Space for the People

System Testing and Analysis

The thermal analysis outlined here is based on the assumption that the satellite’s temperature must return to the same value after each thermal cycle. It is meant only to identify major risk areas in the design of EQUiSat and to determine whether the satellite will require any active means of thermal control. Before designing the configuration of the satellite subsystems it will be necessary to model the spacecraft and orbit conditions computationally, using much more sophisticated software, such as ABAQUS CAE.

Model

  • The satellite is modeled as a thin plate, which radiates heat from both faces. One face is pointed normal to incident solar radiation and the other is earth-facing
  • The heat flux is calculated using a step-wise process in increments of 200 seconds
  • Solar exposure for 54.26 minutes (assuming 300 km orbit), eclipse for 36.24 minutes
  • Due to relatively short orbital period, the satellite reaches dynamic equilibrium
  • Heat produced by components estimated by component efficiency (worst case scenario)

Conclusions

  • Maximum temperature of 36.8 degrees Celsius
  • Minimum temperature of 29.0 degrees Celsius
  • Equilibrium range is within the operating range of all components

Model

  • Magnetic torque, gravity gradient, aerodynamic alignment, and solar pressure were considered using a disturbance torque model
  • The magnetic torque dominated with an order of magnitude of 10E-3 N-m
  • Despite a small moment arm, gravity gradient followed with a maximum torque of magnitude 10E-5 N-m
  • Drag and solar pressure were calculated to be insignificant
  • All calculations were performed with an assumed orbital height of 300 km

Conclusions

  • A dominating magnetic disturbance torque will cause the satellite to tumble randomly due to the varying directional currents experienced during each period in absence of attitude control
  • This implies that the flash tube will be earth-facing roughly 1/6th of the time
  • In order to ensure reliable sighting and encourage greater and more predictable public viewing participation, an Attitude Control System will be employed.
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