Heatshield / Aeroshell Solar Tower Testing

Heat Shield

Challenge

Under NASA sponsorship, the ARA Ablatives Laboratory has been conducting advanced ablator tests in the Sandia Solar Tower Facility since 2003. Initially these tests were performed on 5.0-in. diameter ablator coupons for the purpose of characterizing and modeling ablator responses to high-energy thermal radiation. Starting in 2005, however, the test facility has been used to evaluate thermostructural robustness of ablators bonded to aeroshell composite structures. Because ablators can achieve very high temperatures in flight (e.g., 2000°C) and because they typically have different thermal expansion properties relative to structures, the adhesive bond between ablator and structure becomes highly stressed. It is important to demonstrate that an aeroshell system can accommodate high bondline stresses without failure and ablator debonding. Such testing is best done on relatively large test articles rather than small coupons. However, typical ablator ground test facilities, such as arc-jets, do not have the needed power to test large ablator articles at sufficiently high heating to develop flight-like thermal gradients. In addition, because the TPS ablators give off large quantities of gaseous ablation products, facility contamination from testing large articles would become a concern. The Solar Tower is well suited for such testing on large test articles because of its high power levels and because it is an outdoor, open-air facility.

Solution

To date we have tested three 1.0-m diameter heatshield/aeroshells at Solar Tower to evaluate and verify thermostructural robustness. These were shaped aeroshells with a 70-deg. half-cone angle. The photographs below provide visual images of this type of high-energy testing at a heating rate of 150 W/cm2 (equivalent to "~1,500 Albuquerque suns").

Final Shaping of 1.0-m Test Aeroshell – 3-Axis Milling
Final Shaping of 1.0-m Test Aeroshell – 3-Axis Milling
Mounting Internal Support Structure and Rotation Shaft
Mounting Internal Support Structure and Rotation Shaft
Attaching Aeroshell's Insulating Close-Out Panel
Attaching Aeroshell's Insulating Close-Out Panel
Mounting Aeroshell to Controlled-Rotation System
Mounting Aeroshell to Controlled-Rotation System
200-ft Tower – View from Heliostat Field
200-ft Tower – View from Heliostat Field
Heatshield at 1-Sec Exposure to 150 W/cm2
Heatshield at 1-Sec Exposure to 150 W/cm2
Heatshield at 4-Sec Exposure to 150 W/cm2
Heatshield at 4-Sec Exposure to 150 W/cm2
Heatshield at 200-Sec Exposure to 150 W/cm2
Heatshield at 200-Sec Exposure to 150 W/cm2

Thermal Protection Technology and Engineering

Thermal Protection Technology, Engineering, and Manufacturing

ARA’s Ablatives Laboratory is a NASA-dedicated facility focused on technology advancements for thermal protection systems (TPS) such as planetary... more

Ablatives Lab

Ablatives Laboratory

Research, development and manufacturing of ablative heatshields and thermal protection systems for entry and launch vehicles, and missile systems... more