On April 3, 1965, a nuclear reactor reached space for the first time. It was SNAP-10A, a small, low-output reactor that the United States launched into low Earth orbit. The device was a test model intended for satellites and for lunar and deep-space exploration. SNAP-10A generated power for 43 days before a faulty voltage regulator shut it down. From the 1950s through the 1970s, the U.S. also developed nuclear thermal rockets that used heat from fission, but budget cuts kept them from ever flying.
While the U.S. stalled, the Soviet Union succeeded in putting space reactors to practical use. After stepping up development in the 1960s, Moscow placed more than 30 ground-surveillance satellites powered by small reactors into low orbit during the 1970s and 1980s. No further launches followed, however, because of concerns over technical safety and cost. As an alternative, major countries have developed and used nuclear batteries, which draw heat and electricity from the natural radioactive decay of plutonium nuclei.
Space reactor technology, long dormant, is making a spectacular comeback. The U.S., China and Russia are competing to build nuclear plants for lunar bases. Washington has set 2030 as its target year, while Beijing and Moscow are aiming for 2036. The U.S. plans to build a 20-kilowatt plant on the moon, enough to power about 16 American homes. It is also studying megawatt-class space reactors for use on spacecraft bound for Mars. China and Russia are expected to start with 10-kilowatt units and move toward progressively higher output.
South Korea, a nuclear power heavyweight, is developing space reactors as well, through institutions including the Korea Atomic Energy Research Institute. The country has been moving quickly into space, with the fifth launch of its homegrown Nuri rocket set for the 7th of this month. Its nuclear fuel supply, however, depends on foreign sources, and reprocessing of spent fuel is barred under the nuclear cooperation agreement with the U.S. That leaves limits on any independent push into space. When the government uses its investment in the U.S. as leverage in nuclear talks with Washington, it should keep in mind not only reactor exports and nuclear-powered submarines but also space exploration. Korea's sovereignty in space rests on securing exploration vessels carrying Korean reactors, along with bases on the moon and Mars.
