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

Rockets are pretty much perfectly inertial. Once they get up to speed, there are basically no moving parts or anything – they just keep going. The engines don’t even have to run for very long. Maybe a few weeks at most for an electric rocket engine, but usually on the order of minutes. Jets require turbine engines, which are under a lot of stress and have many moving parts at high temperature.