UK research organisation's ion thruster engine in the driving seat for BepiColombo
Qinetiq has won a competition to provide the ion thruster engine for the European Space Agency's (ESA) BepiColombo mission to Mercury.
Qinetiq's T6 gridded ion engine will push the craft the 92.7 million km to Mercury in three-and-a-half years using only 350kg (770lb) of propellant. The research and development company had already been selected to deliver a throttleable ion thruster for ESA's Global Ocean Circulation Explorer (GOCE) mission.
An ion thruster engine produces thrust by expelling a stream of ionised gas particles; Qinetiq's engines use xenon. Only the gas is carried into orbit, reducing the fuel mass to around 10% that of a traditional chemical rocket engine. The satellite is equipped with solar panels to generate the electricity required to ionise the gas, using electron bombardment.
Qinetiq is running a series of tests of ion-thruster engines at its Farnborough site, including proving that the engine can be throttled.
This is a key requirement for the GOCE mission - designed to finely measure the earth's gravitational field - as the satellite will fly at a very low orbit, where it will encounter drag from the atmosphere. To overcome the drag and allow the satellite to fly at a constant altitude, the engine will have to produce variable thrust. Most satellite engines are not throttleable, being either on or off.
Qinetiq is also running high-temperature tests of its ion thrusters, which are understood to be part of proving the viability of using the engine to fly a satellite to Mercury.
The company says it aims to develop ion thrusters for the next generation of European communications satellites. The fuel weight saving will allow another 1,000kg (2,200lb) payload to be carried on the satellite, or the operational life to be extended from 10 to 15 years, says the company.
The technology also offers opportunities for deep space missions as ion engines can constantly accelerate the craft and reduce the need for slingshot manoeuvres using the planets' gravitational pull.
Throttleable engines will also make missions to fly in formation with comets easier, says Qinetiq, as the craft can be accelerated to catch the comet, then slowed to fly in formation. It will also allow samples to be brought back from such missions.
Source: Flight International
