Using a really big gun to launch stuff into space has so far not been the most practical of ideas. A new concept explores the idea of building a cannon in the middle of the ocean, loading it with a thousand tons of cargo, and then launching the payload into orbit using an underwater thermonuclear detonation.
You'd start with a huge gun barrel. It would be a kilometer long, with a chamber at the bottom for the nuke. The entire thing would be submerged, and then you'd fill the chamber with fresh water before loading in the nuke itself with the payload vehicle on top protected by a sabot. All the air would be pumped out of the barrel, and then you'd find somewhere really really far away to watch from before you set the thing off.
On detonation, the fresh water in the blast chamber turns into a hypersonic plasma, propelling the launch vehicle up the barrel and out of the gun while simultaneously protecting it from the detonation itself. The blast chamber, gun barrel, and everything else nearby will likely be vaporized, but the launch vehicle will be moving too fast to care, and should be safely out of the barrel and on its way to orbit ahead of the actual explosion.
Now, I know thermonuclear detonations sound really, really bad. But this isn't an above-ground explosion: it's a deep underwater explosion, and it's estimated to be thousands of times safer (to humans, anyway) than any of those above-ground tests that we used to do all the time. It's basically the same as an underground explosion, except that the radiation would disperse itself through the water afterwards. That sounds bad too, but apparently the thinking is that the ocean is really big and can handle the occasional nuking, and detectable radioactivity would be gone in weeks.
A single launch from a system like this has the potential to send more material into space than every launch of the Saturn V rockets combined. A 150 kiloton nuke is estimated to have enough usable energy to send a 1,000 ton launch vehicle to the moon with a further 1,000 tons of cargo aboard. This is about the same mass as the space shuttle plus its external fuel tank and solid rocket boosters. The cost? Maybe $200 million, which is less than it costs to launch the space shuttle. That's under $100 a pound to get to the moon, and good luck finding a cheaper way to get there. Just make sure you watch out for that initial acceleration, since it's likely to turn you into a quivering puddle of goo.
Via Next Big Future