Propulsion technologies are key to exploring the outer solar system, and many organizations are working on novel technologies. One of them with a long history of success is the Ad Astra Rocket Company, which has been developing its Variable Specific Impulse Magnetoplasma Rocket (VASIMR) system for decades. However, since this type of electric propulsion system requires a lot of energy, the company chose a unique combination for a power plant that could solve this problem – a nuclear reactor. Ad Astra recently entered into a strategic alliance with the Space Nuclear Power Corporation (SpaceNukes), which is responsible for the development of the Kilopower reactor, a 1 kW nuclear reactor for use in space missions.
There are many synergies that justify such a merger between the companies, but let's look at each of their technologies in turn to understand why. VASIMR, the propulsion system that 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 popular form of electric propulsion and are known for their exceptional fuel efficiency. They aren't strong enough to lift a spacecraft out of a planet's gravity well, but once in low-gravity space, they excel at long, slow bursts of acceleration that translate into enormous speeds if used long enough become.
The problem is that they require a lot of energy to do this. They need to ionize their fuel, which requires a significant amount of energy, and that energy is hard to come by unless connected to a power grid. Current solutions use either solar panels, which would require a huge area to provide enough power to something like VASIMR, or a radioisotope thermal generator (RTG), which has been widely used for years to power the systems of various spacecraft, including Voyager and Voyager becomes Perseverance, but is unable to provide enough power for a viable electric propulsion system.
Fraser describes how ion engines, a type of electric propulsion system, work.
Enter a different form of nuclear energy – the traditional kind. SpaceNukes has been working on its Kilopower reactor in various forms for more than 10 years and already demonstrated a viable system with 1 kW of power on a ground-based system in 2018. The company is currently working with the US Space Force on a project called JETSON to develop a 12 kW design that could be used in a flight demonstration.
VASIMR scales well with larger power outputs – on the order of 100 kW or more, the rocket's efficiency could be significantly increased. The only viable option for such energy in space is nuclear reactors, so collaboration between the two companies seems appropriate. However, there is still a long way to go before a 100 kW system can be flight tested. The press release announcing the company's MOU said it hoped to conduct a flight demonstration “by the end of the decade” and commercialize the technology “in the 2030s.”
If they manage to meet that schedule – and that's still a big problem – a combined VASIMR and Kilopower-powered spacecraft would realize the dream of nuclear electric propulsion that excites many space propulsion enthusiasts. It could shorten the round-trip time to Mars from over a year to a few months and enable more and better missions to the outer solar system, including interesting moons like Enceladus and Titan.
Fraser describes KRUSTY, one of the experiments that led to the Kilopower reactor.
Given both companies' track records of slow and steady improvements, it is likely that the technologies will eventually see the light of day and enable a revolution in space propulsion. They have to keep going – like the engines they want to fly one day.
Learn more:
Space Nuclear Power Corporation – Ad Astra Rocket Company and The Space Nuclear Power Corporation forge strategic alliance to pioneer high-performance nuclear propulsion
UT – New nuclear rocket design to send missions to Mars in just 45 days
UT – What future propulsion technologies should NASA invest in?
UT – Exploring the universe with nuclear power
Mission statement:
Depiction of VASIMR in flight around Mars.
Credit – Ad Astra Rocket Company
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