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

There is no air in space. The amount of resistance air gives at very high speed is absurdly huge. What they do with rockets is that they make them gain most of their speed higher up where the air is very thin or there isn’t any. The space shuttle is a good example. If you look at the chart I linked below, you will see that the shuttle gained most of it’s speed way above the altitude where commercial jets fly (that is about 10 km in metric).
[https://www.quora.com/Does-the-space-shuttle-heat-up-when-exiting-the-atmosphere-like-it-does-on-re-entry](https://www.quora.com/Does-the-space-shuttle-heat-up-when-exiting-the-atmosphere-like-it-does-on-re-entry)