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NASA NTRSDate not supplied

Response of Ablative Thermal Protection Materials to Degradation in Low Earth Orbit –Characterization of Specimens from MISSE-13

The environment of low Earth orbit presents unique material interactions due to the presence of atomic oxygen and solar spectrum UV. A variety of degradation mechanisms can occur depending, inlarge part, on the specific material system involved. This talk will review the characterization of two ablative materials, PICA-D and HEEET, as well as relevant adhesive joints and coatings. PICA-D is a variant of the phenolic impregnated carbon ablator (PICA) and is the baseline thermal protection system (TPS) on Dragonfly and the lander for Mars Sample Return (MSR). HEEET is a 3D woven system from which MSR’s Earth entry TPS is derived. The samples for these materials were flown in orbit during the Materials International Space Station Experiment-13 (MISSE-13) which launched on March 6, 2020 and returned to Earth on January 13, 2021. Changes to surface microstructure and reflectivity will be presented along with tomographic analysis. The effect of differential erosion rates on the composites and the impacts of the orbit environment on coating performances will be discussed in the context of TPS performance and mission design aspects.

MISSE↗
NASA NTRSDate not supplied

Response of Ablative Thermal Protection Materials to Degradation in Low Earth Orbit – Characterization of Specimens from MISSE-13

The environment of low Earth orbit presents unique material interactions due to the presence of atomic oxygen and solar spectrum UV. A variety of degradation mechanisms can occur depending, in large part, on the specific material system involved. This talk will review the characterization of two ablative materials, PICA-D and HEEET, as well as relevant adhesive joints and coatings. PICA-D is a variant of the phenolic impregnated carbon ablator (PICA) and is the baseline thermal protection system (TPS) on Dragonfly and the lander for Mars Sample Return (MSR). HEEET is a 3D woven system from which MSR’s Earth entry TPS is derived. The samples for these materials were flown in orbit during the Materials International Space Station Experiment-13 (MISSE-13) which launched on March 6, 2020 and returned to Earth on January 13, 2021. Changes to surface microstructure and reflectivity will be presented along with tomographic analysis. The effect of differential erosion rates on the composites and the impacts of the orbit environment on coating performances will be discussed in the context of TPS performance and mission design aspects.

MISSE↗
NASA NTRSDate not supplied

Analysis of PICA-NuSil at the Hypersonic Materials Environmental Test System (HyMETS)

Phenolic Impregnated Carbon Ablator (PICA) gained heritage during the stardust mission and is the baseline material for missions to Mars. The phenolic phase of PICA is friable, and therefore the surface is treated with a siloxane resin (NuSil) to mitigate the shedding of particulate matter. Historically, material response models have not accounted for the presence of this coating. Therefore, a test campaign was executed at the Hypersonic Materials Environmental Test System (HyMETS) to investigate the performance of NuSil under multiple heating rates and gas composition. Sphere-cone models were instrumented with thermocouples to measure the in-depth temperature response, and surface temperatures were monitored with a pyrometer. Furthermore, emission spectrometers were used to collect spectra from species emitting at the surface of the test article and the post-shock stagnation region. Post-test analysis suggests that the coating decomposes according to multiple stages. Inspection of silicon emission data reveals a rapid rise and decline in intensity within the first couple of seconds of testing, which is attributed to pyrolysis of NuSil. Pyrolysis is followed by a stagnation in silicon emission and surface temperature which are attributed to the formation of a thin layer of oxidation-resistant silicon oxycarbide. Moreover, the presence of the silicon oxycarbide layer significantly reduces the in-depth thermal response when compared to the baseline material. Eventually, the silicon oxycarbide layer decomposes via high-temperature reactions, which expose the underlying char layer to a highly reactive flow.

PICA-NuSil↗
NASA NTRSDate not supplied

Development of Advanced Ablative Carbon Phenolic TPS for Future NASA Missions and Commercial Space

Phenolic Impregnated Carbon Ablator (PICA) is a low-density carbon phenolic ablator that has been used as the planetary entry heatshield for several NASA missions since the late 90’s. Its low density and efficient performance characteristics have proven effective for use from Discovery to Flagship class missions, from Sample Return missions such as Stardust, OSIRIS-REx to large Mars lander missions such as MSL and Mars 2020. Continued development of a mass efficient, compliant version of PICA that use a carbon felt as the substrate will be presented. The felt based versions of PICA known as Conformal PICA (C-PICA) is comparable in terms of peak heat-flux capabilities compared to standard PICA. Additionally, a novel all felt PICA-Flex offers further reductions in density, with higher thermal protection efficiency resulting in additional mass savings beyond C-PICA. Furthermore, the compliant nature of these materials allows for application without Strain Isolation Pad to a wide variety of substrates, making attractive for commercial low earth orbit missions as well as NASA’s aerocapture missions to Ice Giants. NASA is currently working with several commercial partners (Varda and Inversion Space) to Technology Transfer C/S-PICA variants for commercial LEO missions. Preliminary thermal and mechanical tests have been conducted comparing the performance of Conformal and Soft-PICA and PICA-Flex materials.

Flexible Ablative TPS↗
NASA NTRSDate not supplied

The Material Response of PICA-NuSil to a Hypersonic Flow Environment

Phenolic Impregnated Carbon Ablator (PICA) is NASA’s baseline thermal protection system for missions to Mars. PICA is friable; therefore, NuSil ® CV-1144-0 is applied to the surface of flight hardware to mitigate the contamination of spacecraft sensors. NuSil is composed of a polysiloxane resin system that can transform into an oxidation-resistant coating upon heating. Therefore, a pathfinder campaign was conducted at the Hypersonic Materials Environmental Test System (HyMETS) at the NASA Langley Research Center to investigate the material response of instrumented sphere-cone models made from PICA coated with NuSil ® . Analysis of the post-test data is presented and suggests that NuSil ® impacts the material response of test articles subjected to oxidizing atmospheres, as evidenced by a reduction of the measured surface temperature and in-depth temperature response. Finally, a four-step ablation mechanism is proposed based on observations from high-speed video, optical emission spectroscopy, thermal analysis, and post-test surface characterization.

PICA PICA-NuSil Siloxane Silicone↗
NASA NTRSDate not supplied

Thermostructural Qualification of PICA-D for NASA Planetary Science Missions

Phenolic Impregnated Carbon Ablator (PICA) has been used as the heatshield TPS material for many NASA planetary science missions. Due to a supply issue with the heritage Rayon fibers used in PICA fabrication, NASA started a project in 2017 to develop a sustainable replacement for PICA using a domestic fiber source, named PICA-D. This material has been selected as the heatshield TPS material for two upcoming NASA planetary science missions, Dragonfly mission to Titan and Mars Sample Retrieval Lander (SRL). While most PICA-D thermal and mechanical properties are very similar to PICA, early test data suggest that PICA-D is stiffer in tension in the in-plane (IP) direction, with higher strength but lower strain-to-failure. Preliminary thermostructural analysis using Finite Element Methods (FEM) tools predict IP compressive failure in the near-surface layers of PICA-D, for both Dragonfly and SRL flight environments. This talk provides an overview of the thermostructural qualification plans for PICA-D. A two-pronged approach is being pursued to demonstrate that the material and heatshield design has adequate capability for both SRL and Dragonfly design environments. The first part is to improve the accuracy of analytical predictions through a comprehensive characterization of PICA-D mechanical properties. The second, and more critical, part of the qualification approach is a subsystem-level test of PICA-D to demonstrate material capability under flight-relevant combined mechanical and thermal loads. The team is currently preparing for two test series in Sandia’s Solar Tower facility, scheduled in September 2023 and focusing on PICA-D acreage, followed by additional tests in the Solar Tower and LHMEL facilities focusing on design features and repair methods.

TPS↗
NASA NTRS2019

Thermal Protection System Technology Maturation and Sustainment in Support of In Situ Science Missions: HEEET and PICA

Challenges faced by the Entry Descent and Landing (EDL) community include the lack of a matured forebody heatshield thermal protection system (TPS) capable of meeting the demanding entry environments for the high priority in-situ science missions identified in the decadal survey at Venus, Saturn and the Ice Giants, and the continued sustainment of thermal protection systems/materials. In response to the identified shortfall in TPS technologies capable of extreme entry environments NASA's Space Technology Mission Directorate (STMD) and Science Mission Directorate (SMD) initiated the Heatshield for Extreme Entry Environment Technology (HEEET) project which has matured a 3D-Woven TPS to Technology Readiness Level 6 and which is ready for infusion into these high priority missions. During the development of HEEET long term sustainability was a key consideration. However existing TPS also continue to face sustainability issues. Phenolic Impregnated Carbon Ablator (PICA) has been/is being utilized by many SMD Missions (Stardust, Mars Science Laboratory, OSIRIS-Rex, Mars 2020, Dragonfly) and is under consideration for others including Mars Sample Return, so maintaining PICA for the long term is a priority for NASA. This presentation will discuss raw material sustainability challenges faced by PICA and the efforts by NASA to work with Fiber Materials Inc (FMI) to resolve these challenges with a more sustainable supply chain. In addition, NASA is working with FMI to increase the manufacturing scale for single piece PICA heatshields and to expand the aerothermal performance envelop maturing PICA for larger sized heatshield and more aggressive entry environments. This presentation will also identify challenges and limitations with these systems, particularly around understanding failure modes in these materials and systems and how understanding these may allow use of these systems in environments that are difficult to achieve in ground based testing

Phenolic Impregnated Carbon Ablator (PICA)↗
NASA NTRS2019

Thermal Protection System Technology Maturation and Sustainment in Support of In-situ Science Missions: HEEET and PICA

Among the challenges faced by the Entry Descent and Landing (EDL) community have been: the lack of a matured forebody heatshield thermal protection system (TPS) capable of meeting the demanding entry environments for the high priority in-situ science missions identified in the decadal survey at Venus, Saturn and the Ice Giants, and the continued sustainment of thermal protection systems/materials. In response to the identified shortfall in TPS technologies capable of extreme entry environments NASA's Space Technology Mission Directorate (STMD) and Science Mission Directorate (SMD) initiated the Heatshield for Extreme Entry Environment Technology (HEEET) project which has matured a 3D-Woven TPS to Technology Readiness Level 6 and which is ready for infusion into these high priority missions. During the development of HEEET long term sustainability was a key consideration. However existing TPS also continue to face sustainability issues. Phenolic Impregnated Carbon Ablator (PICA) has been/is being utilized by many SMD Missions (Stardust, Mars Science Laboratory, OSIRIS-Rex, Mars 2020, Dragonfly) and is under consideration for others including Mars Sample Return, so maintaining PICA for the long term is a priority for NASA. This presentation will discuss raw material sustainability challenges faced by PICA and the efforts by NASA to work with Fiber Materials Inc (FMI) to resolve these challenges with a more sustainable supply chain. In addition, NASA is working with FMI to increase the manufacturing scale for single piece PICA heatshields and to expand the aerothermal performance envelop maturing PICA for larger sized heatshield and more aggressive entry environments. This presentation will also identify challenges and limitations with these systems, particularly around understanding failure modes in these materials and systems and how understanding these may allow use of these systems in environments that are difficult to achieve in ground based testing.

Heatshield for Extreme Entry Environment Technolog↗
NASA NTRS2018

Sustaining PICA TPS for Future NASA Robotic Science Missions

Phenolic Impregnated Carbon Ablator (PICA), invented in the mid 1990's, is a low-density ablative thermal protection material proven capable of meeting sample return mission needs from the moon, asteroids, comets and other "unrestricted class V destinations" as well as for Mars. Its low density and efficient performance characteristics have proven effective for use from Discovery to Flagship class missions. It is important that NASA maintain this TPS material capability and ensure its availability for future NASA use. The rayon based carbon precursor raw material used in PICA preform manufacturing required replacement and requalification at least twice in the past 25 years and a third substitution is now needed. The carbon precursor replacement challenge is twofold – the first involves finding a long-term replacement for the current rayon and the second is to assess its future availability periodically to ensure it is sustainable and be alerted if additional replacement efforts need to be initiated. Rayon is no longer a viable process in the US and Europe due to environmental concerns. In the early 80's rayon producers began investigating a new method of producing a cellulosic fiber through a more environmentally responsible process. This cellulosic fiber, lyocell, is a viable replacement precursor for PICA fiberform. This presentation reviews current SMD-PSD funded PICA sustainability activities in ensuring a rayon replacement for the long term is identified and in establishing that the capability of the new PICA derived from an alternative precursor is in family with previous versions of the so called "heritage" PICA.State of the Art Low Density Carbon Phenolic AblatorsStardust SRC post flight withPICA forebody heat shield(0.8m max. diameter)PICA Processing StepsRole of Rayon/Lyocellin PICA.

Stackpoole, Mairead↗
NASA NTRS2017

Progress Report on PICA Activities in Support of New Frontiers Missions

Phenolic Impregnated Carbon Ablator (PICA) is a TPS material that has been used in a number of previous flight missions (Stardust, MSL) and is planned for a number of future missions (OSIRIS-Rex and Mars 2020) so it has substantial flight heritage, is applicable to a wide range of missions, and is often baselined as the TPS in future NASA proposal activities. As is common with a number of TPS materials, PICA faces a supply chain issue with the rayon precursor from which the carbon fibers used in the PICA preform are derived. PICA uses a non-woven form of the rayon, which once carbonized, is used in the low-density carbon FiberForm (carbon tile) preform utilized in PICA. Current PICA uses a NASA-qualified non-domestic rayon supplier (Sniace), however the qualified supplier is no longer manufacturing the rayon materials. This activity will address PICA sustainability, by initially carbonizing the remaining stockpile of Sniace rayon precursor. A additional FiberForm manufacturing task from alternate rayon sources is also in progress.

thermal protection↗
NASA NTRSDate not supplied

Development of Advanced Conformal and Soft Pica for Future Nasa Missions and Commercial Space

Phenolic Impregnated Carbon Ablator (PICA) is a low-density ablator that has been used as the planetary entry heatshield for several NASA missions since the late 90’s. Its low density and efficient performance characteristics have proven effective for use from Discovery to Flag-ship class missions, from Sample Return missions such as Stardust, OSIRIS-REx to large Mars Lander missions such as MSL and Mars 2020. Continued development of a more mass efficient and compliant versions of PICA that use a carbon felt as the substrate will be presented. The felt based versions of PICA known as Conformal PICA (C-PICA) and Soft PICA (S-PICA), are very comparable in terms of peak heat-flux capabilities compared to standard PICA. The lower density and of C-PICA and S-PICA further show a much higher thermal protection efficiency and hence more mass savings. The compliant nature of these materials allows for use on a wide variety of substrates and therefore makes it very attractive for commercial low earth orbit missions as well as NASA’s aerocapture missions to Ice Giants. NASA is currently working with several commercial partners (Varda and Inversion Space) to Technology Transfer C/S-PICA variants for commercial LEO missions. Thermal, mechanical, and representative environment arc-jet tests have been conducted comparing the performance of Conformal and Soft-PICA materials.

Matthew J Gasch↗
NASA NTRS2019

Bayesian Inference and the Effects of Varying Uncertainty Models in Charring Ablator Calibration and Uncertainty Quantification Problems

The Mars Science Laboratory (MSL) vehicle utilized a heat shield constructed from NASA’s Phenolic-Impregnated Carbon Ablator (PICA) material to protect the main structure from the high enthalpy environment encountered during hypersonic atmospheric entry. During the vehicle’s descent through Martian atmosphere, multiple thermocouples embedded within the heat shield captured in-depth material temperature data that allow for studies to be conducted on current material response reconstruction tools. In the present work, material temperature data obtained from thermocouples within the MISP-4 plug (MEDLI (Mars Science Laboratory Entry, Descent, and Landing Instrument) Integrated Sensor Plug) are utilized in the calibration of Theoretical Ablative Composite for Open Testing (TACOT) model parameters in conjunction with NASA’s Porous material Analysis Toolbox (PATO) through Bayesian inference where uncertainty due to parametric, modeling, and experimental sources is simultaneously quantified. Prior to the study, a sensitivity analysis is performed through computation of the robust Sobol indices in an effort to study the relationship between input space and model response and to reduce the dimensionality of the statistical inverse problem. The Bayesian inference methodology necessitates an a-priori choice to be made for the uncertainty model for which numerous possibilities are available. Across most works, however, only basic additive or multiplicative models are utilized with pre-defined magnitudes of uncertainty based on a-priori knowledge or to-be-calibrated multipliers of static covariance matrix structures. The present effort explores the effects of informed uncertainty models, ones with temporal dependence that are simultaneously calibrated through Bayesian inference, on calibrated results for parameters that make up the uncertain input space.

Sensitivity Analysis↗
NASA NTRS2009

Validation of PICA Ablation and Thermal-Response Model at Low Heat Flux

Phenolic Impregnated Carbon Ablator (PICA) was the forebody heatshield material on the Stardust sample-return capsule and is also a primary candidate material for the Mars Science Lander (MSL), the Orion Crew Module, and the SpaceX Dragon vehicle. As part of the heatshield qualification for Orion, physical and thermal properties of virgin and charred PICA were measured, and an ablation and thermal response model was developed. We validated the model by comparing it with recession and temperature data from stagnation arcjet tests conducted over a wide range of stagnation heat flux of 107 to 1102 W/sq cm. The effect of orthotropic thermal conductivity was evident in the thermal response of the arcjet models. In general, model predictions compared well with the data; however, the uncertainty of the recession prediction was greatest for heat fluxes below 200 W/sq cm. More recent MSL testing focused on the low heat flux regime of 45 to 250 W/sq cm. The new results confirm the recession uncertainty, especially for pressures below 6 kPa. In this work we focus on improving the model predictions for MSL and Orion tests below 250 W/sq cm.

Milos, Frank S.↗
NASA NTRSDate not supplied

Material Response Analysis of PICA-NuSil at the Hypersonic Materials Environmental Test System

Phenolic impregnated carbon ablator (PICA) is a thermal protection system (TPS) that gained heritage during the Stardust mission and is the baseline TPS material for expeditions to Mars (e.g., Mars Science Laboratory and Mars 2020).1 PICA is friable; therefore, a polysiloxane resin (NuSil CV-1144-0) is deposited onto the surface of flight hardware before assembly, test, and launch operations (ATLO) to mitigate particle shedding. Furthermore, the Mars Science Laboratory (MSL) and Mars 2020 heatshields were instrumented with an array of thermocouple plugs (MEDLI Integrated Sensor Plugs or MISP) designed to measure the in-depth thermal response of PICA during flight. Post-flight analysis of MISP data suggests that recession was lower than predicted, and NuSil is suspected as a reasonable cause. NuSil primarily consists of a copolymer blend of dimethyl and diphenyl-substituted polysiloxane resin. Four decades of research in the field of polymer-derived ceramics demonstrate that polysiloxane resins form oxidation-resistant silicon oxycarbide materials at pyrolysis temperatures as low as 800 °C. -2 Furthermore, silicon oxycarbide materials exhibit excellent thermal stability at relatively high-temperatures (< 1200 °C) but eventually decompose via carbothermal reduction. -3 Therefore, it is reasonable to suggest that NuSil forms an oxidation-resistant thermal barrier coating on the TPS surface and influences the material response during atmospheric entry. Evidence for this notion was observed during prior arc-jet testing at both the Aerodynamic Heating Facility (AHF) and the Panel Test Facility (PTF) at the NASA Ames Research Center. Articles of PICA were subjected to testing in airflow, and a temperature discontinuity was recorded at the surface of coupons coated with NuSil. A glassy coating was observed to form at the surface in shear flow configurations (wedge and panel) under moderate heat fluxes. Furthermore, state-of-the-art material response models have yet to account for the underlying physics and chemistry of the temperature discontinuity. To this end, a pathfinder test campaign was executed at the Hypersonic Materials Environmental Test System (HyMETS) to enhance the fundamental understanding of PICA-NuSil ablation phenomena and provide a preliminary data set to aid in the development of material response models.

PICA↗
NASA NTRS2019

Progress in Manufacturing & Characterizing Domestic Lyocell PICA (PICA-D) and Comparison to Heritage PICA

NASA ARC (Ames Research Center) is working with SMD-PSD (NASA Science Mission Directorate- Planetary Science Directorate) to address PICA ( Phenolic Impregnated Carbon Ablator) rayon sustainability concerns. In FY16/17, Lyocell Based PICA (PICA-D (Domestic)) was manufactured and limited testing performed showing it to be a good candidate as a potential replacement for heritage rayon. Establishing PICA-D as a "drop in replacement" will allow missions to depend on and design missions with PICA without any risk typical of a replacement. Establishing the extended capability of PICA-D will allow Sample Return Missions with higher entry speed that were not considered before.

Lyocell↗
NASA NTRS2019

Charactarization of Thermal Protection Systems

In 2012, NASA's mission of landing the Mars Science Laboratory (MSL) on Mars was successful. MSL was protected by an ablative heatshield of tiled low density material known as PICA (phenolic impregnated carbon ablator). The heatshield was instrumented with MEDLI (MSL Entry Descent Landing Instrument) a suite of sensors & thermocouples at discrete locations in order to monitor the in-depth ablator temperature response and surface pressure. MEDLI was designed and developed by NASA Langley, in partnership with NASA Ames Research Center for the purposes of probing Mars and evaluating the performance of the spacecraft upon entry into the Martian atmosphere. The flight data reduces the uncertainty in engineer models for predicting the response of a spacecraft towards the extreme heating environment of an entry into the Martian atmosphere. MEDLI2 is a part of the Mars 2020 mission and is the next-generation sensor suite for entry, descent, and landing. This data will again help engineers validate their flight models. Additionally, the atmospheric data, can help us understand atmospheric density and winds. This is a critical study for reducing risks to both robotic and future human missions to Mars. Engineered models for Mars 2020 are dependent upon parameters related to the materials response to heating and radiation. In this work, the thermal properties and other measurements of various ablative materials are analyzed to achieve greater utility of the 2012 MEDLI flight data and more accurately determine the parameters being used in Mars 2020. The purpose of this study was to measure specific heat, thermal conductivity, char yield, reflectance as a function of wavelength, and other thermal parameters and optical properties of various ablative materials. CO2(g) at extreme temperatures emits radiation impacting MEDLI2 flight predictions. Emissivity & absorptivity as a function of temperature were calculated from FTIR and UV-Vis data as a means of investigating whether these materials might absorb CO2 radiation upon entry into the Mars atmosphere.

HEEET↗
NASA NTRSDate not supplied

Analysis of PICA-NuSil at the Hypersonic Materials Environmental Test System (HyMETS)

Phenolic Impregnated Carbon Ablator (PICA) gained heritage during theStardust mission and is the baseline thermal protection system (TPS) material for missions to Mars. However, PICA is friable, so a thin layer of siloxane resin (NuSil) is applied to the surface of the heat shield to suppress the spread of particulate matter during cleanroom activities. Until recently, the thermochemical response of NuSil had not been accounted for in material response models. Therefore, a test campaign was executed at the Hypersonic Materials Environmental Test System (HyMETS) facility to investigate the material response of NuSil and provide crucial insight for model development. Finally, salient results from an experiment supported by the AsteroidThreat Assessment Project (ATAP) will be discussed, which probed the materialr esponse of the Tamdakht meteorite and notable analogs.

Brody K. Bessire↗
NASA NTRSDate not supplied

Advances in Design Capabilities for Planetary Missions from the NASA Entry Systems Modeling and Instrumentation Portfolio

The Entry Systems Modeling project (ESM) is supported by both the NASA Space Technology and the Science Mission Directorates and focuses on developing simulation tools and validated models for characterizing the performance of entry systems tailored to planetary destinations across the Solar System. ESM is organized into six technical capability areas that together address all relevant factors related to spacecraft entry, as well as some aspects of descent: Thermal Protection System (TPS) Materials; Aerothermodynamics; Entry & Descent Vehicle Dynamics; Guidance, Navigation, and Control; Vehicle Systems Analysis; and Advanced Tools and Numerical Methods. Development within the capability areas is undertaken explicitly with a focus on transition and infusion to science missions, human exploration missions, and commercial space activities. The present talk details developments that specifically impact science missions, including simulation tool capabilities that aid in mission design and model development to understand entry system performance at a given destination. Examples of the successful infusion and transition of such project outcomes to science missions also are provided. Several simulation tool development efforts within ESM have resulted in new design capabilities for missions. One such outcome is improved toolsets for mission trajectory and concept of operations design. Specifically, an initiative to couple a leading tool for entry, ascent/descent, and orbital trajectory optimization (Program to Optimize Simulated Trajectories II or POST2) to those used within the Agency for interplanetary trajectory optimization (Copernicus and Monte) has made substantial progress, with the outcomes to date promising to allow efficient trajectory optimization across mission phases. Additionally, toolchains for the evaluation of vehicle performance during entry and descent have been developed that allow assessment of multi-dimensional aeroheating on detailed vehicle geometries, characterization of deployment and inflation of parachutes, and assessment of vehicle dynamic stability during descent. These capabilities are achieved by coupling diverse sets of physics together – material response, computational fluid dynamics, radiation, and vehicle dynamics – to suitably describe complex entry and descent phenomena. Several model development and validation efforts for specific destinations and entry regimes also are underway within the ESM project. For instance, new experimental capabilities to validate radiation models at low densities/high altitudes recently have been established with project support, specifically the Low-Density Shock Tube (LDST) at the NASA Ames Research Center Electric Arc Shock Tube (EAST) facility. The LDST is being leveraged to develop improved models of shock layer kinetics and radiation in Titan atmospheres, while future studies will be conducted in the LDST and the existing high velocity shock tube to provide validation data for radiation models of Venus, Ice Giants, and Mars atmospheres. Models describing the aerothermal and thermo-structural performance of Thermal Protection System (TPS) materials has been another focus, with multiscale modeling activities on-going for the two leading TPS materials applicable to a range of entry conditions and science missions: the Phenolic-Impregnated Carbon Ablator (PICA) and woven materials like 3D Mid-Density Carbon Phenolic (3MDCP). A continual effort is made to infuse and transition outcomes from ESM simulation tool and model development activities into relevant science missions. Significant progress has been made on this front, with missions such as Dragonfly, DAVINCI, and Mars Missions benefitting from project outcomes. The groundwork also is being laid to provide insights into forward looking missions to Gas/Ice Giants as well as for potential sample returns.

Justin Haskins↗