[quote] resulting in about 8 x 10^27 joules kinetic energy[/quote]

Not actually accurate. That is a severe underestimation. 

We are all familiar with K=1/2 MV^2, however that is only an extremely accurate approximation at low speed. The actual equation is K=(mc^2/(1-(V^2/c^2))^0.5)-mc^2. The first term calculates the total energy and the second calculates rest mass. Subtract rest mass from total energy, you get the energy of motion.

Firing at the speed of light would require infinite energy, and firing over is similarly impossible.