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High Altitude Supersonic Decelerator Test Vehicle
The Low Density Supersonic Decelerator (LDSD) project is tasked by NASA's Office of the Chief Technologist (OCT) to advance the state of the art in Mars entry and descent technology in order to allow for larger payloads to be delivered to Mars at higher altitudes with better accuracy. The project will develop a 33.5 m Do Supersonic Ringsail (SSRS) parachute, 6m attached torus, robotic class Supersonic Inflatable Aerodynamic Decelerator (SIAD-R), and an 8 m attached isotensoid, exploration class Supersonic Inflatable Aerodynamic Decelerator (SIAD-E). The SSRS and SIAD-R should be brought to TRL-6, while the SIAD-E should be brought to TRL-5. As part of the qualification and development program, LDSD must perform a Mach-scaled Supersonic Flight Dynamics Test (SFDT) in order to demonstrate successful free flight dynamic deployments at Mars equivalent altitude, of all three technologies. In order to perform these tests, LDSD must design and build a test vehicle to deliver all technologies to approximately 180,000 ft and Mach 4, deploy a SIAD, free fly to approximately Mach 2, deploy the SSRS, record high-speed and high-resolution imagery of both deployments, as well as record data from an instrumentation suite capable of characterizing the technology induced vehicle dynamics. The vehicle must also be recoverable after splashdown into the ocean under a nominal flight, while guaranteeing forensic data protection in an off nominal catastrophic failure of a test article that could result in a terminal velocity, tumbling water impact.
Thermal Design and Analysis of the Supersonic Flight Dynamics Test Vehicle for the Low Density Supersonic Decelerator Project
The thermal design and analysis of the experimental Supersonic Flight Dynamics Test (SFDT) vehicle is presented. The SFDT vehicle is currently being designed as a platform to help demonstrate key technologies for NASA's Low Density Supersonic Decelerator (LDSD) project. The LDSD project is charged by NASA's Office of the Chief Technologist (OCT) with the task of advancing the state of the art in Mars Entry, Descent, and Landing (EDL) systems by developing and testing three new technologies required for landing heavier payloads on Mars. The enabling technologies under development consist of a large 33.5 meter diameter Supersonic Ringsail (SSRS) parachute and two different types of Supersonic Inflatable Aerodynamic Decelerator (SIAD) devices - a robotic class, SIAD-R, that inflates to a 6 meter diameter torus, and an exploration class, SIAD-E, that inflates to an 8 meter diameter isotensoid. As part of the technology development effort, the various elements of the new supersonic decelerator system must be tested in a Mars-like environment. This is currently planned to be accomplished by sending a series of SFDT vehicles into Earth's stratosphere. Each SFDT vehicle will be lifted to a stable float altitude by a large helium carrier balloon. Once at altitude, the SFDT vehicles will be released from their carrier balloon and spun up via spin motors to provide trajectory stability. An onboard third stage solid rocket motor will propel each test vehicle to supersonic flight in the upper atmosphere. After main engine burnout, each vehicle will be despun and testing of the deceleration system will begin: first an inflatable decelerator will be deployed around the aeroshell to increase the drag surface area, and then the large parachute will be deployed to continue the deceleration and return the vehicle back to the Earth's surface. The SFDT vehicle thermal system must passively protect the vehicle structure and its components from cold temperatures experienced during the ascent phase of the mission as well as from the extreme heat fluxes produced during the supersonic test phase by the main motor plume and aeroheating. The passive thermal design approach for the SFDT vehicle relies upon careful and complex bounding analysis of all three modes of heat transfer - conduction, convection, and radiation - coupled with a tightly managed transient power dissipation timeline for onboard electronics components throughout all mission phases.
Post-Flight Assessment of Low Density Supersonic Decelerator Flight Dynamics Test 2 Simulation
NASA's Low Density Supersonic Decelerator (LDSD) project conducted its second Supersonic Flight Dynamics Test (SFDT-2) on June 8, 2015. The Program to Optimize Simulated Trajectories II (POST2) was one of the flight dynamics tools used to simulate and predict the flight performance and was a major tool used in the post-flight assessment of the flight trajectory. This paper compares the simulation predictions with the reconstructed trajectory. Additionally, off-nominal conditions seen during flight are modeled in the simulation to reconcile the predictions with flight data. These analyses are beneficial to characterize the results of the flight test and to improve the simulation and targeting of the subsequent LDSD flights.
Summary of the First High-Altitude, Supersonic Flight Dynamics Test for the Low-Density Supersonic Decelerator Project
NASA's Low-Density Supersonic Decelerator Project is developing and testing the next generation of supersonic aerodynamic decelerators for planetary entry. A key element of that development is the testing of full-scale articles in conditions relevant to their intended use, primarily the tenuous Mars atmosphere. To achieve this testing, the LDSD project developed a test architecture similar to that used by the Viking Project in the early 1970's for the qualification of their supersonic parachute. A large, helium filled scientific balloon is used to hoist a 4.7 m blunt body test vehicle to an altitude of approximately 32 kilometers. The test vehicle is released from the balloon, spun up for gyroscopic stability, and accelerated to over four times the speed of sound and an altitude of 50 kilometers using a large solid rocket motor. Once at those conditions, the vehicle is despun and the test period begins. The first flight of this architecture occurred on June 28th of 2014. Though primarily a shake out flight of the new test system, the flight was also able to achieve an early test of two of the LDSD technologies, a large 6 m diameter Supersonic Inflatable Aerodynamic Decelerator (SIAD) and a large, 30.5 m nominal diameter supersonic parachute. This paper summarizes this first flight.
Aerodynamic Coefficients from Aeroballistic Range Testing of Deployed- and Stowed-SIAD SFDT Models
This report documents a ballistic-range test campaign conducted in 2012 in order to estimate the aerodynamic stability characteristics of two configurations of the Supersonic Flight Dynamics Test (SFDT) vehicle prior to its initial flight in 2014. The SFDT vehicle was a test bed for demonstrating several new aerodynamic decelerator technologies then being developed under the Low-Density Supersonic Decelerator (LDSD) Project. Of particular interest here is the Supersonic Inflatable Aerodynamic Decelerator (SIAD), an inflatable attached torus used to increase the drag surface area of an entry vehicle during the supersonic portion of the entry trajectory. Two model configurations were tested in the ballistic range: one representing the SFDT vehicle prior to deployment of the SIAD, and the other representing the nominal shape with the SIAD inflated. Both models were fabricated from solid metal, and therefore, the effects of the flexibility of the inflatable decelerator were not considered. The test conditions were chosen to match, as close as possible, the Mach number, Reynolds number, and motion dynamics expected for the SFDT vehicle in flight, both with the SIAD stowed and deployed. For SFDT models with the SIAD stowed, 12 shots were performed covering a Mach number range of 3.2 to 3.7. For models representing the deployed SIAD, 37 shots were performed over a Mach number range of 2.0 to 3.8. Pitch oscillation amplitudes covered a range from 0.7 to 20.6 degrees RMS. Portions of this report (data analysis approach, aerodynamic modeling, and resulting aerodynamic coefficients) were originally published as an internal LDSD Project report [1] in 2012. In addition, this report provides a description of the test design approach, the test facility, and experimental procedures. Estimated non-linear aerodynamic coefficients, including pitch damping, for both model configurations are reported, and the shot-by-shot trajectory measurements, plotted in comparison with calculated trajectories based on the derived non-linear aerodynamic coefficients, are provided as appendices. Since the completion of these tests, two full-scale SFDT flights have been successfully conducted: one in June 2014 [2, 3], and one in June 2015 [3].
Measurements of Parachute Dynamics in the World's Largest Wind Tunnel by Stereo Photogrammetry
Between 2012 and 2017, parachutes for four NASA Projects were tested in the 80- by 120-Ft test section of the National Full-Scale Aerodynamic Complex (NFAC) at NASA Ames Research Center. These projects were: (1) Low-Density Supersonic Decelerator (LDSD); (2) Capsule Parachute Assembly System (CPAS, for Orion); (3) Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight, a Mars mission); and (4) Mars 2020. In all tests stereo photogrammetry was used to measure time-dependent positions of features on the canopies. For the LDSD and CPAS tests, where the purpose was to study the trade-off between stability and drag of different parachute designs, the pendulum motion of the canopies about the riser attachment point was measured by calibrated cameras in the diffuser. The CPAS test also included static measurements where the inflated parachutes were pulled to the side by a system of tethers. The Insight tests were structural qualification tests where each canopy was packed in a bag and launched from a mortar. Cameras in the diffuser measured the trajectory of the bag and the stripping of the bag from the canopy. The Mars 2020 test was a workmanship verification test where the canopies were either launched from a mortar or deployed from a sleeve stretched along the tunnel axis. The deployments were recorded from many directions by thirteen high-speed cameras distributed in the diffuser and test section. Photogrammetry was not planned; however, after a tunnel-related accident ended the test prematurely, photogrammetric measurements were bootstrapped from the images to support the accident investigations. This paper describes how the photogrammetry measurements were made in each test and presents typical results.
V&V on a NASA Technology Demonstration Project: Low Density Supersonic Decelerator
Given their smaller budgets, but higher allowed risk posture, technology demonstration missions face different Verification and Validation (V&V) challenges than typical NASA missions. Despite these challenges, the Low Density Supersonic Decelerator (LDSD) project, managed by NASA’s Jet Propulsion Laboratory (JPL), has been extremely successful in testing new supersonic atmospheric decelerator technologies. A contribution to the project’s success is the unique V&V program that emphasized efficiency and flexibility. This paper will provide an overview of LDSD test objectives, Supersonic Flight Dynamics Tests (SFDT) performed so far, unique requirements structure and V&V processes implemented. The paper will focus on the V&V of the SFDT test architecture. Furthermore, lessons learned will also be presented at the end of the paper to aid future technology demonstration projects.
Overview of the Mars 2020 Parachute Risk Reduction Activity
In 2012, the Mars Science Laboratory (MSL) landed safely on the surface of Mars using a supersonic Disk-Gap-Band (DGB) parachute, which was structurally qualified for flight via a subsonic wind tunnel test program. Results of the Low Density Supersonic Decelerators (LDSD) program have called into question the methodology and principles that form the foundation of the MSL subsonic test program. LDSD discovered that quasi-static subsonic proof loading a parachute via ground testing may not provide canopy stresses that sufficiently bound the stresses experienced during a rapid supersonic inflation at Mars. Additionally, deeper scrutiny of the materials and structural margins present in previously successful supersonic DGBs indicated that the MSL parachute flew with lowest margins of any previous parachute. These factors have increased the perceived risk of reusing a heritage MSL DGB parachute design with a subsonic test program for Mars 2020. To reduce this risk,a series of risk reduction steps were initiated starting in 2016. First, two parachute assemblies have been pursued in parallel: a Build-to-Print (BTP) MSL parachute, designed and manufactured by Pioneer Aerospace Corporation, which maintains the heritage of the successful MSL parachute, and a strengthened parachute, designed and manufactured by Airborne Systems North America, which uses higher strength materials throughout the parachute assembly but maintains the same overall size as the MSL parachute. Second, each parachute system was tested in a subsonic wind tunnel to examine the canopies in their fully inflated state and assess the workmanship of each canopy. Finally, full-scale parachutes from each vendor will experience at least one supersonic inflation at Mars relevant Mach numbers and atmospheric densities at Earth via a supersonic sounding rocket test campaign. This paper presents high-level details regarding the risk reduction strategy, the two candidate parachute configurations, the ground test program, and the supersonic flight test program, and brief results from each of the test programs.
Pyrotechnically Actuated Gas Generator Utilizing Aqueous Methanol
A gas-generating device was developed to supplement the ram-air inflation of a supersonic ballute. The device is designed to initially pressurize the ballute following deployment, exposing and orienting its ram-air inlets to free-stream air for complete inflation. The supplemental pressurization decreases the total inflation time, and increases the likelihood of a successful inflation. The device contains a reservoir filled with an aqueous mixture of methanol that, when released in to the interior of the ballute, rapidly vaporizes due to the low ambient pressure. Upon activation of the device, a pair of redundant ring mechanisms initiate pyrotechnic charges that pressurize and rupture the reservoir, resulting in ejection of the methanol in to 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 ring mechanism and reservoir under several temperature and pressure conditions. Finally, the device was successfully operated during the first Supersonic Flight Dynamics Test (SFDT) of NASA's Low Density Supersonic Decelerator (LDSD) project. The design architecture is scalable to accommodate different quantities of gas generation, 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.
Multi-Mission Simulation and Visualization for Real-Time Telemetry Display, Playback and EDL Event Reconstruction
he Jet Propulsion Laboratory's Entry, Descent and Landing (EDL) Reconstruction Task has developed a software system that provides mission operations personnel and analysts with a real time telemetry-based live display, playback and post-EDL reconstruction capability that leverages the existing high-fidelity, physics-based simulation framework and modern game engine-derived 3D visualization system developed in the JPL Dynamics and Real Time Simulation (DARTS) Lab. Developed as a multi-mission solution, the EDL Telemetry Visualization (ETV) system has been used for a variety of projects including NASA's Mars Science Laboratory (MSL), NASA'S Low Density Supersonic Decelerator (LDSD) and JPL's MoonRise Lunar sample return proposal.
Supersonic Flight Dynamics Test 1 - Post-Flight Assessment of Simulation Performance
NASA's Low Density Supersonic Decelerator (LDSD) project conducted its first Supersonic Flight Dynamics Test (SFDT-1) on June 28, 2014. Program to Optimize Simulated Trajectories II (POST2) was one of the flight dynamics codes used to simulate and predict the flight performance and Monte Carlo analysis was used to characterize the potential flight conditions experienced by the test vehicle. This paper compares the simulation predictions with the reconstructed trajectory of SFDT-1. Additionally, off-nominal conditions seen during flight are modeled in post-flight simulations to find the primary contributors that reconcile the simulation with flight data. The results of these analyses are beneficial for the pre-flight simulation and targeting of the follow-on SFDT flights currently scheduled for summer 2015.
SFDT-1 Camera Pointing and Sun-Exposure Analysis and Flight Performance
The Supersonic Flight Dynamics Test (SFDT) vehicle was developed to advance and test technologies of NASA's Low Density Supersonic Decelerator (LDSD) Technology Demonstration Mission. The first flight test (SFDT-1) occurred on June 28, 2014. In order to optimize the usefulness of the camera data, analysis was performed to optimize parachute visibility in the camera field of view during deployment and inflation and to determine the probability of sun-exposure issues with the cameras given the vehicle heading and launch time. This paper documents the analysis, results and comparison with flight video of SFDT-1.
Technology Demonstration Missions
Technology Demonstration Missions (TDM) is in its third year of execution, being initiated in 2010 and baselined in January of 2012. There are 11 projects that NASA Marshall Space Flight Center (MSFC) has contributed to or led: (1) Evolvable Cryogenics (eCryo): Cyrogenic Propellant Storage and Transfer Engineering Development Unit (EDU), a proof of manufacturability effort, used to enhance knowledge and technology related to handling cryogenic propellants, specifically liquid hydrogen. (2) Composites for Exploration Upper Stage (CEUS): Design, build, test, and address flight certification of a large composite shell suitable for the second stage of the Space Launch System (SLS). (3) Deep Space Atomic Clock (DSAC): Spaceflight to demo small, low-mass atomic clock that can provide unprecedented stability for deep space navigation. (4) Green Propellant Infusion Mission (GPIM): Demo of high-performance, green propellant propulsion system suitable for Evolved Expendable Launch Vehicle (EELV) Secondary Payload Adapter (ESPA)-class spacecraft. (5) Human Exploration Telerobotics (HET): Demonstrating how telerobotics, remote control of a variety of robotic systems, can take routine, highly repetitive, dangerous or long-duration tasks out of human hands. (6) Laser Communication Relay Demo (LCRD): Demo to advance optical communications technology toward infusion into deep space and near Earth operational systems, while growing the capabilities of industry sources. (7) Low Density Supersonic Decelerator (LDSD): Demo new supersonic inflatable decelerator and parachute technologies to enable Mars landings of larger payloads with greater precision at a wider range of altitudes. (8) Mars Science Laboratory (MSL) Entry Descent & Landing Instrumentation (MEDLI): Demo of embedded sensors embedded in the MSL heat shield, designed to record the heat and atmospheric pressure experienced during the spacecraft's high-speed, hot entry in the Martian atmosphere. (9) Solar Electric Propulsion (SEP): 50-kW class spacecraft that uses flexible blanket solar arrays for power generation and an electric propulsion system that delivers payload from low-Earth orbit to higher orbits. (10) Solar Sail Demonstration (SSD): Demo to validate sail deployment techniques for solar sails that are propelled by the pressure of sunlight. (11) Terrestrial HIAD Orbit Reentry (THOR): Demo of a 3.7-m Hypersonic Inflatable Aerodynamic Decelerator (HIAD) entry vehicle to test second generation aerothermal performance and modeling.
Low Density Supersonic Decelerator Flight Dynamics Test-1 Flight Design and Targeting
NASA's Low Density Supersonic Decelerator (LDSD) program was established to identify, develop, and eventually qualify to Test [i.e. Technology] Readiness Level (TRL) - 6 aerodynamic decelerators for eventual use on Mars. Through comprehensive Mars application studies, two distinct Supersonic Inflatable Aerodynamic Decelerator (SIAD) designs were chosen that afforded the optimum balance of benefit, cost, and development risk. In addition, a Supersonic Disk Sail (SSDS) parachute design was chosen that satisfied the same criteria. The final phase of the multi-tiered qualification process involves Earth Supersonic Flight Dynamics Tests (SFDTs) within environmental conditions similar to those that would be experienced during a Mars Entry, Descent, and Landing (EDL) mission. The first of these flight tests (i.e. SFDT-1) was completed on June 28, 2014 with two more tests scheduled for the summer of 2015 and 2016, respectively. The basic flight design for all the SFDT flights is for the SFDT test vehicle to be ferried to a float altitude of 120 kilo-feet by a 34 thousand cubic feet (Mcf) heavy lift helium balloon. Once float altitude is reached, the test vehicle is released from the balloon, spun-up for stability, and accelerated to supersonic speeds using a Star48 solid rocket motor. After burnout of the Star48 motor the vehicle decelerates to pre-flight selected test conditions for the deployment of the SIAD system. After further deceleration with the SIAD deployed, the SSDS parachute is then deployed stressing the performance of the parachute in the wake of the SIAD augmented blunt body. The test vehicle/SIAD/parachute system then descends to splashdown in the Pacific Ocean for eventual recovery. This paper will discuss the development of both the test vehicle and the trajectory sequence including design trade-offs resulting from the interaction of both engineering efforts. In addition, the SFDT-1 nominal trajectory design and associated sensitivities will be discussed as well as an overview of the on-board flight software used to trigger and sequence the main flight events necessary to deploy the deceleration technologies. Finally, as-flown performance of the SFDT-1 system will be discussed.
Rigging Test Bed Enables Development of Multi-Stage Decelerator Extraction
The Low Density Supersonic Decelerator (LDSD) project developed a Parachute Deployment System (PDS) for use on its Supersonic Flight Dynamics Tests (SFDT). The PDS involves a multi-stage pilot driven extraction of a supersonic parachute. The uncertainties and complexities of developing the design for the lines and rigging of the PDS were addressed through testing in the Rigging Test Bed (RTB). The RTB provided a facility capable of simulating a variety of extraction scenarios with full scale hardware on the ground. 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.
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.
Applied Multi-Mission Telemetry Processing and Display for Operations, Integration, Training, Playback and Event Reconstruction
Conveying spacecraft health and status information to mission engineering personnel during various mission phases, including mission operations, is a requirement to achieve a successful mission. For NASA/JPL spacecraft, that often means displaying hundreds of telemetry channels from a variety of sensors and components emitting data at rates varying from 1hz-100hz (and faster) in a way that allows the operations team to quickly evaluate the health of the vehicle, identify any off-nominal states and resolve any issues. In this paper we will discuss the system design, requirements and use cases of three telemetry processing and visualization systems recently developed and deployed by our team for NASA's Low Density Supersonic Decelerator (LDSD) test vehicle, NASA's Soil Moisture Active/Passive (SMAP) orbiter, and JPL's Sampling Lab Universal Robotic Manipulator (SLURM) test bed.