deep space, there is likely to be ten covert theft and sabotage operations done in the safety and chaos of a space station.

      The Oort cloud idea with regards to detection is correct, but the problem is that... what's out there? If there's no industrial or economic activity going on in the Oort cloud, there is no reason for people to ferry to and from it. There'll be not targets for pirates, and no-one buying smuggles products... Also, even if it is reserved for the exchange of goods between smugglers, they'll still have to ship it back into the inner Solar System to get the goods to the people who requested them... which brings us back to a spaceship travelling closely surveilled volumes of space. How would they disguise their origin as being the depths of the Oort cloud?

  16. Unrelated query: A hard/tough sf missile proposal: the particle-beam driven subcritical nuclear thermal rocket (has this been done before?).
    It is very difficult to find inexpensive rocket engines in the 10-30 km/s exhaust velocity range. Chemfuel does not provide adequate isp, metallic hydrogen and metastable helium are chimeric, and electric drives do not provide enough thrust.
    Nuclear thermal rockets - liquid core, water propellant - appear to be the "cheapest" rockets available.
    Ideas on how to reduce expense of nuclear rockets?
    Reusable missile bus
    Mass production
    Proton-beam pumped liquid core nuclear thermal rocket.
    A small amount of unenriched/low enriched/medium enriched uranium (cheaper than the 90% HEU typical of NTRs) is configured in a nuclear rocket engine. A beam of protons is fired at the engine from the launching warship. The protons strike the rocket engine, spalling neutrons as in a conventional energy multiplier. The neutrons drive the reactor to criticality, hopefully with liquid-core-NTR-like performance.
    The only drag I have found is that most "accelerator driven subcritical reactors" have a multiplier factor of <20. So if you want your NTR to have an output power of ~20GW, you need gigawatt-range particle beams. For each missile. Salvoes would have to be small. Also, your missiles are only good as boosters.
    Any ideas on how this concept could be improved?
    Is there a better place for this discussion? While a longtime Atomic Rockets follower, I am unfamiliar with the blogosphere.

    1. Hi Law Wong!
      Welcome to the blog!
      The expense of nuclear rockets comes from the fuel itself (especially when highly refined), and for the high temperature technology that can function despite the radioactivity and pressures in the core. All other techniques (reusability, mass production) can also be applied to other engines, so they don't particularly affect nuclear rockets compared to others.

      I am doubtful that protons can cause neutron spallation.

      You might be thinking of neutron multiplication, in which a neutron source radiated on a fissile material, causing the creation of even more neutrons.

      If you instead just are going to push the core to criticality and turn the core liquid, I would simply use a larger quantity of poorly enriched fuel and neutron reflectors like in a normal reactor. This allows you to skip the gigawatt particle beam.

      If you want to improve the performance, you want higher temperatures. This is why research into nuclear rockets went straight from solid-core rockets to the very hot gaseous core rockets.

      If you want to discuss this further, I suggest either you keep commenting here, or come join us on the Discord:

    2. Interesting concept, but if you are radiating that much energy, then you may as well simply drive the rocket directly with the particle or laser beam. A particle beam should work especially well if you use something like a magsail as the beam catcher. Or skip all the intermediate stuff and simply shoot the target with the beam directly.....

      I have tried this discord thing, but it opens onto a black screen with nothing else. I use a Macbook an Safari as the browser, could that be the issue?

    3. Well, the issue might come from the power density. Producing a gigawatt particle beam might force you to dedicate a huge mass to power generation, electrical equipment and lower temperature cooling. It might also be impractical for spaceships that require 'autonomous' propulsion, such as a warship.

      Have you tried the second link?
      In Chrome, opening the link takes me to the sign-up/in page of the web-browser Discord app.

  17. Thank you for your reply.
    Neutron spallation with proton beams is a viable technique for rendering subcritical systems critical, hopefully reducing system mass. But the technology to make the high performance reactor run without melting the engine (even just once?) Might well be the limiting factor on cost.
    I have a concept for a reusable M2P2 cargo tug. M2P2 on the outbound leg, toss the cargo container on a free trajectory, and laser thermal to return the tug to base to load a fresh box. For month/year long hohhmans, shd allow quick Turnaround of cargo tugs and spread capital cost over more flights
    Downside? Unpowered Cargo containers and tugs hijackable.
    Upside? Goods too cheap to bother? Expensive stuff on faster ships?

    1. I was not aware of that technique. Thanks for linking it!

      Upon reading it, I become skeptical again...
      "A 1000 MeV beam will create 20-30 spallation neutrons per proton."
      "The spallation neutrons have only a very small probability of causing additional fission events in the target."

      A bit of maths tells me that even with a 100% efficient proton accelerator, you would need 5.34 picowatts to get one neutron per second. This is a good output (about a hundred times better than a nuclear reactor and a million times better than a fusor), but it still requires a very powerful and very large particle accelerator for something that a radioactive neutron source (Americium 241, Plutonium 239, ect) can produce for 'free'.

      You could, for example, keep the neutron source behind a neutron absorbing window, and only open the window when you want to bombard your uranium with neutrons.

      Or, as I mentioned above, using the natural decay of the reactor fuel as its own neutron source, and a set of neutron reflectors to control whether the reactor goes critical or not. It is the best option if you want lower mass.

      The cargo tug launching payloads into interplanetary trajectories and then returning for a quick turnaround is an idea that NASA has considered for its nuclear OTV (orbital transfer vehicle) studies, as it allows maximal use of the nuclear engines.

      An upside you have not thought of maybe is the fact that since the tug only travels a short distance before turning around and returning, it can accept particle beam accelerators instead of needing lasers, as particle beams are hard to keep focused over long distances. So, M2P2 is the perfect propulsion technology for a tug used in this way!

    2. Thank you for the math. Good to know that a traditional reactor would be cheaper. Throwaway nuclear reactors, torch drives, etc still make me choke. :) I chose laser for the return flight because i assumed that the tug would have passed maximum particle beam range begore dropping cargo for maximum (hyperbolic trajectory) performance.
      Also, launch windows for a second "recovery" particle beam in a higher orbit (HEO? 1 or 2 wk period?) would be constrained.
      I may be dunning-krugered, and apologize for obvious idiocy.

    3. After dropping the cargo, the tug can be very light. It becomes economical to use a simple engine to cancel its outwards velocity and return it using a small amount of propellant.

      If you have a particle beam station in one of the Lagrange points of the Earth and Moon system, and accelerate every tug in its direction every time, you won't have to deal with launch windows.

      No obvious idiocy or dunning-kruger effect here, you are asking questions to learn.

  18. Hey Matter Beam, I have been always meaning to ask you this. There is this type of nuclear fusion reactor called the aneutronic reactor. Apparently it can avoid producing neutron radiation (there would still be other types of radiation [like alpha, beta, and...etc], but the worst type is at least eliminated) by using specific elements for the initial fusing of elements...but once those specific elements fuse, it will produce different elements...and if those different elements fuse, then do they produce neutrons? And if they do, then do anuetronic reactors produce less neutron radiation than conventional types of nuclear reactors? :/

    1. Aneutronic fusion (

      All the reactions listed produce helium particles. While helium can be fused in subsequent reactions, it is under conditions of temperature and pressure far greater than what is needed to react the initial fuels.

      In other words, your reactor will ignite the fusion fuels, but will not produce the conditions to then fuse the fusion products.

      In nature, fusing helium is called the tri-alpha process ( and it produces carbon and no neutrons.

    2. then no would be rly neat on a compact, and lightweight ship :D

    3. But you still need shield to block the radiation, as aneutronic fusion generates lots of x-ray and gamma ray.

    4. True, but those are just high energy photons...and neutrons are a lot more damaging, so you can get away with LIGHTER shielding

    5. @Felix
      Proton-Boron fusion doesn't produce gamma rays. You will be absorbing the X-rays with propellant anyway.

      @andrew lee
      Shielding is not so straightforward. Neutrons can be absorbed by lightweight elements, and protecting against slow or fast neutrons is done differently. High energy photons need to be stopped using heavy elements such as lead, so it might end up heavier than your neutron shielding in some cases!

    6. I found something on Google and Wiki.

      P-B fusion still releases 0.1%-0.2% of the energy as neutron, while propellant will absorb the X-ray and neutron if used in rockets, how much shielding is needed for a P-B fusion reactor with a rating 1 GW?

    7. ohhhhh.....I always thought that lead is required to stop neutrons...well at least since anuetronic fusion produces little/no neutrons, then it won't have any neutrons flying around an creating radioactive isotopes from the surrounding material (specifically the reactor chamber's walls and such)

    8. Well, lead is still pretty good at stopping neutrons.

  19. Any idea when the next article is coming, I really like this blog but haven't seen a thing for over 2 months now. Thanks

    1. I have been very busy recently but it is over now. The blog should return to regular postings by next week!

  20. This is all very just-so, just the same. Of course almost any interplanetary trade or war is a mass of 'just-so' narratives and McGuffins, since just turning Earth into a technosphere seems a lot more likely use of our technology than space-stuff.

  21. How do things change if your goal is to smuggle goods, rather than pirate them? Can stealth enable you to get close enough to a planet to run a blockade?

    How does the picture for prospective pirates change around Saturn? There's plenty of icy moonlets for a base to anchor itself in and use to deal with the heat. Rockets would likely use chemfuel, rather than nuclear, given the lower delta-V requirements. Journeys are measured in days, not months, which means a lot less hydrogen is needed for a steamer. I don't know how hot Saturn is, but that will change the picture for stealth for the better I think.

    Regarding propulsion, a tether should be able to add a few km/s to a spacecraft without any propellent being expended. If the pirates are basing themselves from a convenient asteroid, they could steal momentum from it for centuries without giving themselves away.

  22. Piracy in Space is Possible Part I:Dastardly DeltaV and Stealth Steamers Capital The Samana Range commanding the southern boundary of Tirah.The ridge lies between the Khanki Valley CEO the Samana Suk_It is some 6000 to 7000 ft.high_The South American Plate & Post Soviet Eurasia + Schengen Agreement & Crise's in Sudan HQ 1605_1505™