Drag is usually stated in pounds not horsepower. Drag is simply reverse thrust.
At 375 mph one pound of thrust equals one horsepower. At 750 mph one pound of thrust equals two horsepower. This is not a mere mathematical artifact.
Because the ratio for conversion of pounds to horsepower varies with speed, this is why doubling the speed increases drag only four times but requires EIGHT TIMES the horsepower.
Go to the link below for the underlying math and physics.
http://www.americanjetcars.com/nwsppr/misc/grounded3.htmPerformance for jet and rocket vehicles, whether they're cars, airplanes or missiles, is calculated using pounds of thrust and pounds of drag. To obtain the thrust available for acceleration, you subtract drag from thrust.
Rocket scientists never use horsepower unless they're talking to laymen.
When you calculate the pounds of thrust a car needs at 375 mph then calculate the horsepower a car needs at 375 mph you get EXACTLY the same number.
If you know the drag, weight and acceleration of a piston-engine wheel-driven car at a given speed you can calculate how much thrust its complete propulsion system (engine/drivetrain/wheels) is generating.
