Strategic alliance brings high-energy nuclear electric propulsion closer to reality

Propulsion technologies are the key to exploring the outer solar system, and many organizations have been working on novel ones. One with a long track record is the Ad Astra Rocket Company, which has been developing its Variable Specific Impulse Magnetoplasma Rocket (VASIMR) system for decades. However, this type of electric propulsion system requires a lot of energy, so the company has opted for a unique tie-up for a power plant that could solve that problem—a nuclear reactor.

Ad Astra has recently entered into a strategic alliance with the Space Nuclear Power Corporation, or SpaceNukes, responsible for developing the Kilopower reactor, a 1kW nuclear reactor for use in space missions.

There are plenty of synergies to justify such a tie-up between the companies, but let’s look at each of their technologies, in turn, to understand why. VASIMR, the propulsion system Ad Astra has been working on for more than 20 years, is a magnetoplasma rocket, a type of electric propulsion system.

Ion drives are the most commonly known form of electric propulsion and are known for being exceptionally fuel efficient. They aren’t powerful enough to lift a craft out of a planet’s gravity well, but once in space with little gravitational pull, they shine at long bursts of slow acceleration that translate into massive speeds when engaged for long enough.

The problem is they need lots of power to do so. They must ionize their fuel, which requires a significant amount of energy, and that energy is hard to come by when not connected to a power grid. Current solutions utilize either solar panels, which would require a massive area to provide enough power to something like VASIMR, or a radioisotope thermal generator (RTG), which has been in common use for years to power the systems of different spacecraft, including Voyager and Perseverance, but isn’t capable of providing enough power for a viable electric propulsion system.

Enter another form of nuclear energy—the traditional kind. SpaceNukes has been working on its Kilopower reactor in various guises for more than 10 years and has proven a functional system at 1kW of power on a ground-based system back in 2018. It’s now working with the US Space Force under a project named JETSON to develop a 12kW design that could be used in a flight demonstration.

VASIMR scales well with larger power outputs—on the order of 100kW or more could significantly increase the rocket’s efficiency. The only viable option for such power in space is nuclear reactors, so the tie-up between the two companies seems apt. However, there is still a long way to go before a 100kW system would be flight tested—the press release announcing the company’s memorandum of understanding says they hope to have a flight demonstration done “by the end of the decades” and to commercialize the technology “in the 2030s.”

If they manage to pull that timeline off—and that is still a big if—a combined VASIMR and Kilopower-driven spacecraft would achieve the dream of Nuclear Electric Propulsion that excites many space propulsion enthusiasts. It could cut down the round-trip travel times to Mars from over a year to a few months and allow for more and better missions to the outer solar system, including interesting moons like Enceladus and Titan.

Given both companies’ track records of slow and steady improvement, it seems likely that eventually, the technologies will see the light of day and enable a revolution in space propulsion. They have to keep pushing—like the engines they hope to fly someday.