Left as exercises for the student:
Calculate the amount of energy required to heat 10,000 tons of steel to the point of boiling.
Calculate the power required to do this in ten seconds.
If 1% of this energy is absorbed by the air above the target, what will cameras and people looking at the target site observe?
What effect will 10,000 tons of steel vapor being generated in 10 seconds have on surrounding structures and observers? Determine radius of any resulting blast and thermal effects.
Determine the size of the power plant required to power this energy beam. Assume a fission-powered plant as the weapon will be in a vacuum.
Assuming 50% efficiency of energy conversion in the beam generator and power plant, calculate how the radiators required to handle the waste heat generated will be.
From the size of the radiators, determine their visual magnitude if placed in low earth orbit.
Produce a rough estimate of the combined mass of the beam generator, power plant, and radiators. Calculate the cost to place the entire assembly into orbit at current launch prices, and the number of launches required. Remember to include the cost and time required for in-orbit assembly if this will take more than one launch.
Determine the number of people required for the design, construction, assembly, and operation of this orbital weapon system. Propose a method for keeping them all silent.
Show your math on all questions. Any advanced technology assumed must be demonstrated to be at least theoretically possible.
Extra credit: come up with a plausible justification for pursuing the above plan rather than simply crashing airplanes into the building.