New Space and Tech

Chris Hadfield Calls Momentus’ Water-Based Spacecraft Propulsion “Great Freedom”

By James Careless
May 17, 2023
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Chris Hadfield Calls Momentus’ Water-Based Spacecraft Propulsion “Great Freedom”
The Momentus Vigoride uses distilled water as a propellant to change its orbit.
Image credit: Momentus Space.

Depending on who you ask, retired astronaut Chris Hadfield is famous either for his tenure commanding the International Space Station during Expedition 35 (March to May 2013), or for his viral cover of David Bowie’s song “Space Oddity,” which he performed while in orbit. Now, however, he’s serving on the board of Momentus Space, a company that’s successfully built and tested spacecraft propelled just by solar energy and distilled water.

Momentus is unique because its spacecraft, the Vigoride Orbital Service Vehicle (OSV) (it recently launched its sixth) relies on Microwave Electrothermal Thruster (MET) propulsion technology that uses solar energy to heat onboard distilled water to a hot boil and release it from multiple, small thrusters for attitude control.

Hadfield told SpaceRef that being able to propel spacecraft in and outside of Earth’s orbit using distilled water is “a great freedom.” Unlike conventional chemical rocket propellants, water is proving to be widely available in outer space — albeit in forms that require processing and distillation. “We are finding far more water in our solar system,” he told SpaceRef. (Indeed, the James Webb Space Telescope just found water vapor around a comet in the asteroid belt). “I mean, we think there’s a hundred billion gallons of water in the craters at the poles of the Moon. And we used to think that it was drier than the Sahara.”

Recently, the Vigoride-5 successfully used its unusual propulsion system to increase the altitude of its orbit around the Earth by more than 1.86 miles (3 km), Gizmodo reports, which the company says is evidence of the spacecraft’s operational capabilities.

Chris Hadfield also likes the simplicity of Momentus’ MET propulsion system. “Basically, we microwave water using solar power and that provides thrust,” he said. “It’s as if you put a nozzle on your microwave and when the water boils — instead of just sort of spattering all around the inside of the microwave — it comes shooting out as a high energy jet. And if you can get enough energy into it, it does more than just boil water: It actually takes it into the next state and becomes plasma.”

The ultimate goal is for Momentus’s spacecraft to serve as tugs that can help shuttle satellites to their target orbits, or elevate or lower the altitude of those orbits later on. The company’s successful in-orbit MET tests have also motivated the company to propose a mission to rescue the Hubble space telescope by boosting it into a higher orbit, and then clearing that path of space debris. Like an ion engine, the MET produces a gentle thrust that lasts for a long time to build up speed — unlike the fast, hard acceleration delivered by a chemical rocket. Such gentleness could make the difference between saving Hubble or damaging it in the attempt, Hadfield suggests.

“I was in Mission Control as the CapCom during one of the Hubble (servicing) missions,” Hadfield recalled. “When we opened the (space shuttle) airlock to go outside and do a spacewalk, the puff of air that came out of it spun one of the solar arrays on Hubble right all the way around a couple times and slammed it against the hard stop … Whatever it is that’s going to come in to try and do good for Hubble can’t be spraying it with any sort of residue from propellant, nor can it provide an impulse to the solar array that might do it damage.”

Looking ahead, Chris Hadfield sees all kinds of potential for the Momentus’ MET engine to power spacecraft to the Moon, Mars, and nearby asteroids. “All of those are potential applications for it,” he said. “You just have to do the trade-off studies as to what makes sense for this particular technology.”

“I am really impressed with the team of people that I work with at Momentus,” added Hadfield. “CEO John Rood has brought in a lot of really bright young engineers — it’s your classic startup ‘working long hours and living on pizza and so proud of what they’re doing’ — and also some real industry veterans.”

James Careless

James Careless is an award-winning satellite communications writer. He has covered the industry since the 1990s.