For seventy years, space exploration has required ever more advanced technological advances. Throughout our Solar System, probes and devices observing the cosmoscosmos use various resources to power their instruments. One of the oldest and most reliable energies available: nuclear power. On June 29, 1961, NASA launched the Transit IV-A satellite. Mainly covered with photovoltaic cellsphotovoltaic cells aimed at powering its batteries, it carries a source of energy called a “thermoelectric generator radioisotoperadioisotope » (RTG, « Radioisotope thermoelectric generator “). The latter uses plutoniumplutonium-238, whose degradation of dioxide causes a emissionemission of heatheatitself converted into electricity on the basis of a thermoelectric couple (CTE).
The Transit program represents a real success for the American space agency, collaborating with the laboratory of physiquephysique applied from John Hopkins University. it then marks the beginning of a long nuclear epic in aerospace.
The power of the atom across the cosmos
The RTG demonstrates almost infallible effectiveness. He was once again employed by NASA on various missions, including the legendary Voyager. The two probes were launched on August 20 and September 5, 1977 respectively. Voyager 2Voyager 2 is currently 20 billion kilometers from Earth, while Voyager 1 is transiting 25 billion kilometers. Still active despite recent problems, they are operational thanks to their nuclear batteries, regularly sending data to the ground. The probes require approximately 250 W to operate properly.
Nuclear batteries were part of a number of missions, including those of Apollo, between the twelfth mission in 1969 and the end of the program in 1972. The implementation of nuclear technology on spacecraft, capable of crossing millions and billions of kilometers, already constituted a technological leap sixty years ago. As explained Pierre HenriquetPierre Henriquet In Polytechnique Insightsthe conversion of plutonium heat into energy turns out to be relatively low, only 10%. But, an RTG produces this energy continuously and offers increased longevity, thus meeting the prerequisites for long missions across the Solar System, and even further afield.
Always further, always stronger?
Several ideas are mentioned to improve the capabilities of space probes. Today, many devices flying overhead are equipped with photovoltaic cells. But as soon as they move away from the Earth and the SoleilSoleilthe capture of sunlight becomes more tenuous. A bad inclination can also influence the perception of photonsphotons and alter the power supply to the systems. Solar technology is a viable energy source orbitorbit low and medium, but its effectiveness is reduced during more distant missions, or long durationduration.
Nuclear power is the alternative of choice. The American mission DragonflyDragonflyscheduled for launch in 2028, will carry an RGT. NASA plans to send an octocopter drone to explore the surface of Saturn’s moon Titan. The nuclear battery will power the whole thing during the journey to TitanTitanas well as the drone once the octocopter has been placed on the natural satellite. Engineers are also working to think bigger about the propulsion of systems that have left Earth. The Office of Space Nuclear Propulsion (SNPSNP« Space Nuclear Propulsion “) is developing nuclear propulsion mechanisms, much lighter and twice as efficient as nuclear-powered systems. propergolpropergol current. Nuclear propulsion is based on the principle of fissionfissionused in land-based power plants. The heat induced by fission would generate electricity, which would ionize the propellant contained in the form of gazgazgenerating a thrust that can propel the device.
Other avenues are being studied, particularly for implantimplant reactors on the LuneLune. They would be used to provide electricity and heat to future inhabited bases, in a cold and austere environment. In 2023, the Defense Advanced Research Projects Agency (Darpa, “ Defense Advanced Researched Project “) announced that it was collaborating with NASA and several players in the aerospace industry to build a new type of launcherlauncher. Named Draco, for Demonstration Rocket for Agile Cislunar Operationsce demonstratordemonstrator nuclear-powered would fly in 2027. For scientists and industrialists, there are certainties: the use and improvement of space nuclear power in the coming years is one of them.
