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Nuclear Rockets Moving Along
AKAImBatman writes "Bruce Behrhorst of NuclearSpace.com recently stumbled across a new engine from everyone's favorite Jet Engine maker, Pratt & Whitney. Unlike P&W's previous engines, however, this engine is not a jet, and is powered by Nuclear Fission.
It seems that P&W has responded to the need for Mars transportation by inventing the first commercially viable nuclear thermal rocket. They have heavily improved upon the NERVA NRX design from the 60's, and have even solved the graphite ablation problem! With this new engine, it seems that an inexpensive trip to Mars is now firmly within our grasp. Will we rise to the challenge?"
Too bad the public fear of anything with the word 'nuclear' in it will grind this project to a halt. :(
This technology is not already doomed because of politics...
I'd rather be sailing...
and have even solved the graphite ablation problem
I was just lamenting over the seemingly unsolvable graphite ablation problem!
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...this will ever be used. Not because it is dangerous, uneconomical, or anything even remotely having to do with reason. Nay. Rather, because the public has a knee-jerk reaction to the word "nuclear," or "atomic," or "nucular." Fact hardly matters in the opinions of an uneducated, uninformed public.
A blog like any other.
"They have heavily improved upon the NERVA NRX design from the 60's, and have even solved the graphite ablation problem!"
Really? I always found that the ablation problems were rarely touched on by my professor. We spent several weeks in the library and online researching this before coming to the conclusion that the vortex efflunziation was inherent with the NRX designs, especially seeing how the rocket designs went from paper to production in 5 months.
> Perhaps they should solve other problems of being able to visit Mars such as its gravitation and the fact that the surface is quite uninhabitable.
Last I heard, both Earth orbit and the Moon are quite uninhabitable, yet we've visited both of those.
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So Nuclear subs have been operating in secret? Well, yeah...
Take off every 'ZIG' !!
Exploration of mars should be second on our list of things to do in the US. Number one should be to have a clear goal on replacing oil as the main source of energy within, say 10 years. Then the US government can shift it energy policy from war to something that benefits us and the world. Why can't we say, ok, first, lets get this urgent problem behind us, and then focus on the next big thing.
This isn't meant as a panicky "omg! nucular!" question. But we have seen a few space craft blow up spectacularly. Now, I assume the designers are bright enough that these engines could not actually produce a nuclear explosion, but wouldn't a conventional explosion at high altitude run a high risk of scattering nuclear material all over the place? Is there a good reason I shouldn't be worried about that?
What's wrong with Project Orion? ;-)
I mean, if we're going to go to Mars, we might as well do it properly - even if it does end up filling the atmosphere with radioactive fallout...
Tedious Bloggy Stuff - hooray?
A trip to Mars will be many things, but it won't be inexpensive.
Everyone get out your wooden clogs and prepare to throw them into the evil machines!
It means they can run the engine and not wear it down from friction. Or at least not wear it down at a rate that is greater than the projected lifecycle of the engine. Having only STFA (Skimmed), I don't know if they are intended for single or multiple use.
Gravitation? What do you mean? Lack of on the surface? Or lack of gravity in space. Either way, we've solved this problem.
Uninhabitable surface? In what sense? No, I won't go strolling on Mars in my jockeys, but it's not that bad once you have a spacesuit on.
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Nothing is 100% safe; consequently the real question is "what is the acceptable rate of failure?".
A nuclear explosion has to push against something, in this case a graphite pusher which would theoretically erode too quickly.
s ion
More info on nuclear propulsion efforts
http://en.wikipedia.org/wiki/Nuclear_pulse_propul
It's too bad that silly public hysteria when they started filling the atmosphere with radioactive fallout in the 1950s doomed such projects (at least until those who remember the 1950s die off).
We coulda had Project Orion. We coulda sea-level canal across Nicaragua excavated by peaceful nuclear blasts. We coulda had electricity too cheap to meter.
All spoiled, spoiled I tell you. Just on account of a few dead sheep, some irradiated Japanese sailors, a few U.S. soldiers with cancer, a little bit of fogged film (cardboard cartons made from fallout-tainted woodpulp), and a few "Sunshine Units"-worth of strontium-90 in the milk. And some problems working the bugs out of Windscale, Detroit Fermi, Browns Ferry, Three Mile Island, and Chernobyl.
"How to Do Nothing," kids activities, back in print!
Did you read the article? It has 15000 pounds of thrust, at nominal output. Totally useless for ground-orbit missions. It is designed to fly from orbit here to orbit somewhere interesting.
"I do not agree with what you say, but I will defend to the death your right to say it"
With this new engine, it seems that an inexpensive trip to Mars is now firmly within our grasp. Will we rise to the challenge?
There are so many other things standing in our way before we get to Mars, it's not even funny. Do you seriously think that we only need a good rocket to get to Mars? There's no way any trip to Mars in the next 50 years will be considered "inexpensive".
Not to sound paranoid, but when the reactor overheats and falls off where does it go?
Launch profiles are designed so that everything falls into the ocean. NASA has aborted quite a few launches, and has never dropped anything on people's heads. China on the other hand...
What happens if the reactor falls off over a populated area?
Well, since it's not supposed to be activated until the craft is already outside of the atmosphere, I suppose someone gets a bump on the head. Even if we assume that the reactor overheated, the titanium shell will melt down and scram the reactor before the reactor itself melts down. It should be nice and cool (and still wrapped in titanium shielding) by the time it hits the water.
Say the reactor falls off on the way to mars. Unless there is a shift in the momentum of the ship or the reactor it'll just melt down beside the ship. Then imagine the case where the ship can separate itself from the reactor. Now how do they get back?
The mission profile suggests three engines. Unless there's a critical failure in all three, a modified flight path could be developed.
While this is probably an improvement, I'd hardly consider it safe.
Consider a chemical rocket on the way to Mars. What happens if the tanks explode? That's right, you've got no way back. Even the failure of one engine could spell doom for the mission. This engine is more powerful, and FAR safer than any chemical engine. Even if the tanks leaked on the way, fuel could still be scooped from Mar's atmosphere. No chemical rocket can make that claim.
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RTFA
It's for propulsion in Space not for getting into orbit. You can put the powersource in containers that survive being blown up, and fit them to the engines in orbit.
>public fear of anything with the word 'nuclear' in it
We can't start polluting space with all of that radiation. It'll kill all the trees!
(For those of you who went to American public schools, a) space is a big place and b) it's pretty well irradiated already by all those pesky stars. There are no trees in space.)
sigs, as if you care.
Nuclear power generation is self-contained, and only problematic in case of catastrophic failure. The other two are problematic when functioning as designed. Associating the three is precisely what has prevented the use of nuclear power generation.
You of course scare-monger by mentioning nuclear power plant failures, but you'll notice that the world has (shock!) survived just fine. While the death toll from an event like Chernobyl is certainly tragic, there are risks associated with developing any technology. Beyond which, I have the sneaking suspicion that more people have died from the effects of air pollution caused by fossil-fuel power generation than have died due to nuclear reactor failure by orders of magnitude.
I also suspect (based on broad stereotyping, admittedly, so feel free to tell me I'm wrong) that you also buy into global warming as a result of mankind's CO2 production, in which case the death toll from fossil fuel plants will be yet more orders of magnitude higher than would be caused by the occasional nuclear plant failure.
Reality has a conservative bias: it conserves mass, energy, momentum...
I think that is probably the number one obstacle to ever putting this type of propulsion system to work. In the event of an explosion during liftoff, it would become the largest dirty bomb ever conceived. I suppose it may be possible to try to launch the engine components separately and assemble them in orbit. (Similar to what the crew of the B-29 which dropped the atomic bombs on Hiroshima did (because of similar concerns). But you'd still have the possibility of radioactive material raining down in the event of a problem during liftoff.
- dj
discovery wings is at the moment running a show on Project Pluto, the government's project to develop a nuclear-powered ramjet in the 50s/60s. the research got up to successfully running the full-scale Tory-IIC 500Mw prototype for 5 minutes at 35,000lbs thrust. i realize a ramjet design is different from a thermal rocket design, but does anybody know why 'they' can't use the basic design of the tory reactor, homogenous uranium/beryllium oxide fuel tubes, at the heart of the rocket engine? seems an ideal situation, theres no graphite to ablate and AFAIK the oxide ceramics stand up pretty well to hydrogen.
Facts do not cease to exist because they are ignored. - Aldous Huxley
All excited, the trip takes its toll on your body but you finally get to Mars, severely disappointed because there's nothing to do and the environment is too severe to enjoy, cry and want to go home to earth, go crazy on the way back to earth, have lost your job, get committed to a mental institution.
This is why we don't launch over populated land masses, like the Russians did (and do). I believe there were some radioactive elements on board the Shuttles, but when it all falls deep in the ocean it's as bad. OK, not as bad for the human population. That said, don't forget it did spew a great deal of rocket fuel which is really nasty stuff. Solid rocket fuel, once lit, will not extinguish, even underwater. Again, though, we plan for these things in launching and mitigate their risks. There will be nuclear power in space in future systems. Right now there's too much baggage to make it viable anyway. Nuclear creates a lot of heat which makes heat dissipation a dominating reason to not use it with current technology.
Was not NERVA somehow proscribed by the NTB?
You're confusing NERVA with Orion. The NTB is about nuclear explosives, which neither the NERVA or Triton engines use. In fact, the Triton engine is really nothing more than your average, power generating reactor. It's primary difference from NERVA is that they're not trying to build the most powerful reactor in the universe.
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The risk I worry about isn't Chernobyl. It's waste products that have been stored in metal barrels for decades. This country has an abysmal record on safely disposing toxic waste products of all kinds, and there STILL is not a single site working site for permanent disposal of nuclear waste (which will change with Yucca mountain I know). Too bad many experts say that Yucca mountain is seismically unstable....
The problem with nuclear energy is a false economy. How much expense will running Yucca mountain for the next 10,000 years rack up? How much of its running expenses are currently subsidized by the federal government? That offsets any advantages nuclear fission has in my opinion.
Fusion obviously has none of those problems, and research into it is drastically underfunded. If the government funded a research program on 1/10 the scale of the Manhattan project into fusion I'm convinced it would become a viable power source and overshadow any of the other alternative energy sources being talked about.
The space program is full of good side effects that many never expected. You can get a whole lot more imagination going when you propose magnificent problems to scientist.
Mundane problems generate less interest which usually means they never get solved completely.
* Winners compare their achievements to their goals, losers compare theirs to that of others.
That being said, to dismiss the fear as ridiculous is unfortunately as narrow minded and confined a view as the fear itself.
Quite simply: People (even the smart ones) are nervous about nuclear power because of two major reasons
Nuclear power has so much potential to assist humanity, but we need to understand the legitimate fears before we can approach those who are afraid of its equally great potential to destroy humanity, and try to convince them to look to the future rather than to the past.
Are you serious??? You want the United States to focus on one scientific goal? You are saying, in effect, that even though there are well over 290 million people in the US, each and every citizen should be forced by the government to be focused solely on what you think is the Right Thing(tm). Give me a break!
The US is still (ostensibly) a free market, capitalist country. Each citizen and industry is free to pursue their own interests. And yes, that even includes interests that might not fit perfectly into narrow-minded people's ideas of what is Best For The Country(tm).
Thanks to visionaries pursuing their unique interests in a free market economy, non-conformists have made leaps of creativity and ingenuity that have created some of the most helpful technologies used around the world. Don't ruin it for the rest of us with your command-and-control utopia.
Been there, done that, realised it wasn't the smartest idea ever.
I'm not a rocket scientist, or I'd have something more informative to say.
I did skim over the Wikipedia article, though, and I was curious -- the impression given is that these sorts of rocket engines can't escape Earth gravity and would have to be put together in orbit (again -- going strictly by Wikipedia article on subject).
I have 2 questions. First, if you build it in space, and you make it to Mars, would you have enough thrust in the lower gravity of Mars to lift off again with a full payload, say, of people and Mars rocks? Would a Mars lander be required with conventional rockets to get back to a control vehicle?
My second question is -- how the hell would they put this together at a reasonable cost in space? The Russians blew the hell out of their Mir space station at least a few times. And I seem to remember that the new ISS crew nearly rammed the hell out of the space station when they hooked up with the station last week. Feel free to pile on with other minor news stories about lost tools, broken this and that, etc. with the ISS.
And you want politicians with money from taxpayers to approve funding for NASA to build something "nuclear" in orbit with this kind of scary news history? I have full faith that NASA or an international consortium could make it work, but what about Joe Public, the environmentally-motivated voter, who fears a mushroom cloud screwing up astronomy night for his kids?
Finally, and this is most important -- with this nuclear rocket engine, would the guy from Sliders and Gary Sinise be able to save Tim Robbins before he burned up in the Mars atmosphere?
IronChefMorimoto
You simplify this too much. The public tends to fear nuclear power because very specific groups spin nuclear power as the evil demonic force opposed to mother nature. These same groups often use nuclear power as fear-leverage in politics. "Gasp! They want to open up more evil nuclear powerplants and refineries that pollute and readioactivate! Don't vote for them or your child wil grow up with 5 arms! Nuclear waste spill across the highways and nich impreganable underground containment will leak into the ground water, killing us all in several thousand years assuming our technology doesn't advance whatsoever from this point forward. Fear teh nuk3z!"
It's simple to say the public fears it. It's important to know who is driving that fear.
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Burning coal puts 25 tons of bomb grade Uranium into the air every year and I forget the exact amount of U238. The U238 gets hit by high energy neutrons from cosmic ray impacts and changes into
Launching a little dab of Uranium under highly controlled conditions doesn't seem like such a big deal when you know this fact.
I am very easy to get along with, but I don't have time to waste being nice to people who are being stupid. -Theo
Noticeably
Untested
Kinetic
Yellow
Undercarriage
Low-Riding
Antigravity
Rocket
Note that the engineering term "intrinsically safe" has a substantially different meaning than "inherently safe". Although the terms are used interchangably by some, those who live by the "law of milspecs" never confuse the two.
In any case, it'd be wise for P&W to rename it something other than a nuclear engineer. That's dumb marketing. Hell, they don't call the Army's M1 tank the "nuclear tank", despite its use of depleted uranium.
And anyhow, many jet engine parts use radioactive materials for hardness and during the manufacturing process. This is not news.
VASMIR seems like a far more generally useful form of space propulsion. The basic premise is the use of radio and magnetic fields to accelerate propellants. Its also inline with the general plan for societal advancement. It is rooted in many of the same technology we'd use to build Fusion reactors, relying upon superconductors, magnetofluid-dyanmics and plasmas. It was derived from plasma manipulation techniques discovered in fusion experiments.
Whereas a nuclear rocket will aid one given form of space travel: moving to mars and back, VASIMR systems are useful from launch to interplanetary, using extremely dynamic engines which consume virtually neglidgible reaction mass (aka fuel). They do, however, require a power source, which could well some nuclear variety, particularly for takeoff. VASIMR's fuel is hydrogen, which is a) readily available anywhere in the galaxy (including mars) and b) the most effective radiation shield we know.
This guy said one nuclear engine should cost about $1 Bil to produce. ITER is estimating $10 Billion for the first working Fusion power plant and will indirectly aid useful space travel more than a nuclear rocket. The ITER project aims to create a 500MW sustainable power plant. Compare this to JET, our current Tokamaka, which bursted at a world record 16MW. Yes, this is an apples to oranges comparison.
We need to stop dumping cash at quick easy bandaids to solve the next problem and begin evaluating our long term priorities as a society. We are wasting money on a hydrogen economy which will make coal plants burn the fuel our current cars would be burning anyways. We are wasting money building nuclear rockets. There is an energy crisis at hand and a environmental problem looming. We need reknewable resources. If we're going to be dumping billions in to space flight again, we might as well research two things which will go hand in hand.
Harness plasma. Make fusion go. Learn how to D-T react, and then get D-D reactions as fast as possible. Miniaturize.
Finish cleaning up the mess your old toys made before you ask for new toys.
Then it might be a bit easier to convince the public that new applications of nuclear power are safe and cost effective.
You encapsulate the burnt fuel in ceramic modules, and dump them into tectonic subduction zones. Fairly cheap, fairly simple, and very safe.
I think Gas Core is the way to go. As the article mentions, a solid core reactor engine is expected to have a specific impulse of only 800-900 seconds, compared with 1500-2000 for a Gas Core engine of the closed loop type (no radioactive emissions). This translates into heavy lifting capability. As the article says, the solid core engine weighs to much it is only useful for vehicles already in orbit, so it would have to be lifted up in pieces by other ships. For really grand-scale work, like putting factories and hotels into space and hauling significant loads to Mars in a reasonable time, we need the big kahuna lifting power of a gaseous core engine.
Here is a highly detailed 12-part article that discusses a Saturn-V size gas core rocket that would lift a payload of 1000 TONS from the ground to orbit and return with an equal payload to a powered landing. Skip the first 5 parts (author's justification of why to build it) if just want to know how it works.
It's pretty safe to say that the likelihood of a nuclear reactor crushing into a critical configuration despite the normal measures taken to keep it "off" (neutron-absorbing control rods inserted, etc) is vanishingly small. In that you are correct.
In a gun design you only need to move one mass. This only appears to be feasible with U-235. Faulty thinking; the temperature and radiation (which turns the bomb core into high-pressure gas and pushes it apart again) are caused by the reaction; they are not separate from it.One point you appear to be missing is that the nuclear reaction takes a certain amount of time; neutrons are not infinitely fast, nuclei do not fission instantaneously, the exponential change rate of the reaction (whether growth or decay) is controlled by the composition of the material and its geometry. The geometry controls whether a splitting atom has a > 1 or < 1 probability of causing another fission. If the probability is >>1, you've got an explosion in progress; if it is < .5, you've got a lump.
The goal of the bomb designer is to turn the sub-critical mass into a prompt-supercritical mass before a chain reaction can begin and take the mass apart again; to this end they design implosion mechanisms and neutron generators to make everything happen when desired and not a microsecond before. The goal of the reactor designer is to make certain that the chain reaction is always under control. We can see that this isn't overly difficult; even Three Mile Island had a nicely-controlled reaction (its problem was lack of coolant), and only the Russians appear to have been careless enough to have a major incident (and without any containment building either, tsk tsk).
Sustainability and energy independence essay