Tommaso P. Rivellini

Mars Science Laboratory Entry, Descent, and Landing System Overview

In 2010, the Mars science laboratory (MSL) mission will pioneer the next generation of robotic entry, descent, and landing (EDL) systems by delivering the largest and most capable rover to date to the surface of Mars. In addition to landing more mass than prior missions to Mars, MSL will offer access to regions of Mars that have been previously unreachable. The MSL EDL sequence is a result of a more stringent requirement set than any of its predecessors. Notable among these requirements is landing a 900 kg rover in a landing ellipse much smaller than that of any previous Mars lander. In meeting these requirements, MSL is extending the limits of the EDL technologies qualified by the Mars viking, Mars pathfinder, and Mars exploration rover missions. Thus, there are many design challenges that must be solved for the mission to be successful. Several pieces of the EDL design are technological firsts, such as guided entry and precision landing on another planet, as well as the entire sky crane maneuver. This paper discusses the MSL EDL architecture and discusses some of the challenges faced in delivering an unprecedented rover payload to the surface of Mars.

Mars Science Laboratory entry, descent, and landing system

In 2010, the Mars Science Laboratory (MSL) mission will pioneer the next generation of robotic entry, descent, and landing (EDL) systems by delivering the largest and most capable rover to date to the surface of Mars. In addition to landing more mass than prior missions to Mars, MSL will offer access to regions of Mars that have been previously unreachable. By providing an EDL system capable of landing at altitudes as high as 2 km above the reference areoid, as defined by the Mars Orbiting Laser Altimeter (MOLA) program, MSL will demonstrate sufficient performance to land on a large fraction of the Martian surface. By contrast, the highest altitude landing to date on Mars has been the Mars Exploration Rover (MER) MER-B at 1.44 km below the areoid. The coupling of this improved altitude performance with latitude limits as large as 60 degrees off of the equator and a precise delivery to within 10 km of a surface target will allow the science community to select the MSL landing site from thousands of scientifically interesting possibilities. In meeting these requirements, MSL is extending the limits of the EDL technologies qualified by the Mars Viking, Mars Pathfinder, and MER missions. This paper discusses the MSL EDL architecture, system, and subsystem design and discusses some of the challenges faced in delivering such an unprecedented rover payload to the surface of Mars

Mars Pathfinder Airbag Impact Attenuation System

The Mars Pathfinder spacecraft, scheduled for launch in November 1996, is designed to validate a low cost Entry, Descent, and Landing system and to perform scientific surface operations. The Jet Propulsion Laboratory and Sandia National Laboratories teamed to design, fabricate, test and validate a prototype 0.38 scale model of an airbag impact attenuation system. A computer code was developed to predict the performance of the airbag system. A test program in Sandia`s High Altitude Chamber was performed to validate the code and demonstrate the feasibility of the airbag concept and design. In addition, freefall tests were performed at representative velocities to demonstrate the structural integrity of the airbag system design. The feasibility program demonstrated that the airbag impact attenuation design will protect the lander upon impact with the Martian surface.

Low Density Supersonic Decelerator Parachute Decelerator System

The Low Density Supersonic Decelerator Project has undertaken the task of developing and testing a large supersonic ringsail parachute. The parachute under development is intended to provide mission planners more options for parachutes larger than the Mars Science Laboratory’s 21.5m parachute. During its development, this new parachute wil be taken through a series of tests in order to bring the parachute to a TRL-6 readiness level and make the technology available for future Mars missions. This effort is primarily focused on two tests, a subsonic structural verification test done at sea level atmospheric conditions and a supersonic flight behind a blunt body in low-density atmospheric conditions. The preferred method of deploying a parachute behind a decelerating blunt body robotic spacecraft in a supersonic flow-field is via mortar deployment. Due to the configuration constraints in the design of the test vehicle used in the supersonic testing it is not possible to perform a mortar deployment. As a result of this limitation an alternative deployment process using a balute as a pilot is being developed. The intent in this alternate approach is to preserve the requisite features of a mortar deployment during canopy extraction in a supersonic flow. Doing so wil alow future Mars missions to either choose to mortar deploy or pilot deploy the parachute that is being developed.

SIAD-R: A Supersonic Inflatable Aerodynamic Decelerator for Robotic missions to Mars

Nomenclature A_Vehicle = Projected area of the vehicle prior to SIAD-R deployment A_Vehicle+SIAD = Projected area of the vehicle and deployed SIAD-R Cd_Vehicle = Drag coefficient of the vehicle prior to SIAD-R deployment Cd_Vehicle+SIAD = Drag coefficient of the vehicle and deployed SIAD-R ∆(CdA) = Change in the product of drag coefficient and projected area due to SIAD-R deployment LDSD = Low Density Supersonic Decelerator Program MSL = Mars Science Laboratory P = Gauge pressure of the inflation gas inside the SIAD-R Q = Dynamic pressure Q:P = Ratio of the instantaneous dynamic pressure to instantaneous SIAD-R inflation pressure R&R = Retention and release assembly SFDT = Supersonic flight dynamics testing SIAD-R = Supersonic Inflatable Aerodynamic Decelerator for Robotic-class missions

Mars Science Laboratory's Parachute Qualification Approach

The Mars Science Laboratory mission will use a 21.5 meter reference diameter Viking scaled disk-gap-band parachute to slow the entry body from supersonic to low subsonic speeds during its entry into the Martian atmosphere. This parachute is larger than any diskgap-band parachute tested or flown in the high Mach, low dynamic pressure opening conditions that are required for use on a Mars surface mission. Early in the development process it was decided that qualification of the parachute via high altitude high Mach testing was cost prohibitive so direct testing would not be performed. Instead, the JPL team formed a qualification strategy to address readiness for flight by breaking the parachute’s function down into five key phases of operation: mortar deployment, canopy inflation, inflation strength, supersonic performance, and subsonic performance, which are then independently assessed. This paper addresses the salient aspects of these five phases and the Mars Science Laboratory’s methodology and test results that were used to qualify the parachute for flight in the absence of a full scale high altitude test program.

Mars Science Laboratory entry, descent and landing system verification and validation program

The Mars Science Laboratory (MSL) mission will land the next generation of robotic entry, descent, and landing (EDL) systems on Mars in 2010. Relative to previous missions, the MSL EDL architecture will deliver a significantly larger mass to a significantly higher altitude while maintaining a significantly tighter delivery ellipse. MSL is pushing the limits of EDL technologies qualified previously by the Mars Viking, Mars Pathfinder, and Mars Exploration Rover missions as well as introducing new elements into the architecture. Given the difficulties of conducting a meaningful end-to-end flight test on Earth, this combination introduces numerous challenges for the EDL verification and validation program. This paper discusses how system validation challenges influenced the design of the EDL architecture and highlights how some of the remaining challenges will be addressed to assure a successful landing of this unprecedented rover on Mars

Aerodynamic Characterization of New Parachute Configurations for Low-Density Deceleration

The Low Density Supersonic Decelerator project performed a wind tunnel experiment on the structural design and geometric porosity of various sub-scale parachutes in order to inform the design of the 110 ft nominal diameter flight test canopy. Thirteen different parachute configurations, including disk-gap-band, ringsail, disksail, and starsail canopies, were tested at the National Full-scale Aerodynamics Complex 80by 120-foot Wind Tunnel at NASA Ames Research Center. Canopy drag load, dynamic pressure, and canopy position data were recorded in order to quantify the relative drag performance and stability of the various canopies. Desirable designs would yield increased drag above the disk-gap-band with similar, or improved, stability characteristics. Ringsail parachutes were tested at geometric porosities ranging from 10% to 22% with most of the porosity taken from the shoulder region near the canopy skirt. The disksail canopy replaced the ringslot portion of the ringsail canopy with a flat circular disk and was tested at geometric porosities ranging from 9% to 19%. The starsail canopy replaced several ringsail gores with solid gores and was tested at 13% geometric porosity. Two disksail configurations exhibited desirable properties such as an increase of 6-14% in the tangential force coefficient above the DGB with essentially equivalent stability. However, these data are presented with caveats including the inherent differences between wind tunnel and flight behavior and qualitative uncertainty in the aerodynamic coefficients.

Rigging Test Bed Development for Validation of Multi-Stage Decelerator Extractions

The Low Density Supersonic Decelerator project is developing new decelerator systems for Mars entry which would include testing with a Supersonic Flight Dynamics Test Vehicle. One of the decelerator systems being developed is a large supersonic ringsail parachute. Due to the configuration of the vehicle it is not possible to deploy the parachute with a mortar which would be the preferred method for a spacecraft in a supersonic flow. Alternatively, a multi-stage extraction process using a ballute as a pilot is being developed for the test vehicle. The Rigging Test Bed is a test venue being constructed to perform verification and validation of this extraction process. The test bed consists of a long pneumatic piston device capable of providing a constant force simulating the ballute drag force during the extraction events. The extraction tests will take place both inside a high-bay for frequent tests of individual extraction stages and outdoors using a mobile hydraulic crane for complete deployment tests from initial pack pull out to canopy extraction. These tests will measure line tensions and use photogrammetry to track motion of the elements involved. The resulting data will be used to verify packing and rigging as well as validate models and identify potential failure modes in order to finalize the design of the extraction system.

Mars Science Laboratory Parachute Inversion Phenomenon and Flight Risk Assessment

During full-scale wind tunnel testing of the parachute for the Mars Science Laboratory two of the test parachutes experienced an inversion. These were unexpected occurrences and required an analysis of the phenomenon as observed in test and an assessment of what risks it may imply for flight on Mars. The test conditions and the inversion morphology are discussed as they relate to the wind tunnel tests and the impacts on the test effort. The timeline for the formation of the inversions is described and compared to the timeline expected in flight. Differences between the physics and behavior in test and flight are discussed as they relate to the threat of inversion. Mitigating actions are described as well as arguments used in determining the final configuration for use in flight. Nomenclature Do = parachute reference diameter DGB = disk-gap-band parachute M = Mach number MD = mortar deployment SD = sleeve deployment I. Introduction HE Mars Science Laboratory (MSL) mission will use a 21.5 m reference diameter (Do) Viking scaled disk-gapband (DGB) parachute as a critical component of its entry, descent, and landing system. Structural testing of the MSL parachute was performed in the 80’x120’ test section of the National Full-Scale Aerodynamics Complex (NFAC) operated by the Arnold Engineering Development Center (AEDC) at NASA’s Ames Research Center, Moffett Field, California. These developmental tests were conducted in five different tunnel entries over a ten month period from October of 2007 through July of 2008, while the final flight lot qualification tests were conducted in April of 2009. During the second tunnel entry in December, 2007, the parachute that was used in the second of three planned mortar deployment (MD) tests inverted below the band of the canopy. This was the first time that a DGB parachute had ever inverted in any nominally executed test which includes all wind tunnel, low altitude, high altitude, subsonic, supersonic, and Mars flight condition deployments. Following the MD2 inversion a Risk Assessment Workshop (RAW) was convened in January, 2008, at Pioneer Aerospace in South Windsor, Connecticut, to discuss possible mitigations to the inversion phenomenon both for NFAC testing as well as for flight. The historical flight and test experience was reviewed and a number of options were considered before a down selection exercise reduced the design space to two modifications which were implemented for the third NFAC entry in March, 2008. The two modifications were shown to have no ill effects on the mortar deployment of two 21.5 m and two 23 m parachutes and all four of the openings were observed to be within expectations. Observations made during the second and third tunnel entries showed that the weakest point in the design was at the suspension line to band joint and this junction could fail under certain conditions during test. In order to build some added strength margin into the parachute the suspension line material was changed from Kevlar-29 to Technora-T221 which necessitated a fourth tunnel entry to verify the new material margins. In addition, the testing