What is its role?
Once up in orbit, the ability to produce precisely controlled, lower-energy thrusts becomes very important to meet mission goals. ESA’s Propulsion Lab tests methods of controlling the motion of spacecraft once they have reached space. In particular, the Lab has acquired a great deal of expertise on various methods of electric propulsion as well as chemical propulsion systems.
What services does it offer?
Much of the Lab’s work involves characterising engine performance during firing. The Lab has a certified ability to obtain these measurements. As well as possessing general ISO 9001 quality management accreditation, the facility has specific ISO 17025 accreditation for measuring thrust, mass flow and electrical parameters related to propulsion system operations, along with related calibration processes.
Another test the Lab offers is endurance firings. As ion thrusters in particular deliver low initial acceleration they often need to operate for extended periods of time to yield full benefit – hundreds or even thousands of hours at a time.
How is it equipped?
An ISO class 8 cleanroom, the Lab incorporates seven vacuum chambers of various sizes – from a maximum 2 m in height and 5 m in length down to a compact 0.8 m by 1 m – customised for testing different types of engine. Elaborate multi-stage pumping systems take the air inside down to a maximum 11 orders of magnitude below standard atmospheric pressure. Temperature and humidity are rigorously controlled, and the Laboratory is served by an uninterruptible power supply.
Four vacuum chambers are located above a 160-tonne concrete slab known as the Seismic Isolation Block. This block can be raised up on eight pneumatic dampers to filter external vibration. To damp seismic ‘cross-talk’ between experiments running on the block, smaller isolation blocks can be jacked up within individual chambers.
Experiments require extremely accurate measurements of thrust force down to millinewton and micronewton levels, so the Laboratory has worked with external specialists including the UK’s National Physical Laboratory (NPL) to develop custom made thrust stands. These stands work on a basis of displacement to derive thrust.
With higher-power kilowatt-range ion engines, plume force damage is minimised using a beam target. Electrostatic probes acquire plume charging data while mass spectrometers and gas analysers are available to measure plume composition. Highresolution,
high-rate cameras acquire plume appearance. Flow measurements of thruster propellants are also made.
The latest vacuum chamber, known as the Small Plasma Facility, is large enough to place sections of a spacecraft inside as well as a thruster, to study interaction with adjacent spacecraft surfaces. The Lab is also working with NPL on a nil force pendulum design capable of measuring previously undetectable 0.1 micronewton displacements.
Who are its customers?
Working closely with ESA project teams, the Laboratory’s research during the last two decades has underpinned ESA’s adoption of ion thrusters. Future deep-space missions BepiColombo and Solar Orbiter will employ ion engines and chemical propulsion respectively to fly close to the Sun. The Lab has also made considerable progress in both electric and chemical micropropulsion, delivering unprecedented precision spacecraft control with numerous scientific applications.
The Lab also coordinates a European network of industrial and academic propulsion labs known as EPNET, serving to pool test resources when required and establish common test standards.
How do I find out more?
Contact Lab Manager Jose Gonzalez Del Amo