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Their starship was bullshit. On earth they needed a big Saturn 5 like rocket to bring it into space and later they fly into orbit like it's nothing. If the planets they visited had much lower gravity then earth this may be possible, but this wasn't noticeable or talked about. And even on Mars you need much more fuel to get into orbit than could be stored in their tiny ship.
Eh, this isn't actually that bad. It's quite easy, using a jet aircraft, to (via a ballistic trajectory) get into space. Surrounded by reaction mass as you are, the rocket equation isn't nearly so bad. You could conceivably dock with something in orbit, if you had elastic tethers or something to make the acceleration survivable. If you're much lighter than what you're docking with, you won't knock the satellite out o…
A jet engine requires atmosphere. Spaces requires no (or very little) atmosphere.
The edge of space is usually defined at 100km (the Karman line).
The highest altitude reach by an air breathing jet is around 37km. https://en.wikipedia.org/wiki/Flight_altitude_record
A scramjet might get to ~75km according to: https://aviation.stackexchange.com/questions/44837/what-is-t...