Testing and analysis of separation joints for Mars Science Laboratory

Each of the separating subsystems on the Mars Science Laboratory incorporates the use of separation joints. These joints serve as the structural connection between the mating subsystems during all dynamic loading prior to separation. Once the separation command is given, the structural connection is severed via actuation of pyrotechnic release nuts that let loose the structural bolts that hold the subsystems together. The use of a cup-and-cone design is utilized at the subsystem interfaces. Analysis and testing was performed to capture the stresses and deflection of the separation joint hardware under maximum shear loading. Testing included the use of an instrumented bolt that allowed bending moments down the length of the shank to be captured while the joint slipped from induced shear loading until the cup-and-cones engaged and took the shear across the joint. Extensometers were also used to capture the shear displacement of the structures to capture the slip event as well as elastic deflection of the cup-and-cone and parent structure. An analytical model was created and validated based on the test results. This analytical model was then used to calculate the structural margins of the separation joint at each of the subsystem's separation pianes(12).