STEWART PENNEY / FARNBOROUGH
Qinetiq is testing ion propulsion engines in close proximity as part of trials to develop a space propulsion system suitable for the European Space Agency's BepiColombo mission to Mercury (Flight International, 18-24 March).
Last week the UK research agency began testing two 220mm (8.7in)- diameter T6 gridded ion engines separated by a 500 to 800mm gap to assess the interaction between the units and their ion beams, says Neil Wallace of Qinetiq's space sector. The trials will help assess whether ion engines can be clustered in a similar way to rocket engines.
The 7.5kg (16.5lb) T6 engine generates 30-210mN of thrust by emitting a stream of Xenon ions, accelerated across a 1,500V potential difference, at around 45km/s (147,500ft/s), compared with an exhaust velocity of around 3km/s for a chemical rocket.
Wallace says ion thrusters offer more than 10 times the efficiency of a conventional rocket engine which makes extended range space science missions more practical.
A neutraliser near the engine exhaust ejects further electrons and the propulsion beam collects as many as it needs to establish charge equilibrium. Xenon has the advantage of being an inert substance and does not react with materials used in the spacecraft or engine.
The tests will last around 100h in Qinetiq's Large European Electric Propulsion 2 (LEAP2) test cell at Farnborough. As part of the proximity tests the engines will be run with one neutraliser switched off.
The engines have been installed so that electrons from one neutraliser will flow through the propulsion beam while the other will allow the electron flow to remain clear of the main propulsion beam.
Following the proximity trials, one engine will be removed and the other will be subject to gradually increased heating, says Wallace.
Source: Flight International