The Variation of Radiative Heat Loss As a Function of Actuation Angle for an Isothermal Square Twist Origami Radiator
Authors: Najeeb Mohammed Farhan Aziz , Price Jeremy , Warburton David , Mulford Rydge 
Published: September 2024

Abstract
Origami-inspired dynamic spacecraft radiators provide the ability for spacecraft to reject adjustable quantities of heat to account for orbital variations in onboard heating. These radiators might also find utility for planetary applications especially for Lunar surface, where more extreme temperature variations complicate the rejection of heat from Lunar power plants. The square twist origami tessellation provides large increases in rejecting surface area as the tessellation is actuated from fully closed to fully deployed. However, the variation of radiative heat loss as a function of actuation position is not found in the literature. This study determines the radiative heat loss behavior of an isothermal square twist origami radiator as a function of actuation position. The geometric locations of square twist origami tessellation panels are modeled using vector algebra for an infinitely thin (2D) square twist tessellation as well as a “thick origami” (3D) rigidly-foldable tessellation, both characterized by an adjustable closure angle.
The heat loss characteristics of both the 2D and 3D square twist origami radiators over a 180-degree range of actuation angle have been calculated. Monte Carlo Ray Tracing is used to simulate the radiative losses from the 2D surface over a range of emissivity values (0.1, 0.5, 1.0) and diffuse ray directions. The 3D surface is modeled with a radiosity balance implemented in the ANSYS thermal modeling environment.
Results show a divergence between the 2D and 3D square twist origami radiators. At different emissivities, the ratio of escaped to emitted rays showcases distinct behavior. The 3D square twist origami radiator demonstrates a slower decrease in this ratio as the closure angle increases, culminating at a ratio of 0.4 at an actuation angle of 180 degrees. Conversely, the 2D square twist origami radiator exhibits a linear decline, reaching a ratio of 0.32 at an angle of 180 degrees. Thermal simulations across the range of motion with uniform surface temperatures showcase a turndown ratio (largest to smallest heat transfer) of 4.42. These results substantiate the practicality and efficacy of the rigidly foldable square twist model for radiative heat loss control.
Further analysis extends to derivative geometries, including the “StarTwist,” and “Sloped-Edge Twist.” Ray tracer simulations were conducted, adhering to the same range of emissivities. The results showcase the potential of these derivative geometries as promising contenders for advanced thermal management systems. Results demonstrate the efficient thermal management capable with origami radiators for space exploration, with origami-based designs offering adaptable surface area and dynamic thermal control capabilities. These initial insights underscore the merits of origami-based design, with the potential for further optimization and enhanced thermal efficiency.
Furthermore, the study highlights turndown ratios across different emissivity levels. At an emissivity of 1, the turndown ratios are 3.32 for the square twist, 1.96 for the sloped-edged twist, and 2.88 for the star twist. At an emissivity of 0.5, these ratios are 3.27 for the square twist, 1.95 for the sloped-edge, and 2.87 for the star twist. Finally, at an emissivity of 0.1, the turndown ratios are 3.08 for the square twist, 1.91 for the sloped-edge twist, and 2.78 for the star twist, demonstrating the variable thermal management efficiencies of these designs.