The Use of LS-DYNA to Simulate the Water Landing Characteristics of Space Vehicles

Irvin Aerospace, Inc. has been involved with the recovery/landing systems of re-entry and interplanetary space vehicles spanning a number of years. A significant aspect in the assessment of recovery and escape systems is the performance of such vehicles in the event of a water landing. One method used to reduce the loads imparted to the crew as the vehicle enters the water is to increase the drag area of the falling body. Increasing the drag area of the recovery system is a simple resolution, however, integration leads to an unfavorable increase in the total system mass and volume requirements. An alternative solution, utilized by the Apollo Earth Landing System, is to dictate the orientation of the vehicle prior to water impact. The results of an exhaustive test program showed that the accelerations experienced by the crew could be reduced by a factor of five simply by changing the vehicle water entry angle. This paper presents an application of the Eulerian-Lagrangian penalty coupling algorithm and multi- material ALE capabilities within LS-DYNA. Documented in the report are the results of a series of validation simulations undertaken by Irvin in an IRAD program to ascertain the capacity of LS-DYNA to replicate the water- landing characteristics of an Apollo Command Module and predict the performance of future landing systems