The objective of the Large Platform Mission Project (known as AlphaBus) is to develop a new European multipurpose platform for large telecoms payloads. AlphaBus is being developed by Alcatel (F) and Astrium (F), and is supported by the European and French space agencies.
QinetiQ has completed a contract from the European Space Agency to perform for AlphaBus the necessary pre-development activities for the supply of the electric thruster based on ion propulsion including the Power Supply and Control Unit (PSCU) and Xenon Flow Controller (XFCU).
Objectives were to develop a high power 5 kW gridded ion thruster referred to as the T6 Mk3 and its associated PSCU for Alphabus station keeping. The key requirements are:
- Thrust > 145 mN
- Specific impulse > 4000 seconds
- Total impulse >2.65 MNs (excluding 1.5 qualification margin) plus 1.5 months LEOP firing duration
- Input power (into PSCU), < 5000 watts
- On/off cycles 8200 (including 1.5 qualification margin)
- Lifetime 15 years
The T6 under test in the QinetiQ electric propulsion facilities at Farnborough is shown in the photograph below.
A thruster has been built that is capable of meeting the key requirements. The required performance has been demonstrated, along with a prediction of lifetime, through the completion of a partial life test. The partial life test was completed in as realistic a manner as possible in order to closely match the erosion characteristics expected to occur in space.
A PSCU EM has been built to meet the demands of the thruster, and has undergone a successful coupled test with the thruster. This has shown the ability of the PSCU to satisfactorily operate under the complex variable plasma loads associated with the operation of electric thrusters.
The benefits to be achieved from the T6 ion propulsion system are:
- Cost effective solution,
- Minimal impacts on Alphabus (e.g. low mass, high reliability),
- Repeatable product design and performance (ensure interchangeability),
- Design for manufacture (minimising recurring cost and risks) and
- Ability to manufacture the qualified hardware long-term.
In addition to the above we expect to:
- Maximise capability for future expansion of the system and to cope with changes to the Alphabus requirements,
- Maximise common heritage and
- Maintain operational flexibility (minimise development risks and in-flight risks).
The core system comprises of the QinetiQ T6 gridded ion thruster, EADS Astrium Crisa PSCU and Marotta (UK) XFCU.
The most cost and mass effective system architecture for the Alphabus T6 ion propulsion system is based upon a one PSCU controlling two thrusters and is shown in the figure below.
The Pre-development has been completed involving: the build and characterisation of thruster engineering model, PSCU electrical model (EM) and XFCU breadboard model; the completion of a thruster partial life test and coupled test with the PSCU; and a successful PDR Meeting.
Phase 1 of the project has been completed with the PDR on 2-3 September 2004.
On the basis of the pre-development activities completed in Phase 1 the T6 High Power Electric Propulsion System (HPEPS) was "clearly and unanimously selected as being the best technical choice for Alphabus" by the ESA and CNES selection board with the participation of the Alphabus Joint Project Team.
A full development qualification and life test of the T6 HPEPS is to be kicked off in September 2005 and is to be completed by April 2009. The full development will also include the Electric Propulsion Pointing Mechanism (EPPM) to be developed by Austrian Aerospace.