Design and Analysis of V-Groove Passive Cryogenic Radiators for Spaceborne Telescopes & Instruments

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2020 International Conference on Environmental Systems

V-groove passive radiators are extremely efficient passive designs to thermally isolate a cryogenic telescope or instrument from warm environments in space, like the Sun, Earth, Moon or Spacecrafts. Compared to traditional multi-layer insulation blankets employed for thermal isolation, the V-Groove radiators provide as much as an order of magnitude improvement. The V-Groove design typically constitutes three low emissivity, lightweight and thin aluminized Mylar/Kapton sheets angled from each other by just few degrees. These successively reflect heat from warmer shields to space via their angular openings, thus minimizing heat flow into the cryogenic system. Thermal analysis of these V-Groove radiators is typically performed by sophisticated thermal software that uses hundreds of thousands of rays to simulate radiative heat flow between successive shields via reflections, which can be very time & resource intensive. We have arrived at very simple closed form equations to predict the thermal behavior of these radiators, that includes their radiative heat transfer factors and temperatures as a function of their basic thermo-optical properties and inter-shield angles. These predictions can be done by hand calculators or in spreadsheet tools like MS-Excel. They compare very well to those from sophisticated computer programs. The ease in the use of these simple equations allow for instantaneous predictions of cryogenic temperatures and their trends for design options and trade studies. A case study of this was utilized for the SphereX project that is currently being designed for an all sky spectral survey of the universe. This paper will describe the derivations of these equations, their comparison with computer software results and their applicability for current and future cryogenic space telescope and instrument missions.

Pradeep Bhandari, Jet Propulsion Laboratory (JPL)/California Institute of Technology, USA
Bradley Moore, Jet Propulsion Laboratory (JPL)/California Institute of Technology, USA
Douglas Bolton, Jet Propulsion Laboratory (JPL)/California Institute of Technology, USA
Asad Aboobaker, Jet Propulsion Laboratory (JPL)/California Institute of Technology, USA
ICES108: Thermal Control of Cryogenic Instruments and Optical Systems
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.
V-groove radiators, V-groove, Cryogenics, Passive, Telescope, SphereX