GOCE spacecraft fires up QinetiQ ion engines

07 Apr 2009
Electric engines – designed, built and tested at QinetiQ's space centre in Farnborough, UK – are ready to play a crucial role in the European Space Agency's (ESA) gravity mission following their successful commissioning onboard the GOCE spacecraft this week.

GOCE's ultra-sensitive measurements of the Earth's gravitational field depend on the ability of QinetiQ's engines to maintain the spacecraft's orbit by finely controlling its altitude and speed.

The strength of the Earth's gravitational field diminishes with altitude, so GOCE's orbit skirts the outer reaches of the atmosphere at just 260-280 kms (160-175 miles) above the Earth. As a result the spacecraft experiences small but significant disturbances in its motion from atmospheric drag. QinetiQ's electric engines act as cruise control for the spacecraft, providing tiny but continuous levels of thrust to compensate for atmospheric drag without disturbing the sensitive science payload – quite literally preventing the spacecraft from falling out of the sky.

ESA mission manager Dr Rune Floberghagen said that all systems on the spacecraft had now been activated following the launch from Russia on 17 March and that the mission will become fully operational in the next few weeks. "Now we must learn to drive our super-satellite," he said.

The full commissioning proved that the main and back-up engine chains are performing precisely to specification across the full thrust range, providing very stable thrust with no interruptions and a perfect thrust vector.

"This is an historic moment for the QinetiQ space team – the first real, in-orbit qualification for our ion engines," said Neil Wallace, QinetiQ's chief electrical propulsion engineer. "You work on these things for so many years that you should be cold and confident that it will all work, but there is nothing better than results from commissioning that show performance in space perfectly matches the on-the-ground thrust results."

QinetiQ's engines – known T5 ion thrusters – are around ten times more efficient than rocket thrusters that have traditionally been used to propel spacecraft, requiring only 40kgs of xenon propellant for the whole 30-month GOCE mission.

In the next few years electric propulsion could make previously impossible missions into deep space a reality and extend the operational life of commercial communications satellites, reducing costs. QinetiQ is currently working with partners to qualify its T6 thruster, an even more advanced electric propulsion system that has been designed for use on the next generation of deep space and interplanetary science missions, such as the ESA BepiColombo mission to the planet Mercury.
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GOCE spacecraft fires up QinetiQ ion engines