L3Harris NG RTG passes critical design review

L3Harris Technologies said on May 14 that its Next-Generation Radioisotope Thermoelectric Generator, or Next Gen RTG, had cleared a critical design review completed on April 2, moving the deep-space nuclear power system closer to manufacturing and eventual flight use. The company disclosed the milestone in a newsroom post and on its social media account this week. Bill Sack, general manager of RocketWorks and Power Systems at L3Harris, said the review showed the design met technical requirements and could be built. NASA materials describe the Next Gen RTG as a higher-power successor to the current Multi-Mission RTG used on Mars missions. ### What exactly did L3Harris say passed review? The April 2 review covered the design of the Next Gen RTG, a radioisotope thermoelectric generator intended for spacecraft operating far from the Sun. L3Harris said passing critical design review validated that the design met all technical requirements and was manufacturable. Sack said the milestone also showed the company had “successfully re-established this critical capability after years of limited production.” (l3harris.com) The May 14 L3Harris post described the unit as a flight-configuration system designed to provide 250 watts of power for decades-long missions in deep space. NASA’s own fact sheet puts the beginning-of-mission output at an estimated 245 watts per unit, while NASA’s radioisotope power systems page lists an estimated 252 watts for the system under development. (l3harris.com) ### How is this different from the RTGs NASA already flies? NASA says RTGs generate electricity by converting heat from the decay of plutonium-238 through thermocouples, without moving parts. The current flight model, the Multi-Mission RTG, powers NASA’s Curiosity and Perseverance rovers on Mars and is designed for either deep space or planetary atmospheres. (l3harris.com) NASA’s Next Gen fact sheet says the new system is based on the heritage General Purpose Heat Source RTG design flown on Galileo, Ulysses, Cassini and New Horizons. The agency says the Next Gen RTG would provide more than twice the power of an MMRTG and degrade more slowly over long cruises, using silicon-germanium unicouples derived from earlier systems flown on Voyager-era hardware. (science.nasa.gov) ### Why do spacecraft need this kind of power at all? NASA says solar arrays become less practical for missions headed to the outer solar system, where sunlight is weak and spacecraft need steady electricity and heat for years. RTGs have been used for more than six decades on missions that cannot rely on solar power alone. (science.nasa.gov) L3Harris said the vacuum-optimized design is aimed at deep-space missions rather than surface operations on planets. The company said that distinction allows more efficient heat rejection and power generation in the environment where missions such as a proposed Uranus orbiter would operate. ### Which missions could use the new generator? (science.nasa.gov) L3Harris said flight units could power NASA deep-space probes starting in the early 2030s, including a proposed Uranus orbiter that would use two Next Gen RTGs. The National Academies’ planetary science decadal survey lists the Uranus Orbiter and Probe as the highest-priority new flagship mission for initiation in the 2023-2032 decade. (l3harris.com) L3Harris is also building an RTG for NASA’s Dragonfly mission to Titan, though that mission uses the current MMRTG rather than the new design. NASA says Dragonfly is scheduled to launch in June 2027 and arrive at Titan by 2034. ### What still has to happen before it flies? NASA says the objective of the Next Gen RTG effort is to establish a production line for a new flight-ready RTG by 2030. (l3harris.com) The agency’s fact sheet says the project is part of the NASA-DOE Radioisotope Power Systems Program, which is reviving and modernizing the earlier GPHS-RTG capability for future missions. (l3harris.com) No contract award for a flight mission was disclosed in L3Harris’s May 14 announcement. The next concrete markers are manufacturing work and NASA mission selections that would assign the power system to a spacecraft, with L3Harris saying potential flight units could support probes beginning in the early 2030s. (l3harris.com) (science.nasa.gov)