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Comment by mcguire | Hacker News Reader

1) "The system charges for two minutes..." One shot per two minutes is pretty bad; the current 5" gun shoots 16-20 rounds per minute.

2) "...at speeds up to Mach 6." One of the issues with old school, large caliber naval guns was that the blast from the guns would damage or destroy equipment near the muzzle. (I was just reading Pursuit by Ludovic Kennedy, about the British pursuit of the Bismark, and (IIRC) one ship (the Prince of Wales?) had its bridge windows blown out when firing the B turret "over its shoulder".) Is the shockwave from a railgun going to be similarly dangerous?

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No because "chemical" guns accelerate their loads by putting enormously high pressure gases behind them. Obviously, then, once the load is off the gases spew out the end (and make a really, really loud bang noise). Railguns, IIRC, use a chemical charge to get the first couple of mach but then the magnets to pull the load to full speed so it's not followed out the barrel by a mountain of hot gas.

The flames you see coming out the end are chemical charge and/or bits of the sled melting and it travels down the barrel. (people who know better, please feel free to correct me)

Thanks, that answers a question I had about the flames/discharge after the round exits. I expected to see nothing other than the round.

A good question to ask is if it would still take 2 min if hooked up to a ship's nuclear reactor power grid, or if the 2 min is more of an artifact of it being an alpha test rig designed more for data and refining the design.

I'm positive that at the very least they've got plans for making the version fire faster than one shot ever 2 min in a production model, even if that means throwing 16 times the hardware / capacity at the charging and cooling components.

A previous article mentions a "a five shots per minute minimum goal": https://www.thedrive.com/the-war-zone/12716/watch-the-navys-...

No, beyond the initial propellant. The projectile accelerates constantly (hand waving here) so it's a constant force on the origin (relative mass should make this a wash), whereas the projectile enjoys exponential velocity.

Two minutes is pretty short, I'm actually blown away. If only we could all charge our electric vehicles that quickly.

Nitpick: the velocity grows linearly, not exponentially.

Most of the muzzle blast from a powder gun is from the hot gases that escape after the projectile, not the shockwave from the projectile itself. The rail gun has very little hot gas escape so the blast should be much diminished.

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