Earth from orbit

Miniature satellites could be propelled using water vapour

Image credit: Dreamstime

Engineers at Purdue University in West Layfayette, Indiana, USA, have developed a new propulsion system for CubeSats. These systems release water vapour from nozzles to steer the small spacecraft.

Miniaturised satellites such as CubeSats have exploded in popularity, with 500 expected to be launched between 2015 and 2019. These small, inexpensive satellites can enter orbit with a small payload, making them ideal for focused scientific research projects, military surveillance, internet services or to monitor the earth and its atmosphere.

“They offer an opportunity for new missions, such as constellation flying and exploration that their larger counterparts cannot economically achieve,” said Professor Alina Alexeenko, a researcher in Purdue University’s School of Aeronautics and Astronautics.

In order to help these miniaturised satellites achieve more during their missions, Professor Alexeenko and her colleagues set about developing micro propulsion devices which could allow for delicate steering. She chose to use ultra-purified water as the propellant, given its purity and its abundance on other bodies in the solar system, such as Phobos, a Martian moon.

The new system, the Film-Evaporation MEMS Tunable Array (FEMTA) thruster, uses tiny nozzles on silicon wafers, small enough to utilise water’s microscopic properties.

The surface tension of the water prevents it from flowing out, until small heaters are activated. This creates water vapour, producing thrust. The technology is similar to an inkjet printer, which coordinates tiny heaters to exude droplets of ink.

The team attached four FEMTA thrusters loaded with approximately a teaspoon of water into a CubeSat and tested the prototype within Purdue University’s High Vacuum Facility. They found that the system could operate on very low power, requiring less than a quarter watt to rotate 180 degrees in 60 seconds.

“What we really want to do next is integrate our system into a satellite for an actual space mission,” said Professor Alexeenko.

A fully functional satellite would require 12 FEMTA thrusters for full three-axis rotation.

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