Nuclear rockets

All this talk of oxygen and energy is all well and good, but before you can start deploying these technologies on Mars you’ve got to get there. NASA has explored the Solar System using a range of chemical rockets and gasfuelled manoeuvring systems, but is investigating two methods of nuclear propulsion to speed humanity to the Red Planet.

The first is nuclear electric propulsion, otherwise known as the ion drive, which supplies low thrust over a long interval to gradually build high acceleration. The other is nuclear thermal propulsion, which provides high thrust and twice the propellant efficiency of chemical rockets. NASA is looking into preliminary reactor design concepts for such a rocket, which heats a fluid, usually liquid hydrogen, in a nuclear reactor. Once it reaches a high enough temperature, the fluid expands through a rocket nozzle to create thrust.

Nuclear thermal propulsion has been on NASA’s radar for more than 60 years. Research on the subject once concentrated on fission reactors, but these came with a number of problems, notably that no one wanted a flying fission reactor with even a chance of exploding over their heads. Recent research has moved to nuclear fusion power, and such a rocket could be constructed in orbit as an additional safety measure. Nuclear propulsion could enable missions to Mars at times when the planet is not favourably positioned relative to Earth, and could cut the round trip time of a crewed mission to just two years.