Speaker
Description
ESA’s HERA mission launching in October 2024 is the follow-up to NASA’s DART mission, investigating planetary defence measures by impacting the Dimorphos asteroid, part of the Didymos binary asteroid system. HERA’s mission is to measure the momentum transfer from DART as well as catalogue in greater detail the asteroids’ properties. HERA will carry two CubeSats: Milani and Juventas. Juventas with payloads of GRASS: a gravimeter, and JuRa: a Low-Frequency Radar, will assist with the investigation into the makeup of Dimorphos.
This presentation will describe the thermal design and validation of the Juventas Structural Thermal Interface Model (STIM). With a complex thermal environment, the CubeSat is designed for the full mission duration: stowed inside HERA, deployed but still attached to the HERA spacecraft, and when fully commissioned with deployed solar panels and antennas in deep space (1.26AU to 1.72 AU).
Albeit a simplified model, the STIM was designed to have the same structural, thermal, and electrical interfaces representative of the flight model. It was used to validate a Finite Element Analysis (FEA) model which replicated the mass and specific heat capacity of the STIM within 5% and 10% respectively.
The primary validation effort was the Thermal Balance Test (TBT) done at two plateaus: a hot TBT was performed at 10DegC to investigate the dissipations of the spacecraft and a cold TBT was performed at -10DegC to investigate the heaters and insulating spacers on the propulsion tank. A COMSOL FEA model and Lumped Parameter Model (LPM) were created of the STIM in a TVAC chamber, replicating the environmental conditions of the TBT. Comparing the results of the TBT test to the FEA model and LPM; allowed for the validation of the FEA modelling technique. The revised assumptions have been updated in the flight model FEA. The difference between the TBT and LPM resulted in a less than 5DegC difference on the spacecraft body. Comparing the results of the thermocouples on STIM, with the equivalent probed nodes on the FEA model, resulted in an average difference of 0.87 DegC during cold validation, and 3.98 DegC for hot validation.
The Juventas flight model is ongoing and is being led by GomSpace Luxembourg and supported by GomSpace Denmark.
