8. Experimental Test of Spacecraft Parachute Deployment using Real-Time Hybrid Substructuring

Spacecraft are subjected to a variety of extreme loads during the course of a mission. One such demanding period during reentry is parachute deployment when a mortar on the spacecraft is used to deploy the parachute. Firing the mortar to expel the parachute imparts an impulsive force on the spacecraft and results in vibration throughout the spacecraft. Successful deployment of the parachute is critical to the success of the mission, and accurate prediction of the impulsive forces exerted on the spacecraft during deployment is paramount to the design and safety of the spacecraft. Typically the time history of the reaction force of the mortar is measured experimentally using a rigid mounting system. This approach neglects the structural compliance of the spacecraft and thus neglects the dynamic interaction between the mortar and spacecraft. This may lead to differences between the force profile observed during laboratory testing and those observed during the mission of the spacecraft.

In this paper, a cyber-physical test procedure called real-time hybrid substructuring (RTHS) is proposed to test the parachute deployment of the Mars Pathfinder spacecraft. The proposed RTHS test couples, in real-time, a numerical substructure, consisting of a dynamic model of the Mars Pathfinder with a physical substructure, consisting of a mortar being fired in the Shock and Vibration Laboratory at the University of Connecticut. The proposed RTHS test will be shown to fully capture the effect of spacecraft compliance on the force profile generated during the mortar firing. The Mars Pathfinder RTHS test is used to demonstrate this new approach in aerospace testing that can allow for component testing during the design phase to provide more realistic load profiles and more certain dynamic response at critical locations throughout the spacecraft.