Nuclear, Pro & Con

Palomar · 2004-02-01 20:50:14

[=http://www.oosa.unvienna.org/SpaceLaw/nps.html]Office for Outer Space Affairs/UNO @ Vienna

[http://www.ne.doe.gov/space/space-desc.html]Office of Space & Defense Power Systems

[http://www.space.com/businesstechnology … 30204.html]space.com article (dated 4 February 2003)

*I'm not sure where this might go (as a topic), but I'm brushing up on the subject as pertains to space exploration. I'm also curious for opinions from folks of the *anti-nuclear* persuasion (if there are any such persons here).

I'm not really seeking debate (though if others want to carry it to that point with others, feel free...and who knows, I might join in eventually!); again, I'm simply seeking a better working knowledge of the matter.

--Cindy

Michael Bloxham · 2004-02-02 04:06:45

I agree. Space is perhaps one of the safest places for a nuclear power plant to malfunction. What you don't want, however, is millions of tiny particles of radioactive plutonium raining down on the earth. Nuclear reactors should be capable of surviving a booster explosion, re-entry, and impact, without spilling uranium. I've become curious of Antarctica in recent years, and have concluded it would be greatly beneficial to store radioactive and other wastes there (deep under the ice sheet). Unfortunately (IMO), the antarctic is protected from this sort of thing. Antarctica is unique, as it is nearly completely isolated from the rest of the world. As is space. So the same idea holds true for space. If we can find a way to safely transport radioactive material off the earth. As for the 'greens'; they can be a little short-sighted at times, imho...

dicktice · 2004-02-02 10:50:21

Honestly, "greens" or not, I have to ask if the last two who posted above really know whereof they speak, using nuclear fission based power--which is what you mean--right?
To "get off this rock" you'd leave fission products behind in our precious atmosphere the Earth's ecosphere depends on for all life. If you don't agree, I challange you to spell out the engineering details for avoiding such contamination.
Anarctica, just because it is relatively inaccessible now, and covered by ice (like Mars's poles) doesn't mean you should bury a "time-bomb" like nuclear fission waste products out of sight there, any more than you'd wnt to do the same, eventually, on Mars. All that freshwater-ice is a resource to be cherished, not spoiled for want of intelligent forethought.
As for space, the key word missing is: DEEP space, meaning no way available for fission products to re-enter Earth's atmosphere from orbit, or Moon's orbit, or Mars's orbit. In other words, know that it's going to end up in the Sun, before you throw it away. At least, use that as your ultimate objective, when we get our space transportation system established. Let's hear a little more from you concerning HOW instead of just "what-if" ideas. Atomic fusion, for instance, would be nice . . . even space elevators. Right--but not in my lifetime, or yours. We know so much more about ways and means that would work if only we'd stop objecting to 'em because of short-term expenses and/or questions of job security centered about 30-year-old technology nostalgia--including nuclear fission launching schemes. Read your history. Even Mars Direct needs to be updated, regarding the initial part, because of the existence of the ISS. We've gotta pull up our space-socks and get with it, or I'm gonna die before it happens--get me?

Michael Bloxham · 2004-02-02 14:53:03

To "get off this rock" you'd leave fission products behind in our precious atmosphere the Earth's ecosphere depends on for all life

I wasn't referring to a nuclear rocket; but a nuclear power generator, launched via chemical rocket or otherwise. And besides, we already have had launch failures involving a few russian RTG's, and atleast one american failure. Both releasing a few kilograms of plutonium (uranium?) into the atmosphere. And we're still alive, right? I hate to be candid, but there are worse things we can do (have done?) to our environment.

jadeheart · 2004-02-02 16:00:26

it would be greatly beneficial to store radioactive and other wastes there (deep under the ice sheet)

Au contraire. The Navy had a fission reactor at McMurdo station thru the 60s and (I think) part of the 70s. They eventually removed it (due to pressure from scientists and partly some greenies), leaving a spot with low-level radioactive contamination. Nothing has subsequently been built on this spot.

As for putting nuke waste in Antarctica, under the ice sheet-- probably won't happen, fortunately. It costs a lot of money to get stuff down there, would have to go by ship (which would threaten any maritime environments the ship might sink in), and the ice sheet is moving. Any shear effects in the ice could compromise the integrity of your containers. Not to mention the fact that there is a potential goldmine of exobiological-oriented research to be had under that same ice--Lake Vostok being a prime example:

(See [http://astrobiology.arc.nasa.gov/storie … _0899.html]this and [http://www.nsf.gov/od/lpa/news/02/fslakevostok.htm]this, and if you're really hungry for info on Antarctic subglacial lakes a google search will turn up a banquet.)

Antarctica is a giant laboratory for all different branches of science... the less contamination there, the better.

Some other Antarctic science links:

[http://amanda.wisc.edu]Muon & Neutrino Detector Array (AMANDA)

[http://astro.uchicago.edu/cara/]South Pole Astrophysics (CARA has evolved into some newly-named entity which I can't find, but all the instruments are still down there gathering data...)

Well, back on-thread, nothing wrong with nukes in space IMO, as long as they're used outside the Earth's magnetosphere. I'm all for em... I think JIMO will be a big first step toward making this tech practical, if it survives the congressional knife.

Michael Bloxham · 2004-02-02 21:36:36

The Navy had to remove its reactor as part of the antarctic treaty of 1959. Tons of 'contaminated' soil was removed from the site, not as a precaution, but under treaty rules. And yes, the site may still be radioactive, but since it is largely isolated (perhaps not at this site) from the ecosystem, it is of little danger to the environment. The surface of antarctica is mostly ice, the bedrock being up to 15,000 ft below. The ice sheet moves very slowly (taking thousands of years to reach the coast from the center of isolation), and there are areas that don't move at all. A slowly moving ice sheet is an extremely stable environment, nevertheless. At projected rates of global warming it would take millions of years for the ice to melt to sufficient depth, and by that time all the continents would have been flooded anyway... Finally, concerning nuclear fission power plants, antarctica may be one of the better places for a chernobyl type incident to occur: The atmospheric pressure over the extremely cold and arid continent is relatively low, (The extreme dryness of the air over the antarctic may be another advantage. This is all conjecture on my behalf, I'm not exactly sure of the science involved.) so winds there nearly always blow inward (towards the south pole) in a giant spiral; thereby containing radioactive air-borne particles. For this reason nuclear testing there may also be less environmentally damaging.

Hey, isn't this thread about space based nuclear power? My imagination has no self-control.

jadeheart · 2004-02-03 13:18:56

so winds there nearly always blow inward (towards the south pole) in a giant spiral; thereby containing radioactive air-borne particles. For this reason nuclear testing there may also be less environmentally damaging

Are these surface winds or at altitude? If you are referring to the circumpolar vortex which helps create the ozone hole, you're talking about high altitude circulation. But the surface is different, at least near the coast-- you get ferocious katabatic winds in the winter from the cold air falling off the 2-mi. high ice sheet. The question is, from how far inland do these winds come?

As for nuclear testing, there are several geological agencies which will have a problem with this if it is at the surface or below. Antarctica, being seismically quiescent, is highly valued as a platform for seismography of distant southern-hemisphere earthquakes. Shock waves from nuclear testing would be an interference.

While some parts of the interior are probably suitable for nuclear waste disposal, I think the economic barriers (due to transportation) will be insurmountable into the forseeable future. Not to mention political ramifications.

OK, I'll shut up now before this turns into a free-chat topic on the Antarctic...

Both releasing a few kilograms of plutonium (uranium?) into the atmosphere. And we're still alive, right?

yeah, but I have all these weird growths and sick-looking black moles all over my body, and my hair is falling out, and i can't hold down any meals... :laugh:

Palomar · 2004-02-03 13:28:40

*Let's please not let this thread (started by me) swerve onto Antarctica. Thank you.

I'm curious how persons here more knowledgeable than I about nuclear materials, etc., would respond to "greenie" organizations such as Greenpeace (no, I'm not a member of Greenpeace, just in case you are wondering) who are fully set on ending all nuclear programs and etc. I mean well-reasoned, pointed arguments pro-nuclear and against "the greenie" stance, as though you were debating the issue on "60 Minutes" for instance (NOT knee-jerk "damn you greenies, you blah blah blah treehuggers, nuclear forever!!" type responses).

What would you say? How would you defend nuclear materials, etc...especially as space exploration goes? What guideline for development do you approve or disapprove of as regards nuclear space? What standards should developers be held to, if any?

I'd offer my own thoughts, but again...I'm not greatly familiar with the subject. Right now my response is unfortunately limited to the observation of the fact that both sides seem nearly totally polarized on this issue and also I don't have a problem with nuclear space to the point that it is carefully managed, responsibly controlled, and has low impact on whatever environment it is found in...I suppose some might refer to me as a "minimalist" (but I'm not sure).

I'm really wet behind the ears on this topic, so bear with me PLEASE. I'm trying to feel my way through this topic.

I'm not seeking debate, but rather genuine input...your point of view (pro- or con-). Thanks.

--Cindy

Byron · 2004-02-03 14:08:17

What would you say? How would you defend nuclear materials, etc...especially as space exploration goes? What guideline for development do you approve or disapprove of as regards nuclear space? What standards should developers be held to, if any?
I'd offer my own thoughts, but again...I'm not greatly familiar with the subject. Right now my response is unfortunately limited to the observation of the fact that both sides seem nearly totally polarized on this issue and also I don't have a problem with nuclear space to the point that it is carefully managed, responsibly controlled, and has low impact on whatever environment it is found in...I suppose some might refer to me as a "minimalist" (but I'm not sure).

Well, I haven't given a whole lot of thought to this issue, but if you were to ask me how I feel about the space nuclear issue...I would say, yes, nuclear power should be kept open as an option for space travel and/or settlement. Unfortunately, the "greenies" have a very valid point about getting nuclear material from Earth into space, as there's a very real risk of an explosion upon takeoff and spreading nuclear material over a wide area. (I live in South Florida, so this is something I would be personally concerned about..lol.) I have no idea if it's possible to transport nuclear material in an inert state, so there would be no risk of contamination, but if they could, then I would have no problem with it.

This is why I feel so strongly about space elevators...to me, that would be the safest and most practical way to transport nuclear reactors and rockets up into space (and not just LEO, either.) I don't see why anyone would be opposed to nuclear power once it's put into use in space, as there's no worry of contamination (except for the astronants, of course.)

Of course, it goes without saying that future settlers should take every step possible to safely dispose of nuclear waste, making sure it doesn't cross-contaminate everything, etc.

B

TJohn · 2004-02-04 07:55:50

Cindy,

To get both sides of the issue, I suggest that you look at the [http://www.nuclearspace.com/]NuclearSpace and [http://www.space4peace.org/]Global Network Against Weapons and Nuclear Power in Space

Of course I'm biased to Nuclear Space!

Palomar · 2004-02-04 09:01:56

Cindy,
To get both sides of the issue, I suggest that you look at the [http://www.nuclearspace.com/]NuclearSpace and [http://www.space4peace.org/]Global Network Against Weapons and Nuclear Power in Space
Of course I'm biased to Nuclear Space!

*Thanks TJohn. I will check them out.

--Cindy

Gennaro · 2004-02-04 19:09:29

Hello.
Time for a stupid question, maybe. Let's just say it could be done. Does anybody know how dangerous the exhaust gasses of a ground launch nuclear thermal rocket would be?
After all, the working fluid has just passed through a red hot fission reactor.

Palomar · 2004-02-10 06:31:28

*There's currently (10 February 2004) a poll at space.com which asks: "Should the U.S. pursue nuclear-powered manned missions to the Moon and Mars?"

I was surprised at the results:

Yes, it's the best way: 87%
No, it's not safe enough: 13%

I thought more people would be opposed, or at least it'd be pretty much "Even Steven."

Um, by the way...why do we need nuclear power to get to the Moon? I'm not opposed to nuclear space, btw; I'm asking this in a practical vein. We've gone to the moon many times without nuclear power, it's not that far away, there is the free-return trajectory (provided you don't fire an engine along the way which destroys the FRT), etc.

?

--Cindy

Shaun Barrett · 2004-02-11 05:26:42

Maybe they don't mean using nuclear propulsion to get to the Moon but nuclear power to provide electricity for a lunar base(?).
I wonder whether people really appreciate how difficult living on the Moon will be during the long periods of cold and darkness. With temperatures dropping to -180 deg.C and no sunshine for 340 hours at a time, a nuclear reactor would be a good thing to have handy!

[P.S. I know there'll be ethereal Earthlight to provide at least some relief but there's still that searing cold to contend with.]

Byron · 2004-02-11 05:57:53

*There's currently (10 February 2004) a poll at space.com which asks: "Should the U.S. pursue nuclear-powered manned missions to the Moon and Mars?"
I was surprised at the results:
Yes, it's the best way: 87%
No, it's not safe enough: 13%
I thought more people would be opposed, or at least it'd be pretty much "Even Steven."
Um, by the way...why do we need nuclear power to get to the Moon? I'm not opposed to nuclear space, btw; I'm asking this in a practical vein. We've gone to the moon many times without nuclear power, it's not that far away, there is the free-return trajectory (provided you don't fire an engine along the way which destroys the FRT), etc.
?
--Cindy

My take is that most people who visit Space.com are avid space enthusiasts who see nuclear power as a practical means of space travel and power. Unfortunately, I don't think most people are thinking about the ramifications of getting nuclear engines/power plants out of Earth's atmosphere safely.

To me, that's the biggest obstacle to using nuclear power in space...getting it off-Earth in the first place.

B

Palomar · 2004-02-11 06:12:06

Maybe they don't mean using nuclear propulsion to get to the Moon but nuclear power to provide electricity for a lunar base(?).
I wonder whether people really appreciate how difficult living on the Moon will be during the long periods of cold and darkness. With temperatures dropping to -180 deg.C and no sunshine for 340 hours at a time, a nuclear reactor would be a good thing to have handy!

*Well, the question specifically centered on manned missions -- not bases -- but yes I do see your point (electricity, etc.).

That lack of daylight likely might cause some psychological difficulties (depression, restlessness, etc.)...ever heard of "seasonal affective disorder"? There'll be a different name for it on a lunar base (if one is ever established), but it'll be a problem for a few folks at least.

Byron: Unfortunately, I don't think most people are thinking about the ramifications of getting nuclear engines/power plants out of Earth's atmosphere safely.
To me, that's the biggest obstacle to using nuclear power in space...getting it off-Earth in the first place.

*I agree.

--Cindy

Byron · 2004-02-11 06:28:21

That lack of daylight likely might cause some psychological difficulties (depression, restlessness, etc.)...ever heard of "seasonal affective disorder"? There'll be a different name for it on a lunar base (if one is ever established), but it'll be a problem for a few folks at least.
--Cindy

If you look at the people who "winter-over" at the South Pole in Antarctica, there is plenty of evidence of depression induced by the lack of daylight and the usual 24-hour cycle; this is why such high priorty is placed on pyschological screening for these folks.

I'm hoping they'll (NASA, et al) quickly figure out that the Moon is nothing but a useless (not to mention costly) dead-end, and focus their resources elsewhere, like Mars...lol

B

GCNRevenger · 2004-02-11 08:58:43

Its not so much a question should we use nuclear fission, but how we use it... it would be pretty hard to store enough power on the Moon during the Lunar "night" produced by solar power. Plus, you would have to make much more energy during the "day" than your base needs. On Mars, with its winds and dust, keeping solar arrays clean enough to operate would be a major headache. Solar might be fine for driving non-essential equipment, but nuclear is vital for power. Period.

As far as a nuclear thermal engine is involved, there shouldn't be much fear that it would be used for ground launch, due to the high weight of the engine and the bulky liquid hydrogen tanks. As an upper stage though, it would work just fine... a well-designed Nerva NTR style engine would not produce a huge amount of "fallout," and it would be so finely dispursed that exposure would be essentially zero. US and Russian space nuclear systems have re-enterd before, and nobody was harmed; two of three of the American RTG units that came back down didn't leak at all.

In general, it would not be that hard to re-entry proof a decent sized reactor; graphite and carbide casings have proven effective at keeping Plutonium sealed tightly enough to prevent release, and the fuel itself is made of a sinterd oxide, nitride, or carbide, which won't vaporize readily, shatter into dust, or disolve in salt water in the event of a leak. Better yet, when dealing with a space reactor, Uranium-235 is simply not very radioactive. Uranium 235 is not very radioactive. The "bad" part is the daughter particles produced after the reactor is activated, not the Uranium, which would be effectivly trapped in the sinterd fuel matrix in any event, and would simply not be produced until the reactor is switched on... A freshly fueled reactor is no little more dangerous than a pile of dirt.

A little radiation won't kill you anyway, we are radioactive from the potassium and such in our bodies, and in fact we need some for our DNA to work.

Gennaro · 2004-02-20 08:43:22

About the "fear" of nuclear ground launch.

What about using ammonia instead of hydrogen for ground launch? Ammonia is denser which means less bulky and less heavy propellant tanks. It also has higher molecular weight which should translate into higher thrust at the cost of Isp.

Hull made of boron doped polyethylene (courtesy to Bill White in the Science & Technology section; love the sound of that!). Lighter and protects better against radiation than aluminium.

Small sized nuclear engine for a given performance pursued in order to cut down on shielding mass.

Maybe use depleted uranium for engine shielding instead of lead (though heavier, seems marginally superior).

What do you think?

GCNRevenger · 2004-02-20 16:08:31

The Russians actually did try this out I believe, but the Isp was pretty low, you might as well use regular LOX/LH2 engines... liquid Ammonia is no fun to handle either, since its somewhat toxic.

The lightest kind of shielding is no shielding at all... standing far enough away from a small reactor will protect you well enough when its running. Nuclear engines are heavy enough without adding a great deal of shielding mass to them, a nuclear thermal engine because of its very high operating power produces a vast amount of radiation (though not fallout) over its short lifespan, save the weight for crew/cargo shielding.

Uranium 238 would make TERRIBLE radiation shielding, because when it is struck by a neutron it can convert into much more radioactive materials, like Plutonium. Remeber the Breeder reactor? Just like that, except really really fast.

C M Edwards · 2004-03-05 08:59:31

Hello all.

I must contradict a misconception:

Hydrogen is not always the fuel that gives the most bang for the buck. For a thermal rocket propulsions system (like NERVA or a resistojet), in which the propellant is heated by the transfer of thermal power through heat exchanger, hydrogen can be one of the least desirable propellants to use.

Hydrogen has the highest specific heat of any known substance. This means that it can absorb considerable heat energy with only a small change in temperature. While it is true that hydrogen flows through a nozzle at a given temperature faster than any other gas at that temperature, getting the hydrogen to that temperature is problematic.

For example, a conventional chemical rocket engine burning hydrogen and oxygen propellant releases water as its exhaust. It can attain an operating temperature of about 4700K using the energy of that chemical reaction. (Any hotter and the water breaks back down into hydrogen and oxygen, taking energy away from the reaction.) At this temperature, it can attain an exhaust velocity of about 4.5 km/s. A thermal rocket having hydrogen exhaust only needs an operating temperature of 700K to reach an exhaust velocity of 4.5 km/s (the same as the H2/O2 rocket). However, reaching this 700K for any given thrust requires almost as much thermal power as burning the same amount of hydrogen and oxygen. In a chemical rocket engine, all this heat comes directly from the chemical reaction, but in a thermal rocket engine it has to come from contact with a heat exchanger (such as a nuclear reactor core). Thermal energy doesn't flow against an increase in temperature, which means that the heat exchanger has to be hotter than the fuel. And heat exchangers have specific heat, too -- likely much lower than that of hydrogen. So, if the hydrogen flow gets shut off without shutting off the heat source, the heat flow from the heat exchanger stops, causing heat to build up in the heat exchanger at the same rate it was being transferred to the propellant. That equates to applying nearly the same thermal power as you get from an oxy-hydrogen torch, over every part of the heat exchanger's surface simultaneously.

Under that circumstance, meltdown could take place in as little as a few seconds. Modern nuclear reactor controls are quite good, and could probably prevent a full meltdown even under these conditions in a properly constructed nuclear thermal rocket. But there would be extensive cracking and other thermal damage by the time the control rods got inserted from one end of the reactor to the other, which could result in release of nuclear material.

There are design features that could be incorporated into a thermal rocket to address this safety problem. However, only two of them do not drastically increase the mass of the thermal rocket engine:

1) Do not use hydrogen as a propellant (or anything else with an obscene specific heat),

and/or

2) Do not use nuclear thermal power as a heat source.

You may chose one, the other, or both. Either is effective.

Contrary to some opinions, neither of these is a show-stopper for thermal rocket propulsion. There are other propellants besides hydrogen, and there are other heat sources besides nuclear power.

Thanks for your time.

CME

GCNRevenger · 2004-03-05 09:49:28

I believe you may be overestimating how high a temperature need be reached to make a NTR practical, 3000K should be quite plenty to aproach 1,000sec ISP, and that can be tollerated without core damage by a good ceramic fuel long enough for the core to be quenched, which can be a very rapid process. Modern ceramics are quite resistant to heat, and modern turbopumps can be made nearly fullproof for a limited number of firings.

[http://www.inspi.ufl.edu/research/ntp/square/index.html]http://www.inspi.ufl.edu/research/ntp/square/index.html
Thats right, fuel elements capable of withstanding temperatures of up to 4000K. If you run your reactor at 3000K, then the whole thing should remain stable long enough below the 4000K limit to shut it down.

No other fuel except hydrogen makes sense, otherwise you may as well employ a regular chemical engine instead. The beauty of nuclear power is that it can meet the challenge and produce the vast amounts of thermal energy needed to heat the superlight hydrogen, its a feature not a bug.

GCNRevenger · 2004-03-05 15:50:17

I would also like to add, what would happen if a reactor were to fail and explode? The fuel is hard enough that it wouldn't simply vaporize, and infact could be made to come apart into large chunks like with a RTG. Large pieces of lightly to moderatly radioactive material are of little risk to the environment as a whole since their radiation remains localized, and are virtually harmless if they fall in water - which can effectively block radiation - since the material is insoluble even in salt water. Since it is likly any nuclear mission will be launched from KSC, even an exploding reactor would produce only a limited, localized radiation hazard.

Oh and nobody except the crazy USAF is proposing the use of an NTR engine for ground launch, and would only be used as an upper stage, so the reactor would not be powerd on until the reactor reached altitude, where if it did melt and partially vaporize, the material would dispurse and the dose on the ground would be minimal.

Edit//Addition: Oh, and don't forget, that Uranium reactor fuel unlike Plutonium RTG fuel produces essentially no harmful radiation until the reactor is actually switched on, so if it did blow up between the pad and power up, then you have a better chance of being killed by lightning than by cancer from the accident.

C M Edwards · 2004-03-05 17:26:07

Hello GCNRevenger.

I should clarify.

I am not fundamentally opposed to all possible instances of any use of hydrogen fuel, thermal rocket propulsion, or any combination of the two. You can, if you're willing to put in enough power, heat hydrogen to temperatures in excess of 700K -- the point at which its performance in a rocket engine becomes superior to any chemical propellant. Mechanically, one can make such a propulsion system operate without a meltdown. That's not my point.

I've got no problem with nuclear power, either. As long as it doesn't leak or disintegrate, a well shielded nuclear reactor is just one more heat source. Most of what I've said can be applied to resistojets, heat beds, or any other type of thermal rocket. That's not my point either.

My point is that there are better alternatives.

My principle difficulty with hydrogen as a propellant is the amount of power you have to put into it to make it work as a superior propellant, when there are other propellants that will yield similar performance at a fraction of the heat flow.

Two excellent examples are methane and ammonia. Both have much higher molecular weights than hydrogen in their stable, room-temperature forms. Fortunately, thermal rocket engines don't run at room temperature. Methane and ammonia have relatively low specific heats -- closer to that of water than hydrogen -- and break down into much lighter molecules with relatively low molecular weights -- closer to that of hydrogen than water -- at temperatures in excess of 1300K. And methane and ammonia require less than a third and less than a fifth, respectively, of the energy hydrogen requires to get to that temperature. That means that if you were really interested in pouring in enough power to make a methane (or ammonia) thermal rocket's exhaust velocity comparable to that of a hydrogen thermal rocket, you could do it and still have some power left over. You could produce higher thrusts using methane or ammonia as your propellant, at similar exhaust velocities, with a greater chance that your engine's heat exchanger would still be in one piece at the end of the day.

Thanks for your time.

CME

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