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Space Colony Art from the 1970s

settlement.arc.nasa.gov

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Re: Space Colony Art from the 1970s

#51

Post by DennisP »

dredmorbius wrote: post #50
DennisP wrote: post #47

Earlier quoted context omitted.

The fuel supply for conventional reactors is limited because they rely on U235, which is 0.7% of uranium. Fast reactors could use the rest of the uranium. That multiplies the supply by more than 100x because it means you can economically retrieve fuel from lower-grade ore, or even from seawater, which would extend the supply to millions of years. Russia has several fast reactors in production right now, and is buildi…

My understanding of seawater is that uranium concentrations are 0.01 - 0.02%, and that it's not thermodynamically feasible to extract it for energy at those concentrations.

A quick google of "extracting uranium from seawater" gives a different impression. For example: http://spectrum.ieee.org/energy/nuclear/nuclear-fuel-from-th...

...which says that EROI is 22 assuming a conventional reactor. Ie., we'd get 22 times as much energy out as we spent on extraction. With a fast reactor the ratio would be a hundred times better, since we could use all that uranium instead of 0.7% of it.

Re: Space Colony Art from the 1970s

#52

Post by DennisP »

DennisP wrote: post #51
dredmorbius wrote: post #50

Earlier quoted context omitted.

My understanding of seawater is that uranium concentrations are 0.01 - 0.02%, and that it's not thermodynamically feasible to extract it for energy at those concentrations.

A quick google of "extracting uranium from seawater" gives a different impression. For example: http://spectrum.ieee.org/energy/nuclear/nuclear-fuel-from-th... ...which says that EROI is 22 assuming a conventional reactor. Ie., we'd get 22 times as much energy out as we spent on extraction. With a fast reactor the ratio would be a hundred times better, since we could use all that uranium instead of 0.7% of it.

Also, geological processes bring more uranium to the surface, and rivers are constantly putting more uranium in the oceans, at a rate that would provide 25 times our current electricity usage. If we keep our usage at that level, uranium will last until the sun goes out.

http://www-formal.stanford.edu/jmc/progress/cohen.html

Of course in the context of the current discussion we should also consider the possibility of getting uranium from various other spots in the solar system: http://nextbigfuture.com/2009/08/how-much-uranium-is-in-sola...

Re: Space Colony Art from the 1970s

#53

Post by dredmorbius »

marktangotango wrote: post #48
dredmorbius wrote: post #38

Earlier quoted context omitted.

I suspect the powersat evolved as a mission justification: so, we can conceive of human-habitable structures in space, but why would we do that. From Heppenheimer's book, it seems that the colony concept emerged first, then the powersat concept. Once you've arrived at "orbiting solar power stations built from lunar regolith", questioning your premises and realizing that the colonies really don't make all that much se…

>> It's given me a good sense of the sorts of change which are possible and likely, and those which aren't. And no, not all progress is subject to Kurzweil's Law of Accelerating Returns. Indeed, we may be in Vinge's "Age of failed dreams".

Interesting Vinge reference. I wasn't familiar with that.

Re: Space Colony Art from the 1970s

#54

Post by dredmorbius »

evantish wrote: post #45
dredmorbius wrote: post #40

Earlier quoted context omitted.

Not enough fuel. Projections that there's enough uranium for 200 years[1] are based on levels of present utilization: around 3.7% of global energy use[2]. Bump that to 100% and we'd run through all available reserves in less than a decade (7.4 years, if you're counting). Solar energy (including solar mediated via plants, wind, or water), hydrogen fusion, possibly geothermal energy, or with really long odds: hydrocarb…

typeof fusion !== typeof fission

Sorry?

I'm not claiming otherwise.

Re: Space Colony Art from the 1970s

#55

Post by rbanffy »

sirkneeland wrote: post #26
rbanffy wrote: post #18

Earlier quoted context omitted.

Mars colonies, at least, can rely on Nitrogen and CO2 from the Martian atmosphere. Orbital habitats have to import everything but sunlight. Having the colonies underground may have an extra advantage, both on Mars and on the Moon, as they may be closer to sources of ice. I remember hearing something about the Moon being much less dry than previously thought. No running water nor blocks of ice, but maybe crunching roc…

"No running water nor blocks of ice, but maybe crunching rocks yields something useful" Space Fracking?

The bright side is you have no ecosystem to worry about.

Re: Space Colony Art from the 1970s

#56

Post by rbanffy »

afhdshufdufdo wrote: post #20
rbanffy wrote: post #18

Earlier quoted context omitted.

Mars colonies, at least, can rely on Nitrogen and CO2 from the Martian atmosphere. Orbital habitats have to import everything but sunlight. Having the colonies underground may have an extra advantage, both on Mars and on the Moon, as they may be closer to sources of ice. I remember hearing something about the Moon being much less dry than previously thought. No running water nor blocks of ice, but maybe crunching roc…

Right on. To add to this, early stage terraforming is in the immediate rather than long-term plan for Mars. As soon as we start producing CO2 on Mars, we're on our way. I'm not against colonizing space itself, but early seagoing explorers didn't attempt to colonize the ocean. We need to establish ourselves in environments that allow easy production of oxygen, water, and food. In the end, it is about money. It takes a…

There is no reason to require the place to hold an atmosphere - you just need to build your colony underground (which you already have to do to protect it from radiation). The Moon may be interesting for magnetic launch systems (no atmosphere, plenty of energy and reduced propellant requirements) and all kinds of metallurgic processes (no atmosphere, low - but not too low - gravity). Mars is also interesting if you can industrialize the manufacture of fuel and oxidiser from the atmosphere - gravity is low enough you can make it into a chemical rocket fueling station (landers and such will still use chemicals for a long time), at least until we develop some icy moons further out.

Re: Space Colony Art from the 1970s

#57

Post by dredmorbius »

TheSpiceIsLife wrote: post #43
dredmorbius wrote: post #40

Earlier quoted context omitted.

Not enough fuel. Projections that there's enough uranium for 200 years[1] are based on levels of present utilization: around 3.7% of global energy use[2]. Bump that to 100% and we'd run through all available reserves in less than a decade (7.4 years, if you're counting). Solar energy (including solar mediated via plants, wind, or water), hydrogen fusion, possibly geothermal energy, or with really long odds: hydrocarb…

I've read that Thorium and Fast Breeder technology pushes that out to somewhere beyond 50,000+ years - http://www.skepticforum.com/viewtopic.php?f=18&t=21247

Looking over that page, there's a critical error materially affecting his supply estimate.

Rob Lister gives global annual energy consumption as 140 TWh.

The true number is 211,782 TWh, for 2011, from IEA (expressed as 18,210 Mtoe -- million tons of oil equivalent)

http://www.iea.org/Sankey/index.html

That's 1512x higher than Lister's value. Dividing his 64,000 year supply by 1512, we get 42 years supply of thorium.

I see a problem.

Re: Space Colony Art from the 1970s

#58

Post by bdunbar »

ekianjo wrote: post #35
bdunbar wrote: post #31

Earlier quoted context omitted.

Well, we also didn't have the Cold War go hot. Win some, loose some.

Maybe, but we are still stockpiling weapons that can destroy our whole civilization at any time. It's not because we are currently in a relatively peaceful era that it's going to last in the long term.

Yup. That's a reason why I'm a big fan of the High Frontier, space exploration, and settlement.

So when something goes boom, here, there will be some people, elsewhere, to help rebuild.

Worst case, the species will carry on.

Re: Space Colony Art from the 1970s

#59

Post by onnoonno »

dredmorbius wrote: post #57
TheSpiceIsLife wrote: post #43

Earlier quoted context omitted.

I've read that Thorium and Fast Breeder technology pushes that out to somewhere beyond 50,000+ years - http://www.skepticforum.com/viewtopic.php?f=18&t=21247

Looking over that page, there's a critical error materially affecting his supply estimate. Rob Lister gives global annual energy consumption as 140 TWh. The true number is 211,782 TWh, for 2011, from IEA (expressed as 18,210 Mtoe -- million tons of oil equivalent) http://www.iea.org/Sankey/index.html That's 1512x higher than Lister's value. Dividing his 64,000 year supply by 1512, we get 42 years supply of thorium. I…

That's only proven reserves, though. Thorium right now is in basically no demand. Given the extremely high energy density of the fuel, A LOT of ores will become economically extractable.

It might not be 64ky, but >1ky seems to be very realistic.

Edit: See also the Wikipedia section on it: http://en.wikipedia.org/wiki/Thorium#Reserve_estimates

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