Earthbound air travel can be a hassle, even for careful planners. So if you’re heading to the Moon or beyond, it’s time to shift your planning into hyperdrive. Our advice, when there’s no guidebook, no proven vehicle, and your destination is a moving target? Don’t forget to pack your nuclear power bank.
Big plans: Wernher von Braun
Wernher von Braun had his eye on nuclear rockets even as he led the development of U.S. chemical rockets in the 1950s and 1960s. In remarks delivered at the 1968 American Nuclear Society Winter Meeting and published in the December 1968 issue of Nuclear News, von Braun, then director of the Marshall Space Flight Center, said:
“Today I believe the role of the nuclear rocket program is analogous to the comparison of the piston-engine airplane, and today’s modern jetliners. Ten years ago many of our experts stated there was no requirement for the turbojet engine in the aircraft business. Not only has history proven them wrong, but this advancement in airplane propulsion technology has paid for itself many times over. Development of a nuclear stage not only provides a major advancement in our space propulsion capability but gives needed flexibility in our mission planning.”
Far-flung science machines
Radioisotope thermoelectric generators (RTGs) have powered the exploration of the solar system and beyond for more than 60 years. NASA’s longest running mission—the twin Voyager probes—set off on their solar system flybys in 1977 with eight-track tape players to record data. While their available power dwindles each year and their technology is archaic by today’s standards—they have about 3 million times less memory than modern cellphones and transmit data about 38,000 times slower than a 5G Internet connection, according to the NASA/Department of Energy Radioisotope Power Systems Program—they are still getting power from the plutonium-238 onboard.
Dragonfly, a mission to explore Titan, Saturn’s largest moon, is set to launch in 2027, 50 years after the Voyager probes. As a planned mission, Dragonfly is depicted in this graphic of type and destinations of RTG-powered missions with a dotted line.
It’s a SNAP
NASA is working with the DOE and industry to design a fission power system to provide at least 40 kilowatts of power on the Moon for 10 years—and to have it ready to launch by the end of the decade for a lunar demonstration. It would be the first fission reactor on the Moon, but not the first time nuclear energy has been used for lunar power. That first was achieved during the Apollo 12 mission in November 1969, when U.S. astronaut Alan L. Bean deployed a SNAP-27 RTG on the lunar surface to power experiments for at least one year.
From the time the Atomic Energy Commission first set up the Systems for Nuclear Auxiliary Power (SNAP) program in 1955, SNAP included both RTGs and fission power distinguished by number: odd-numbered SNAPs used radioisotope heat sources, and even-numbered SNAPs had fission reactor heat sources.
The SNAP-10A was launched and operated in space in April 1965 as a satellite designed to produce 500 watts of electricity from its onboard fission reactor. An electrical fault in the spacecraft carrying the SNAP-10A led to its premature shutdown after just 43 days of operation. The reactor remains in polar orbit today—and remains the only U.S. reactor launched into space to date.
Attention Mars travelers: Your flight has been delayed
In August 1969, Wernher von Braun proposed landing astronauts on Mars in 1982. According to NASA, von Braun told a Space Task Group that “although the undertaking of this mission will be a great national challenge, it represents no greater challenge than the commitment made in 1961 to land a man on the Moon.”
The word “commitment” is key. In 1973, NASA’s nuclear rocket programs were canceled. But NASA released a set of 63 Moon to Mars objectives in September 2022 based on a new goal to minimize a round trip between Earth and Mars to as close to two years as practical. One of five principles behind the new objective-based approach is identified as “Constancy of Purpose”—further defined, in NASA’s words, as “Stick with the Plan: once documented, the goal, top-level objectives, and overall plan should be clear and remain consistent over time.”