Chris Karlgaard

Assessment of the Reconstructed Aerodynamics of the Mars Science Laboratory Entry Vehicle

On 5xa0Augustxa02012, the Mars Science Laboratory entry vehicle successfully entered the atmosphere of Mars, flying a guided entry until parachute deploy. The Curiosity rover landed safely in Gale crater upon completion of the entry, descent, and landing sequence. Preflight aerodynamic predictions are compared with the aerodynamic performance of the entry capsule identified from onboard flight data, including inertial-measurement-unit accelerometer and rate gyro information, and heat shield surface pressure measurements. From the onboard data, static force and moment coefficients have been extracted. These data are compared with the preflight aerodynamic database. The Mars Science Laboratory flight data represent the most complete and self-consistent record of a blunt capsule entering Mars collected to date. These data enable the separation of aerodynamic performance from atmospheric conditions. The comparisons show the Mars Science Laboratory aerodynamic characteristics have been successfully identified and ...

The aerodynamics of axisymmetric blunt bodies flying at angle of attack

The Mars Science Laboratory entry capsule is used as an example to demonstrate how a blunt body of revolution must be treated as asymmetric in some respects when flying at a non-zero trim angle of attack. A brief description of the axisymmetric moment equations are provided before solving a system of equations describing the lateral-directional moment equations for a blunt body trimming at an angle of attack. Simplifying assumptions are made which allow the solution to the equations to be rearranged to relate the roll and yaw stability with sideslip angle to the frequency of oscillation of the vehicle body rates. The equations show that for a blunt body the roll and yaw rates are in phase and proportional to each other. The ratio of the rates is determined by the static stability coefficients and mass properties about those axes. A trajectory simulation is used to validate the static yaw stability parameter identification equation and a simple method of identifying the oscillation frequency from the body rates. The approach is shown to successfully extract the modeled yaw stability coefficient along a simulated Mars entry. Mars Science Laboratory flight data results are presented from earlier work which indicate that results from both the validation case and flight data are in agreement with preflight predictions. A brief discussion of the dynamic stability is also provided. Trimming at a nonzero angle suggests that the typical axisymmetric models of the dynamic stability coefficients should be modified. However, further experimental or computational work must be done to separate damping due to body rates and wind relative rates before the correct lifting formulation would affect simulation results.

Mars 2020 Entry, Descent and Landing Instrumentation (MEDLI2)

This paper will introduce Mars Entry Descent and Landing Instrumentation (MEDLI2) on NASAs Mars2020 mission. Mars2020 is a flagship NASA mission with science and technology objectives to help answer questions about possibility of life on Mars as well as to demonstrate technologies for future human expedition. Mars2020 is scheduled for launch in 2020. MEDLI2 is a suite of instruments embedded in the heatshield and backshell thermal protection systems of Mars2020 entry vehicle. The objectives of MEDLI2 are to gather critical aerodynamics, aerothermodynamics and TPS performance data during EDL phase of the mission. MEDLI2 builds up the success of MEDLI flight instrumentation on Mars Science Laboratory mission in 2012. MEDLI instrumentation suite measured surface pressure and TPS temperature on the heatshield during MSL entry into Mars. MEDLI data has since been used for unprecedented reconstruction of aerodynamic drag, vehicle attitude, in-situ atmospheric density, aerothermal heating, transition to turbulence, in-depth TPS performance and TPS ablation. [1,2] In addition to validating predictive models, MEDLI data has highlighted extra margin available in the MSL forebody TPS, which can potentially be used to reduce vehicle parasitic mass. MEDLI2 expands the scope of instrumentation by focusing on quantities of interest not addressed in MEDLI suite. The type the sensors are expanded and their layout on the TPS modified to meet these new objectives. The paper will provide key motivation and governing requirements that drive the choice and the implementation of the new sensor suite. The implementation considerations of sensor selection, qualification, and demonstration of minimal risk to the host mission will be described. The additional challenges associated with mechanical accommodation, electrical impact, data storage and retrieval for MEDLI2 system, which extends sensors to backshell will also be described.

LDSD supersonic Flight Dynamics Test 1: Post-flight reconstruction

The Low Density Supersonic Decelerator projects first Supersonic Flight Dynamics Test (SFDT) occurred on June 28, 2014, off the west coast of Kauai, Hawaii, over the Pacific Ocean. The test vehicle traveled to speeds above Mach 4 and to an altitude of over 200,000 feet. This flight, although classified as a test architecture shake-out flight, tested two technologies: a robotic class Supersonic Inflatable Aerodynamic Decelerator and a Supersonic Disksail Parachute. The reconstruction team was tasked with collecting all relevant pre-flight and flight data to accurately reconstruct the trajectory and technology performance during the science phase of the flight. Furthermore, the reconstruction team has been involved with reconstructing and exploring all aerodynamic and test vehicle properties that affected the entire flight phase. This reconstruction provided insight into the technology performance, which is a key deliverable for the LDSD project, as well as provided insight into lessons learned for subsequent SFDT flights, in the fields of data recovery, reconstruction, and pre-flight trajectory simulations.

Reconstruction of the Advanced Supersonic Parachute Inflation Research Experiment Sounding Rocket Flight Test

The Advanced Supersonic Parachute Inflation Research and Experiments project is a flight test program for development of supersonic parachutes for potential future use at Mars. The flight tests are designed to reduce risk for the Mars 2020 mission. The flight tests involve two Disk-Gap-Band parachute designs to be tested at relevant Mach number and dynamic pressure conditions for the Mars 2020 entry capsule. The first of these parachutes is a built-to-print design that was successfully employed by the Mars Science Laboratory lander at Mars in August 2012, and the second is a design that is strengthened in material properties and construction methods but has the same geometry as that used by Mars Science Laboratory. The first flight test of the built-to-print parachute took place on October 4, 2017 at NASA’s Wallops Flight Facility. This paper describes the instrumentation, data analysis techniques, and atmospheric and trajectory reconstruction results from this flight test.

Planetary Probe Entry Atmosphere Estimation Using Synthetic Air Data System

This paper develops an atmospheric state estimator based on inertial acceleration and angular rate measurements combinedwith a vehicle aerodynamicmodel. The approachuses the navigation state of the vehicle to recast the vehicle aerodynamic model to be a function solely of the atmospheric state. Force and moment measurements are based on vehicle sensed accelerations and angular rates. Thesemeasurements are combinedwith an aerodynamicmodel and a Kalman–Schmidt filter to estimate the atmospheric conditions. The method is applied to data from theMars Science Laboratory mission, which landed the Curiosity rover on the surface of Mars in August 2012. The results of the estimation algorithm are compared with results from a flush air data sensing algorithm based on onboard pressure measurements on the vehicle forebody. The comparison indicates that the proposed method provides estimates consistent with the air data measurements, without the use of pressure transducers. Implications for future missions such as the Mars 2020 entry capsule are described.