First conceived of in 1945, this is a rocket that replaces burning chemical fuel with a nuclear reactor that is used to heat up a propellant. This propellant is most likely hydrogen, though ...

No hydrogen-oxygen rocket of appreciable size has flown so far, but for a year Aerojet-General Corp. has been ground-testing hydrogen rocket motors at its Sacramento plant.

NTP was first theorized in the 1940s. Instead of burning chemical propellant, a rocket would use a nuclear reactor to heat propellant – most likely hydrogen.

"This must include sustainable liquid hydrocarbon fuels, electrification and hydrogen." Formula One is due to use 100% sustainable fuel from 2026 and plans to be net zero as a sport by 2030.