COVER STORY ADVERTISEMENT FEATURE N SATELLITE THERMAL IMAGING
solar radiation can also damage the standard PVC insulation to the motor and encoder, so a PTFE replacement, featuring higher radiation compatibility, has been used.
PERFORMANCE IN SPACE “One of the main drivers for us in motor choice was operation in harsh environments – specifically the space environment, so seeing that these motors had heritage in other space projects was a huge plus for us,” explains Gomez-Jenkins. Considering the working points required
for the space environment, the drive system also requires careful sizing. In a vacuum, the convection heat path is lost, and the only means of heat dissipation is via conduction. To ensure long-term operation without overheating, the drive system is oversized compared to terrestrial atmospheric conditions, yet the motor must still optimise the high torque density and low mass profile required to compliment Hibiscus’ compact footprint. Crucial to achieve the performance the deployment system requires, the DCX motors also ensure smooth control thanks to features such as the ironless core that removes cogging.
A DRIVE SYSTEM FOR A SPACE ENVIRONMENT Once the telescope satellite has been set into orbit, two maxon DCX motors, in combination with a GPX high efficiency gearbox and extended temperature encoder, will drive the deployment system of each petal. A further four DCX motors will also control robotic arms assisting with the fine adjustment of the mirror configuration. Initially, the drive system must survive
the extreme vibrations of launch. Once deployed in space, the motors must operate in a vacuum –
Fiona Neufeldt, Conor O'Donoghue and Billie Cook, SuperSharp engineers, utilising the optics table
and face the extremes of low temperature operation. To achieve this, the design and materials of the motor have been developed and tested to withstand the highest shock and vibration. In space, motor lubrication also needs special
consideration to prevent outgassing, the release of volatile substances trapped within lubrication when exposed to a vacuum. As well as degrading the long-term performance of the drive system, outgassing can also cause condensation that can damage wider components, so maxon has specified a vacuum-compatible grease. High
NEW POSSIBILITIES Before Hibiscus can launch, multiple prototypes continue to undergo rigorous testing to de-risk the technical elements. However, as the technology of satellite thermal imagery is still an emerging field, not yet economically viable for most organisations, education of its advantages is ongoing. “Thermal imaging from space is still something
very new,” says Gomez-Jenkins. “Not many organisations are aware what can be achieved, so we’re continuing to push the advantages of cost-effective, precise analysis of heat maps, for the benefit of a wide variety of applications.” When Hibiscus is set into orbit at the end of
next year, the result will be the world’s first closed loop, unfolding thermal telescope.
maxon
www.maxongroup.co.uk
Cosima Pitman, Richard Parker and Brett Wakley, SuperSharp engineers, working on the electronics bench
FEBRUARY 2025 DESIGN SOLUTIONS 13
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