Energy Density, it's as simple as that

[crix]

http://prometheus.jpl.nasa.gov/index.cfm?pageL1=homePage<br /><br />Just saw this on /. and wanted to bring it to everyone's attention. I'm so excited about this program. Fission based propulsion will truly open up the solar system.

 

[starfhury]

Energy density. I said that a long time ago when I first joined this board. The problem has was and will probably always be energy density, or the lack of it we have available today. This is the reason why I came to the conclusion that going nuclear is the only way we can really open up the rest of the solar system to human travel. Ion, hall effect or similar type technology is not the way to go for human travel though unless we can create some pretty powerful reactors producing the kinds of energy density to make it feasible. <br /><br />Atleast NASA is on the right track. I'm hoping once the space nuclear reactor is created, tested and vetted, then it will be used for manned travel between the earth, moon and even out to Mars, perhaps even beyond. I'm of the opinion that we need a nuclear powered ground launched shuttle to really open space up. Unlike programs like Nerva which had the reactor plume venting directly to atmosphere, I think we need to get several small but very powerful reactors to drive a combined cycle engine. The reactors would provide electrical power to drive air turbines for in atmosphere launch, then once above the atmosphere switching over to system similar to VASMIR. Thats why you'd need a lot of power from the reactors. If we can't move on from using chemical rockets, then we really need to get something like a space elevator going otherwise going to space will be for the few and extremely wealthy. <div class="Discussion_UserSignature"> </div>

 

[the_ten]

I'm all for nuclear-powered space travel. Let's go!

 

[starfhury]

You and me both. But it's going to take a lot of convincing to bring others onboard. Making nuclear safe is a tough gig especially when you are talking about launching from the ground. If it's anything like Orion, it will never fly and I'd never be onboard such a thing. This goes for a NERVA type engine as well since they vent radioactive exhaust to the atmosphere which is just unacceptable. If the reactor is taken out of the direct loop and instead used as a power source, then it's possible that it'd be more enviromentally and politically acceptable. <div class="Discussion_UserSignature"> </div>

 

[spacester]

Radioactive exhaust during the launch phase is a non-starter. It just won't happen.<br /><br />Nuclear propulsion would be great, but can it be used in LEO with the approval of society?<br /><br />An extremely valid point is made with respect to energy density. Many people don't get it. But I ask you to take the next step in the analysis:<br /><br />Nuclear propulsion is probably <i>sufficient</i> to become a Space Faring Society. But is it really <i>neccessary?</i><br /><br />IOW, it would be very very nice to have nuclear propulsion, but is it the only way to get where we want to go?<br /><br />My answer is "no". IMO what we need is nuiclear <b>power</b>. Let's get that in place, get society to accept that, and then move on to Nuclear propulsion.<br /><br />Interplanetary propulsion by chemical rockets requires massive amounts of propellant, and the problem with that is getting it to LEO. If we can't use nukes in the atmosphere, we're stuck with chemical propulsion to get all that propellant to LEO. That being the case, nuclear propulsion does not really solve the fundamental problem.<br /><br />We need to use what we've got and do the best we can with it. That means Big Friggin Rockets and / or lots of smaller but cheaper rockets. <div class="Discussion_UserSignature"> </div>

 

[crix]

I'm confused by the recent headlines of NASA wanting to open up a discussion or get feedback from the population on nuclear engines in space. What does the public know? I know and smart NASA engineers know that it is the obvious next step. A NASA engineer wants a space bsaed nuclear reactor spinning out of control and falling on their hometown neighborhood just as much as the next person. I just get nervous when I hear about taking advice from people that don't know anything about space or that can't see past their own noses.<br /><br />ps. I've been playing Nexus: The Jupiter Incident on my PC and man are the solar system visualiations slick. You can rotate and zoom around and the scales are still pretty far off but they are still insightful and the texture maps for the planets/objects are high res. Additionally this game is really exciting because, at least in the beginnign of the game, you are traveling around our own solar system with what could be assumed to be nuclear-fusion thermal engines. I love it because it is so plausible. They talk abotu the several months journey goign to meet some people orbiting Europa... it's so cool. <img src="/images/icons/smile.gif" />

 

[termite]

I thought there was an international ban on nuclear power for sattilites?

 

[crix]

I don't know about that, but the site linked at top is NASA's nuclear-power initiative, Prometheus. It's happening.

 

[shyningnight]

The BIGGEST hurdle is not technical...<br />It's PR.. plain and simple.<br /><br />You use the word "Nuclear" and the hardware will never fly. It may be DEVELOPED in a lab.. but the ignorant masses will do everything they can (out of ignorance) to keep it from actually GOING anywhere.<br /><br />Look at how close Cassini was to not being launched because it was powered by RTG's...<br /><br />Maybe I'm a bit overly pessimistic.. but I see what we COULD be doing if we had continued development on nuclear applications for space back in the freakin' 60's (!!) and, well.. I get bummed.<br /><br />Had Nuclear Thermal engines KEPT being developed, I have little doubt that designs that do NOT release "fallout" would be a reality now. <br /><br />Reactors run quite successfully (with minimum maintenance) aboard naval vessels, for months or years at a time. Granted, operating in space IS a different environment.. but if you can run a reactor in a sub for an 8 month deployment.. you can build one to run in space! <br /><br />OK.. I'm going to stop before I start using words like "luddite" and "moron" in the same sentence when describing those ignorant masses I alluded to.<br /><br />Paul F.

 

[crix]

<blockquote><font class="small">In reply to:</font><hr /><p>You use the word "Nuclear" and the hardware will never fly.<p><hr /></p></p></blockquote><br /><br />That used to be the case. The MSL rover will have an RTG and Project Prometheus will use nuclear fission, damnit. heh. I know, I know. The uninformed public may still fear it but the people that know what's best will push this through. In the past I just don't think it was economical to build these systems. I guess I'm saying: No regrets. It was appropriate that we continue to build our LEO confidence and get what we could out of chemically propelled probes. I think the public is much more familiar now with space exploration and some may even have the awareness that if we want to do a lot more in space we're going to need more power. Americans should be able to relate to this requirement, ie "American muscle."

 

[najab]

><i>Look at how close Cassini was to not being launched because it was powered by RTG's... </i><p>GNAWnPISS might have <i>thought</i> they were going to stop Cassini from flying, but they were only fooling themselves. One way or the other, it was going to fly. Remember, the Government doesn't have to actually listen to the people, as long as it <i>seems</i> to be listening.</p>

 

[starfhury]

"Radioactive exhaust during the launch phase is a non-starter. It just won't happen." I totally agree with that. That's why ORION can never happen or be allowed to happen. This also rules out NERVA type engines as well. We don't want any radioactive exhaust going into the atmosphere. Hell, I have to live here too.I don't want to glow in the dark from inhaling that nasty stuff. Using the reactors as a source of power, we can convert it to other means of propulsive force without it directly venting to the atmosphere. <br /><br />As far as I can tell, only fighter jets produce enough engine power to fly vertical on their tails much like a rocket during flight. Most if not all other aircraft takes advantage of air over wings to reduce the power needed to fly level or climb higher. The problem with nuclear is that the sheilding makes them heavy, but I'm sure that with real research into the problem we can make them lighter and even more powerful. I also know that most of the larger commerical airliners use fanjets as opposed to turbojets. So the idea then would be to use the reactors power to spin up the fanjets compressors instead of burning fuel in a combustion chamber. With that, you can fly to almost 100k ft or almost 20 miles. That's a third of the way to where space begins. At that height, even if you are only doing a couple hundred miles per hour you can switch the engines over to running on hydrogen for the final climb to orbital speed and altitude. Even if our thrust level is low, as long as we are not using Ion or Hall effect type propulsion systems we can slowly accelerate to where we need to go. So what if it takes two hours as opposed to the current 8 minutes on a regular rocket? The overall stress and strain on passengers and payload would be a lot less. Since the reactors don't need refueling every mission, all we'd need to do is add more prop and go. With this idea, we eliminate the radioactive exhaust, take advantage of wings in atmosphere <div class="Discussion_UserSignature"> </div>

 

[starfhury]

The one good thing I can say about O'Keefe was that he immediately recognize our need for more power and initiated or atleast not hinder the use of nuclear reactors in space or otherwise. We need them not only for deep space missions, but because more power in smaller space can reduce weight, there by reducing propellant load and thus vehicle structure to contain it. <div class="Discussion_UserSignature"> </div>