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
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.
* Space is mostly empty.
* Earth’s atmosphere is packed with air molecules.
* Compared to literally nothing (space) the air molecules create a huge amount of friction against the things trying to move through it.
The atmosphere is stuff and space isn’t. The shuttle Columbia didn’t get destroyed in space, but in the atmosphere because it was moving so fast. Remember they reentry heat is caused by compressing the air and not friction and is an issue with super fast planes as well. The SR-71pumoed fuel through the hot parts before the going to the engine to keep things cool and it ‘only’ went Mach 3.2.
Back to Columbia, the damaged insulation didn’t keep that heat away from parts of the structure and they failed. Now that it was unbalanced it tumbled, and the air tore it apart. None of that would happen in space.
In space nothing is slowing you down.
It’s kinda like the difference between bicycle and walking. With bicycle, using the same amount of energy, you end up going much faster. That’s because air is basically the only thing slowing you down when biking, but when walking you gotta keep moving your legs which adds extra energy requirement constantly slowing you down.
In space, you don’t have air slowing you down. No matter how fast you go, nothing is pushing against you, slowing you down.
If you need to explain this to a 5 year old have them wave their hand in the air then have them stick it in water and wave it. Tell them see how it was harder to move your hand in the water? That is because air is less dense than water. Space is even less dense then air so moving in space is easier than moving in air.
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