Protecting Satellites from the Dynamics of the Launch Environment

Abstract : Reduction of the vibration and shock loads seen by spacecraft during launch would greatly reduce the risk that the spacecraft and its instruments will be damaged during their ascent into orbit, and would also allow more sensitive equipment to be included in missions. As the severe launch environment also accounts for much of the expense of designing, qualifying, and testing spacecraft components, significant cost can also be saved if dynamic responses seen by the spacecraft are reduced. The launch events include low frequency dynamic loads such as liftoff, motor excitation, buffet, motor starts and shutoffs. Spacecraft are also subjected to shock loads in the several thousands of g's level during their trip to orbit. These high shock loads usually result from some separation event, such as staging, spacecraft separation, and fairing separation. Protecting the satellite from these loads by whole-spacecraft vibration and shock isolation systems has now been demonstrated. The basic concept of whole-spacecraft isolation is to isolate the entire spacecraft from the dynamics of the launch vehicle. This paper discusses two different systems: the SoftRide system, which is a lower frequency (10 - 50 Hz) isolation system and the ShockRing system, this is designed to attenuate higher frequency loads (70 Hz and above), including shock. All seven flights of CSA's SoftRide systems have shown excellent loads reductions in the coupled loads analyses and verified in the flight telemetry data Component tests have been performed on the ShockRing using a specially built pneumatic gun that can generate 10,000 g's on the test article. Results from these tests demonstrate substantial reductions of the shock being transmitted to the payload. Results from a system test consisting of a spacecraft simulator, payload attachment fittings, avionics section, and shock plate will be discussed.