Low-density ablative heat shield fabrication

Abstract

Spacecraft heat shields are fabricated as one-piece assemblies using low-density ablative thermal protection materials. The heat shield assembly is built from modular pieces formed by ablative impregnation processing. Once the full-size heat shield is assembled from the modular blocks, heat treatment is used to bond the individual blocks together by facilitating polymeric cross-linking of impregnant material within and/or between each block. This provides a structurally integral one-piece heat shield assembly that can be further machined to final dimensions and attached directly to a spacecraft structure or a carrier panel separately attached to the spacecraft

1 . A method for fabricating an ablative heat shield, comprising:
 impregnating each piece of a plurality of pieces of ablative thermal protection material with polymeric resin;   assembling said plurality of pieces into a desired heat shield shape; and   heat-treating said shape to bond said plurality of pieces into a solid heat shield.   
   
   
       2 . The method of  claim 1 , wherein said ablative thermal protection material comprises fiber matrix material. 
   
   
       3 . The method of  claim 1 , wherein said ablative thermal protection material comprises refractory porous substrate material. 
   
   
       4 . The method of  claim 1 , wherein each said piece of said plurality of pieces is selected from a group consisting of a modular piece and a block. 
   
   
       5 . The method of  claim 1 , wherein each said piece is machined to press fit to another said piece. 
   
   
       6 . The method of  claim 2 , wherein said fiber matrix material comprises refractory fiber matrix material. 
   
   
       7 . The method of  claim 1 , wherein said ablative thermal protection material is selected from the group consisting of carbon, silica, alumina, aluminosilicate and silicon carbide. 
   
   
       8 . The method of  claim 1 , wherein said polymeric resin comprises ablative thermal protection materials. 
   
   
       9 . The method of  claim 1 , wherein said polymeric resin comprises phenolic resin. 
   
   
       10 . The method of  claim 9 , wherein said phenolic resin comprises Phenolic Impregnated Carbon Ablator. 
   
   
       11 . The method of  claim 1 , wherein said polymeric resin comprises a phenolic, silicone, epoxy or pre-ceramic polymer compound. 
   
   
       12 . The method of  claim 1 , wherein the step of heat-treating comprises polymeric cross-linking (i) within and between each said piece or (ii) within or between each said piece. 
   
   
       13 . The method of  claim 1 , further comprising machining said solid heat shield to desired dimensions. 
   
   
       14 . The method of  claim 13 , further comprising attaching said heat shield to a spacecraft structure. 
   
   
       15 . The method of  claim 13 , further comprising attaching said heat shield to a carrier panel. 
   
   
       16 . The method of  claim 15 , further comprising attaching said heat carrier panel to a spacecraft structure. 
   
   
       17 . The method of  claim 1 , where the step of impregnating each piece of a plurality of pieces fiber matrix material with polymeric resin comprises immersing said plurality of pieces into said polymeric resin. 
   
   
       18 . The method of  claim 1 , further comprising remove excess solvent from said heat shield. 
   
   
       19 . The method of  claim 1 , wherein the step of assembling said plurality of pieces into a desired heat shield shape includes assembling said pieces against a mandrel. 
   
   
       20 . The method of  claim 1 , wherein the step of heat-treating is carried out at a temperature within a range from 50° C. to 300° C. 
   
   
       21 . An ablative heat shield, comprising:
 a plurality of pieces of ablative thermal protection material configured in a heat shield form;   polymeric resin attached to said ablative thermal protection material; and   a bond between adjacent pieces of said plurality of pieces, wherein said bond comprises polymeric cross-linking.   
   
   
       22 . The apparatus of  claim 21 , wherein said ablative thermal protection material comprises fiber matrix material. 
   
   
       23 . The apparatus of  claim 21 , wherein said ablative thermal protection material comprises refractory porous substrate material 
   
   
       24 . The apparatus of  claim 21 , wherein each said piece of said plurality of pieces is selected from the group consisting of a modular piece and a block. 
   
   
       25 . The apparatus of  claim 22 , wherein said fiber matrix material comprises refractory fiber matrix material. 
   
   
       26 . The apparatus of  claim 25 , wherein said refractory fiber matrix material is selected from the group consisting of carbon, silica, alumina, aluminosilicate and silicon carbide. 
   
   
       27 . The apparatus of  claim 21 , wherein said polymeric resin comprises ablative thermal protection materials. 
   
   
       28 . The apparatus of  claim 21 , wherein said polymeric resin comprises phenolic resin. 
   
   
       29 . The apparatus of  claim 28 , wherein said phenolic resin comprises Phenolic Impregnated Carbon Ablator. 
   
   
       30 . The apparatus of  claim 21 , wherein said polymeric resin comprises a phenolic, silicone, epoxy or pre-ceramic polymer compound.