Tech Briefs

Advanced Ablative Insulators and Methods of Making Them

Reinforced, filled silicones and carbon phenolics are laser-milled to final shapes.

Advanced ablative (more specifically, charring) materials that provide temporary protection against high temperatures, and advanced methods of designing and manufacturing insulators based on these materials, are undergoing development. These materials and methods were conceived in an effort to replace the traditional thermal- protection systems (TPSs) of reentry spacecraft with robust, lightweight, better-performing TPSs that can be designed and manufactured more rapidly and at lower cost. These materials and methods could also be used to make improved TPSs for general aerospace, military, and industrial applications.

The ablative materials belong to two families. One family comprises filled, fiber reinforced elastomeric carbon phenolics with mass densities that range from 18 to 40 lbm/ft3 (288 to 641 kg/m3); these materials are designed to protect against heating rates up to about 1,300 Btu/(ft2s) [≈15 MW/m2]. The other family comprises filled, fiber-reinforced silicones with mass densities that range from 12 to 50 lbm/ft3 [192 to 800 kg/m3]; these materials are designed to protect against heating rates from 5 to about 400 Btu/(ft2s) [about 0.06 to about 4.5 MW/m2]. The fillers in these materials help to minimize their mass densities, while the fibers help to maximize their strengths.

Design and manufacture of TPSs according to the present approach involve the use of computer-aided design and computer-aided manufacturing (CAD/CAM) methods, including computer numerically controlled (CNC) laser milling. This approach eliminates the labor-intensive steps of machining, fitting, and trimming heat-shield parts in the prior approach to manufacturing. In the present approach, molded panels of the ablative materials are CNC-lasermilled to precise final sizes and shapes and are thus made ready for bonding to heat-shield structures.

This work was done by William M. Congdon of Applied Research Associates, Inc., for Johnson Space Center. For further information, contact the Johnson Technology Transfer Office at (281) 483-3809. MSC-23141