On Aug 5, 2012 the Mars Science Laboratory (MSL) Entry, Descent, and Landing Instrumentation (MEDLI) suite on MSL entry vehicle heatshield suc-cessfully returned surface pressure and in-depth temperature data.1,2 The MEDLI data has given scientists and engineers an unprecedented ability to reconstruct entry environment, atmospheric density, and flight trajectory, and flight validation of predic-tions vehicle aerodynamics and thermal protection system (TPS) performance. This presentation will dis-cuss key findings from MEDLI, some of which are being applied to improve definition of aerothermal environment and TPS sizing margins for existing NASA entry missions. The postflight analysis has shown that a significant thermal protection mass saving upon redesign is possible for an MSL-class vehicle. The success of MEDLI has also demonstrated and qualified robust flight instrumentation technologies at very low risk to the mission. The potential benefits of MEDLI to planetary exploration and sample return missions, as well as to exploration class missions to Mars will be presented.
A new analysis framework for wedge testing in the Arnold Engineering Development Center (AEDC) H2 arc-jet has been developed. The technique uses the aerothermal nonequilibrium DPLR flow solver, specialized routines, and the FIAT material response code. The framework takes advantage of null-point sweep profiles from testing, and when coupled with a new automated process using flow solver has been used to analyze the recession of ablative TPS samples. Results are shown for the recent Mars Science Laboratory (MSL) Phenolic Impregnated Carbon Ablator (PICA) shear testing at AEDC, demonstrating the good agreement between aerothermal and material response simulations and the experimental data.
The Mars Science Laboratory (MSL) mission is scheduled to enter the Martian atmosphere in August 2012. Aboard the heatshield is the MSL Entry Descent and Landing Instrumentation (MEDLI) system that includes a series of embedded sensor plugs to measure in-depth response of the thermal protection system (TPS). The general objectives of the MEDLI system are to assess the TPS performance and reconstruct the aerothermal environment experienced during entry. Some specific objectives, such as measuring TPS temperature, can be addressed with direct measurements. Other objectives, such as determining surface heating, must be inferred using measurements combined with analytical tools. This paper describes the specific objectives, the expected sensor responses to the entry environment based on aerothermal and material response simulations, and the reconstruction analysis process being developed for the flight data.
A total of seventeen instrumented thermal sensor plugs, eight pressure transducers, two heat flux sensors, and one radiometer are planned to be utilized on the Mars 2020 missions thermal protection system (TPS) as part of the Mars Entry, Descent, and Landing Instrumentation II (MEDLI2) project. Of the MEDLI2 instrumentation, eleven instrumented thermal plugs and seven pressure transducers will be installed on the heatshield of the Mars 2020 vehicle while the rest will be installed on the backshell. The goal of the MEDLI2 instrumentation is to directly inform the large performance uncertainties that contribute to the design and validation of a Mars entry system. A better understanding of the entry environment and TPS performance could lead to reduced design margins enabling a greater payload mass-fraction and smaller landing ellipses. To prove that the MEDLI2 system will not degrade the performance of the Mars 2020 TPS, an Aerothermal Do No Harm (DNH) test series was designed and conducted. Like Mars 2020s predecessor, Mars Science Laboratory (MSL), the heatshield material will be Phenolic Impregnated Carbon Ablator (PICA); the Mars 2020 entry conditions are enveloped by the MSL design environments, therefore the development and qualification testing performed during MEDLI is sufficient to show that the similar MEDLI2 heatshield instrumentation will not degrade PICA performance. However, given that MEDLI did not include any backshell instrumentation, the MEDLI2 team was required to design and execute a DNH test series utilizing the backshell TPS material (SLA-561V) with the intended flight sensor suite. To meet the requirements handed down from Mars 2020, the MEDLI2 DNH test series emphasized the interaction between the MEDLI2 sensors and sensing locations with the surrounding backshell TPS and substrucutre. These interactions were characterized by performing environmental testing of four 12 by 12 test panels, which mimicked the construction of the backshell TPS and the integration of the MEDLI2 sensors as seen in Figure 1. The testing included thermal vacuumcycling, random vibration, shock, and arc jet testing. The test panels were fabricated by Lockheed Martin, establishing techniques that will be utilized during the Mars 2020 vehicle installation. Each test panel included one thermal sensor plug (two embedded thermocouples), one heat flux sensor, and multiple pressure port holes for evaluation.This presentation will discuss the planning and execution of the MEDLI2 DNH test series. Selected highlights and results of each environmental test will be presented, and lessons learned will be addressed that will feed forward into the planning for the MEDLI2 flight system certification testing.
The Mars Entry, Descent, and Landing Instrumentation 2 (MEDLI2) sensor suite for the Mars 2020 mission includes a radiometer on the backshell to measure the radiative heating during entry into the Martian atmosphere. Thermal Protection System (TPS) ablation products may be deposited on the radiometer window which would degrade the transmission and thus alter the accuracy of the radiometer readings. Testing in NASA Ames Research Center's miniature arc jet (mARC) facility was conducted to deposit TPS ablation products on radiometer windows in an effort to characterize how the ablation products change the window transmission and thus alter radiometer performance. Heat flux and stagnation pressure characterization of the mARC facility in a 90 percent CO2, 10 percent N2 (by mass) Mars-like environment are presented. The spectral transmission of the radiometer windows before and after mARC testing are compared. Additionally, a discussion of how flight-like these test conditions were and future work to further characterize the effect of TPS ablation on radiometer performance are presented.
The Mars Science Laboratory entry vehicle successfully landed the Curiosity rover on the Martian surface on August 5, 2012. A phenolic impregnated carbon ablator heatshield was used to protect the spacecraft against the severe aeroheating environments of atmospheric entry. This heatshield was instrumented with a comprehensive set of pressure and temperature sensors. The objective of this paper is to perform an inverse estimation of the entry vehicle’s surface heating and heatshield material properties. The surface heating is estimated using the flight temperature data from the shallowest thermocouple. The sensitivity of the estimated surface heating profile to estimation tuning parameters, measurement errors, recession uncertainty and material property uncertainty is investigated. A Monte Carlo analysis is conducted to quantify the uncertainty bounds associated with the nominal estimated surface heating. Additionally, a thermocouple driver approach is employed to estimate heatshield material properties using the flight data from the deeper thermocouples while applying the shallowest thermocouple temperature as the surface boundary condition.
NASA Mars Science Laboratory (MSL), which landed the Curiosity rover on the surface of Mars on August 5th, 2012, was the largest and heaviest Mars entry vehicle representing a significant advancement in planetary entry, descent and landing capability. Hypersonic flight performance data was collected using MSLs on-board sensors called Mars Entry, Descent and Landing Instrumentation (MEDLI). This talk will give an overview of MSL entry and a description of MEDLI sensors. Observations from flight data will be examined followed by a discussion of analysis efforts to reconstruct surface heating from heatshields in-depth temperature measurements. Finally, a brief overview of MEDLI2 instrumentation, which will fly on NASAs Mars2020 mission, will be presented with a discussion on how lessons learned from MEDLI data affected the design of MEDLI2 instrumentation.
