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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. :(
and have even solved the graphite ablation problem
I was just lamenting over the seemingly unsolvable graphite ablation problem!
Trolling is a art,
So Nuclear subs have been operating in secret?
That's why it's up to you, me, slashdot, and anyone else who cares about space travel, to make it clear to the public that "Nuclear" is not a dirty word. Odd as it may sound, two thirds of Americans are currently in favor of nuclear power! If we can keep that number rising, perhaps the public will finally ditch their ridiculous fear!
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> 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' !!
Nuclear is only okay on things that are designed to kill people. Didn't you get the memo?
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 design is significantly different from the NRX. For one, they didn't attempt to build the most powerful reactor in the universe. For another, they took advantage of LHOx afterburners. With both of those design choices in mind, they were then able to use a titanium shell to act as the heat sink for the reactor. Not only does it not ablate, but the titanium will melt and scram the reactor long before the reactor itself experiences meltdown.
:-)
In other words, this is an extremely safe reactor design.
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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...
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Most Americans are in favor of garbage dumps too as long as it's not in their back yard and their taxes don't increase.
I, like many of those in your two-thirds 'statistic,' am not afraid of fission. I'm afraid of idiots who don't know what to do with the products of fission, but take on the job anyway and truck it to some underground facility. I'm afraid of a for-profit utility that cuts corners. I'm afraid of backroom legistlation that looks the other way for the "Mr. Burns" in your town. In other words, the social risks need to be considered, for they are as significant as any technical issue. No different from building a dam upstream; do you want them to bid on the job based on cut-rate concrete? In this issue, the risks are potentially very large and long-lasting, and technology simply isn't enough.
So the fear isn't ridiculous; what's ridiculous is looking at the problem like a technocrat.
Damn those pesky terrorists
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.
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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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The fear is ridiculous because nuclear plants have an excellent track records, because modern designs are inherently safe, because nuclear waste is compact and relatively easy to store. You counter this with some generic arguments about "cutting corners". Yeah, I am not afraid of building libraries per se, but rather of idiots who build them using a lot of asbestos and poor materials so that they make every reader sick and then eventually collapse, burying hundreds of people underneath the ruins. So let's not build libraries, right?
You completely fail to grasp the real picture, as if you don't understand a definition of risk. Let me clarify - risk is not that the sky is falling, it's that there is a certain measurable uncertanty over the sky's future position, which we must take into account.
In real world the risks related to nuclear energy are small. Contrary to what you and your alarmist friends may believe, building a new nuclear reactor doesn't mean a Chernobyl and Hiroshima combined for everyone in 1000 km radius.
P.S. If you think only technocrats know basic math and are rational, that's rather sad.
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Except for all those contaminated fish. I have photos. (Not secret or amateur stuff either; this was published in the Time-Life Science Library decades ago.)
It's "okay" to do nuke stuff underwater because the people who shout the loudest *think* it not harmful, just as above-water nuke stuff is evil because the same people *think* it is evil.
Nuclear policy is probably one of the best arguments for keeping the common man away from the levers of government, alas. We know less than we should about cleaning up power reactor accidents, for example, not because nobody bothered to wonder about it, but because Congress got wind of the SPERT trials and realized they'd never survive the public finding out that we were deliberately making experimental reactors fail in order to understand how to deal with the real thing. (Not to say that we know a lot about cleaning up the mess from coal-fired plants, waste from manufacturing photovoltaic cells, etc. either....)
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...
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.
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.
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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As I said I am all for nuclear power; as I realize the statistics are in favor of it over other sources of energy. In my parent post my aim was to prevent people, such as yourself, from stubbornly denouncing the counter-arguments (and their derived fears) against nuclear power, as you did.
Now, just to be patronizing and make sure you understand I will repeat: I am for nuclear power, because statistically it is Safer, and I think that most uses of nuclear power will not lead to proliferation.
HOWEVER, the fears mentioned are not completly illegitamite, and it is essential we understand them to convice people otherwise.
Sure, coal power is far more deadly to society as a whole, but people (think they) understand how coal works and how it kills people (suffocation, burning, crushing, carcinogens). People aren't as familiar with nuclear power, and the idea that so little can be so powerful gives them the willies.
The second point I find far more persuasive against nuclear power. If nuclear power is used in more industries, and more often, then it is invariably exposed (both in terms of concepts and engineering, and raw materials) to more people. The more people it is exposed too, the less secure it is and more possible (statistically!) that one of those people might not be worthy of entrusting with such powerful concepts/materials. Whether or not the nuclear power will be sent to Mars, silently glide 300m below the water off the Siberian coastline, or power an office building, the more widespread it is, the greater the potential that someone who wants to abuse it will get access.
Since you so drastically misunderstood my post, I will yet again, since I am still frustrated, emphasize that I am For nuclear power and I Agree with the rational, and obvious conculsions you felt necessary to post but I understand that others are not aware of this, and you stubbornly denouncing them as ignorant and blasting out facts will Not quell their fears. You must Understand those fears, especially the legitimate points of those fears, and then maybe you won't copy and paste your canned "Now sit and think for a moment which technology is more dangerous" response, which is part of the reason We pro-nuclear power people never get anywhere. phew!
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).
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