Speakers
Description
Thermoplastic composite (TC) structures offer a promising alternative to conventional
aluminium spacecraft architectures by combining low mass, high specific stiffness, and
increased manufacturing flexibility. This paper presents the thermal characterization
and thermal vacuum (TVAC) validation of the TeSat to assess the applicability of LMPAEK thermoplastic composites for small satellite primary structures.
The test article consisted of a ~100 kg class satellite platform featuring a primary
structure manufactured from LM-PAEK reinforced with carbon fibres. A comprehensive
TVAC campaign was performed, including bakeout at +80°C, thermal balance tests at
−40°C and +40°C, and thermal cycling between −40°C and +80°C under vacuum levels
below 1×10⁻⁵ mbar. More than 240 hours of thermal data were collected from
distributed temperature reference points located on structural panels, payload
simulators, avionics units, and external antennas.
The spacecraft successfully completed all test phases without structural degradation,
sensor detachment, or violation of operational temperature limits. During thermal
balance testing, the highest measured temperature reached approximately 76-80°C,
while the coldest structural regions reached −18°C, resulting in local thermal gradients
approaching 100°C across the platform. The thermal response was primarily driven by
internal power dissipation rather than environmental boundary conditions. In the coldactive case, top patch antennas dissipating 14.5 W reached temperatures of
approximately 65°C despite the chamber environment being maintained at −42°C. A 15
kg steel mass simulating the SVPX assembly dominated transient behaviour, extending
stabilization times to up to 21 hours for the most demanding thermal balance cases.
Correlation of the thermal mathematical model against TVAC measurements revealed
significant discrepancies in the initial analysis. The non-correlated model
underestimated temperatures of composite walls and interface regions by up to 28°C,
mainly due to overestimated surface emissivity and uncertainties in composite-to-metal
thermal contact conductance. Following correlation, including adjustment of thermooptical properties and interface conductances, the maximum error was reduced to
14°C, while prediction accuracy for most equipment temperatures improved to within 1-
7°C of measured values. The average error for critical wall sensors was reduced by
approximately 50-70%.
The results demonstrate that LM-PAEK composite structures exhibit substantially
different thermal behaviour than conventional aluminium satellites. While the assumed
bulk thermal conductivity values (10 W/mK in-plane and 3 W/mK through-thickness)
were largely validated, metallic inserts and fasteners were found to create significant
conductive pathways that strongly influence overall thermal performance. The study
highlights the need for dedicated characterization of emissivity and composite-to-metal
interface conductance and provides valuable experimental data for future thermal
design, modelling, and qualification of thermoplastic composite spacecraft structures.