A Summary of Dynamic Testing of the Mars Exploration Rover Parachute Decelerator System

Abstract

In May and June of 2003, NASA will launch the Mars Exploration Rover (MER) spacecraft on the next planetary exploration mission. The spacecraft will enter the Martian atmosphere and a mortar deployed, Disk-Gap-Band (DGB) parachute will slow the craft from supersonic entry conditions. The Parachute Deceleration System will then stabilize the spacecraft for optimal retrorocket firing just above the surface of Mars. Pioneer Aerospace Corporation (Pioneer), under contract to the Jet Propulsion Laboratory (JPL), used design experience from the Mars Pathfinder (MPF), Mars Polar Lander (MPL), and Mars 2001 programs to develop a system for a larger payload without large increases in weight or volume. Extensive wind tunnel and aerial drop testing was conducted to define and verify the design. This paper discusses the test methods used to determine a parachute configuration for optimized drag, stability, and structural performance. These methods included: the use of aerial drop testing to identify flight performance differences between canopies with slight variations in configuration, scale model wind tunnel testing to quantify stability and drag characteristics, mortar deployed full scale aerial structural testing, and mortar deployed full scale structural testing in the NASA Ames 80 ft by 120 ft wind tunnel. Discussions include an overview of measurements taken, general outcome of the tests, and practical issues regarding test operations. Introduction The MER mission will employ an Entry, Descent, and Landing (EDL) sequence that includes a combination of parachute, retrorocket, and airbag decelerators similar to that used for the Mars Pathfinder mission. In this sequence, the retrorocket descent radar requires a stable platform to compute the optimal initiation and timing of the terminal descent events. Because of the requirements for this type of EDL approach, the Mars Pathfinder program developed a DGB parachute that included an extended band for increased stability. The MER system requires similar descent stability. Pioneer began development of the MER Parachute Decelerator System (PDS) in the fall of 2000 with a program to explore stability and drag trades for the Disk Gap Band (DGB) parachute. Flight-testing in rapid succession qualitatively compared four designs, with common reference area but varying band length. This initial testing bounded the relative drag and stability for the DGB parachute configurations under consideration. Following assessment of data in the initial design study, the most promising configurations were selected for further scaled parachute testing in the NASA Langley Transonic Dynamics Tunnel (TDT). Scale model wind tunnel test data was used to select the geometry for the prototype, full-scale, MER PDS. The initial full-scale prototype was then drop tested to achieve flight representative inflation loads to identify structural component improvements necessary for the final design. Structural design improvements, based on results from the initial prototype drop testing, were incorporated into the final MER PDS prior to proof testing. The production canopy was tested in the Ames 80 x 120 wind tunnel using a pyrotechnic, flight-like, mortar deployment of the parachute. Wind tunnel parachute testing observed no structural anomalies in the canopy fabric, risers, or suspension lines. With the flight stability, drag and structure verified, production of the flight lot MER PDS canopies was completed, and the assemblies delivered in February of 2003.