Ballistic coefficient range: 200–350 kg/m2 (in steps of 50 kg/m2) Inertial entry flight path angle range that covers deceleration loads between 50 and 200 g • Uranus: -16.5° to -36.5° Neptune: -16° to -26° • no pressure and/or heat flux constraints imposed Inertial entry velocity: Uranus: 23 km/s Neptune: 26 km/s Stagnation point convective heating estimates obtained from correlations based on freestream density and velocity; radiative heating likely to be small at both destinations All trajectories terminated at flight Mach number of 0.8 (heatshield jettison) • Step #2: Size HEEET using FIAT [4] to stagnation point aerothermodynamic environments estimated in Step #1 Planet-specific B’ tables for material thermal response, and a margins policy [5] that accounts for uncertainty in environments & material properties Thicknesses determined with: (a) initial temperature of -10°C, and (b) a maximum allowable back face temperature of 250 °C • Step #3: Adjust stagnation point sizing from Step #2 to margin against turbulent heating on the conical flank Flank heating can be as high as stagnation point heating, but at a lower (≈50%) pressure level – increased material recession Current solution: Scale up stagnation point recession layer thickness by 1.2, and scale down insulation layer thickness by 1.2 • Step #4: Add manufacturing margins to estimates of flank thicknesses (recession and insulation layers) Manufacturing margins: 0.51 cm for the insulation layer, and 0.38 cm for the recession layer References: [1] Hwang, H., et al., (2018), 15th IPPW, Boulder, CO, June 11–15. [2]Ice Giants: Pre-Decadal Survey Mission Study Report (2017), JPL D-100520. [3] Allen, G. A., Jr., Wright, M. J., and Gage, P. J. (2005) NASA/TM-2005-212847. [4] Milos, F. S. and Chen, Y.-K. (2013) J. Spacecraft and Rockets, 50(1), pp.137-149. [5] Mahzari, M. and Milos, F. (2018), 15th IPPW, Boulder, CO, June 11–15. Heatshield for Extreme Entry Environment Technology (HEEET) TPS for Ice Giants Probe Missions D. Ellerby§, T. Boghozian*, D. Driver§, J. Chavez-Garcia*, M. Fowler$, P. Gage#, M. Gasch§, G. Gonzales*, C. Kazemba, C. Kellermann$, S. Langston%, J. Ma§, M. Mahzari §, F. Milos§, O. Nishioka§, G. Palmer*, K. Peterson §, C. Poteet%, D. Prabhu*, S. Splinter%, M. Stackpoole§, E. Venkatapathy§ , J. Williams*, and Z. Young§ §NASA ARC; %NASA LaRC; $NASA JSC; *AMA.-Moffett Field, CA; #NEERIM Corp.-Moffett Field, CA

Phenolic Impregnated Carbon Ablator (PICA) is a low-density ablator that has been used as the planetary entry heatshield for several NASA missions since 1999. Due to the obsolescence of the input fiber source, new PICA materials were developed using Lyocell, a domestic rayon fiber source. Results are presented from this effort. Manufacturing included fiber conversion, fabrication of tile component and near net shaped heatshield preforms, and conversion to PICA materials. Thermal, mechanical, and representative environment arc-jet testing have been conducted. Initial testing indicates comparable performance with respect to heritage PICA material, and likely drop-in replacement for future NASA mission needs.

Starting in 2013 and completing in 2019, the Heatshield for Extreme Entry Environment Technology (HEEET) project has been working to mature a 3-D Woven Thermal Protection System (TPS) to Technical Readiness Level (TRL) 6 to support future NASA missions to destinations with extreme entry environments such as Venus, Saturn, Uranus, Neptune and high-speed sample return missions to Earth. A key aspect of the project has been the building and testing of a 1-meter base diameter Engineering Test Unit (ETU) representative of what could be used for a Saturn probe. This paper provides a high-level overview of the HEEET project including 1) manufacturing and testing of the ETU for structural model verification, 2) establish system capability and 3) verify manufacturing workmanship.

D. M. Driver, D.T. Ellerby(Presenting Author), M. J. Gasch, M. Mahzari, F. S. Milos, O. S. Nishioka, K. H. Peterson, M. M. Stackpoole, E. Venkatapathy, Z. W. Young, P. J. Gage, T. Boghozian, J. F. Chavez-Garcia, G. L. Gonzales, G. E. Palmer, D. K. Prabhu, J. D. Williams, C.D. Kazemba, A. S. Murphy, S. L. Langston, C. C. Poteet, S. C. Splinter, M. E. Fowler, C. M. Kellermann, NASA Ames Research Center Moffett Field, CA 94035, Neerim Corp Moffett Field, CA 94035, Analytical Mechanics Associates, Inc. Moffett Field, CA 94035, Science and Technology Corp, Moffett Field, CA 94035, Millennium Engineering and Integration Co. Moffett Field, CA 94035,NASA Langley Research Center Hampton, VA 23681, NASA Johnson Space Center Houston, TX 77058, Jacobs Technology, Inc. Houston, TX 77058

Average Rayon TTT properties 1.22 1.66 • In 2016 NASA ARC learned that the heritage rayon utilized in PICA was stopping production, leading to a flight-qualified PICA sustainability challenge • In FY16/17, NASA ARC was funded by SMD/PSD to address PICA rayon sustainability • Lyocell Based PICA (PICA-D) was manufactured and limited testing performed showing it to be a good candidate as a potential replacement for heritage rayon • Phenolic Impregnated Carbon Ablator (PICA) is a low density (~ 0.27g/cm 3 ) ablator first used as the forebody heatshield for the Stardust sample return capsule where it was used as a single piece heatshield • Since Stardust, PICA was used on the Mars Science Lab (MSL) in a tiled configuration, on the OSIRIS-REx sample return capsule as a single piece and slated for Mars 2020 as a tiled configuration 4. Exploration of Lyocell PICA (PICA-D) for Future Missions

System for Small and Large Scale Missions: Approaching TRL 6 for Planetary and Human Exploration Missions and TRL 9 for Small Probe Missions R. A. S. Beck1, M. J. Gasch1, F. S. Milos1, M. M. Stackpoole1, B. P. Smith1, M.R. Switzer1, E. Venkatapathy1, M. C. Wilder1, T. Boghhozian2, J. F. Chavez-Garcia2, T. Gokcen2, D. K. Prabhu2,G. T. Swanson2, C. D. Kazemba3, W. Congdon4, D. DePasquale5, B. A. Woollard6, A. Sidor6

NASA's future robotic missions utilizing an entry system into Venus and the outer planets, namely, Saturn, Uranus, Neptune, result in extremely high entry conditions that exceed the capabilities of state of the art low to mid density ablators such as PICA or Avcoat. Therefore mission planners typically assume the use of a fully dense carbon phenolic heat shield similar to what was flown on Pioneer Venus and Galileo. Carbon phenolic is a robust TPS material however its high density and relatively high thermal conductivity constrain mission planners to steep entries, with high heat fluxes and pressures and short entry durations, in order for CP to be feasible from a mass perspective. The high entry conditions pose challenges for certification in existing ground based test facilities and the longerterm sustainability of CP will continue to pose challenges. In 2012 the Game Changing Development Program (GCDP) in NASA's Space Technology Mission Directorate funded NASA ARC to investigate the feasibility of a Woven Thermal Protection System (WTPS) to meet the needs of NASA's most challenging entry missions. This project was highly successful demonstrating that a Woven TPS solution compares favorably to CP in performance in simulated reentry environments and provides the opportunity to manufacture graded materials that should result in overall reduced mass solutions and enable a much broader set of missions than does CP. Building off the success of the WTPS project GCDP has funded a follow on project to further mature and scale up the WTPS concept for insertion into future NASA robotic missions. The matured WTPS will address the CP concerns associated with ground based test limitations and sustainability. This presentation will briefly discuss results from the WTPS Project and the plans for WTPS maturation into a heatshield for extreme entry environment.

Sol-gel derived hafnia coatings are being developed to provide an oxidation protection layer on ultra-high temperature ceramics for potential use in turbine engines (ultra-efficient engine technology being developed by NASA). Coatings using hafnia sol hafnia filler particles will be discussed along with sol synthesis and characterization.