NASA returning to NERVA?

Point out news stories, on the net or in mainstream media, related to polywell fusion.

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TheRadicalModerate
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Re: NASA returning to NERVA?

Postby TheRadicalModerate » Thu Feb 12, 2015 9:44 pm

Skipjack wrote:A little bit of radioactivity in the atmosphere is completely irrelevant. Besides, the hydrogen reaction mass barely gets radioactive anyway. Also want to point out that subsequent projects to NERVA demonstrated much higher T/W than 1, high enough to SSTO.


If we're talking about a solid-core engine, then yes, the radioactivity is trivial. If we're talking about a leaky solid core engine (which Tom was), we're probably fine unless we're talking about a sizable percentage of the core disintegrating, or a lot of flights with the cores disintegrating. On the other hand, a fission fragment rocket wouldn't be a good thing to use in the magnetosphere ever--nor would Orion itself.

Remember, all of this stuff is likely to enter in a localized region at the poles. What happens after that exceeds my meteorological competence. I can't think of a regulatory regime that would allow more than a few tens of terabecquerels of fission products per year to be deposited into the atmosphere, and the odds of anybody approving a fission-based SSTO seem vanishingly small if for no other reason than you couldn't get it to pass a safety review.

That said, I'd think that using even a dusty nuke would be relatively uncontroversial (except to the arithmetically challenged) as long as the exhaust trajectory didn't intersect the magnetosphere. I think we're stuck with chemical launchers until we can get some kind of fusion SSTO going.

MSimon
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Re: NASA returning to NERVA?

Postby MSimon » Thu Feb 12, 2015 9:49 pm

The economic problem of nuclear is not the cost of the reactor. It is the cost of the BOP.

Now if we could eliminate the BOP with something simpler.....
Engineering is the art of making what you want from what you can get at a profit.

Tom Ligon
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Re: NASA returning to NERVA?

Postby Tom Ligon » Thu Feb 12, 2015 9:59 pm

I think there will be a negative reaction to anything nuclear in space. Hopefully the US has the cajones to ignore the objections. Russia would build it without a second thought. I don't think the ESA would touch it, considering that they built Rosetta as a solar-powered mission, instead of using nuclear thermoelectric or thermionic power sources.

Skipjack
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Re: NASA returning to NERVA?

Postby Skipjack » Fri Feb 13, 2015 12:32 am

TheRadicalModerate wrote:
Skipjack wrote:A little bit of radioactivity in the atmosphere is completely irrelevant. Besides, the hydrogen reaction mass barely gets radioactive anyway. Also want to point out that subsequent projects to NERVA demonstrated much higher T/W than 1, high enough to SSTO.


If we're talking about a solid-core engine, then yes, the radioactivity is trivial. If we're talking about a leaky solid core engine (which Tom was), we're probably fine unless we're talking about a sizable percentage of the core disintegrating, or a lot of flights with the cores disintegrating. On the other hand, a fission fragment rocket wouldn't be a good thing to use in the magnetosphere ever--nor would Orion itself.

Remember, all of this stuff is likely to enter in a localized region at the poles. What happens after that exceeds my meteorological competence. I can't think of a regulatory regime that would allow more than a few tens of terabecquerels of fission products per year to be deposited into the atmosphere, and the odds of anybody approving a fission-based SSTO seem vanishingly small if for no other reason than you couldn't get it to pass a safety review.

That said, I'd think that using even a dusty nuke would be relatively uncontroversial (except to the arithmetically challenged) as long as the exhaust trajectory didn't intersect the magnetosphere. I think we're stuck with chemical launchers until we can get some kind of fusion SSTO going.

There are ways to prevent them from leaking. Some of the early prototypes had issues with the fuel matrix getting brittle after a while and fuel sputtering out with the exhaust. Modern materials (tungsten carbide and others) are less prone to become brittle and they allow for higher temperatures which means more thrust and/or higher Isp.

choff
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Re: NASA returning to NERVA?

Postby choff » Fri Feb 13, 2015 3:05 am

Whatever you do, don't tell the greens there's radiation in space, or they're going to demand a multitrillion dollar cleanup plan complete with radiation taxes, credits and currency.
CHoff

Maui
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Re: NASA returning to NERVA?

Postby Maui » Fri Feb 13, 2015 3:14 am

No I'm not.

Skipjack
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Re: NASA returning to NERVA?

Postby Skipjack » Sun Feb 15, 2015 9:31 pm

choff wrote:Whatever you do, don't tell the greens there's radiation in space, or they're going to demand a multitrillion dollar cleanup plan complete with radiation taxes, credits and currency.

I wished there was a "like" button here. I second that notion ;)

Maui
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Re: NASA returning to NERVA?

Postby Maui » Mon Feb 16, 2015 6:45 pm

Come on guys, seriously. Can we keep the petty strawman politics out of this the News forum? Remember, it was Nixon --not the Greens-- that killed NERVA in the first place.

KitemanSA
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Re: NASA returning to NERVA?

Postby KitemanSA » Mon Feb 16, 2015 11:09 pm

There are "Greens", and then there are "FauxGreens". Watermelons are FauxGreens but then so are the paid shills on the petro-carbon industries.

choff
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Re: NASA returning to NERVA?

Postby choff » Tue Feb 17, 2015 2:22 am

Sorry Maui, I'm not responsible and I'll try to remember not too do it again.
CHoff

MSimon
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Re: NASA returning to NERVA?

Postby MSimon » Tue Feb 17, 2015 6:47 am

KitemanSA wrote:There are "Greens", and then there are "FauxGreens". Watermelons are FauxGreens but then so are the paid shills on the petro-carbon industries.


Ah. but the petro-carbon boys deliver actual wealth. The Watermelons deliver negative wealth.
Engineering is the art of making what you want from what you can get at a profit.

alexjrgreen
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Re: NASA returning to NERVA?

Postby alexjrgreen » Tue Feb 17, 2015 2:37 pm

MSimon wrote:Ah. but the petro-carbon boys deliver actual wealth. The Watermelons deliver negative wealth.
Since this is a thread about the potential consequences of fission power in space, and since you've mentioned Watermelons, here's a quote from James Delingpole:

Imagine if it didn’t matter one jot how big your carbon footprint was and you could go out and buy as many Hummers as you liked or accumulate as many air miles as you wanted without the need to feel the slightest sliver of guilt about the environmental damage you were causing.

Any course of action that ignores or fails to account for its negative consequences is going to be problematic. An ecologically sustainable business plan makes more money in the long run, because it correctly accounts for all costs, not just the short-term ones. Ask Coca Cola, who've successfully implemented such a plan because it delivers better shareholder value.
Ars artis est celare artem.

GIThruster
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Re: NASA returning to NERVA?

Postby GIThruster » Tue Feb 17, 2015 5:36 pm

Maui wrote:Come on guys, seriously. Can we keep the petty strawman politics out of this the News forum? Remember, it was Nixon --not the Greens-- that killed NERVA in the first place.

Likewise it's worth noting that the Clean Water Act was overseen by Nixon, and the Comprehensive Environmental Response or Superfund, was created by Reagan. Conservatives have a history of championing environmental issues as these are part and parcel to traditional values. Most conservationists are conservative. Liberals mainly provide self-righterous adolescents to the cause and they don't do more than make a fuss. It's the conservatives to get down in the trenches and get real environmentalism done.
"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis

GIThruster
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Re: NASA returning to NERVA?

Postby GIThruster » Tue Feb 17, 2015 5:41 pm

alexjrgreen wrote:Any course of action that ignores or fails to account for its negative consequences is going to be problematic. An ecologically sustainable business plan makes more money in the long run, because it correctly accounts for all costs, not just the short-term ones. Ask Coca Cola, who've successfully implemented such a plan because it delivers better shareholder value.

You sound like you have real training in environmental science or environmental ethics. This is entirely right and a critical issue. Environmentalists are right to call our attention to the "hidden costs" of any issue but especially those that have negative environmental impacts.

Fission for space has more positive environmental impacts than negative, even given a terrible accident.

BTW, note it is Coca-Cola that is taking the Slingshot water purification system worldwide. That's going to save millions of lives in the short term and billions in the long term, all paid for by what most consider mere "greed" but in fact is a move toward vested self interest.
"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis

derg
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Re: NASA returning to NERVA?

Postby derg » Tue Feb 17, 2015 8:17 pm

Skipjack wrote:Also want to point out that subsequent projects to NERVA demonstrated much higher T/W than 1, high enough to SSTO.


Wasn't this contingent on ISPs of 1600 or more?


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