John C. Gallon

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.

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.

Parachute Decelerator System Performance During the Low Density Supersonic Decelerator Program's First Supersonic Flight Dynamics Test

During the first Supersonic Flight Dynamics Test (SFDT-1) for NASA’s Low Density Supersonic Decelerator (LDSD) Program, the Parachute Decelerator System (PDS) was successfully tested. The main parachute in the PDS was a 30.5-meter supersonic Disksail parachute. The term Disksail is derived from the canopy’s constructional geometry, as it combined the aspects of a ringsail and a flat circular round (disk) canopy. The crown area of the canopy contained the disk feature, as a large flat circular disk that extended from the canopy’s vent down to the upper gap. From this upper gap to the skirt-band the canopy was constructed with characteristics of sails seen in a ringsail. There was a second lower gap present in this sail region. The canopy maintained a nearly 10x forebody diameter trailing distance with 1.7 Do suspension line lengths. During the test, the parachute was deployed at the targeted Mach and dynamic pressure. Although the supersonic Disksail parachute experienced an anomaly during the inflation process, the system was tested successfully in the environment it was designed to operate within. The nature of the failure seen originated in the disk portion of the canopy. High-speed and high-resolution imagery of the anomaly was captured and has been used to aid in the forensics of the failure cause. In addition to the imagery, an inertial measurement unit (IMU) recorded test vehicle dynamics and loadcells captured the bridle termination forces. In reviewing the imagery and load data a number of hypothesizes have been generated in an attempt to explain the cause of the anomaly.

Preliminary Design of the Cruise, Entry, Descent, and Landing Mechanical Subsystem for MSL

Mars Science Laboratory is a scientific mission to the surface of Mars that would include a rover with 10 science instruments. In order to accomplish this mission, the rover must be transported from Earth to the Martian surface. The mechanical hardware that transports the rover is developed by the cruise, entry, descent, and landing (CEDL) mechanical subsystem team. This mechanical hardware includes the cruise stage structure, the aeroshell subsystem, the parachute deceleration subsystem, the descent stage structure, the bridle & umbilical device, and the pyro and separation devices that allow for the numerous separation events that occur in the EDL sequence. The key challenges for this system lie in the complex configuration (both geometric and subsystem accommodations), multiple unique load cases, and numerous separation events. This paper will describe the preliminary design and key challenges of each of these mechanical assemblies that comprise the CEDL mechanical subsystem.

Verification and Validation Testing of the Parachute Decelerator System Prior to the First Supersonic Flight Dynamics Test for the Low Density Supersonic Decelerator Program

The Parachute Decelerator System (PDS) is comprised of all components associated with the supersonic parachute and its associated deployment. During the Supersonic Flight Dynamics Test (SFDT), for the Low Density Supersonic Decelerators Program, the PDS was required to deploy the supersonic parachute in a defined fashion. The PDS hardware includes three major subsystems that must function together. The first subsystem is the Parachute Deployment Device (PDD), which acts as a modified pilot deployment system. It is comprised of a pyrotechnic mortar, a Kevlar ballute, a lanyard actuated pyrotechnic inflation aid, and rigging with its associated thermal protection material (TPS). The second subsystem is the supersonic parachute deployment hardware. This includes all of the parachute specific rigging that includes the parachute stowage can and the rigging including TPS and bridle stiffeners for bridle management during deployment. The third subsystem is the Supersonic Parachute itself, which includes the main parachute and deployment bags. This paper summarizes the verification and validation of the deployment process, from the initialization of the PDS system through parachute bag strip that was done prior to the first SFDT.

Deployment of the 30.5 meter Parachute on the Supersonic Flight Dynamics Test

The NASA Low Density Supersonic Decelerators (LDSD) project includes a highaltitude Supersonic Flight Dynamics Test (SFDT) that tests aerodynamic decelerators in the correct Mach/dynamic pressure environment for use on Mars landing missions. The 30.5 meter parachute of LDSD was developed to be mortar-deployed for future Mars use. However, the unique design of the Supersonic Flight Dynamics Test, with a center-mounted solid rocket, and the mass of the parachute (100 kg) precluded the use of a CG-aligned parachute mortar and required the development of a staged pilot deployment that preserved the canopy extraction characteristics of a mortar-deployed parachute. The architecture of the parachute deployment is discussed, including the use of a stiffened triple bridle, the elimination of the metallic bridle confluence fitting, the use of two deployment bags and the separation of the pilot device prior to line stretch. The extensibility to a mortar-deployed parachute is discussed along with the parameters that were assumed for a successful deployment and inflation. A multi-body dynamic simulation was developed to predict the performance of the parachute deployment and to tune the deployment parameters. The results of the simulation are compared to the performance of the system in the first SFDT flight, as well as ground-based development tests of the deployment sequence.

Pyrotechnically Actuated Gas Generator Utilizing Aqueous Methanol

A mechanically-initiated pyrotechnic gas generator was developed to aid in the inflation of the supersonic pilot ballute used by the Low Density Supersonic Decelerator (LDSD) project. The device is designed to pressurize the ballute following deployment, exposing and properly orienting its ram-air inlets to the freestream flow, to assist in its inflation process. The supplemental pressurization decreases the total inflation time and increases the likelihood of a successful inflation. Upon activation of the device, a pair of redundant firing mechanisms initiate pyrotechnic charges that pressurize and rupture a reservoir containing a mixture of methanol and water, ejecting the solution in to the ballute. The methanol subsequently rapidly vaporizes due to the low ambient pressure and latent heat in the ballute fabric, pressurizing the ballute. In addition to its role in inflation, the device serves as the structural connection to the ballute. Analytical models were developed for the inflation capability of the device, which were verified using vacuum chamber testing of developmental hardware. Static, deployment, and environmental testing demonstrated the functionality of the firing mechanism and reservoir under several temperature and pressure conditions. Finally, the device was successfully operated during the first Supersonic Flight Dynamics Test (SFDT) that occurred in June 2014. The design architecture is scalable to accommodate different quantities of the liquid solution, can be adjusted to operate in a variety of temperature and atmospheric pressure regimes, and provides a robust device that may be installed with minimal risk to personnel or hardware.

Verification and validation testing of the Bridle and Umbilical Device for Mars Science Laboratory

The Bridle Umbilical Device (BUD) subsystem is used during the Skycrane maneuver of the Mars Science Laboratory (MSL) during the final phases of the Entry Descent and Landing (EDL). During this phase the BUD subsystem will control the deployment of the MSL Rover from the Descent Stage. This paper covers the verification and validation testing of the subsystem. Testing included component through full system level testing. Testing ranged from simple bench top extraction tests to full system deploy drop test that included external disturbances such as the Rover mobility impulse. This paper will discuss the test that were performed, why they were performed and how these test results were used in the overall Verification and Validation of the MSL Skycrane phase.

Rigging test bed enables development of multi-stage decelerator extraction

The Rigging Test Bed (RTB) is a ground facility capable of simulating a variety of extraction scenarios with full scale Parachute Decelerator System (PDS) hardware for the Low Density Supersonic Decelerator (LDSD) project. The PDS involves a multi-stage pilotdriven extraction of a supersonic parachute used in a Supersonic Flight Dynamics Test (SFDT). The uncertainties and complexities of developing the design for the lines and rigging of the PDS were addressed through testing in the RTB. Through more than 100 tests conducted in the facility, a wealth of data and experience were gained that fueled the PDS development. The utility of this testing and the lessons learned are presented in this paper. The goal is to inform the development of similar systems in the future and highlight the value and flexibility this type of testing offers rapid hardware development. The RTB provided a great compliment to the analytical models greatly compressing what would have otherwise been a very lengthy analytical effort or potentially much expanded flight test campaign.