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The future of satellite propulsion in space could be … water?

CubeSat Propulsion System Uses Water as Propellant
When you think about next-gen propulsion technologies for space travel, your mind probably goes to something like NASA’s EmDrive project or ion engines before it does a material like boring old water. After all, we like our propulsion materials to be rare and science fiction-sounding, as opposed to a freely available liquid that covers two-thirds of our planet.

That could be where you are making a mistake, though. At Purdue University, researchers are developing a smart new micropropulsion system which uses a configuration of tiny nozzles that release precise bursts of water vapor to maneuver outside Earth’s atmosphere. The propulsion system is not designed for big spacecraft, however.

“[What we] have developed with the Film Evaporation MEMS Tunable Array (FEMTA) is a tiny microthruster rocket engine for orienting CubeSats or other very small satellites,” Anthony Cofer, a spacecraft laboratory engineer at Purdue, told Digital Trends. “The thruster uses microscale effects to obtain a thermal valve with no moving parts.”

Purdue University/Erin Easterling
Purdue University/Erin Easterling

CubeSats refer to some of the (relatively) low-cost “microsatellites” and “nanosatellites” which are currently being launched to carry out various tasks — ranging from high-res imaging to internet services to military surveillance. These satellites are much smaller than traditional ones or other spacecraft, therefore necessitating a smaller propulsion system.

The Purdue engine works using small heaters which create water vapor as the water inside is forced through tiny capillaries, just 10 micrometers in diameter. The result is something that functions much like an inkjet printer, which employs heaters to push out ink droplets — only in this case the droplets provide thrust.

In demos, the thruster exhibited a thrust-to-power ratio of 230 micronewtons per watt for impulses lasting around 80 seconds. The entire prototype weighs just six pounds, including electronics and an inertial measurement unit sensor for monitoring the thrusters’ performance.

Looking to the future, the team is optimistic about the project. “Our plan is to work with NASA Goddard to progress to the required Technology Readiness Level for insertion into a space flight mission,” Alina Alexeenko, a professor in Purdue’s School of Aeronautics and Astronautics, told us.

Best of all, if it turns out that there is indeed an abundant source of water on the Martian moon Phobos, a water-based propulsion system such as this will have a ready-made refueling station in space. Smart, huh?

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