From: shanleyl@ducvax.auburn.edu
Subject: Re: Shuttle tiles
Organization: Auburn University, AL
Distribution: sci
Date: Mon, 25 Jan 1993 07:09:06 GMT

In article <C0q04z.KH9.1@cs.cmu.edu>, roberts@cmr.ncsl.nist.gov (John Roberts) writes:
> 
> -From: gary@ke4zv.uucp (Gary Coffman)
> -Subject: Re: Let's be more specific (was: Stupid Shut Cost arguements)
> -Date: 11 Jan 93 15:48:12 GMT
> 
> -Shuttle designers... chose to use refractory silicates in the form of
> -tiles. These are very poor conductors of heat, you can place your bare
> -hand against one side of the tile while playing an oxy-acetylene torch
> -on the other and not notice a temperature rise. 
> 
> I think perhaps you mean a propane torch, or butane torch like Mary described.
> Pulling some numbers from the Rogers report and elsewhere, the leading
> edges of the Shuttle wings have to withstand heating up to 2750 F, and are
> made of layers of graphite cloth in a carbon matrix, with the outer layers
> chemically converted to silicon carbide. The upper fuselage, the coolest
> portion during reentry, is only heated to about 600 F. The Shuttle has 
> high-temperature and low-temperature ceramic tiles, which are described in
> this report as being "nearly pure glass" (I had thought they were silica),

Not sure what the difference is,  silica/sand/glass,. Same different thing isn't
it?.


> with nearly 90% of the volume being "air". The low-temperature ceramic tiles
> are are rated to 1200 F, and the high-temperature tiles to a higher value,
> but something below wing leading-edge temperatures.
> 
> While such temperature resistance is admirable, a properly-designed
> acetylene torch can heat a thermally isolated object to 6000 F (~ 3300 C).

That's great, not all  acetylene torches rate much lesss run up to 6000F.  I've
used one myself with the tile in my hand just for kicks.

> I wouldn't expect any trouble melting most ceramics - I've accidentally
> melted fire bricks that I was using as a backstop for acetylene welding.
> 
>>From the 1961 CRC handbook, here are some temperature ratings for ceramics
> and other materials:
> 
>   SAFE CONTINUOUS OPERATING TEMPERATURE / MELTING POINT
>      Material          C         F      /    C        F
>      --------        ----      ----        ----     ----
>      Porcelain       1195      2185     /  ....     ....
>      Alumina (84%)   1400      2550     /  ....     ....
>      Zircon          1455      2650     /  2500     4530
>      Silicon carbide 1510      2750     /  2295     4160 (volatilizes)
>      Silica          1620      2950     /  1670     3038
>      Alumina (96%)   1700      3100     /  ....     ....
>      Alumina (100%)  1950      3540     /  2050     3720
>      Zirconia        2316      4200     /  2680     4850
>      Magnesia        ....      ....     /  2800     5072
>      Titanium boride ....      ....     /  2900     5250
>      Thoria           ...      ....     /  3110     5630
>      Titanium carbide ...      ....     /  3125     5660
>      Tantalum nitride ...      ....     /  3440     6050
>      Tungsten         ...      ....     /  3370     6100
>      Zirconium carbide ..      ....     /  3520     6370
>      Graphite         ...      ....     /  3800     6870
>      Tantalum carbide ...      ....     /  3850     7025
>      Hafnium carbide  ...      ....     /  4160     7520
> 
> John Roberts
> roberts@cmr.ncsl.nist.gov


lets not be more specific, let's allow some linguistic (not always the same as
scientific) lattitude.

Paul S. Shanley