Pale Blue

Pale Blue makes satellite thrusters that run on water. Water needs no pressure vessel, poisons nobody, and passes rideshare safety reviews that pressurised propellants complicate, so a Pale Blue unit can bolt onto a small satellite with little ceremony. The line runs from a simple resistojet that vaporises water for gentle thrust up to the PBI, a water ion thruster that fits, propellant included, in a ten-centimetre cube.

The company is a 2020 spinout from the University of Tokyo propulsion laboratory of Hiroyuki Koizumi, whose group spent years proving water propulsion on university CubeSats. The bet is that adoption is blocked by handling rather than performance: an operator will accept a less efficient propellant if it removes the pressurised tank, the toxic loading procedures and the paperwork.

The record is three in-orbit firings on three different platforms, which for a company this size is genuinely rare. The resistojet fired on Sony's camera satellite in March 2023 and still worked two years later. The water ion thruster ran aboard a D-Orbit transfer vehicle in 2025, the first of its kind in orbit, and an integrated system fired on JAXA's RAISE-4 demonstration satellite after that. All three are demonstrations measured in minutes, and no customer has yet flown a mission that depended on Pale Blue thrust for its delta-v budget. The physics tax is real too: water gives less impulse than xenon and less thrust than chemistry, and every performance figure public so far comes from the company itself.