Design and Testing of a Low Shock Discrete Point Spacecraft Separation System  Pete Wolf and Daryn E. Oxe"  Abstract  A separation system was designed for use on a standard Lockheed Martin satellite bus structure to allow  the satellite to separate from standard launch vehicles. The separation system had two key design  requirements: six discrete point attachments and a low shock separation (e1600 GIs). The design solution  was a system utilizing a heritage separation system component and a previously unused low shock  release device for booster separation, a Split Spool Release Device (SSRD). This paper describes the  overall design of the system as well as the unique challenges encountered during component and system  level design and test. The challenges were primarily associated with achieving the low shock requirement  imposed on the system and the integration of previously unused components into a new separation  system.  Introduction  The Discrete Point Spacecraft Separation System key requirements are: six discrete point attachments  and a low shock separation. These requirements were dictated by the spacecraft bus structural design  and the use of shock sensitive electronics. The structure is comprised of hexagonal bulkheads that are  connected to a central cylinder via radial panels. The radial panels are the primary mounting location for  all component electrical boxes on the spacecraft. They are also the primary load path for all launch loads  and the location of the discrete point attachments. In order to meet the low shock requirement, a new low  shock device had to be implemented because a standard pyro-actuated separation nut could not meet  the low shock requirements. After evaluating several candidate device designs, a Split Spool Release  Device (SSRD) was chosen as the restraint device in the separation system. This device has never been  used in a spacecraft separation system to date and there were many challenges associated with using  this relatively new device.  Design Description  The LM9OOA spacecraft bus does not mount directly to a standard Payload Attach Fitting, instead using a  secondary structure called a Booster Adapter Assembly (BAA). By using a secondary structure, the  separation plane as well as all associated separation components can be tested with the spacecraft to  minimize the amount of testing that occurs at the launch base. This allows a separation demonstration to  be performed prior to shipment to the launch base. The BAA is a large cylindrical ring that bolts on to an  industry standard 66 Payload Attach Fitting. Attached to the cylindrical ring of the BAA are 6 A-frame  brackets. These brackets are where the six SSRD's are mounted along with six Spring Mechanisms. The  SSRD's provide the restraint of the spacecraft during launch and provide a low shock release upon  command. The Spring Mechanism provides the separation tip-off force for the spacecraft during  separation. Shear loads between the launch vehicle and space vehicle during launch are carried by a  cup/cone interface. The A-frame brackets contain the conical half and the cup half is located in the aft  bulkhead of the spacecraft. Mounted inside the radial panels of the spacecraft, is a custom designed low  shock Retraction System used in conjunction with the SSRD's. The Retraction System ensures the  preload bolt clears the separation plane after release and provides positive retention for the life of the  spacecraft. The Discrete Point Separation System and the components -have been completely qualified  for use in a space environment and several system-level separation demonstrations have been  performed. Figure 1 shows the basic components of the Discrete Point Separation System.  ** NEA Electronics, Inc., Chatsworth, CA  Lockheed Martin Space Systems Company, Sunnyvale, CA  Proceedings of the 38'" Aerospace Mechanisms Sympsosium, Langley Research Center, May 17- 19,2006  149