The delicate art of building and testing spacecraft structures


Specialists gathered recently at ESA's technical heart to discuss the fundamental issue of how to build spacecraft: designing structures for space, selecting optimal building materials and then testing the results against the rigours of spaceflight.

More than 500 participants attended the 12th European Conference on Spacecraft Structures, Materials and Environmental Testing, hosted at ESA's technical centre at Noordwijk, the Netherlands, on 20-23 March, with a total of 218 papers presented.
Participants shared their experiences of designing and testing spacecraft and launcher structures to operate in space. Space structures and mechanisms need to be strong, stiff, thermo-elastically stable and resilient enough to cope with the violence of a rocket launch then endure the space environment, typically for years, while fulfilling specific mission requirements.

Temperature extremes risk causing vibration and distortion in structures. Meanwhile, moving parts have to operate without failure and without causing micro-vibration disturbances in the spacraft. And all these factors need to be properly simulated on the ground for effective preflight validation.

"Spacecraft structures, materials and environmental testing are fundamental and key areas for all space missions, and are therefore subject to continuous evolution and development," said Constantinos Stavrinidis, head of ESA's Mechanical Engineering Department during the opening session.

"I would like to see this conference contributing to such effort. Knowledge is not a privilege - it has to be earned through hard work."

The first day included an overview of the mechanical design and testing performed for Europe's new Vega launcher, which flew for the first time on 13 February, incorporating a number of lightweight composite materials.

Other presentations focused on work supporting Europe's Galileo satellites, which ride to medium orbits atop a special dispenser. Ground testing checked that the shock of separation as the two satellites spring away from the dispenser do not affect the satellites' sophisticated navigation payloads.

And ESA's new Alphasat mission - Europe's largest telecommunnications satellite when it is launched early next year - required validation of its structural and mechanical design, including a deployable 12 m-diameter antenna.

Other presentations covered the Gaia mission, whose billion-pixel CCD imager needs an ultrastable silicon carbide ceramic structural ring to rest upon as it creates its 3D map of a billion stars, and BepiColombo, whose mid-decade mission to Mercury will send it into sunlight 10 times more intense than at Earth.

The Swarm trio of satellites, due for launch later this year, presented mechanical challenges of a different order: their structures need to remain magnetically 'clean' and free of microvibration to measure slight variations in Earth's magnetic field.

Presentations also recounted how the ESTEC Test Centre facilities have been upgraded to meet the needs of missions such as BepiColombo and Solar Orbiter, a follow-on mission that will venture even closer to the Sun.

"Specialist sessions dealt with state-of-the-art developments in related design and verification tools and methodologies," said Torben Henriksen, head of ESA's Structures and Mechanisms Division, and conference co-organiser.

"These included advancements in vibroacoustic analysis of spacecraft structures, new manufacturing methodologies, application of new thermo-elastically stable materials, correlation methodologies for mathematical models of launchers and spacecraft, micro-vibration characterisation, vibration attenuation and design and verification of inflatable and deployable structures."

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