Coupled Thermally Induced Transverse Plus Torsional Vibrations Of A Thin Walled Cylinder Of Open Section

Long thin-walled cylinders of open section (STEM type booms) have been used on many satellites either for experimentation or Gravity Gradient stabilization. Equations for the coupled transverse plus torsional oscillations of a long open section cylinder in direct sunlight are derived. Numerical results show that unstable thermally induced oscillations can be excited solely by the impinging thermal energy of the sun. It is shown that this is a direct result of the boom's extreme weakness in torsion. By literally zippering the boom's open section, to increase its torsional rigidity, the problem can be eliminated. Flight data from OGO IV, V, VI and RAE are cited to support the theoretical findings.