Pale Blue PBR-20 is a miniaturized water vapor propulsion system in a 1U form factor. It is a fully integrated system that incorporates thruster head, fluidics, electronics and propellant tank, and is clusterable to meet a wide range of spacecraft sizes.

The PBR-20 uses water as propellant and does not require a high-pressure storage. The propellant is preloaded to the tank prior to delivery from factory so that satellite integrators would not have to deal with complex fueling work.