In the United States, the NERVA project, which envisaged the use of a nuclear reactor to heat a propellant that would be used as thrust for a mission to Mars, was cancelled; this technology was successfully tested in the 1960s in New Mexico: 24 nuclear reactors were built, each with several GW of power; through the use of any gaseous propellant, it develops a thrust 10 million times greater than a chemical rocket with the same amount of propellant: a trip to Mars would be a matter of days; the return would be guaranteed by the CO2 present on Mars which would act as propellant.
