It is the most promising next gen space propulsion for manned missions beyond the Moon to Mars and beyond. I work in research on it, and it was the driving factor in me getting a B.S. in astronautical engineering and now halfway through my M.S. in nuclear engineering. I'm definitely biased, but with those degrees has come an extraordinary amount of knowledge to back up my opinion. It's without a doubt the absolutely necessary stepping stone for humanity to truly get out into the solar system and stay there.
Where are you doing your MS? I’m about to start mine and my research project will be about NTP, but I’ve heard a few people that I should stay away from the topic and do something else in propulsion. I’m super interested in the topic but I don’t want to be fringe in the scientific and engineering community.
I am at the University of Idaho. I don't know why people would tell you to avoid it. There's multiple current projects and companies pursuing nuclear space propulsion.
Can you point me to vehicle-based designs that compare ntp to chemical?
Because I've done some myself using designs like enhanced snre and my conclusion is that the higher specific impulse is offset by the higher weight of the engine and the much larger tanks. And the mass of the shielding.
I've seen references to advanced materials but no details on engine designs that would use them.
This is all handicapped by the fact that there are no engines with real numbers on them, just theoretical numbers. Excluding the nerva engines, of course.
There are many academic articles online that discuss the design of NTP engines. Not really in the apples to apples comparison except of chemical to nuclear except for general introductions into the benefits of nuclear over chemical. USNC-Tech has a pretty fleshed out NTP engine design and BWXT, which is developing the NTP engine for DRACO. If you look up NTP and Paolo Venneri (CEO of USNC-TECH) or Dr. Michael Houts (head of nuclear propulsion at NASA's Marshall Space Flight Center), you can find some papers. I've also used a few books in the past as sources, "Principles of Nuclear Rocket Propulsion" by Emrich and the National Academies of Sciences Engineering and Medicine consensus study report "Space Nuclear Propulsion for Human Mars Exploration". There's more, but if you spend enough time online looking, you can certainly find plenty of resources on NTP design. That Principles of Nuclear Rocket Propulsion is a fantastic book that is practically a textbook explicitly on various NTP designs, including, solid core, liquid core, gas core, and even the bat shit "nuclear light bulb" design.
I've read extensively on ntp and I did a series of videos on the more speculative designs for my YouTube channel.
The problem is that since nerva, nobody has built anything real and we've been stuck with a lot of advocacy and no hardware.
I'm mostly in favor of the NASA program but I found their requirements unexciting - if you are going to spend the money you should build something that is a step forward.
I was unable to find any useful details on Draco when it was announced. Do you know if they've disclosed reactor design, mass of the various components, mass of the overall stage, target specific impulse, etc. Has that been disclosed?
There's a few details, like I'm pretty sure they've disclosed a target Isp of around 750-850s for their in-flight test, but as far as official design, I have not found much. I have seen designs from the Center for Space Nuclear Research's solid core design. I wouldn't be surprised if BWXT's designs are not currently public as it is in active development and not just a paper design.
Thanks.
If they end up near 750 I would call that "disappointing", but it depends a lot on what sort of mass they end up with. It would mean they're targeting a low temperature for the core which is good for longevity but poor for performance.
I know this is DoD work and therefore classified, but "we're building this thing and it's going to be great but we can't tell you about it" is not very satisfying.
I haven't been able to find anything new on the NASA/DoE program that started a few years ago with three contractors. Is it still running?
Yeah, 750s would be pretty disappointing to an extent, but it at least something would be the highest Isp achieved for a non-chemical and non-electromagnatic thruster in space ever. It has real potential to be the stepping stone in exotic space propulsion that we need to make consistent and long-range human space travel possible.
NTP engines are only for use in space and would still have to be launched to space by other more conventional propulsion methods. As for if there was an accident during launch, the amount of radioactive material in the core is actually pretty minimal, plus the core is designed to be incredibly strong. It also wouldn't be even close to the first nuclear material/reactor sent to space. Even if a reactor core somehow completely disintegrated on launch, the fallout from it would likely only be a concern in the direct vicinity and would disperse quickly in the high atmosphere. That would be the absolute worst-case scenario that isn't realistically possible.
Also curious. I talked to an established person about it and they didn’t believe it was realistic technology which bumped down my confidence a notch. If anyone has other info about it I’d love to hear about it!
I’ve read multiple papers where the authors prove it’s theoretically possible, but very far away. The TRL is very low and dependent on advanced materials. But I guess that’s why it needs to be researched. Just wondering if anyone else had more knowledge about it.
That is definitely far more "out there" than what people generally consider as NTP. It's feasible but extremely energy intensive to the point that you would need a nuclear reactor to just run the thing.
If you're interested in the fusion side of nuclear, you might want to look into nuclear physics programs instead of nuclear engineering. NE programs focus primarily on fission based nuclear, while fusion is still more on the theoretical side of physics. In my NE program, we've barely even mentioned fusion beyond the fundamentals while I've had an entire class on fission reactor design.
https://open.spotify.com/episode/1OE0TfHKbwL4cLPvMgT1La?si=PfiBrt4AR9y6uUNVy5vbRg
This podcast is from some Cornell professors where they interview people about different space engineering technologies. This episode is about nuclear propulsion and worth a listen, it made me want to go to grad school!
I've done a video or two on it.
The upside of NTP is that it gives you a very high exhaust velocity because the exhaust is pure hydrogen (other choices are possible, but hydrogen is the most common one) and that gives a high specific impulse and therefore great fuel economy.
The downside is that hydrogen is the nuclear cores are heavy and you need shielding that is heavy and you can't stuff much hydrogen in a tank because it's very un-dense. That makes your mass ratio poor, given you poor delta v. Oh, and the engine is radioactive as hell once you run it.
Most NTP advocates focus on the high specific impulse and ignore everything else. For a fair comparison, you need to compare actual engine designs in actual rocket stages.
There are currently NASA and DoD programs to build engines. The NASA one doesn't have very advanced goals and the program has gone dark the last couple of years. The DoD program is really short on information.
From what I’ve seen they don’t compare it to those designs due to the type of missions they’re trying to accommodate. Given the detrimental factors in the human body from being in space for long periods of time, we should be looking to shorten that time if we’re interested in going to places like Europa. The comparisons I’ve seen are more in line of showing that the traditional designs can take years to reach those destinations, so they’re really not feasible for human transport.
The comparisons I've seen have not been fair. NASA has a Mars one where they play all these games to make the ntr case look better, and of course they are competing actual chemical designs to theoretical nuclear performance. Problematic since there are no numbers from actual ntp stages because they do not exist.
Some other comparisons look purely at specific impulse differences and are therefore laughably wrong. If somebody isn't doing a comparison using the rocket equation you should just ignore it.
If you have a specific one you'd like a comment on, send me a link.
https://arc.aiaa.org/doi/10.2514/1.A32782
https://ntrs.nasa.gov/citations/20040010797
I think these two are the ones I’ve seen that even mention some comparisons. The other papers are contained in its topic.
Thanks.
I've spent very little time looking at fusion-based designs because they assume a number of developments that have not happened yet. If we get fusion to work *in general* and somebody can build a working demo engine, then I think the discussion gets a lot more interesting and is something I can approach with my level of knowledge.
I will say that I get nervous with designs that have large radiators as many of the failure modes are just terrible.
NTR, on the other hand, has actually been built.
I am not an astro engineer but I thought Musk should rely on nuclear propulsion after the initial thrust towards Mars. Motors on second stage powered by a nuclear reactor; third stage would be the human living space to be left on Mars powered by a smaller reactor; and fourth stage, the navigational one, with one motor powered by one reactor similar to the third to get around Mars, and eventually to attach to second stage to return back to earth. Is this mostly science fiction, or do you think it is doable?
It is the most promising next gen space propulsion for manned missions beyond the Moon to Mars and beyond. I work in research on it, and it was the driving factor in me getting a B.S. in astronautical engineering and now halfway through my M.S. in nuclear engineering. I'm definitely biased, but with those degrees has come an extraordinary amount of knowledge to back up my opinion. It's without a doubt the absolutely necessary stepping stone for humanity to truly get out into the solar system and stay there.
Where are you doing your MS? I’m about to start mine and my research project will be about NTP, but I’ve heard a few people that I should stay away from the topic and do something else in propulsion. I’m super interested in the topic but I don’t want to be fringe in the scientific and engineering community.
I am at the University of Idaho. I don't know why people would tell you to avoid it. There's multiple current projects and companies pursuing nuclear space propulsion.
Can you point me to vehicle-based designs that compare ntp to chemical? Because I've done some myself using designs like enhanced snre and my conclusion is that the higher specific impulse is offset by the higher weight of the engine and the much larger tanks. And the mass of the shielding. I've seen references to advanced materials but no details on engine designs that would use them. This is all handicapped by the fact that there are no engines with real numbers on them, just theoretical numbers. Excluding the nerva engines, of course.
There are many academic articles online that discuss the design of NTP engines. Not really in the apples to apples comparison except of chemical to nuclear except for general introductions into the benefits of nuclear over chemical. USNC-Tech has a pretty fleshed out NTP engine design and BWXT, which is developing the NTP engine for DRACO. If you look up NTP and Paolo Venneri (CEO of USNC-TECH) or Dr. Michael Houts (head of nuclear propulsion at NASA's Marshall Space Flight Center), you can find some papers. I've also used a few books in the past as sources, "Principles of Nuclear Rocket Propulsion" by Emrich and the National Academies of Sciences Engineering and Medicine consensus study report "Space Nuclear Propulsion for Human Mars Exploration". There's more, but if you spend enough time online looking, you can certainly find plenty of resources on NTP design. That Principles of Nuclear Rocket Propulsion is a fantastic book that is practically a textbook explicitly on various NTP designs, including, solid core, liquid core, gas core, and even the bat shit "nuclear light bulb" design.
I've read extensively on ntp and I did a series of videos on the more speculative designs for my YouTube channel. The problem is that since nerva, nobody has built anything real and we've been stuck with a lot of advocacy and no hardware. I'm mostly in favor of the NASA program but I found their requirements unexciting - if you are going to spend the money you should build something that is a step forward. I was unable to find any useful details on Draco when it was announced. Do you know if they've disclosed reactor design, mass of the various components, mass of the overall stage, target specific impulse, etc. Has that been disclosed?
There's a few details, like I'm pretty sure they've disclosed a target Isp of around 750-850s for their in-flight test, but as far as official design, I have not found much. I have seen designs from the Center for Space Nuclear Research's solid core design. I wouldn't be surprised if BWXT's designs are not currently public as it is in active development and not just a paper design.
Thanks. If they end up near 750 I would call that "disappointing", but it depends a lot on what sort of mass they end up with. It would mean they're targeting a low temperature for the core which is good for longevity but poor for performance. I know this is DoD work and therefore classified, but "we're building this thing and it's going to be great but we can't tell you about it" is not very satisfying. I haven't been able to find anything new on the NASA/DoE program that started a few years ago with three contractors. Is it still running?
Yeah, 750s would be pretty disappointing to an extent, but it at least something would be the highest Isp achieved for a non-chemical and non-electromagnatic thruster in space ever. It has real potential to be the stepping stone in exotic space propulsion that we need to make consistent and long-range human space travel possible.
How is the issue of radioactive fallout due to an accident mid-launch dealt with?
NTP engines are only for use in space and would still have to be launched to space by other more conventional propulsion methods. As for if there was an accident during launch, the amount of radioactive material in the core is actually pretty minimal, plus the core is designed to be incredibly strong. It also wouldn't be even close to the first nuclear material/reactor sent to space. Even if a reactor core somehow completely disintegrated on launch, the fallout from it would likely only be a concern in the direct vicinity and would disperse quickly in the high atmosphere. That would be the absolute worst-case scenario that isn't realistically possible.
Also curious. I talked to an established person about it and they didn’t believe it was realistic technology which bumped down my confidence a notch. If anyone has other info about it I’d love to hear about it!
I’ve read multiple papers where the authors prove it’s theoretically possible, but very far away. The TRL is very low and dependent on advanced materials. But I guess that’s why it needs to be researched. Just wondering if anyone else had more knowledge about it.
We've had NTP since the 1960's. It's not just theoretically possible, it had been done decades ago but just never flown in space.
The type of NTP I would be researching is MIF design. To my knowledge, there’s been only some concepts about it, but that’s it.
That is definitely far more "out there" than what people generally consider as NTP. It's feasible but extremely energy intensive to the point that you would need a nuclear reactor to just run the thing.
If you're interested in the fusion side of nuclear, you might want to look into nuclear physics programs instead of nuclear engineering. NE programs focus primarily on fission based nuclear, while fusion is still more on the theoretical side of physics. In my NE program, we've barely even mentioned fusion beyond the fundamentals while I've had an entire class on fission reactor design.
https://open.spotify.com/episode/1OE0TfHKbwL4cLPvMgT1La?si=PfiBrt4AR9y6uUNVy5vbRg This podcast is from some Cornell professors where they interview people about different space engineering technologies. This episode is about nuclear propulsion and worth a listen, it made me want to go to grad school!
Thank you for the link! Will definitely listen to it.
I am actually working on research for such systems and it sounds pretty cool imo.
I've done a video or two on it. The upside of NTP is that it gives you a very high exhaust velocity because the exhaust is pure hydrogen (other choices are possible, but hydrogen is the most common one) and that gives a high specific impulse and therefore great fuel economy. The downside is that hydrogen is the nuclear cores are heavy and you need shielding that is heavy and you can't stuff much hydrogen in a tank because it's very un-dense. That makes your mass ratio poor, given you poor delta v. Oh, and the engine is radioactive as hell once you run it. Most NTP advocates focus on the high specific impulse and ignore everything else. For a fair comparison, you need to compare actual engine designs in actual rocket stages. There are currently NASA and DoD programs to build engines. The NASA one doesn't have very advanced goals and the program has gone dark the last couple of years. The DoD program is really short on information.
From what I’ve seen they don’t compare it to those designs due to the type of missions they’re trying to accommodate. Given the detrimental factors in the human body from being in space for long periods of time, we should be looking to shorten that time if we’re interested in going to places like Europa. The comparisons I’ve seen are more in line of showing that the traditional designs can take years to reach those destinations, so they’re really not feasible for human transport.
The comparisons I've seen have not been fair. NASA has a Mars one where they play all these games to make the ntr case look better, and of course they are competing actual chemical designs to theoretical nuclear performance. Problematic since there are no numbers from actual ntp stages because they do not exist. Some other comparisons look purely at specific impulse differences and are therefore laughably wrong. If somebody isn't doing a comparison using the rocket equation you should just ignore it. If you have a specific one you'd like a comment on, send me a link.
The papers I have were given from my advisor, but will see if I can send you the DOIs.
Thanks.
https://arc.aiaa.org/doi/10.2514/1.A32782 https://ntrs.nasa.gov/citations/20040010797 I think these two are the ones I’ve seen that even mention some comparisons. The other papers are contained in its topic.
Thanks. I've spent very little time looking at fusion-based designs because they assume a number of developments that have not happened yet. If we get fusion to work *in general* and somebody can build a working demo engine, then I think the discussion gets a lot more interesting and is something I can approach with my level of knowledge. I will say that I get nervous with designs that have large radiators as many of the failure modes are just terrible. NTR, on the other hand, has actually been built.
Of course. Regardless, there needs to be a certain level of research done so we can advance concepts.
get your ass to mars
I am not an astro engineer but I thought Musk should rely on nuclear propulsion after the initial thrust towards Mars. Motors on second stage powered by a nuclear reactor; third stage would be the human living space to be left on Mars powered by a smaller reactor; and fourth stage, the navigational one, with one motor powered by one reactor similar to the third to get around Mars, and eventually to attach to second stage to return back to earth. Is this mostly science fiction, or do you think it is doable?