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

Abstract

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.

Reconstruction of the Mars Science Laboratory Parachute Performance and Comparison to the Descent Simulation

“…The deployment model implemented in the POST2 simulation 4 was set to yield a time from mortar fire to suspension lines stretch between 1.226 and 1.454 s, with a uniform probability distribution between these two values. The reconstructed value for this time interval was 1.135 s; this was 0.091 s lower than the model's lower bound.…”

“…The reconstructed value for this time interval was 1.135 s; this was 0.091 s lower than the model's lower bound. Similarly, the inflation model 4 was set to yield a time from suspension lines stretch to first peak force between 0.636 and 0.812 s, with a uniform probability distribution between these two values. Again, the reconstructed value for this time interval, 0.635 s, was lower than the model's lower bound although just barely so (0.001 s) and within the reconstruction timing uncertainty of the event (given that data was collected at 200 Hz with a corresponding time steps of 0.005 s).…”

“…2,3 This simulation included numerous models related to the parachute system and its performance. 4 This paper's secondary objective is to compare the parachute models and simulation's predictions against parachute performance reconstruction results.…”

“…In the companion paper, 4 the POST2 simulation and parachute models are discussed in more detail. The descriptions of the MSL parachute system and its operation, as presented herein, are also included in reference 4.…”

Mission Profile and Design Challenges for Mars Landing Exploration

“…Figure 9. A typical Disk-Gap-Band Parachute (Cruz et al, 2013) The drag coefficients as a function of Mach number for the DGB parachute are tested via wind tunnel ( Figure 10). The rocket flight test (Figure 11) will supply the real Mach number and dynamic pressure environment to verify every phase, but it can not cover the extreme conditions due to the limited times.…”