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Entry System Technology Readiness for Ice-Giant Probe Missions


NASA has successfully developed a new and innovative Heatshield for Extreme Entry Environments Technology, or HEEET, which, at a Technology Readiness Level (TRL) of 6, is ready for use in Ice Giant missions. HEEET is not just a replacement for the legacy full-density carbon-phenolic (FDCP) material, which was used in NASA’s Pioneer-Venus and Galileo missions; it is also a more mass efficient and robust alternative, and a technology that has a sustainable manufacturing base. HEEET is a dual-layer, 3-dimensionally woven material. It has a dense outer layer, made of pure carbon fibers, that comes into contact with and protects against extreme entry environments. Below this layer is an integrally woven, lower density insulating layer, made of a blend of carbon and phenolic yarn, that reduces heat-conduction to the carrier structure. The present paper describes development of this material, its thermal, structural, and aerothermal testing, production of an engineering test unit at flight scale, and maturation for infusion into missions to various planetary destinations, with a focus on Ice Giant in situ missions. Finally, for representative entry velocities at Uranus and Neptune, and a range of entry masses and flight path angles, margined thicknesses of HEEET are computed. When the limits of heat fluxes and pressures that can be achieved in ground-test facilities, and loom limits, are imposed on these thickness estimates, it is shown that several atmospheric entry missions are possible at the two destinations.

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Engineering Test Unit


Full-density carbon-phenolic


Finite element method


Heritage carbon-phenolic


Heatshield for Extreme Entry Environments Technology


Interaction Heating Facility


Ice Giant probes


Insulation Layer


Preliminary Design Review


Phenolic-Impregnate Carbon-Phenolic


Recession Layer


Solar-Electric Propulsion


Thermal protection system


Technology Readiness Level


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The HEEET project is grateful to NASA’s Space Technology Mission Directorate, the Game Changing Development Program and the Planetary Science Division, Science Mission Directorate for their support. Any endeavor of the magnitude of HEEET requires the support of a large number of folks within the agency, primarily at NASA’s Ames, Johnson and Langley centers, that deserve acknowledgment, and are too many to name here. The project gratefully acknowledges the arcjet complex at NASA Ames Research Center, the High Enthalpy Arc Heated facilities at Arnold Engineering Development Complex in Tullahoma, TN and the Laser Hardened Materials Evaluation Laboratory (LHMEL) at Wright Patterson Airforce Base in Dayton OH. The industrial partners, Bally Ribbon Mills Inc of Bally, PA and Fiber Materials Inc. of Biddeford, ME were invaluable. The Independent Review Board (IRB) provided continual critical review and feedback from the beginning to the end of the project and eventually certified that HEEET achieved TRL 6, and so the project extends its appreciation to the members of the IRB: Prof. Robert Braun of University of Colorado, Boulder (chair); Robin Beck, NASA ARC; Pam Hoffman, NASA JPL; Christine Szalai, NASA JPL; Stan Bouslog, NASA JSC; Michael Amato, NASA GSFC; Anthony Calamino, NASA LaRC; Michelle Munk, NASA LaRC; Ken Hibbard, Johns Hopkins University, Applied Physics Laboratory; and Steve Gayle, NASA LaRC. The project is thankful to the management at NASA Centers and the organizations mentioned above for their continued support through the duration of the project.

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In Situ Exploration of the Ice Giants: Science and Technology

Edited by Olivier J. Mousis and David H. Atkinson

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Venkatapathy, E., Ellerby, D., Gage, P. et al. Entry System Technology Readiness for Ice-Giant Probe Missions. Space Sci Rev 216, 22 (2020).

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  • Ice giants
  • Atmospheric entry
  • Entry system
  • Thermal protection system
  • Ablative material
  • 3D woven material
  • Carbon-phenolic