Will SpaceX ever go nuclear propulsion?

[zd4]

I know this is quite speculative, but following reading 'The Martian' by Andy Weir, and SpaceX's push for Mars, got wondering, is there any merit to go from chemical rockets to nuclear at some point in the future?

[Coastal Ron]

I know this is quite speculative, but following reading 'The Martian' by Andy Weir, and SpaceX's push for Mars, got wondering, is there any merit to go from chemical rockets to nuclear at some point in the future?

I just finished reading that book.  As far as hard SF goes, it should be required reading for future explorers and hardware architects.

As far as nuclear power for space exploration uses, sure there is merit.  But the nuclear industry is so regulated, not to mention expensive, that it would be hard to see any private company pursue nuclear power for their own use.

The U.S. Government will have to decide that it's in it's best interests to get back into producing nuclear power sources for off-Earth applications...

[Moe Grills]

I know this is quite speculative, but following reading 'The Martian' by Andy Weir, and SpaceX's push for Mars, got wondering, is there any merit to go from chemical rockets to nuclear at some point in the future?

I'm sure Elon Musk fantasizes about such a possibility; but will the AEC and the White House allow it?

[Robotbeat]

I know this is quite speculative, but following reading 'The Martian' by Andy Weir, and SpaceX's push for Mars, got wondering, is there any merit to go from chemical rockets to nuclear at some point in the future?

I'm sure Elon Musk fantasizes about such a possibility; but will the AEC and the White House allow it?

From what I hear from people who used to work at SpaceX, Musk isn't terribly fond of nuclear. There were some slides showing speculative NTR rockets, but I think it was disavowed by Shotwell or Musk and was just an employee's ideas.

Personally, I think that surface nuclear power makes much more sense than nuclear thermal rockets. There are a lot of headaches making nuclear thermal rockets that can be easily and rapidly and cheaply reused. Basically all the NASA proposals have them thrown away after each use. And really, due to their high dry mass, they really aren't much better than hydrolox chemical rockets.

But we're getting to the point that solar + batteries actually makes some sense on Earth. With higher specific power lithium sulfur batteries and another decade or two of continual cost reduction and improved efficiency for solar photovoltaics, solar + batteries could easily be competitive with surface nuclear power even on Mars. But both seem viable for Mars surface power (especially given the fact that Mars has an atmosphere to dump the heat into), although nuclear power will always have some added (geopolitical) risk that may cause investors to shy away (which isn't to say it can't be engineered around, just pointing that out).

[guckyfan]

I know this is quite speculative, but following reading 'The Martian' by Andy Weir, and SpaceX's push for Mars, got wondering, is there any merit to go from chemical rockets to nuclear at some point in the future?

I'm sure Elon Musk fantasizes about such a possibility; but will the AEC and the White House allow it?

I am not so sure. If Elon Musk comes even close to his cost goal, it will be very hard for nuclear power spaceships to compete. Maybe some futuristic direct fusion drive but I don't see that happen anytime soon even with unlimited funding. The technology to allow even starting to develop it simply isn't there.

[ArbitraryConstant]

SpaceX's methodology emphasizes quick iteration, low capital costs, and pushing experiments hard enough to make craters.

It's really hard to do that with nuclear technology.

[Roy_H]

I just wanted to point out that there are a number of nuclear power variations. My favorite is the LFTR/VASIMR combination. Liquid Flouride Thorium Reactors were researched in the 1960's but despite very promising results, budget cuts and the decision to pursue the Fast Reactor approach killed the project. Read all about it at http://energyfromthorium.com/ This reactor promises much higher safety, low cost, and almost no long term nuclear waste. For space travel, it has advantages of relatively small size/mass but faces the same radiation challenges regards crew protection. Read about VASIMR ion drive here: http://www.adastrarocket.com/aarc/space-propulsion

I know my views are contrary to most here, but I think the best way to build the MCT is as a space-only interplanetary LFTR/VASIMR powered craft that goes from Earth Orbit to Mars Orbit and back again, never landing and being served by small rockets to deliver passengers and cargo to/from the planet's surfaces. I suspect it might be more cost effective if these orbits were above LEO, above the Van Allen belts.

[Ben the Space Brit]

A valid question is 'if not nuclear, then what?' Raptor-VAC is anticipated to have a vacuum ISP in the range of 400s, IIRC. However, it's still a chemical engine with the efficiency issues that brings. At the very least, it will need lots of launches to keep MCTs tanked up. In the long run, there will need to be some kind of higher-efficiency in-space engine.

[Robotbeat]

A valid question is 'if not nuclear, then what?' Raptor-VAC is anticipated to have a vacuum ISP in the range of 400s, IIRC. However, it's still a chemical engine with the efficiency issues that brings. At the very least, it will need lots of launches to keep MCTs tanked up. In the long run, there will need to be some kind of higher-efficiency in-space engine.

But why? Think about how much liquid hydrogen it would take to replace all the methane and liquid oxygen.

Also, RE:LFTR: LFTR is a bad fit for in-space propulsion. Too heavy. If you disagree with me, ask foremost LFTR developer and evangelist Kirk Sorenson, who visits this forum regularly and has strong opinions about NTR.

[Nindalf]

I think SpaceX will be planning for non-nuclear operations, with potentially some nuclear components as part of NASA bootstrapping missions.

The biggest issue with nuclear is regulatory.  However much or little sense it makes, you can't make long-term plans based on the assumption that the use of nuclear technology will be permitted.

[R7]

A valid question is 'if not nuclear, then what?'

Outsource the nuclear part to mother nature; solar thermal propulsion

[Robotbeat]

A valid question is 'if not nuclear, then what?'

Outsource the nuclear part to mother nature; solar thermal propulsion

Thermal propulsion of any sort still basically needs liquid hydrogen to ever be better than chemical. And considering how much liquid hydrogen you need, probably greater delta-v could be had if you added the stoichiometric amount of oxygen and used it as a chemical rocket instead of a (solar/nuclear) thermal rocket.

[Ben the Space Brit]

But why? Think about how much liquid hydrogen it would take to replace all the methane and liquid oxygen.

More than you could carry if you replaced the LOX and LCH4 tanks with an LH2 tank?

[hellofu]

nuclear power is needed no matter what given that once you want to go past mars solar power becomes very large and difficult due to diffusion of the suns light. so nuclear is the only short term option and still the best even for a colony on starting given the size of a solar field and production requirements to continue the grown with new waves of people.
elon also doesn't seem to be the person to shy away from a problem given all the problems/companies he has co-found/found. he also isn't a fan of space based solar power. just think about how much power a craft carrying 100 people need and then compare to how much space and mass is need for solar just to keep the iss running. now think how big it need to be in earth orbit now enlarge it to provide enought power at mars. it not feasible.

[R7]

Thermal propulsion of any sort still basically needs liquid hydrogen to ever be better than chemical.

Methane STR beats methalox chemical propulsion with flying colors. It's nice if your future plans revolve around methane. You can also improve chemical propulsion by preheating the propellants as much as you can.

And considering how much liquid hydrogen you need, probably greater delta-v could be had if you added the stoichiometric amount of oxygen and used it as a chemical rocket instead of a (solar/nuclear) thermal rocket.

Baffling argument; going stoichiometric decreases Isp.

[Nindalf]

Thermal propulsion of any sort still basically needs liquid hydrogen to ever be better than chemical.

Depends on your definition of "better".  If there's an efficient way to collect large amounts of water, ammonia, or other suitable inert propellant from a source in space, or design a system to leverage a small amount of suitable working fluid (such as volatiles baked off solid materials) to accelerate large amounts of solid material available in space (for instance, launched from a moon by catapult), inferior specific impulse might not be a problem.

The specific impulse of a turbofan engine would be pretty gruesome if you had to carry the air around with you, but you don't, so it's a lot better than rockets in Earth's atmosphere.  Similarly, if you can find your reaction mass and energy in space, the efficient thing may be to spend them freely, rather than minimize their consumption.

[docmordrid]

Guess we cross our fingers for MSNW's IPA fusion to pan put.

[ArbitraryConstant]

This reactor (LFTR) promises much higher safety, low cost, and almost no long term nuclear waste. For space travel, it has advantages of relatively small size/mass

Nope, people advocating LFTR for space propulsion invariably get this wrong. The point of the thorium cycle is to reduce the volume of material needed and long lived wastes produced. The point of going to a liquid fuel is to deal with the poor neutron abundance of the thorium cycle. The alleged advantage is over that of fast spectrum reactors and thermal spectrum reactors with low enrichment.

Once you go to HEU fuel as space applications always have, all those bets are off. It doesn't have a problem with neutron abundance and lacks all that U238 to take up space and breed higher actinides. It also doesn't have to process liquid fuel to remove Xenon-135. Hence, HEU is the only fuel to actually fly in space, and the only fuel anyone is even talking about flying.

There is zero point talking about thorium until you're on the surface and trying to build a reactor from native materials.

[kfsorensen]

Also, RE:LFTR: LFTR is a bad fit for in-space propulsion. Too heavy. If you disagree with me, ask foremost LFTR developer and evangelist Kirk Sorenson, who visits this forum regularly and has strong opinions about NTR.

LFTR is a thermal breeder reactor and likely too massive for a space reactor. A simpler molten salt reactor design might be an appropriate space reactor, however.

[sugmullun]

   I don't believe NTRs were researched to the point of an adequate estimation of it's real potential.
   My crystal ball says that:
*A robust civilization throughout the solar system will require fission power.
*Without fission, the "average" person will never travel space on his/her own dime. (except possibly on one way trips such as Musk envisions).
*After the development of fusion powered engines, fission engines will continue for some time due to the maturity of the technologies.
   I don't expect to be around to see it, but some posting on these forums will, I'm sure. My crystal ball gives me almost all the satisfaction that I need about that. 
   Musk has spoken recently of leaving his company in the hands of someone who will continue with his vision, and I'm sure that, even if his "vision" isn't prescient enough to see it, they'll travel (if at all) with NTRs at some point.
  One of my pet peeves with experts (with all due respect) is the tendency to apply their ability limits to their "expert" opinions of future development.

edit: "to see it"