What are your thoughts about nuclear rockets?

Question

This is a proven technology that could be the future of space travel that requires less fuel with higher output.

This is some notes on the subject from the included links:

Sean O'Keefe, has talked up nuclear propulsion for about a year. He requested $125M to start the effort in NASA's 2003 budget. Now, Project Prometheus has been announced, and appears to have the blessing of the Bush White House. The objective of Project Prometheus is to speed up travel around the solar system.

During the years from 1956 to termination in 1971, the programs accomplished the following records:
1) Highest power - 4500 megawatts thermal power
2) 5500 degress Fahrenheit exhaust temperature
3) 250,000 pounds thrust
4) 850 seconds of specific impulse
5) 90 minutes of burn time
6) thrust to weight ratios of 3 to 4

http://internet.cybermesa.com/~mrpbar/rocket.html

http://www.chris-winter.com/CATS_Quest/Nuc_Rkt.html

http://en.wikipedia.org/wiki/Nuclear_thermal_rocket

What I have read about this states that it will be used on the upper stage of rockets, it's in space by then.

Answer 1

Awesome. My kind of question.

I designed a nuclear thermal rocket system for my senior design project along with my group. I agree wholeheartedly that as far a manned flight going out to Mars or beyond, nuclear-powered propulsion systems are one of the most promising new rocket technologies...

EP (electric propulsion) is not. At least not for manned flights, as it accelerates much to slow. (~ 1N is average thrust for EP, compare that with 1 million N for a common conventional rocket) However, it is excellent for long-range unmanned missions, and EP was responsible for the fastest speed ever attained by a man-made craft with Deep Space 1 reaching 10 km/s... Solar sails are also not a very promising technology. Even less thrust than EP, and not very reliable as we know it today. It would take 50-100 more years of research to even think about using solar sails for ANY part of a manned mission.

If we launch to the upper atmosphere, or LEO, with conventional rockets before firing the nuclear rockets we skip the environmental issue. No matter what, natural solar radiation in space is far more dangerous than anything a nuclear rocket will spit out. A nuclear system is also capable of just as much thrust as a conventional system with a much greater efficiency.

With theoretical Isp's of 1000 s about twice that of our best liquid rockets and 3 times that of our best solid rockets, this is a huge efficiency increase... A big problem however, is that Hydrogen the lightest/least dense atom is the best fuel for Nuclear Thermal systems. Being the lightest and least dense has the advantage that it can take on enormous amounts of energy and draw heat off of the reactors... however, it takes up more volume due to its density, and must be stored in rather large cryogenic tanks for long term storage. After engine shut-down, cooling is another issue (because the fuel is used as the coolant during the fire)... so, either a new colling system, pulsed cooling, or other methods must be developed...

I am impressed with your research, I am glad someone on this site looked into the NERVA program... the Russians also had their own share of success in nuclear rocketry...

I've read a few AIAA papers recently, and it seems a resurgence is beginning in nuclear rocket theory and research... so hopefully in the next 10-15 years we'll start hearing some more about it.

Good question.

Answer 2

I believe it's the wrong approach, politically and environmentally. Even if it was safe 99 shots out of a hundred, the repercussions of that one failure could put the kibosh on the whole effort... and then we would have wasted all that energy on a false start.

I think there are other ideas out there for getting us into space, some without rocketry, that have merit. And as other posters have noted, once you are in space, solar sails take away the need for any sort of stored chemicals for propulsion.

You know, the proposal has been on the table for some time, and I've never really heard a good explanation for why it can't work: what about the space elevator? Yes, it's a monolithic project... but then so are transoceanic cables.... so indeed is the network of roads that covers our planet.

I think if we found a way to attain orbit that did not require massive explosions and pollution we would be doing the right thing.

Perhaps some other breakthroughs are right around the corner.

But when you consider the risks of nuclear propulsion, you have to take a moment and ask if it's really worth it?

Don't take me for a luddite. I support nuclear technology; but I strongly believe that the people who manage it have to really do their safety homework. Part of which is finding the will as a nation for a safe waste repository.

But this is an interesting and important question. The solution to which will pave the way to more rapid expansion into space.

Answer 3

Will NEVER happen in the U.S. People in the U.S. are too scared to build a new nuclear power plant 60 miles away from their house, do you really think they want it flying directly over their house? And another thing: Solar winds would be FAR more promising then that. Cheaper, easeir, and most importantly it is simpler.

Answer 4

Hm,

Ion drives are better when you leave the earth's atmosphere. Nuclear engines have to have an exaust, ie. they need to propel something