[Bob]

I’m still trying to convert magajoules to megawatts...

One megajoule is one megawatt of power expended over a one second time period. Since I'm fairly sure that the firing energy is applied over a much shorter time, the peak power is probably in the range of hundreds of megawatts.

[Eric in the Ozarks]

I’m looking at a standby electric generator for my house. I need 26 amps for the furnace, and another 10 for the fridge, microwave and computer. I think I can get by with a two cylinder motor, fired by propane. Fortunately, I have not been confronted with joules yet...

[pjd]

Since I'm fairly sure that the firing energy is applied over a much shorter time, the peak power is probably in the range of hundreds of megawatts.

You're right. I estimated that, if the rail gun is 10 meters long, and assuming constant acceleration, it should take the projectile about 0.008 seconds to accelerate from rest to mach 7.

Thus, if the total energy is 1 MegaJoule, the power is about 125 MegaWatt - unless I made a stupid mistake, here.