Microsatellite Thermal Control: Shape Memory Alloys Sensing And Actuation For Louver Devices
- Paper number
IAC-07-E2.3.02
- Author
Ms. Alessandra Palli, University of Bologna, Italy
- Coauthor
Mr. Davide Bruzzi, University of Bologna, Italy
- Coauthor
Mr. Alberto Corbelli, University of Bologna, Italy
- Coauthor
Mr. Valentino Fabbri, University of Bologna, Italy
- Year
2007
- Abstract
In the last years, space education activities have been characterized by a large number of university small satellites that have been developed, assembled and operated in space, with a wide range of scientific/educational payloads. The main requirements for these missions are reliability, low power consumption and low cost design and manufacturing processes. Following this trend, at the II School of Engineering of the University of Bologna in Forlì a research program was started for the development of a small satellite platform, called ALMASat. ALMASat shares the requirements and drawbacks of all small satellite mission, in particular for what concerns the need for low power consumption of all devices installed on-board. Motivated by this need, and having in mind future ALMASat applications where active thermal control might be necessary, an innovative low-power solution for active thermal control has been conceived. It makes use of shape memory alloys (SMA) through which it is possible to merge in a single device both sensor and actuator capabilities. Thanks to mechanical properties of SMA, depending on the environmental temperature, it is possible to design spring-type actuators in order to change the orientation of mobile surfaces which form a louver array. In general, microsatellite layouts allow the mounting of louver arrays on the nadir and zenith pointing surfaces of the spacecraft, while four body mounted solar panels are on the spacecraft sides. Both the louvers and the satellite surface are covered with specific paints: the action of the louvers modifies the thermal radiation coefficients thus regulating the heat fluxes and consequently the satellite temperature. The SMA springs sizing has been performed focusing both on the admissible target temperature for the satellite subsystems and structural requirements, which depend on the desired louvers deflection and the need for minimum size. In order to test the benefits of these devices, a thermal analysis as been performed by running a series of simulations using a software code implemented in Matlab® programming language. The results obtained with a simple nodal structural model, have been definitely confirmed by further simulations performed in Ansys® environment, using APDL programming features and the actual satellite geometry (ALMASat-1 has been used as the reference target system). The thermal active control technique and the analysis discussed herein are suitable for application to a wide range of small satellite missions, designed following the same principles of modularity and reliability used in the ALMASat program.
- Abstract document
- Manuscript document
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