Nasa has been testing the new RS-25 engine in America.
It's designed to go in the next rocket system which could take astronauts to Mars.
The tests check whether the engine can handle the extremely low and very high temperatures that it's likely to experience on its journey through space.
Nasa has described it as the most complicated engine on the market.
"It's the Ferrari of rocket engines," said Kathryn Crowe, one of the engineers on the team.