As NASA targets its first crewed Mars mission in the late 2030s, nuclear propulsion emerges as the key to slashing travel times and enabling sustainable exploration.
Space agencies and companies have long depended on chemical propulsion rockets to escape Earth's gravity. These systems generate thrust by combusting fuel in a chamber, producing high-pressure gases that expand through a nozzle and propel the vehicle forward.
This proven technology powered the Apollo Moon landings and remains central to NASA's plans for lunar return. However, for Mars, it falls short: trips would take six to nine months one-way, requiring massive amounts of propellant—making missions prohibitively expensive and logistically challenging.
Such limitations cap our reach, underscoring the need for faster, more efficient propulsion to push beyond Mars.
A recent report from the National Academies of Sciences, Engineering, and Medicine—commissioned by NASA—evaluates nuclear thermal propulsion and nuclear electric propulsion for a 2039 crewed Mars mission.
“One of the main conclusions of the report is that if we want to send humans to Mars, and we want to do so repeatedly and sustainably, nuclear space propulsion is the solution,” says Bobby Braun of NASA's Jet Propulsion Laboratory.
Nuclear thermal propulsion uses a reactor to heat liquid hydrogen propellant, generating thrust. Nuclear electric propulsion converts fission heat to electricity, which ionizes and accelerates propellant like xenon for efficient, continuous thrust.
These systems demand far less fuel—under 500 metric tons versus 1,000 to 4,000 metric tons for NASA's chemically powered SLS—while dramatically shortening transit times to Mars.
Though NASA has prioritized SLS development, the report urges immediate investment in nuclear tech. No such rocket has flown yet, despite decades of concepts, highlighting the engineering hurdles ahead.
Two years ago, Congress allocated $125 million (about €112 million) for NASA research, but experts like Braun warn that full-scale development and Mars cargo demos by the mid-2030s will require significantly more funding.
SpaceX's Starship aims to conquer Mars via high-frequency, low-cost reusable launches. Engineers plan orbital refueling: a Super Heavy booster deploys an empty Starship to low Earth orbit, followed by tanker variants that dock and transfer fuel for the interplanetary leg.
Leveraging five years of reusability expertise, SpaceX prioritizes volume over efficiency. NASA, lacking this focus, must pursue nuclear alternatives for reliable, sustainable deep-space travel.
