Well, it's pretty simple. Try to get the longest hover time on a spacecraft.
This is my first post on the KSP forums. I have been playing the game for a few years though.
Rules:
Must be between 10-1000m
Can't touch the ground during hover
No jet engines, only solid/liquid rocket fuel
No use of aerodynamics/wings to fly
Be honest :-)
A video isn't required but it would be better.
No parallel staging
No engine more than once
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vyznev - 9.5 minutes