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

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated into and form a part of the disclosure, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

FIG. 1 shows an exemplary individual refractory fiber matrix or refractory porous substrate block.

FIG. 2 illustrates the impregnation of a refractory fiber matrix or refractory porous substrate block with resin from all sides.

FIG. 3 shows the assembly on a mandrel of a section of a heat shield having a plurality of fiber matrix or refractory porous substrate blocks.

FIG. 4 shows an oven containing an exemplary heat shield assembly.

FIG. 5 shows a one-piece bonded heat shield attached to a spacecraft structure.

FIG. 6A shows a side-view of a test sample of bonded PICA attached to a low density ceramic fiber insulation which is attached to a metal model holder.

FIG. 6B shows a front view if the PICA material of the test apparatus of FIG. 6A.

Claims

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; andheat-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; anda 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.