How is it that we engineer vehicles in space to travel for millions of miles at absurdly fast speeds? When we can only have vehicles on earth (jets) travel for thousands of miles at lower speeds? Why is the gap SO BIG?

Question

We can send vehicles/rovers to space and have them travel at very high speeds for millions of miles to other planets. But vehicles on earth (jets/planes) have significantly shorter range and speed. Why is this? ELI5

In: Physics

Answer 1

The atmosphere. In space, depending on exactly where you are, there’s basically no resistance. You can go as fast as you want and there’s nothing pushing back on you. Have you ever stuck your hand out the window and had the air blow it back? Imagine that at 25,000 miles per hour or more. Imagine what that would do the structure of anything going that fast. And the heat would pretty much vaporize anything. You know how spacecraft need heat shields to reenter the atmosphere so they don’t burn up? That’s what would happen to anything going that fast. The Concorde, which flew at roughly mach 2, got so hot that the inside of the windows were warm to the touch, an this was at an altitude where the air was already super thin and the outside temperature was 100 degrees below zero. Spacecraft go more than 10 times that fast.