Flight Model Thermal Design and Verification for the 6U Deep Space CubeSat EQUULEUS



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2020 International Conference on Environmental Systems


EQUULEUS is a 6U CubeSat developed by the University of Tokyo and JAXA, which will fly to a libration orbit around the second Earth-Moon Lagrange Point (EML2) as a piggy-back payload of the Space Launch System (SLS). At the libration orbit, EQUULEUS will conduct three scientific missions, such as detection of lunar impact flashes. To realize these observations, the thermal design of EQUULEUS faces three major constraints coupled with other subsystems, including the orbital design and the water propulsion system it utilizes. Firstly, since EQUULEUS is a piggy-back satellite, there is an uncertainty in the launch date. Therefore, the thermal design of EQUULEUS must consider all sun directions right after release, which affects the heater wattage to achieve the required thrust value to reach EML2. Secondly, during the observation phase around EML2, EQUULEUS will also experience sunlight from multiple directions. Finally, the water resist jet propulsion system EQUULEUS adopts for trajectory control and angular momentum unloading makes the thermal design more difficult than utilizing other propulsion systems, in terms of propellant freezing and the large latent heat required for propellant vaporization. Under these constraints, the thermal design of EQUULEUS Engineering Model was established and implemented to the actual spacecraft. However, the results of validation by numerical simulations and a thermal vacuum test showed a temperature excess at one mission component, and insufficient heat conductance at two critical component connections. In this presentation, design changes in the Flight Model are proposed to solve the problems in the Engineering Model. A thermal vacuum test for the Flight Model verified that the final thermal design of EQUULEUS can meet the complicated requirements to reach and conduct scientific missions at EML2.


Toshihiro Shibukawa, The University of Tokyo, JP
Shuhei Matsushita, The University of Tokyo, JP
Keidai Iiyama, The University of Tokyo, JP
Akihiro Ishikawa, The University of Tokyo, JP
Keita Nishii, The University of Tokyo, JP
Ryu Funase, The University of Tokyo, JP
ICES107: Thermal Design of Microsatellites, Nanosatellites, and Picosatellites
The proceedings for the 2020 International Conference on Environmental Systems were published from July 31, 2020. The technical papers were not presented in person due to the inability to hold the event as scheduled in Lisbon, Portugal because of the COVID-19 global pandemic.


Thermal design, CubeSat, Deep space exploration, Water resist jet