Aug 27 – 29, 2018
Paris, France
Europe/Paris timezone

The design and analysis of INSPIRE’s structure and thermal subsystems

Aug 28, 2018, 9:30 AM
Charpak room (Paris, France)

Charpak room

Paris, France

Pierre and Marie Curie campus Sorbonne University


Mr Spencer Boyajian (LASP)


The structures of the INSPIRE satellites are all custom designs and assembled at the Laboratory of Atmospheric and Space Physics. The designs of the structures are heavily affected by the method of deployment from the launch vehicle and their respective mission for component placement. INSPIRESat-1, 3, and 4 will use a ring style deployer to separate from an Indian PSLV. These devices require that their mounting planes are completely clear, eliminating the exterior use of that side of the satellite. Additionally, they require the center of gravity to be within 5mm of the center of this ring, having the center of gravity projected no more than 150mm from the mounting plane. To simplify on orbit operations and reduce ADCS use, we have implemented smart component placement to align like pointing requirements within groups of components. For example, the CIP must face in the velocity vector direction during science operations and by placing the UHF antenna (monopole) in the opposite direction; you guarantee both pointing requirements are satisfied simultaneously. Then the S-Band patch antenna, ADCS with star tracker, and solar panel placement is decided, completing the pointing modes possible. (sun, nadir, velocity). This creates operations that are more robust and better ADCS function. The GPS antenna, Sun Sensors, radios, battery, and card-stack are placed according to which group of pointing they align with. (both for pointing of antennae and thermal radiation) Aluminum 6061-T6 is the only material used in the structure of the satellite. The hinges of the solar panel of stainless steel and brass whilst the UHF deployer is delrin. #4-40 socket head cap screws can assemble almost the entire satellite with the exceptions being the CIP, the ring, solar panels, and patch antennae. The structural analysis are performed in Solidworks using ANSYS to evaluate stresses in launch conditions. Analyses including but not limited to; Vibrational, Shock, Modal, and Static G. Methods in design and analysis from CSSWE and MINXSS were leveraged heavily for their heritage and we utilize a similar FEA and thermal desktop method to approximate the bolt-holes of the structure and reduce the computational power required to run simulations. This method involves mating the invisible pressure cones created around bolt-holes to one another, allowing for accurate testing for spreading between parts fixed around bolt-holes. The total mass for INSPIRESat-1 is approximately 8.5kg and passed all the structural analyses with a minimum safety factor of 13. The thermal subsystem of INSPIRESat-1 is passive, using only radiation aided by silver Teflon tape and careful duty cycling of components. The 3rd and 4th satellites will contain active cooling elements for their payloads requiring some active heat rejection be a part of the system. Similar to structure, smart component placement allows for their grouping by temperature preference. The temperature biases within the satellite are decided by the pointing regimes of the mission. Thermal Desktop was used to simulate the entire satellite and all physical interfaces. A powerful computational tool, it allows for appropriate radiation calculations throughout an orbit with different pointing and power usage scenarios. Two extreme and one nominal scenarios are run for each mission. The hot case when the beta angle reaches its absolute maximum of the orbit’s lifetime, the cold case at the beta angle closest to zero. The nominal case chosen to represent a day in the life of operations uses the median beta angle of the orbits lifetime. The results allow for fine tuning of component duty cycling and where different surface properties are required to keep all components within operational temperatures during any mode of operation in any condition.

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