NASA has developed a class of low-density, flexible ablators that can be fabricated into heat shields capable of being packaged, stowed, and deployed in space. Several flexible versions have been developed by infiltrating a pyrolyzing silicone resin into flexible, low-density felts made of carbon, polymer, or ceramic materials. The material is produced by immersing a flexible fibrous substrate in a diluted polymer resin, curing the polymer resin using heat and/or catalyst, and removing the solvent.
The ablative thermal protection system (TPS) is conformable to a vehicle’s curved external mold line surface, or can be stowed in the shroud of a launch vehicle and deployed in space without compromising the TPS functionality. The flexible, ablative TPS can perform at heating rates above the capability of a current state-of-the-art flexible TPS like the Space Shuttle Flexible Reusable Surface Insulation (FRSI) or Advanced Flexible Reusable Surface Insulation (AFRSI). Recent preliminary experiments show that the flexible ablators can function up to 115 W/cm2 for silicaceous embodiments, and up to 400 W/cm2 for the carbonaceous-based versions of this TPS, as well as for a second heat pulse at 30 W/cm2 to simulate a dual pulse entry.
The flexible, ablative TPS has been shown in preliminary tests to be capable of dual heat pulse operation, as required for fuel-efficient aerocapture and landing maneuvers, whereby a vehicle experiences a first heat pulse when it uses atmospheric drag to decelerate and enter into atmospheric orbit, cools down during one or more orbits, and then undergoes a second heat pulse during landing. Aerocapture strategies have been proposed to deliver large (40 metric tons) payloads to the Mars surface. This invention can be enabling to the development of affordable and reliable commercial access to, and return from, low-earth orbit (LEO).
This invention offers flexible ablators that can be shaped to a rigid surface without extensive machining, or deployed for use after launch, and yet withstand a range of heating rates at a level appropriate for conventional low-density ablative TPS, with the current upper limit of the thermal capability comparable to that of rigid ablators such as PICA and Avcoat. The amount and composition of polymer resin can be readily tailored to specific mission requirements. The invention offers a simple and versatile manufacturing method to produce large-area heat shields that can be relatively easily deployed when appropriate or attached to the exterior of spacecraft.