A Safer Landing with Water Impact Analysis

The Orion Crew Module houses NASA astronauts during space travel and allows them to safely descend back to Earth from orbit after mission completion. The structural design of the module considered various loading conditions such as liftoff, launch abort, re-entry and impact landing. It was determined that one of the largest loading conditions impacting the structure of the Crew Module was an Earth water landing which is a highly complex and dynamic event. In order to maintain structural integrity and increase safety of the astronaut crew, a more clear understanding of the dynamic loads generated during water impact was required.

The NASA Engineering and Safety Center (NESC) collaborated with Altair ProductDesign to establish a clear understanding of the specific modeling methods needed to perform dynamic simulations of the module during a water landing. In order to ensure that any simulation of the landing accurately matched the real world event, a limited amount of physical testing was required. NASA fabricated a full scale module and fitted it with various data collection devices before conducting a total of sixteen physical tests from varying impact angles and velocities.

Using Altair’s own HyperWorks virtual simulation suite, Altair ProductDesign built an accurate finite element model of the module from CAD data supplied by NESC, as well as a section of water and air which matched the conditions from the lake used during the physical tests. The effect on the module’s structure during impact was simulated to gauge how well the results correlated with the physical tests.

The results showed excellent correlation between the simulation and physical tests, identifying areas where the model, input parameters and meshing methods could be improved to give a more accurate prediction of the event. A mesh sensitivity study revealed that the mesh size ratios of the Crew Module to the fluid were vital in obtaining a good correlation. The findings from the study will prove invaluable to provide accurate simulation data for the rest of this ongoing project. With a tried and tested simulation methodology, NESC can be confident that the simulation results from future development activities are an accurate representation of real world impact behavior, thus allowing for the development of improved landing safety systems.

NESC presented a Group Achievement Award to the Altair ProductDesign team for their outstanding contribution to this project.