Participant: PROMISE AGEP Research Symposium
Department: Aerospace Engineering Department
Institution: University of Maryland College Park (UMCP)
Planetary Defense Mission Using Artificial Collision of NEOs
A conceptual demonstration mission using a “billiard-ball” method for planetary defense was investigated. This concept included the development of a spacecraft that would capture a small (<10m in diameter) Near Earth Asteroid (NEA) and redirect its orbit to cause a collision with a larger NEA (about 100m diameter). For this demonstration mission, neither the captured asteroid nor the target asteroid posed any threat to the Earth, either before or after the collision. The selection criteria resulted in 4 possible candidates for the capture asteroid. A much broader list of target NEAs was found because of the larger known population of NEAs with diameters over 100 m. In order to find a candidate pair, the ephemeris data for each of the 4 capture NEA candidates was compared to the ephemeris data for the list of target NEAs until a match with favorable conditions was found. In order to ensure a detectable collision, requirements were established for intercept velocity, angle of intercept, date of collision, distance at desired collision and other criteria. The spacecraft was designed with inspiration from the Dawn mission and the Asteroid Redirect Mission. A low thrust ion engine system would provide maneuvering and redirect thrust, while a high-thrust system would provide any final corrections just before the collision. A cost model was developed using previous NEA mission data in order to estimate the cost of the spacecraft development and launch.
GENERAL SUMMARY OF GRADUATE RESEARCH
As part of my graduate research, I have developed closed-loop controls for a pneumatic cylinder. This cylinder has applications as the main actuation for a legged walking rover. The rover would be optimized for walking on planetary bodies in the solar system, such as Mars. Specifically, I developed a Proportional Integral (PI) controller for the cylinder in a vertical configuration to achieve a specific profile of motion that would provide the walking motion once integrated into the leg. Root-mean-square error (RMSE) was selected as the primary metric of success for the desired motion. A literature survey of current systems set a target RMSE of about 1% the stroke length of the cylinder. An initial “experimental” PI controller was developed by experimentally determining the appropriate PI gains. This resulted in a controller which provided about 1.5% RMSE of the six inch stroke length for the Clippard pneumatic cylinder. As part of ongoing controller development, a plant function was derived for the dynamics of the cylinder system. This is being implemented and simulated in Simulink in order to optimize gains in software to achieve better performance. Additionally, a pressure sensor was incorporated, which was a prominent method of control development noted in the literature survey.
SELECTED LIST OF PRESENTATIONS AND PUBLICATIONS
- AIAA YPSE 2013 – Control Development for a Walking Rover (Presented)
- IAA Planetary Defense Conference 2014 – BILLIARDS: Baseline Instrumented Lithology Lander, Inspector and Asteroid Redirection Demonstration System (Poster presentation)
- IAA Student Paper Conference 2014 – Control Development for a Pneumatic Rover Leg