The Pale Blue Water Resistojet Thruster is a low pressure (<60 kPa) propulsion system with a scalable water tank and a redundant flow control system with a fail-safe valve. The thruster unit is modular and it is possible to expand the overall system by clustering multiple units and scaling the propellant tank as needed. The limits of such clustering or scaling are determined by the mass, volume, or power of a spacecraft.

The individual units provide a total impulse of >200 Ns and a specific impulse of >50 s, with a thrust of 1.0 mN. The first model was demonstrated aboard a 3U ISS-deployed CubeSat in 2019 and two flight model thrusters are to be delivered in 2021 and launched by SLS and Falcon-9, respectively. The thruster operated in low earth orbit in March 2023 on board Sony 'EYE' satellite.

Flight heritage

The Pale Blue Water Resistojet Thruster has acheived flight heritage since 2019.

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Last updated: 2023-06-21

Water Resistojet Thruster




wet mass
1.5 kg
20 W
1.0 mN
9.5 cm
9.5 cm
10.5 cm
specific impulse
> 50 s
total impulse
> 200 N s


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