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mopc
2004-Dec-23, 04:05 PM
I was reading the excellent book Mining the Sky the other day and there's a lot there on how Solar System resources might provide us with unlimited energy especially when we master nuclear fusion, in particular fusion of helium-3. The book was written in 1996 and it says that some projects "are close to the brake-even point" where more energy is produced then consumed by the reactor.

What is the stand now? How important could fusion become in the next 50 years?

electromagneticpulse
2004-Dec-24, 03:18 AM
I was reading the excellent book Mining the Sky the other day and there's a lot there on how Solar System resources might provide us with unlimited energy especially when we master nuclear fusion, in particular fusion of helium-3. The book was written in 1996 and it says that some projects "are close to the brake-even point" where more energy is produced then consumed by the reactor.

What is the stand now? How important could fusion become in the next 50 years?

I would have to say very important its power to weight ratio is well amazing. I read something on ST designs using deuterium and tritium.
D + T -> He4 + N
I don't think it is as efficient as deuterium and He3 but we have almost no He3 on earth so there isn't much hope for it unless we start the Proton-Proton fusion process. Without that we're going to the moon, jupiter has enough fusion fuels to last 2,000 years burning as a star so a lot longer for us.

The next 50 years i think it would become extremely important, once they got it working i think it would quickly become the only power source used. I think there would still be use for solar power and natural ways as you need power just incase you need to start it again.

Van Rijn
2004-Dec-24, 04:13 AM
Break-even isn't that big a deal these days. The real issue is developing a practical commercial reactor. Typical estimates are 30-40 years for a practical D-T power reactor. D-He3 is much harder, so add one or two more decades to that. Then you need the He3, and it has not been demonstrated that lunar He3 mining could be practical or economical. Meanwhile, you can't test a D-He3 reactor without He3 ... pure chicken and egg.

My opinion is that Lunar He3 Mining is a "Holy Grail" energy solution that is long on hype and short on practicality. It just gets repeated all the time because of the mania about a so-called "clean" nuclear reactor. Let's build nuclear reactors that we know how to build. For that matter research on solar PV and advanced power storage would probably be a more worthy goal.

mopc
2004-Dec-24, 05:21 AM
Break-even isn't that big a deal these days. The real issue is developing a practical commercial reactor. Typical estimates are 30-40 years for a practical D-T power reactor. D-He3 is much harder, so add one or two more decades to that. Then you need the He3, and it has not been demonstrated that lunar He3 mining could be practical or economical. Meanwhile, you can't test a D-He3 reactor without He3 ... pure chicken and egg.

My opinion is that Lunar He3 Mining is a "Holy Grail" energy solution that is long on hype and short on practicality. It just gets repeated all the time because of the mania about a so-called "clean" nuclear reactor. Let's build nuclear reactors that we know how to build. For that matter research on solar PV and advanced power storage would probably be a more worthy goal.

But lets not forget that once we tap such huge energy source, we'll be able to travel to anywhere in the Solar System affordably, not to mention that here on earth abundant energy will foster a creative and technological revolution that will lead to unpredictable advances in every field, including new fusion reactors.

electromagneticpulse
2004-Dec-24, 12:31 PM
Break-even isn't that big a deal these days. The real issue is developing a practical commercial reactor. Typical estimates are 30-40 years for a practical D-T power reactor. D-He3 is much harder, so add one or two more decades to that. Then you need the He3, and it has not been demonstrated that lunar He3 mining could be practical or economical. Meanwhile, you can't test a D-He3 reactor without He3 ... pure chicken and egg.

My opinion is that Lunar He3 Mining is a "Holy Grail" energy solution that is long on hype and short on practicality. It just gets repeated all the time because of the mania about a so-called "clean" nuclear reactor. Let's build nuclear reactors that we know how to build. For that matter research on solar PV and advanced power storage would probably be a more worthy goal.

But lets not forget that once we tap such huge energy source, we'll be able to travel to anywhere in the Solar System affordably, not to mention that here on earth abundant energy will foster a creative and technological revolution that will lead to unpredictable advances in every field, including new fusion reactors.

Once they get a fusion reactor maintaining controlled fusion then they will start working on smaller ones. There is new advances on super conductors happening all the time, with better super conductors comes better magnetic confinement. Got them working at 180K now (IIRC) opposed to 1K when they were first been discovered.

We could make He3 with a plus if we get efficient enough, Deuterium-Proton fusion gives 5.49 MeV. Tritium breeding gives 4.8 MeV, D+T gives 18.3 MeV. Fission is a much less efficient reaction, which is why fusion is such a big deal. IIRC the only inefficient fusion reactions are after iron.

Ilya
2004-Dec-24, 04:08 PM
D + T -> He4 + N
I don't think it is as efficient as deuterium and He3


Sorry, no. D + T is easier to achieve than D + He3. The advantage of He3 fusion is that it is "clean" -- no neutron radiation. Neither type of fusion produces radioactive waste -- the bugaboo of nuclear fission, -- but any reactor not using He3 eventually becomes "hot" and must be disposed of.


but we have almost no He3 on earth so there isn't much hope for it unless we start the Proton-Proton fusion process. Without that we're going to the moon, jupiter has enough fusion fuels to last 2,000 years burning as a star so a lot longer for us.

Actually, at present there is over half ton of He3 on Earth -- inside aging fusion warheads. You most certainly DO NOT neet P-P fusion to make He3 -- it is decay byproduct of tritium. People have been making tritium for 60 years by now -- mostly for fusion bombs. The process is fairly easy and cheap -- just wrap a fission reactor in lithium blanket. Neutron bombardment turns lithium into tritium. If you are willing to wait a while (tritium half-life is about 13 years), you can get all He3 you want, much cheaper than mining it from Moon or Jupiter. For that matter, you can turn lithium into tritium (and ultimately into He3) with neutrons from D + T reactors.

Somehow, space/lunar mining enthusiasts never mention this :)

electromagneticpulse
2004-Dec-24, 05:04 PM
Sorry, no. D + T is easier to achieve than D + He3. The advantage of He3 fusion is that it is "clean" -- no neutron radiation. Neither type of fusion produces radioactive waste -- the bugaboo of nuclear fission, -- but any reactor not using He3 eventually becomes "hot" and must be disposed of.

My mistake, i just read what i found for the MeV's of the reactions i read ^3H as Helium 3 :oops:


Actually, at present there is over half ton of He3 on Earth -- inside aging fusion warheads. You most certainly DO NOT neet P-P fusion to make He3 -- it is decay byproduct of tritium. People have been making tritium for 60 years by now -- mostly for fusion bombs. The process is fairly easy and cheap -- just wrap a fission reactor in lithium blanket. Neutron bombardment turns lithium into tritium. If you are willing to wait a while (tritium half-life is about 13 years), you can get all He3 you want, much cheaper than mining it from Moon or Jupiter. For that matter, you can turn lithium into tritium (and ultimately into He3) with neutrons from D + T reactors.

Somehow, space/lunar mining enthusiasts never mention this :)

I understood that D+He3 gave about 0.6MeV more than D+T.

I know about tritium breeding i just forgot about tritiums beta decay to helium3. The only problem i can remember with the lithium breeding is that it would only give us about 130 or so years at the present energy use but that is still a lot of time and money saved before we need a trip to the moon. It's just is it more efficient to breed lithium and wait for the decay or take a trip to the moon and steal some of the He3 the solar wind dropped off.

Kaptain K
2004-Dec-24, 06:24 PM
How far are we from fusion?
About 20 years, just like we were 50 years ago and will be 50 years from now!

Am I the only one who remembers "Electricity will be too cheap to meter."?

Donnie B.
2004-Dec-24, 06:58 PM
Dang it, Kaptain, you ToSeeked me. i was going to say 20 years... it's always 20 years.

Van Rijn
2004-Dec-25, 01:08 AM
Sorry, no. D + T is easier to achieve than D + He3. The advantage of He3 fusion is that it is "clean" -- no neutron radiation. Neither type of fusion produces radioactive waste -- the bugaboo of nuclear fission, -- but any reactor not using He3 eventually becomes "hot" and must be disposed of.


Not truly aneutronic, though far better than D-T. There are the D-D reactions with some neutrons, and occasional other reactions given all the high energy particles flying around.

My bet is that true anti-nukes would still not be satisfied.



About 20 years, just like we were 50 years ago and will be 50 years from now!

Am I the only one who remembers "Electricity will be too cheap to meter."?


I know you are being ironic, but typical estimates today are in the 30 year+ range if you are talking about a practical power reactor (as opposed to advanced test reactors).

There have been serious advances in the last 50 years, but there are still a lot of problems. The "Too Cheap To Meter" issue is exactly why I'm not too excited about fusion. The reactors based on known concepts would be large and very complex. There is no reason to assume that fusion will lead to an energy revolution. We CAN have plenty of energy today, the issue is attitude, not available technology.

pteranodon
2004-Dec-25, 03:14 PM
The main problem is the huge energy input required to overcome the electrostatic repulsion between nuclei before the nuclear forces take over.

johnb
2004-Dec-26, 11:31 AM
How far are we from fusion?
About 20 years, just like we were 50 years ago and will be 50 years from now!

Am I the only one who remembers "Electricity will be too cheap to meter."?

No! I remember that quote as well. Since I was 15(at least) now I`m 45 and fusion is still 20-25 years away.

Celestial Mechanic
2004-Dec-27, 05:53 AM
Still about 150 million km... :wink: