Re: what's the big deal about 1000 mph?
Although it is somewhat arbitrary, it also happens to be around where the laws of physics come into play to define a theoretical maximum based on our current technologies. See https://en.wikipedia.org/wiki/Drag_(physics)#Power for why we can't generate enough power to overcome the drag within a buildable vehicle. At least, safely. It might be possible to put a rocket on its side with some wheels but going fast is only half the equation. Staying on the ground and stopping safely is just as important !