New propulsion technologies for space appear to be popping out of the woodwork. The level of innovation behind moving things in space is amazing, and now a company from Japan has just reached a significant milestone. Pale Blue, which I assumed was named in reference to a beloved Carl Sagan book, recently successfully tested its water-based propulsion system in orbit, adding another safe, affordable propulsion system to the repertoire of satellite designers.
Using water to squirt through space might seem relatively simple. However, despite their simplicity and relatively low cost, waterjets for satellite propulsion systems are not yet widely used. This first Pale Blue system, launched with Sony’s EYE satellite as part of its STAR SPHERE program to capture images of Earth, was the first time the company had successfully tested its system in space.
They did this by operating it for about two minutes in early March and adjusting the orbit of the EYE satellite in LEO. The thruster brought EYE closer to an orbit from which the satellite will provide space photography services, which is the business model pursued by Sony with the STAR SPHERE program.
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Light blue video describing his inventive propulsion systems.
Credit – Light Blue YouTube Channel
Pale Blue itself was spun off from the University of Tokyo three years ago and is pursuing a few types of water-based propulsion systems. The one launched on EYE is known as the “Resistojet” – essentially it simply pushes water out of a tube relative to the angle to push the satellite where it wants to go. Simple Newtonian physics does the rest, with attitude control and propulsion both controlled by this system.
Some innovative features of the Resistojet system include keeping the water at a relatively low pressure and evaporating it at relatively low temperatures. It’s evident that a lot of thought went into the design, and now all that effort has been validated by a successful mission.
But the company won’t stop there. They’re working on a different type of water-based thruster that’s more like an ion thruster than a simple jet mechanism. In this configuration, the water is atomized via a microwave plasma source and ejected out the rear of the propulsion system, similar to a typical ion thruster. However, several patented technologies also flow into this system, including the plasma generation system and the design of the vaporization chamber.
UT video describing ion engines – like one of the systems Pale Blue is developing.
Although they haven’t had a chance to test their ion thruster in space, the company is planning something even more ambitious – combining the two thruster configurations into a single hybrid thruster. Such a thruster would benefit from both the relatively high thrust provided by the nozzle system and the specific impulse provided by the ion thrust system. Such a system is still a long way from a test flight like the one just completed, but the most recent test gives the company an excellent basis for further development. Eventually the space propulsion industry will settle on a standard configuration and now Pale Blue has added a new one to that mix. For now, it’s certainly not the last word in this ongoing effort to improve the way we move in space.
Pale Blue – Pale Blue successfully operates its water-based propulsion system in orbit
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Artist’s rendering of the EYE satellite system in space.
Credit – Sony