[LNMNMMMC]

Never, more speed is good because they can program the projectiles to break apart before impact with soft targets. The limiting factor is air resistance, greater initial speeds result in more energy wasted.

Also, I believe they are (were?) looking at the Zumwalt destroyer for this weapon, which actually only has 78 MW of power output.

[tonmoy]

Does power really matter? 25MW instantaneous power vs continuous/average power are different things. With modern clever power electronics you could get pretty high instantaneous power from a lower powered source. The exact energy vs time curve and desired fire rate has to be utilized to make any effective prediction I think.

[myblake]

The article does mention advances in supercapaciter design as one of the enabling technologies, but I suspect just charging the things requires a ton of power. Let's do some back of the envelope physics with what we know (and reasonable ball park guesses when we don't)!

It's traveling 4K mph or about 1800m/s, let's assume since its 24in long and largely tungsten it has a mass of around 60kg. 1/2 * mass * velocity ^2 means it needs 97.2 megajoules of power. That's about 4 seconds for a 25MW reactor, so I guess you're right something smaller could fire it less rapidly, though the one every 6 seconds they cite as desired would require that much power.