Thruster Control Via Environmental Detection

Hey

I'd like to author a script that will enable thrusters based on the environmental conditions. For example, a drone lifting off earth under atmospheric thrusters will get to about 8km or so, at which point the script would switch off atmospherics, and enable hydrogen thrusters. And at a higher altitude or when no gravity is detected, hydrogen thrusters would be switch off and ion thrusters enabled.

I did some searching and really couldn't find anything applicable.