A new ultrastable adhesive identified through ESA research could be a key to assembling rock-solid structures for space, including large telescopes, instruments and antennas to peer deeper into the cosmos or sharpen views of our terrestrial environment.
The resulting ceramic bonding promises composite structures of several metres rigid down to a few thousandths of a millimetre.
Such stability will be essential for new classes of space mission, such as multisatellite telescopes spaced hundreds of kilometres apart, which could combine their light to create images at a resolution equivalent to a single giant telescope – providing they maintain precise alignment.
Space is a difficult place for keeping still, however. In the absence of any atmosphere, temperatures may vary by hundreds of degrees from a satellite’s sunlit face to its shaded side. Use the wrong materials and a satellite’s structure might jitter, go out of alignment or even buckle catastrophically.
The challenge is greatest for optical, radio and other precision instruments, where rigidity is essential. To help ensure this, they are often kept thermally isolated from the rest of the satellite and attached to a steadying ‘optical bench’.
Careful material selection is essential. Take the case of ESA’s GOCE gravity-mapper, which had some of the most extreme stability requirements ever: the distance between its pairs of gravity-detecting sensors was not permitted to vary by more than a hundredth the diameter of an atom for minutes at a time.
These sensors were mounted on sandwiched panels of ‘carbon-carbon’- high-strength carbon fibres embedded in a graphite mix. Lighter than aluminium while stronger than steel, similar carbon composites have found uses in high-performance industries from aerospace to Formula One.
Carbon-carbon, as in GOCE, can also be tailored so that its dimensions remain unaffected by shifting temperatures.
For GOCE, carbon-carbon honeycomb was sandwiched between carbon-carbon sheets for maximum structural stability.
There was only one potential point of weakness, explains ESA materials engineer Laurent Pambaguian: “The adhesive used to bond the honeycomb to the panels was sensitive to moisture-induced distortion.
