tzor wrote:First of all, I'm not talking about recreating the sun, (fusion reactors still require more energy to initiate the fusion conditions than you get from the reaction)
Just to clarify things about fusion.
First, we probably won't be able to recreate the chain of reactions in the sun, ever, because it starts with two protium nuclei combining to form one deuterium nuclei.
Fusion reactors will be using the 2.0nd (D-D, preferably) or 2.5th (D-T) stages. Deuterium is present on Earth in larger quantities and is not radioactive. Tritium is radioactive; storing and using large quantities of tritium presents a complex engineering problem. Achieving ignition on tritium is substantially easier and will probably happen in our lifetimes.
Two basic principles have been proposed: steady state reactors and pulse reactors.
A pulse reactor is essentially a very small bomb. The #1 and #2 problems with pulse reactors are that no one knows how to collect energy* and how to shoot fast enough to be in any way viable.
*
Note that Wikipedia says collecting energy from pulse reactors will be so much easier. To make a stupid analogy, a steady state reactor is like a 30 meter high insane scuplture of T-bars welded together, and a pulse reactor is like a 20 kg metal ball, and the task is to break any of them with your bare hands.
The #1 problem with steady state reactors is the lack of construction materials that (1) won't fucking melt and (2) won't gobble up radioactive tritium to be released when you least expect it. Ignition (self-sustaining reaction) has not been achieved but it's largely a matter of time and funding.
ITER will likely achieve ignition (shutdown in 2038), DEMO (preliminary experiments start in 2033) is supposed to actually produce consumable energy and PROTO (to be constructed when pigs learn to fly at supersonic speeds) will hopefully be commercially viable. ITER and DEMO are D-T reactors, which means delicious, delicious tritium, slippery like an eel dipped in KY, poisoning everything with radiation. Note, however, that even D-D reactors won't be super clean because runaway neutrons
will fuck up the reactor walls.