I created this in MSPaint a while ago, and I tried to analyze it. I'd like some second opinions about the validity of my analysis and the accuracy of the image.
The planet is Earth-sized; so, because it has a diameter of 137 pixels, each pixel is equal to 93 km.
The orbital bombardment is apparently launching the crust into space. Some ambiguity remains on the bottom of the picture; obscured by refalling debris, it is hard to tell the depth of the destruction. It appears to be about two pixels deep -- 180 km -- but for the sake of establishing a lower limit, I will assume only the 60 km crust.
On the bottom of the planet, there is a clear point where some debris is still traveling away from the planet, while others are falling back in. Thus, I conclude that debris was launched at escape velocity, so to establish a lower limit, I use escape velocity as a basis for the calculation. Interestingly, a time frame can now be determined: the slowest-moving debris is 20 px, or 1860 km, establishing 160 s as the approximate duration of the bombardment so far.
The energy imparted into the crust is then going to equal the kinetic energy of that portion of the crust moving at escape velocity.
v = escape velocity of an earth-sized rocky planet = 11.2 km/s
m = mass of bombarded crust = about half of the planet area * depth of the crust * density of the crust = (1/2)(9.5E7 km^2)(60 km)(2.6E3 kg/m^3)(1E9 m^3/km^3)
KE = (1/2)mv^2 = 3.6E26 J = 3.6E14 TJ = 4E14 TJ.
Over the time frame of 160 s, that comes down to about 2E12 TW.[/img]