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 offloading. 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.

Supersonic wind-tunnel tests of 0.813 m disk-gap-band parachutes were conducted in a 10 10 ft cross section of a closed-loop wind tunnel. Four-percent-scale parachutes were attached to a 4%-scale Mars Science Laboratory (Viking-type) entry vehicle to simulate the free-flight configuration. The parachutes were tested from Mach 2 to 2.5 over a Reynolds number Re range of 2 10 5 to 1:3 10 6 , representative of the Mars flight deployment envelope. A constrained parachute configuration was investigated to quantify the effect of parachute trim angle with respect to alignment with the entry-vehicle wake. In the constrained configuration, the parachutes were supported at the vent, using a rod that restricted parachute translation along a single axis. This was investigated for fixed trim angles of 0 and 10 degrees from the velocity vector. In the unconstrained configuration, the parachute was permitted to translate as well as trim and cone, in a manner similar to free flight. Nonintrusive test diagnostics were selected. An in-line load cell provided measurement of unsteady and mean parachute normal force. High-speed shadowgraph video of the upstream parachute flowfield was used to capture bow-shock motion and standoff distance. Stereo particle image velocimetry of the flowfield upstream of the parachute provided spatially resolved measurements of all three velocity components. Multiple high-speed-video views were used to document the supersonic inflation, parachute trim angle, projected area, and frequency of area oscillations. In addition, reflective targets placed in the interior of the canopy enabled photogrammetric reconstruction of the canopy-fabric motion (in both time and space) from the high-speedvideo data. Nomenclatureor constructed diameter D p = projected diameter d = entry-vehicle diameter F D = axial drag force F D;RMS = axial rms drag M = Mach number m p = parachute mass q = freestream dynamic pressure Re = Reynolds number t = time t FI = time to full inflation t = nondimensional inflation time x=d = nondimensional trailing distance v = freestream velocity p = mass ratio ! AO = area oscillation frequency

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In 2010 the Mars Science Laboratory (MSL) mission will deliver NASA's largest and most capable rover to the surface of Mars. MSL will explore previously unattainable landing sites due to the implementation of a high precision Entry, Descent, and Landing (EDL) system. The parachute decelerator subsystem (PDS) is an integral prut of the EDL system, providing a mass and volume efficient som•ce of aerodynamic drag to decelerate the entty vehicle fi•om Mach 2 to subsonic speeds prior to final propulsive descent to the sutface. The PDS for MSL is a mortru• deployed 19.7m Viking type Disk-Gap-Band (DGB) parachute; chosen to meet the EDL timeline requirements and to utilize the heritage parachute systems from Viking, Mars Pathfinder, Mars Exploration Rover, and Phoenix NASA Mars Lander Programs. The preliminruy design of the parachute soft goods including materials selection, stress analysis, fabrication approach, and development testing will be discussed. The preliminaty design ofmottru• deployment system including mortar system sizing and performance predictions, gas generator design, and development mottru• testing will also be presented.