Navy Gets 8-Megajoule Rail Gun Working

prototypo writes "The Free Lance-Star newspaper is reporting that the Navy Surface Warfare Center in Dahlgren, Virginia has successfully demonstrated an 8-megajoule electromagnetic rail gun. A 32-megajoule version is due to be tested in June. A 64-megajoule version is anticipated to extend the range of naval gunfire (currently about 15 nautical miles for a 5-inch naval gun) to more than 200 nautical miles by 2020. The projectiles are small, but go so fast that have enough kinetic punch to replace a Tomahawk missile at a fraction of the cost. In the final version, they will apex at 95 miles altitude, well into space. These systems were initially part of Reagan's SDI program ("Star Wars"). An interesting tidbit in the article is that the rail gun is only expected to fire ten times or less per day, presumably because of the amount of electricity needed. I guess we now need a warp core to power them."

Comments

95 miles altitude is space..Way Cool

[lecithin]

But I was thinking, is this a possible way to launch orbiting vehicles? I first think no, as the initial force necessary to 'shoot' something into orbit would probably destroy any delicate instruments needed for a working satellite.

  However, this seems very interesting as an Anti Satellite/"Star Wars" platform. If they can get the software working to intercept, this should (scaled up version) be able to knock out satellites, ballistic missiles, etc - shouldn't it?

Launch Loop

[cutecub]

You're talking about a Launch Loop.

Basically, its a magnetic rail gun for launching space-craft into orbit. And in order to avoid the crushing G-forces involved, it has to be hundreds of miles long. So, while it may not be economically or politically viable, it is technically feasible. We know how to build a launch loop, as opposed to a Space Elevator, which can't be constructed with current technology.

-Sean

Re:physics of railguns

[sjaskow]

Well, a little googling turned up this which seems to explain it better without of the nasty physics technobabble. And this is how to do it yourself.

Power is relative, I guess.

[LordByronStyrofoam]

When I worked on General Atomic's Doublet-III experimental fusion rector, in the early 80s the energy for the machine was supplied by a three-story motor-generator constructed below-ground at the site. The motor ran off 440V mains and when powered spun itself, the generator and a 400-ton flywheel at 480rpm. It took twenty minutes to get the thing up to speed.

During a 5-second 'shot', when the stored energy was released, the motor, generator and flywheel would go from 480 to ~100 rpm, and dump 960 mega joules of energy into the coils of the experiment. You could feel the vibration in your feet anywhere you stood at the site, all the CRT's images would collapse due to the intense magnetic field generated. Then it was another twenty minutes before they could do it again.

Re:Probably sufficient for a first stage.

[ceoyoyo]

The other problem is finding some sort of material that can survive the heating. If you're going to reach an orbit that doesn't take much fuel to circularize you're going to have to be going at more than orbital speed coming out of the barrel and fly at a fairly shallow angle to the surface -- through dense air. That's going to make the space shuttle's reentry look like child's play.