25 December 2010

Navy Demonstrates a 33 MJ Railgun

Some notes on the video below
The US Navy Surface Warfare division has set a new record for "muzzle" energy from an electromagnetic railgun. (see also here).

You really cannot determine the mass or size of the projectile accurately from the video, but given an energy of 33MJ, and its size appearing near to that of a 5" naval round, one could assume a mass of the round of somewhere between 10 and 32 kg. (The latter is the weight of the current 5" round)

This would give a velocity of somewhere around 1500 to 2500 m/s (5000 - 9000 km/h, 3000-5500 mph, or Mach 4-9.5).

By way of comparison, the 16 inch guns on the Iowa class have a muzzle energy of about 410 MJ, 1225 kg at 820 m/s, but velocity here can translate into a lot more range, something well in excess of 200 km, and this technology is in its early stages, so achieving an order of magnitude improvement in energy is certainly possible.

A note, based on comments with people who have used capacitors to use an arc to generate hypersonic shock waves for high speed simulations.

First, the power cables are almost certainly coaxial to minimize impedance, and the sheath on the outside is doubtless very heavy, because the high current generates forces that would otherwise blow the conducting jacket off. (in the wind tunnel case, the capacitor room looked "like a porcupine turned inside out", I wish that I had been there for that.)


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