Argo Space: Ex-SpaceX Brothers Build Water-Powered Spacecraft

According to the company, this combines the strengths of two approaches. Chemical propulsion delivers high thrust but uses propellant inefficiently, while electric propulsion is very efficient but weak. Electrolyzing water yields strong thrust from combustion and better efficiency overall.

Water brings other benefits. It can be stored as a liquid, so no heavy cryogenic tanks are needed, and it avoids the explosion risk of pressurized cryogenic propellants. It also serves as coolant and radiation shielding, so more of the vehicle's mass is usable propellant. And it is present throughout the Solar System, which makes refueling plausible.

Missions ahead

In July, Argo tried the first test with its Navigator mission on a Falcon 9, but a solar panel failed to deploy properly and the propulsion could not be tested. The next attempt comes in 2027 with the Chiron missions. No SpaceX rockets were available this year, so the company will use a new commercial rocket and a government launcher. One will carry a payload to low Earth orbit and the other to geostationary transfer orbit; no further details have been given.

The Chiron vehicle reaches a delta-v of 2 km/s. If it succeeds, Argo plans Argonaut, a larger craft able to carry 1,400 kg and targeting 17 km/s per tank. In September the company signed with ispace to take a communications satellite to lunar orbit late in the decade, possibly aboard Argonaut.

With fewer than 30 employees, Argo is small. Water has been tested as a propellant in space before, but only at very small scale, which is why a larger demonstration would be a milestone.