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It's difficult to see how DT fusion could be better in space than alternatives. DT fusion reactors will be extremely large and complex. They will be much heav
by pfdietz 2y ago
It's difficult to see how DT fusion could be better in space than alternatives. DT fusion reactors will be extremely large and complex. They will be much heavier than and much less reliable than alternatives. That's not good for space applications.
The high energy density of the fuel is irrelevant if the reactor is very massive and if only a tiny fraction of the reactor's mass in fuel can be fused over the lifespan of the reactor. IIRC, it would take something like 700,000 years for ITER to fuse its own mass in fuel, if it could be operated continuously forever (which it can't, of course.)
- short_sells_poo 2y agoYou are correct, but I wonder if space travel applications allow us to take certain liberties with the reactor design that are not feasible down on Earth. E.g. a simple(r) confinement design that expels the fusion products could work well in space, but is a non starter on Earth for obvious reasons. I'm not sure how much of the design on Earth is bulky and cumbersome because it needs to be vastly safer and more complicated than what a rocket engine needs to be. Taken to the extreme, nuclear propulsion in space can be very dumb: just detonate nukes some distance behind the rocket and ride the shockwave with a pusher plate. It's a radically different design than anything we'd attempt for terrestrial applications.
- pfdietz 2y agoSure, but five orders of magnitude worth of liberties? The Orion spacecraft concept you mention will use fission bombs on any vehicle we might build soon. Thermonuclear driven interstellar Orion has been proposed, but the vehicle would be enormous (and take 400 years to reach the nearest star.)