tag:blogger.com,1999:blog-8150340806781551727.post4114306327540817585..comments2024-03-28T03:34:35.197+00:00Comments on ToughSF: Nuclear Photon Rockets: Flashlights to the StarsMatter Beamhttp://www.blogger.com/profile/16721504049578296529noreply@blogger.comBlogger29125tag:blogger.com,1999:blog-8150340806781551727.post-54323582832275496252024-03-17T08:43:43.990+00:002024-03-17T08:43:43.990+00:00I still find that Positron Dynamics proposal suspi...I still find that Positron Dynamics proposal suspicious until demonstrated.Matter Beamhttps://www.blogger.com/profile/16721504049578296529noreply@blogger.comtag:blogger.com,1999:blog-8150340806781551727.post-27310246251507591982024-02-26T07:37:45.370+00:002024-02-26T07:37:45.370+00:00Looks like Antimatter might be feasible after all—...Looks like Antimatter might be feasible after all—guy promises 20 grams annually <br />https://www.sciencealert.com/antimatter-could-unlock-a-radical-new-future-of-interstellar-travelAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-8150340806781551727.post-72802584356072025642023-06-10T19:30:10.757+01:002023-06-10T19:30:10.757+01:00I am not sure. It would be interesting to try and ...I am not sure. It would be interesting to try and estimate it though...Matter Beamhttps://www.blogger.com/profile/16721504049578296529noreply@blogger.comtag:blogger.com,1999:blog-8150340806781551727.post-91851150617192739602023-06-09T07:05:35.569+01:002023-06-09T07:05:35.569+01:00Why is the effective exhaust velocity of a rotatin...Why is the effective exhaust velocity of a rotating black hole 82% c?Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-8150340806781551727.post-51237755445057040972021-06-25T12:28:20.736+01:002021-06-25T12:28:20.736+01:00Using a solid block of matter to absorb pions is a...Using a solid block of matter to absorb pions is a much simpler system than loading up the fuel into a particle accelerator or requiring an immensely powerful magnetic field.<br /><br />Also, while neutral pions cannot be absorbed, they decay into gamma rays, which can easily be absorbed by the same structures put into place to handle the gamma radiation from antimatter annihilation. <br /><br />As for the erosion problem... we can deal with it by using a liquid target. Matter Beamhttps://www.blogger.com/profile/16721504049578296529noreply@blogger.comtag:blogger.com,1999:blog-8150340806781551727.post-42659161324001814102021-06-20T21:34:15.158+01:002021-06-20T21:34:15.158+01:00On antimatter photon rocket.
Is it necessary to co...On antimatter photon rocket.<br />Is it necessary to convert pions to heat by capture ?<br /><br />Solution 1.<br />If the matter and antimatter are relativisticaly accelerated before annihilation then relativistic beaming will ensure all pions be projected into a tight cone.<br /><br />Solution 2:<br />Beam-core photon rocket deflects charged pions with magnetic nozzle before they decay, thn deflect muons before they decay in turn. This will ensure neutrinos to be beamed into tight cone. If we are ready to make thousand kilometer long magnetic nozzle we can even force lepton annihilation downstream.<br /><br />Pion absorption problem 1:<br />Neutral pions cannot be absorbed due to ultra-low lifetime. They will not survive the flight of one atomic diameter. Neutral pion decay radiation can split a nucleus thus will erode the absorber.<br /><br />Pion absorption problem 2:<br />Charged pions can be readily absorbed by any nucleus (except single proton), by sinking into virtual the pionic condensate of this nucleus binding interactions. The energy a pion imparts into the target nucleus however will exceed that nucleus binding energy and will explode the target nucleus into burst of alpha particles. Charged pions also erode any target material.phdnkhttps://www.blogger.com/profile/07122069714246670810noreply@blogger.comtag:blogger.com,1999:blog-8150340806781551727.post-70386710507747837342020-12-18T16:48:57.451+00:002020-12-18T16:48:57.451+00:00It seems if spacecraft can't provide enough th...It seems if spacecraft can't provide enough thrust that it's can't accelerate more than 10 km/sec in a month, it's not spaceship that can travel to stars, though if using something like solar sails which can get a lot acceleration near a sun/star- say about 100 km/sec in week- it might work.<br />Can photon rocket use solar energy for propulsion?<br /><br />It seems important aspect related to star travel is getting "free energy" from gravity well- robbing orbital velocity and getting a Oberth effect- with planet Earth one can add or remove it's orbital energy and can get an Oberth effect with chemical rockets.<br />Jupiter better than Earth. But if Jupiter was colder, it would work better.<br />Jupiter core temperature may "about 24,000 degrees Celsius" what if it were 1/2 as hot- core temperature cooled to about 12,000 C? Plus if it had less lethal radiation it would be more useful.<br />And question is how many Jupiter or greater mass planets are between us and our nearest stars.<br />And when will solar systems become closer to us.<br />If there was Jupiter mass .1 lightyears from us and in direction one wanted to go, can it be used.<br />It seems if there was Jupiter mass .1 lightyears from us, it would have a good chance of being much colder and not have lethal radiation. <br />gbaikiehttps://www.blogger.com/profile/06229867789958708711noreply@blogger.comtag:blogger.com,1999:blog-8150340806781551727.post-65678380609105506542020-12-15T06:26:36.489+00:002020-12-15T06:26:36.489+00:00Well, what if chemical rocket could get it a 1/3 o...Well, what if chemical rocket could get it a 1/3 of the way there. <br />So chemical rocket have reached Moon distance in 9 hour {New Horizon did it, as did others, I think Ranger probes impacting moon did this. So chemical rocket finished it's burn while still within LEO distance, will throw its payload so it passes by a full Moon within say 6 hours {or say, +10 km/sec added to Earth orbital velocity] and chemical stage brakes and stays within Earth's gravity well. But starting from LEO distance one is adding to velocity with second stage photon rocket. So photon rocket is reducing gravity loss from Sun for third of the way, and Sun gravity weakens as get closer to Mars. <br />1.2 Squared: 1.44, and 1.42 AU is 1/2 of Sun gravity.<br />But if not, perhaps one do it with the ion or a NERVA type nuclear thermal rocket- though, with much longer burn with less thrust.<br />gbaikiehttps://www.blogger.com/profile/06229867789958708711noreply@blogger.comtag:blogger.com,1999:blog-8150340806781551727.post-74618593693960097332020-12-13T20:48:08.577+00:002020-12-13T20:48:08.577+00:00Hi!
Distances like 100 million km might seem huge...Hi!<br /><br />Distances like 100 million km might seem huge to us, but they are rather small on the interplanetary scale. They are in fact too small for photon rockets to be useful for crossing them, because their acceleration is too low. Any other rocket, even 'weak' ion engines, will cross that distance in far less time. <br /><br />You mention non-Hohmann transfers. It is only possible to make a 'near-straight' line from one planet to another if your acceleration greatly exceeds the solar gravity in the space between them. At 1 AU from the Sun, where our Earth orbits, the solar gravity is 6 mm/s^2. For a photon rocket to get that sort of acceleration, it would have to have an engine that has a power density of over 3 MW/kg. That is beyond the capabilities of even the most powerful nuclear thermal rockets. In fact, it is most likely going to be in the handful of kW/kg, a thousand times less than our requirement! <br /><br />Matter Beamhttps://www.blogger.com/profile/16721504049578296529noreply@blogger.comtag:blogger.com,1999:blog-8150340806781551727.post-1589261070125495532020-12-11T20:35:55.795+00:002020-12-11T20:35:55.795+00:00It seems we long way from doing star travel.
It s...It seems we long way from doing star travel. <br />It seems people rather than government will be star traveling.<br />And we need more markets other than just Earth orbital satellite market.<br />Maybe a photon rocket could used to go from Earth to Mars more quickly- so the thrust has to exceed to force gravity of Sun between Earth and Mars and travel a short distance of less than 100 million km distance.<br />And we can develop a photon rocket that does that the best.<br />Or at moment we are at 200 years ago, trying to imagine a car going 100 mph or the airline business.<br />It seems all we need at moment is chemical rockets and cheap chemical rocket fuel in Space.<br />And it seems with chemical rockets and cheap rocket fuel {say made on our moon} one could get to Mars from Earth in less than 3 months. Whereas photon rocket might do it, in 1 month and use less rocket propellent.<br />What is obvious to get to Mars in less than 3 months, requires a trajectory which is not hohmann transfer- which roughly require going from one side of sun {in some solar orbit} to opposite side of the sun.<br />It seems one could do non hohmann transfer from Earth to Mars with a chemical rocket- though we never done it before.<br />We have done non hohmann transfers. One say gravity assists involve them, and ion rocket which spiral up a gravity well are doing a non hohmann.<br />Now to do non hohmann, you would changing the vector- gravity assist are largely used to change vector [but it's robbed from orbital body}. <br />So with photon rocket to Mars in 1 month, one paying for the vector change, but delta-v needed is cheap with the photon rocket.<br />And it seems for intersteller travel {with whatever non chemical rockets] one probably going need a lot of stealing orbital energy or other energy. And/or use most efficient way {as we are mostly using most efficient transfer of hohmann.<br />Plus since humans copy things like birds flying, observation of space aliens might give human something to copy. Or it seems one say large telescopes are "like" star travel, but with large telescope we might discover how other creatures are star traveling.<br /><br />It seems main problem {other than not close to able to do star travel] is we could have wrong kind of star. And finding the right star {or gravity well}, could be needed. <br />Or it seems Trappist solar system is designed to allow star travel.<br />https://en.wikipedia.org/wiki/TRAPPIST-1<br />Though being 40 lightyear away from us, makes it not useful to us.<br />And somehow making our solar system into something that, does not seem possible.<br />But it seems might find stuff within lightyear or 2 of us, which could be useful, perhaps.gbaikiehttps://www.blogger.com/profile/06229867789958708711noreply@blogger.comtag:blogger.com,1999:blog-8150340806781551727.post-63658898288731351772020-12-10T15:47:05.879+00:002020-12-10T15:47:05.879+00:00Regarding onboard vs. offboard creation of antimat...Regarding onboard vs. offboard creation of antimatter, this reminds me of a concept I came up with years ago. One of the biggest disadvantages of antimatter creation is the huge power cost. Could you do an article on the practicality of solar powered antimatter generators located on the sunward side of Mercury? How big of a setup would be required to create antimatter in reasonable volumes needed for interplanetary travel given current (or near-future) antimatter generation technologies?Prisoner881https://www.blogger.com/profile/17588416097821623933noreply@blogger.comtag:blogger.com,1999:blog-8150340806781551727.post-62189898842678611272020-12-10T15:42:51.259+00:002020-12-10T15:42:51.259+00:00Not to mention the handy side-effect of digital im...Not to mention the handy side-effect of digital immortality such a technology would enable! And the not-so-handy side effect of, if it can be digitized and transmitted, it can be COPIED. I can imagine the ethical implications of such a technology are so vast we can't even comprehend how easily it could be abused.Prisoner881https://www.blogger.com/profile/17588416097821623933noreply@blogger.comtag:blogger.com,1999:blog-8150340806781551727.post-6554568169699872862020-11-25T01:58:10.334+00:002020-11-25T01:58:10.334+00:00I was looking at an idealized 'best case' ...I was looking at an idealized 'best case' scenario for photon rockets. Even with those assumptions, they fail to perform well. If we start including all the conversion losses and inefficiencies, they will look even poorer!Matter Beamhttps://www.blogger.com/profile/16721504049578296529noreply@blogger.comtag:blogger.com,1999:blog-8150340806781551727.post-4536312273532960952020-11-25T01:12:00.650+00:002020-11-25T01:12:00.650+00:00More realistically you might get 60% efficiency in...More realistically you might get 60% efficiency in power generation, 95% in power transfer, 80% in photon generation, and 95% in thrust directivity, for a total fuel to thrust efficiency of just over 43%. Still dramatically better than chemical rockets, but the mass penalties for power generation and thermal control are enormous. Andrew Broekerhttps://www.blogger.com/profile/03455959935160897929noreply@blogger.comtag:blogger.com,1999:blog-8150340806781551727.post-78022260392436956452020-11-25T01:05:51.495+00:002020-11-25T01:05:51.495+00:00Thrust = 2 * power / exhaust velocity is not the c...Thrust = 2 * power / exhaust velocity is not the correct equation. That is a Newtonian equation and a photon is as far from Newtonian as you can get. The actual equation for a photon rocket is Thrust = power / c, twice as much. And even after that the assumed 95% efficiency doesn't even have a theoretical basis as far as I'm aware.<br /><br />Source:<br />https://en.wikipedia.org/wiki/Photon_rocket<br />Or just derive it from the equations for photon momentum and photon energy.Andrew Broekerhttps://www.blogger.com/profile/03455959935160897929noreply@blogger.comtag:blogger.com,1999:blog-8150340806781551727.post-72220452112649979352020-11-22T10:42:25.098+00:002020-11-22T10:42:25.098+00:00@Matter Beam, @Luke:
The energy of fission reacti...@Matter Beam, @Luke:<br /><br />The energy of fission reactions manifest themselves mainly as the kinetic energy of fission fragments already, so if these are allowed to simply bounce off against a magnetic field then no acceleration of these fragments is required.<br /><br />In standard fission reactors this is impossible because most of the fragments impact the fuel rod atomic lattice and decelerate, giving off their energy as low-grade heat. But this need not be the case - in fission fragment rockets, the fuel pellets are smaller than the mean free path of the fission fragments, and as a result many of the fragments simply escape the pellets and are collimated into a very high velocity exhaust stream. With fission-fragment rockets you can get close to the theoretical maximum specific impulse of fission-powered rockets, or about 5% light speed.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-8150340806781551727.post-77626713359747251922020-11-20T00:02:28.588+00:002020-11-20T00:02:28.588+00:00Two other related ideas to examine -
Photonic las...Two other related ideas to examine -<br /><br />Photonic laser propulsion as developed by Young Bae is an interesting riff on laser sails, where the beam is reflected from the laser sail, but then reflected back to the sail by a high quality optical mirror. One can imagine a laser battery on the moon illuminating the sail, and a field of mirrors gathering the reflected laser light and refocusing it back on the sail.<br /><br />If you go to Quora.com, there is a poster named William Mook who has written fairly extensively on this, although he extrapolates to some rather extreme energy levels (solar lasers driven by the solar photosphere) to postulate vehicles moving at very large fractions of the speed of light.<br /><br />A demonstration here: https://www.youtube.com/watch?v=QICCrlmBjvY<br /><br />A separate idea uses antimatter, but not in the way most proposals do. Positrons are generated and collected from decaying radioactive material and used to drive fusion reactions in duterium - essentially an antimatter driven fusion drive. While the company seems to have closed shop, the idea is interesting:<br /><br />https://www.youtube.com/watch?v=n2pWv-D84W0<br /><br /> Thucydideshttps://www.blogger.com/profile/09828932214842106266noreply@blogger.comtag:blogger.com,1999:blog-8150340806781551727.post-16860549849322122022020-11-18T12:13:45.550+00:002020-11-18T12:13:45.550+00:00It would be hard to say without more details.
If t...It would be hard to say without more details.<br />If the shielding managed to absorb the mesons very quickly, then an annihilation photon rocket would be more efficient.<br />If the shielding was not effective enough, and the meson had time to decay into an electron and a neutrino, then it would be less efficient as the neutrino would slip away and take energy with it. Matter Beamhttps://www.blogger.com/profile/16721504049578296529noreply@blogger.comtag:blogger.com,1999:blog-8150340806781551727.post-65426506372389000152020-11-18T11:10:57.461+00:002020-11-18T11:10:57.461+00:00Would that make it more efficient )thanks for the ...Would that make it more efficient )thanks for the reply!)?JoseFreitashttps://www.blogger.com/profile/13799512235188753569noreply@blogger.comtag:blogger.com,1999:blog-8150340806781551727.post-53564465891251332382020-11-18T00:57:18.687+00:002020-11-18T00:57:18.687+00:00The exhaust is supposed to be mesons. Mesons decay...The exhaust is supposed to be mesons. Mesons decay very very quickly into electrons and neutrinos. Since these are not photons, it is not a photon rocket. However, it could be modified into a photon rocket by absorbing the energy released from this annihilation-like reaction as heat, and then radiating it away.Matter Beamhttps://www.blogger.com/profile/16721504049578296529noreply@blogger.comtag:blogger.com,1999:blog-8150340806781551727.post-34371499501325670442020-11-18T00:55:00.969+00:002020-11-18T00:55:00.969+00:00Agreed. I would also note that there is no practic...Agreed. I would also note that there is no practical method of creating antimatter onboard a starship. Whatever the original form of the energy used to create antimatter, it will be less dense than antimatter itself, so it would be a net loss to try to transport it instead of just antimatter.Matter Beamhttps://www.blogger.com/profile/16721504049578296529noreply@blogger.comtag:blogger.com,1999:blog-8150340806781551727.post-50364008281730290052020-11-17T13:16:08.357+00:002020-11-17T13:16:08.357+00:00At first glance, I'm not keen on that idea. If...At first glance, I'm not keen on that idea. If you make the antimatter on board ship, you are introducing inefficiencies and adding extra waste heat to the process, all of which does not contribute to thrust. Better to make the antimatter at home, perhaps using the same method, then carry it along as a kind of energy storage medium.Steve Bowershttps://orionsarm.comnoreply@blogger.comtag:blogger.com,1999:blog-8150340806781551727.post-78260190029999597612020-11-17T02:37:56.062+00:002020-11-17T02:37:56.062+00:00What about tha Annihilation Drive that has been po...What about tha Annihilation Drive that has been popping up recently, what category would you file it under?<br /><br />Link to article:<br /><br />https://www.sciencedirect.com/science/article/pii/S0094576520303179JoseFreitashttps://www.blogger.com/profile/13799512235188753569noreply@blogger.comtag:blogger.com,1999:blog-8150340806781551727.post-35050177412246361992020-11-17T00:31:37.515+00:002020-11-17T00:31:37.515+00:00If we are separating out the fission products (as ...If we are separating out the fission products (as was supposed in the article), you can run the reactor as a generator rather than a rocket, and electrically accelerate the fission products (for example). There will be inefficiencies, but the net result should still be orders of magnitude better than using the radiation pressure of the heat of the reaction.Lukehttps://www.blogger.com/profile/09617890536562434320noreply@blogger.comtag:blogger.com,1999:blog-8150340806781551727.post-85316082147779227592020-11-16T22:38:04.967+00:002020-11-16T22:38:04.967+00:00Perhaps then it is our idea of travel that must be...Perhaps then it is our idea of travel that must be adapted. We are used to physically moving our living bodies to a destination, but we also know that many other forms of travel are possible! <br /><br />Imagine how easy it would be to transmit our consciousness if it were digitized? It would feel instantaneous. Matter Beamhttps://www.blogger.com/profile/16721504049578296529noreply@blogger.com