Video: Navy Tests 32-Megajoule Railgun
Popular Science:
Um, wow. This video comes from a test firing of the Navy’s Elecromagnetic Railgun (EMRG), which was carried out yesterday at the Naval Surface Warfare Center in Dahlgren, Virginia. The gun—which generates a powerful electromagnetic field to hurl projectiles at extremely high speeds—is rated at 32 megajoules, but the railgun engineers have to work up to that number slowly: this test was designed to reach a record-setting muzzle energy rating of 10 MJ. (The actual number turned out to be 10.64 MJ, according to Collin Babb with the Office of Naval Research.)
One big question this video begs is, what causes the giant fireball? Rail guns are supposed to be powered solely by electricity, and don’t use explosives of any kind for propellant. Babb told PopSci the answer: The flames are from pieces of the projectile disintegrating; the 7-pound slug is jammed so firmly between the rails that when it’s fired, pieces shear off and ignite in the air. There’s been some speculation online that the flames come from some sort of gas that’s been used to increase conductivity. Wrong: The EMRG uses no secondary propellant — just electricity. As a result, the breech can remain open during firing and the gun produces no blowback whatsoever. In fact, the researchers sometimes place cameras and mirrors inside the breech during tests to get a better sense of what’s going on.
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Ngowa Clyde!
February 2nd, 2008 at 4:49 amHere’s the ONR site:
http://www.onr.navy.mil/emrg/electromagnetic-railgun.asp
10.64 MJ shot = 2520 m/sec = 8270 ft/sec - not much bullet drop with that.
A 32 MJ shot with the same impactor would leave the muzzle at 4370 m/sec (14,340 ft/sec). They are getting up to orbital debris impact speeds. In contrast, meteors enter the atmosphere at up to 70,000 m/sec.
February 2nd, 2008 at 11:04 am