Under a US$33.7-million Air Force Research Laboratory (AFRL) contract, Lockheed Martin is developing a next-generation nuclear-reactor-powered spacecraft for the Joint Emergent Technology Supplying On-Orbit Nuclear (JETSON) High Power program.
As more space missions extend far beyond the inner solar system and mission durations stretch from years to decades, finding ways to power and propel these spacecraft requires thinking outside the box. Chemical rockets and solar panels have served space engineers well for over 60 years, but these were already operating near their theoretical limits at the start of the Space Age, and missions to Jupiter are about as far as they can manage.
Any missions going beyond the orbit of Jupiter have to rely on some form of nuclear power to run their systems, and chemical rockets in that region can only propel the spacecraft by restricting payloads and using complex slingshot orbits to build up the necessary velocity to get to their destination.
Working with Space Nuclear Power Corp (SpaceNukes) and BWX Technologies, Inc. (BWXT), Lockheed's JETSON effort has so far reached the preliminary design stage, with the critical design review an option if it gets the green light. Its goal is to couple a nuclear fission reactor with the electric propulsion Hall thrusters used on Lockheed’s LM2100 satellites.
In its current form, the JETSON spacecraft consists of a reactor in the box of the probe with a fan of radiators behind it. From this extends a boom to keep the electronics and the Hall thrusters as far from the radioactive power source as possible.
The reactor is based on NASA's and the US Department of Energy's 2018 Kilopower Reactor Using Stirling Technology (KRUSTY) demonstration, which uses solid-cast uranium 235 reactor core 6 inches (15 cm) in diameter for fuel, with a beryllium oxide reflector surrounding it. A single rod of boron carbide starts and stops the reactor, while the reflector catches escaping neutrons and bounces them back into the core.
For safety, the reactor is left switched off and isn't activated until the spacecraft is in a safe orbit. Once in operation, the heat from the reactor is used to power a bank of Stirling heat engines, which work by compressing and expanding a gas in a closed cycle. This produces up to 20 kWe of power, or over three times more than current spacecraft solar panels.
This would not only greatly expand the life of deep-space probes, it would also power the Hall thrusters, which can slowly but surely accelerate spacecraft to velocities great enough to escape the solar system or allow the probe to visit a wide variety of potential targets.
"Nuclear fission development for space applications is key to introducing technologies that could dramatically change how we move and explore in the vastness of space," said Barry Miles, JETSON program manager and principal investigator, at Lockheed Martin. "From high-power electrical subsystem and electric propulsion, to nuclear thermal propulsion or fission surface power, Lockheed Martin is focused on developing these systems with our important government agencies and industry partners."
Source: Lockheed Martin