Parachute Models Used in the Mars Science Laboratory Entry, Descent, and Landing Simulation

An end-to-end simulation of the Mars Science Laboratory (MSL) entry, descent, and landing (EDL) sequence was created at the NASA Langley Research Center using the Program to Optimize Simulated Trajectories II (POST2). This simulation is capable of providing numerous MSL system and flight software responses, including Monte Carlo-derived statistics of these responses. The MSL POST2 simulation includes models of EDL system elements, including those related to the parachute system. Among these there are models for the parachute geometry, mass properties, deployment, inflation, opening force, area oscillations, aerodynamic coefficients, apparent mass, interaction with the main landing engines, and off-loading. These models were kept as simple as possible, considering the overall objectives of the simulation. The main purpose of this paper is to describe these parachute system models to the extent necessary to understand how they work and some of their limitations. A list of lessons learned during the development of the models and simulation is provided. Future improvements to the parachute system models are proposed

Phoenix Mars Scout Parachute Flight Behavior and Observations

The data returned from the successful Phoenix Mars Scout mission are analyzed in order to determine characteristics and behaviors of the supersonic parachute that was used to slow the entry body during its descent to the surface. At least one significant drag reduction event was observed when the vehicle was traveling at Mach 1.6; this is consistent with previously reported terrestrial high altitude testing and is likely associated with an area oscillation of the parachute. The parachute is shown to possess some lateral instability relative to the anti-velocity vector that is also at a level that is consistent with the same historic data. Ramifications of the lateral instability and, in particular, the unsteadiness in the parachute drag are discussed as energizing elements of the entry body wrist mode. The apparent coefficient of drag for the parachute is calculated and shown to have relatively small variations on an average basis over the supersonic portion of flight