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From: gregc@cimage.com (Greg Cronau)
Newsgroups: sci.space.shuttle
Subject: Re: Tiles
Message-ID: <1990Nov21.005746.23909@cimage.com>
Date: 21 Nov 90 00:57:46 GMT
References: <90319.213006LABRIE@GECRDVM1.BITNET>
Reply-To: gregc@dgsi.UUCP (Greg Cronau/10000)
Organization: Cimage Corp, Ann Arbor, MI
Lines: 47

In article <90319.213006LABRIE@GECRDVM1.BITNET> LABRIE@gecrdvm1.crd.ge.com writes:
>
>     It may be a little late, but heres the info anyhow.
>
>     Columbia originally used only carbon-carbon tiles for thermal protection
>on re-entry (Except on the OMS pods).

Huh?
Columbia, as well as all the shuttles, uses the black(and expensive!)
carbon-carbon composite tiles for the nose and leading edges of the wings and
vertical stabilizer. The under-bellys of *all* the shuttles use silica tiles
with a black glaze. The OMS pods and other areas use the silica tiles with
a white glaze. The blankets are for the upper surfaces of the wings, the
cargo bay doors, and the rear side fusalage(sp?) areas.
	As I remember, the original material used for the tiles was a special
silica and ????? compound that cost serveral thousand dollars per tile. Later,
they found a boron-silicate substance that, while a little heavier than the
original tiles, cost only several dollars per tile!

>But there is a sort of famous picture on either
>Columbia or Enterprise gliding in with about a third of its tiles missing.

Huh? (again)
No shuttle has ever glided in with a third of it's tiles missing. What you
may be thinking of is when Columbia was first flown in to KSC on top of the
747 transporter. A large number of it's tiles were lost on the flight.

>Technicians have to carefully
>remove the bad tile without dammaging the surrounding tiles or the shuttle
>fuselage, make a cavity casting, and ship the casting to (I think) Rockwell
>so a replacement can be made.

Huh? (once more)
A shuttle tile is machined from a piece of the raw silica compound by computer
controlled milling machines. It is then sprayed with a black glaze and then
stenciled with it's ID number in yellow glaze and then fired. Every tiles
exact size, orientation, and location is stored in a computer. If one needs
to be replaced, they simply read the number off the tile, or look up it's 
number if it is too badly damaged. The tiles have about a 1/8 inch gap between
them and their neighboring tiles.

>An easy way to tell most of the tiles from the blanket
>squares is, the tiles are usually black or grey and the blankets are white.

A fair number of the tiles are white too.

gregc@cimage.com