Brothers Robert, Ryan and Kirby Carlisle, engineers who worked at SpaceX during the Falcon 9 era, founded Argo Space in late 2022 to build transportation infrastructure in space. According to Ars Technica, they chose water as propellant because it can be harvested on the Moon and is found across the Solar System. In their design, water also serves as coolant and radiation shielding.
The first demonstration mission, Navigator, launched in July. One of its two solar arrays failed to deploy, the spacecraft stayed power-negative, and there was not enough energy to test the propulsion system. The company says the flight software, avionics and structure were validated.
The next spacecraft, Chiron, weighs about 200 kg. It launches with liquid water and in space uses solar power to split it into hydrogen and oxygen, which it burns. The company says it will deliver more than 2 km/s of delta-v. Two missions are planned for 2027, both carrying payloads for an undisclosed national security customer: one to low Earth orbit and one to geostationary transfer orbit. Neither will fly on a Falcon 9: the company says the wait list for a ride on it is too long.