BAC Mustard spaceplane

[Mossie]

Chris Gibson mentions molybdenum disilicide coatings in BSP 4 as a coating for hypersonic flight. It's a semi metallic charcoal grey, used for heating elements, brake discs etc.
http://www.machdiamond.com/chambers.html

I found out today that the BOR-2 test vehicle for the MiG Spiral programme was niobium coated in molybdenum disilicide.  The same combination was considered for British hypersonic aircraft, especially for mach 6-7. The BOR-2 was a mid grey, looking a bit battered after re-entry:
https://commons.m.wikimedia.org/wiki/File:BOR-2.jpg

[steelpillow]

Nice find. I suppose a lot of that speckle is subsequent rust from poor storage?

[Mossie]

I don't think so, it's probably due to heating effects.  The test vehicle is in an indoor exhibition and the colour appears quite different from picture to picture.  More here:
http://www.buran-energia.com/bor/bor-photos.php?file_dbt_=1