More Words, Deeper Hole

Fixed.

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kithrup.livejournal.com

I'm only against it if it's not done sustainably.

Sustainable unicorn harvesting is the only way the industry can survive, long-term.

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No, we need to EXTERMINATE THE BRUTES!!! EXTERMINATE THEM, I SAY!!!.

(Reasons: to be published on tor.com at the end of September.)

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Unicorn meat, however, is totally ok.

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nathan helfinstine (from livejournal.com)

I only purchase meat from free-range unicorns. Virgin-caught unicorns are kept in cruelly-small pens-- I've seen the tapestry!

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heron61.livejournal.com

What a bizarre argument - the practical argument against Lunar He3 are obvious, but protecting the landscape of a lifeless rock ball?

From: (Anonymous)

which is what philosophers are paid to do.

is the Moon a culturally significant object? I think we can all agree that it is. well then, is it okay to strip-mine culturally significant objects? you wouldn't want to use Stonehenge or the Pyramids as stone quarries, right?

I think his argument breaks down pretty quickly -- mining the surface of the Moon is comparable to scraping a very thin layer off the surface of the Pyramids, not quarrying them. but it's not a question so stupid as to not be worth raising.

Doug M.

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fridgepunk.livejournal.com

Actually it's more like scraping the top 5 millimetres off of the Atacama Desert - you'd only be destroying some of the most interesting and scientifically useful elements of the Moon.

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Actually, no. We only get to touch the pristine, unmodified lunar surface once. Thereafter, we've changed it. This is a heritage issue for the human species; by going for large-scale resource extraction we are placing our short-term energy requirements over the long-term historic record.

Let me give you an analogy: suppose we determine that there's shale oil under the center of Rome. We can go fracking and extract hydrocarbons! Trouble is, those minor earthquakes will cause the Colliseum and most of the historic center to collapse. (Posit for a moment that remediation is not possible in this example.) Do we have a right to discount the future utility of first-hand access to the historical capital of the Roman empire, for all future human beings, against our short-term convenience?

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What have the Romans ever done for us?

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maruad.livejournal.com

They gave us the Roman nose (it is an old joke I stole from my grandfather).

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And roamin' hands (an old joke from my grandmother).

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All right... all right... but apart from better sanitation and medicine and education and irrigation and public health and roads and a freshwater system and baths and public order... what have the Romans done for us?

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andrewducker

Personally, I care about Rome.

I don't care about the surface of the moon.

I understand that some people feel differently though.

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Do you care about scientific information from the surface of the moon?

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andrewducker

What kind of scientific information?

Because, maybe. I'd need to weigh it up versus whatever we got from utterly destroying the moon and then carving thousand mile long adverts into it.

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History of rate/size of impacts over time.

Information about the formation of the Earth.

Passage of the solar system through interstellar clouds.

Possible preservation of ancient DNA (ejected off the Earth in large impacts and preserved in cold traps at the moon). Maybe dinosaur DNA!

Information on cosmic radiation in past times.

Information on solar activity in past times.

If interstellar meteoroids have struck the moon, particles from them should be mixed into the regolith. Studying the isotopes in these would be invaluable.

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bruce munro (from livejournal.com)

It's a big ol' Moon: surely we're not going to strip the whole surface anytime soon? (And if the resource is quickly exhaustible, it's a poor choice of location anyway).

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chrysostom476.livejournal.com

By the same logic, humans should have never touched any portion of the Earth ever.

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That logic is in fact applied, by international consensus, to Antarctica.

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chrysostom476.livejournal.com

And I think that leaving large portions of the Moon's surface untouched, a la Antarctica is a fine idea.

I think saying we could not use the moon AT ALL is not reasonable.

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sesmo.livejournal.com

The dust just hasn't been the same, since we started mining.

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baeraad.livejournal.com

I keep hearing about lunar Helium-3 around here, and I always feel like I'm missing the joke. I don't suppose anyone could explain to me first what the whole fascination with Helium-3 is all about, and then explain to me why it's stupid?

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gareth-wilson.livejournal.com

It's an impractical fusion fuel not particularly common on the Lunar surface.

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It's a fusion fuel for a type of reactor nobody knows how to build yet.

Its relative abundance in the lunar regolith is roughly the same as the relative abundance of heavy water (D2O) in the Atacama desert.

He3 is rare enough that it's one of the only physical commodities that might be worth mining on the moon -- if we needed it in bulk for burning in magic unobtanium-burning fusion reactors that don't exist.

Even so, the energy costs of GOING TO THE MOOOOOOON!!!1!!!11ELEVENTY!!!! to mine the He3 are so outrageous that we'd spend 20-25% of the net energy dividend just on shipping.

Shorter version: "we can go to the Moon to mine He3 because FUSION!!" is a Hail Mary pass by the Space Cadets to come up with some kind of economic justification for colonizing the Moon. Unfortunately they dropped the ball. Which was made of lead. And the goal posts don't exist.

(If I ever write a book or story with Lunar He3 mining, it'll really be about new and exciting innovations in fraud.)

Edited Date: 2013-08-29 10:39 am (UTC)

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Actually, the energy cost of getting from the Moon to the Earth isn't all that large, esp given the (relatively) small amount we'd need. It's getting it out of the regolith in the first place that eats energy.

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I mean, think about how dinky the mass ratio of the Apollo return leg was. And that was using chemical reactions.

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maruad.livejournal.com

Perhaps it could be fueled with Uup.

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That's right -- when the 3He concentration in the regolith is only 10 ppb, you can't spend much energy per kilogram of regolith or you go energy negative. And the payback has to high, since energy on the moon is going to be rather more expensive than energy on Earth (due to the cost of building and operating things on the moon.)

Once the 3He has been extracted and concentrated by eight orders of magnitude, the mass-dependent energy costs become much more manageable.

One thing to consider about lunar 3He is that all our measurements have been at fairly low lunar latitude. It's possible there's higher concentrations in the regolith near the poles, since the rate of diffusion of implanted 3He should be strongly temperature dependent.

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kithrup.livejournal.com

(If I ever write a book or story with Lunar He3 mining, it'll really be about new and exciting innovations in fraud.)

Ah, so you have started out planning the prequel to Saturn's Children!

duck

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ilya187.livejournal.com

(If I ever write a book or story with Lunar He3 mining, it'll really be about new and exciting innovations in fraud.)

Hope you will write it! (But set in near future, not post-Saturn's Children)

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mmcirvin.livejournal.com

After the Gerard O'Neill vision of an L5 colony/solar-power-satellite economy went out of fashion, fans of large-scale space expansion needed some kind of other justification for why people should do it. Mining helium-3 from the Moon emerged as one of the favorites, even though it doesn't make any sense on its own terms for a variety of reasons.

The space-fan party line is that this is a better and cleaner form of nuclear fusion than deuterium-helium, which is not clear in itself (and of course nobody's taken either type to the point of practical power generation), and that it makes more sense to get 3He from the Moon than to get it on Earth, which it doesn't.

From: (Anonymous)

It's cheaper to manufacture Helium-3 from tritium here on Earth; and if we had fusion power (which we DON'T) it would probably also be cheaper to scoop-mine it from the atmosphere of a gas giant.

It's another stupid marker.

Doug M.

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D-3He is the next easiest fusion fuel combination after D-T. By "next easiest" I mean "50 times less reactive". But it also produces a much lower fraction of its energy output in neutrons, especially if the tritium from DD side reactions can be removed before fusing, which helps solve one of the probable showstoppers for DT fusion (the first wall turning to shit due to every atom in it being displaced like a billiard ball 100 times a year.)

Manufacturing 3He on earth with fission reactors is a non-starter for enabling a "fusion economy". Each excess neutron from a fission reactor comes along with (optimistically) 100 MeV of fission energy output. This would enable the production of a single 3He atom, yielding just 18.6 MeV. So fusion would always be a minor adjunct to fission. In that case, why not just use fission?

3He breeding would be possible in DD reactors where tritium could be rapidly removed and allowed to decay. The levitated dipole is an example of this. Unfortunately, the US LDX experiment had its funding terminated in Nov. 2011 to focus on tokamaks. Not that it's anything to get too upset about, since even it would have been a long shot in the competition with more mundane energy sources.

Very long term, if they discover a moderate sized planet out beyond the Kuiper belt (say, Mars-to-Earth sized), it might be a good place to mine 3He, if the temperature at the planet's exobase was low enough to retain 3He in its atmosphere.

Edited Date: 2013-08-29 06:04 pm (UTC)

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100 Mev... heh. Oops.

But there could be other neutron sources. Spallation, say. Or fusors, though I'm doubting it makes energy sense to force D-T reactions to make neutrons to make He3 with, again unless one is specifically manufacturing rocket fuel.

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Spallation costs maybe 60 MeV of energy per neutron produced. And the best spallation sources are of fissionable materials, where most of the neutrons end up coming from secondary (subcritical) fission.

Spallation reactors might make sense for destroying higher transuranics (curium, etc.), which tend to have so few delayed neutrons when fissioned that you cannot operate a conventional reactor using them (far too much risk of going prompt supercritical -- BOOM). But if you're extracting and concentrating the transuranics for destruction, it's probably easier to just package them up and shoot them into space instead.

Fusors are fun toys, but cannot work as an energy source. Even as neutron sources, they really suck.

Edited Date: 2013-08-29 08:04 pm (UTC)

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What about Bussard Polywell?

Given existing rockets I have trouble seeing that as cheaper or safer than burnup.

Are you expert enough to comment on externally driven fusion rockets like Longshot? E.g. instead of trying to contain and extract power from fusion, simply using e.g. fission power to initiate fusion pulses that squirt out the way plasma wants to? I'd guess worst case it converts fission power to high impulse exhaust, best case you have net fusion energy dominating the exhaust and it's easy because you're not fighting the plasma. Mostly I'm wondering if it's as handwavy as everything else or if it's something we'd have a good chance of building if we wanted to.

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Polywell is bullshit. It's a sterling example of Asimov's corollary to Clarke's first law.

I don't know if Bussard was a con man in his old age, or just senile, but the entire affair was just deplorable. You will notice it has gone absolutely nowhere.

A spallation reactor burning a ton of transuranics a year would cost northward of a billion dollars. The current cost of launch a ton into orbit, on today's launchers, is maybe $5M (Falcon 9), and is projected to drop to about $2M on Falcon Heavy. Yes, shielding and a safety reentry package would be needed, as well as some means to boost beyond Earth orbit, but then these costs SHOULD continue to drop in the next few centuries.

I don't know anything about Longshot, but mixing heavy elements into a fusion plasma sounds like a tremendously bad idea, since they would cause fierce loss of energy to radiation (especially if they were only partially ionized, as they would be in a fusion plasma.)

Edited Date: 2013-08-29 09:24 pm (UTC)

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Why is it bullshit?
I keep hearing it needs $200 million for a proper experiment, so I don't know if "not going anywhere" means anything. One could conclude fusion in general is BS.

Boosting beyond Earth orbit is expensive, and I don't know why rocket costs should fall faster than reactor costs. Assuming between safety binding and GEO costs you get a factor of 3, that's $15 million per Falcon 9 ton. Granted, still compares decently to a billion dollar plant with even a 66 year lifespan. OTOH some of this stuff is really toxic and you really don't want it entering the atmosphere in a failure mode...

There's no mixing of heavy elements. A conventional fission reactor provides the electricity to cause fusion reactions to squirt out the rocket.

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The description of how Polywell was supposed to work never made any physical sense. It was never subject to scrutiny in the peer-reviewed literature (this should be a screaming red flag, btw), or if it was, it failed to pass muster for publication. The results they did report (in non peer-reviewed venues) were very inadequate to support any sort of optimistic assessment, or to bolster the case on how it was supposed to work. Conventional fusion, even if it is impractical, is subject to scrutiny to keep the players more or less honest.

Rocket costs should fall faster than reactor costs because we are building a lot more rockets than we are reactors. Generally, small things improve faster than large things. For the same reason, distributed energy systems (gas turbines, wind turbines, PV) are improving faster than large fixed baseload plants.

As for Longshot: so the fission part was just a distraction? Ok. That's basically "let's pretend we have a pulsed fusion reactor with mediocre Q". Not sure what that really buys you anyway, particularly if it's a DT reactor and 80% of the energy comes out as neutrons, which are pretty much useless for propulsion.

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Fission is where the driving energy is coming from but yes, the detail is unimportant. Like Daedalus, it envisioned D-He3.

"pretend we have a pulsed fusion reaction". Well, I guess that's what I'm asking about. I know that in a lab sense making fusion is easy; getting useful energy out sustainably has been the hard part. But what if you don't care about the fusion plasma being self-sustaining and happily let it escape? I envision it buying you exhaust at fusion fuel energy density and particle velocities, which is as good as we can hope for in an interstellar ship, short of antimatter or giant beams.

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This approach doesn't buy you much. The problem is the fission reactor will require large radiators to get rid of the waste heat, or will require a large mass flow to keep it cool. In the former case, the specfic thrust is bad, in the latter, the Isp will be bad (even if that mass flow is then heated by the fusion reactor output). So I don't really see what this is buying you, for the complexity/mass of having to add a fusion reactor.

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Well, given lack of progress in fusion power, any near-term interstellar ship would need fission for its primary power source anyway. So then the question becomes how to turn that into thrust: ion drive, heating up gas with lasers, lightbulb... Longshot sounded like a fusion afterburner as it were, compared to just hot gas.

The logic is that we're not choosing between fission-fusion and fusion, we're choosing between fission and fission-fusion.

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The system as described has, at high Isp, far too little thrust to be useful for interstellar travel. It's even of questionable value for the outer solar system.

Interstellar travel in reasonable time requires power/mass (in the vehicle) far beyond anything we can build today.

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Lucky you, you got snarky responses that skipped the actual point:
http://en.wikipedia.org/wiki/Helium-3#Fusion_reactions

The easiest form of fusion, D-T, spews lots of neutrons. It's actually way more neutronic per energy than fission, which both has rather high energy per atom (fusion is superior per mass) and consumes lots of its own neutrons.

2He3 fusion is aneutronic, making it safer as well as easier to extract energy from (just decelerate charged particles in an electric field! No need for steam engines!) D-He3 fusion is also aneutronic, but D-D side-reactions can spew a fair bit of neutrons on their own.

So He3 looks attractive to some for cleaner energy in general, or for use in space drives (since you don't need the mass of neutron shielding or of a heat engine), but it's really rare, and some people think He3 from solar wind has conveniently accumulated in the lunar regolith for mining. Others think that'd be an energetic loss and we'd be better off scooping the atmosphere of Saturn if we did this at all.

Note if one were really committed to space, He-3 mining could make sense even if an energetic loss; you'd be converting cheap energy into space-useful energy.

Except, of course, no one's gotten even D-T fusion working as a power source, and that's by far the easiest kind, so we get back to the snark: "you want to do this thing that may not pay off to fuel this other thing that you don't even know how to do?"

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11B+p (and the side-reactions) is cleaner than 3He+D (and the side reactions) and we can get boron down here on Earth. And a majority of it is the right isotope.

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fridgepunk.livejournal.com

I was faffing about with the notion of muonic doped atoms - basically take a regular atom like Carbon-12, and replace some of the electrons with muons that are artificially stabilised or regenerated somehow *handwave*.

One thing I found was that this µ-doping has been observed, in experimentally produced muonic helium at least, to basically make what ever atom you're doping behave chemically like a heavy isotope of an element with atomic number N-µ, where N is the atomic number of the original element you're doping and µ is the number of muons you've snuck into the lepton orbital around the nucleon.

So for instance, 2µ-C12 would behave a bit like Boron, and muons are produced by energetic cosmic rays so while I can't prove scientifically that all the carbon in the lunar regolith are muon doped and thus usuable in 11B+p fusion reactors, I am however tempted to do a powerpoint presentation suitable to get me booked into one of those "future of NASA" drinking and gnoshing events to tell all and sundry about how the hyper-abundance of muonic carbon on the moon and its use in terrestrial fusion reactors totally justifies and indeed REQUIRES the creation of lunar mining camps as a "sensible" solution to the US's shameful and dangerous dependence on foreign oil (gotta squeeze that terror$ teat, even if the foreign oil in question is really mostly canadian).

Note that that fact that all of is largely complete nonsense and gibberish would be less of an impedence to getting pride of place and heavily covered by news media at such a conference than a lack of a suitable engineering degree is not at all depressing or a sad testimony to the full absorbance of NASA by a click-whoring news media.

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