In the atmosphere, craft may use aerodynamic effects to their benefit. As you start getting higher in the atmosphere, the atmosphere becomes rarified, requiring you to model the atmosphere not as a fluid but as the interaction of a bunch of individual air molecules probablistically impacting your vehicle.
Until you get going fast enough, at which point you start getting aero forces again.
This got me thinking: since space is not actually a pure vacuum and there is a little bit of "stuff" everywhere, how fast does a body have to travel to start making use of aerodynamic effects? I expect the answer may be different within a solar system vs outside one, though clarifying this would be appreciated.
My first visual w.r.t. this question is from Stargate where they fire an AMRAAM in space... but AMRAAM doesn't have vectored thrust and its fins wouldn't work. But what if it was traveling really, really fast?
A side question which you may choose to add to your answer or not if it is relevant: will other forces dominate before aero forces become significant?
