Multibody Modeling and Simulation for the Mars Phoenix Lander Entry, Descent and Landing
A multi-body flight simulation for the Phoenix Mars Lander has been developed that includes high fidelity six degree-of-freedom rigid-body models for the parachute and lander system. The simulation provides attitude and rate history predictions of all bodies throughout the flight, as well as loads on each of the connecting lines. In so doing, a realistic behavior of the descending parachute/lander system dynamics can be simulated that allows assessment of the Phoenix descent performance and identification of potential sensitivities for landing. This simulation provides a complete end-to-end capability of modeling the entire entry, descent, and landing sequence for the mission. Time histories of the parachute and lander aerodynamic angles are presented. The response of the lander system to various wind models and wind shears is shown to be acceptable. Monte Carlo simulation results are also presented.
Mars landing engine plume impingement ground interaction
A subscale landing site alteration program was conducted in support of future Mars landed Missions to provide site alteration data including soil erosion mechanisms and dependency on throttle level, altitude, and ground slope. A 25% scale Viking Lander Engine was fired into a representative Mars stimulant soil-media test bed. The test facility was operated at ~633 Pa to match the supersonic plume expansion at mars ambient pressure. The test apparatus utilized quarter symmetry with the use of baffle planes. A media that is 1/3 the density of Mars silica was used to match the 1/3 gravity Mars ballistic coefficient and particle trajectories. Key findings include soil bulk shear failure as the primary erosion mechanism, nonlinear dependence of erosion with throttle level and ground slope, and particle size. Another key finding is that we observed significantly larger erosion rates for supersonic jets (underexpanded) at Mars atmospheric pressure as opposed to jets (highly over-expanded) at Earth atmospheric environment. The highest ground pressures were also observed in the Mars atmospheric regime with jet expansion ratios greater than 2.
Great American Bridges and Dams
Bridges: Spanning the Nation. Dams: Controlling a Precious Resource. Saving Bridges and Dams. Guide to the Guide. THE BRIDGES AND DAMS. New England. Mid-Atlantic. South. Midwest. Southwest. West. Epilogue: The Ones That Got Away. Further Reading. Information Sources. Index.