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From: peterb@pbear.UUCP
Newsgroups: net.columbia
Subject: Re: Re: Columbia's Tiled Damaged by Rain
Message-ID: <900002@pbear.UUCP>
Date: Mon, 19-Aug-85 18:48:00 EDT
Article-I.D.: pbear.900002
Posted: Mon Aug 19 18:48:00 1985
Date-Received: Fri, 23-Aug-85 20:11:41 EDT
References: <199@mot.UUCP>
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Nf-ID: #R:mot:-19900:pbear:900002:000:1598
Nf-From: pbear!peterb    Aug 19 18:48:00 1985



	I think if the shuttle's exterior skin was made from titanium, then
it would weigh quite a bit, and would change its flight charecteristics from
"a set of car keys" to a brick. Sure in the second generation the added
weight can be designed into it, but still what are you going to do with all
the heat the the titanium stores?

	I remember reading a while back about a writer's ride in the
blackbird, and as he was leaving he asked the pilot what the burning smell
was. The pilot pointed out that since the titanium heted up, they had to use
insulation on the inside of the aircraft to preserve avionics, hydralics,
and wiring and conrtol cables from the extreme heat. That is also why
blackbirds are painted black: so the black surface radiates heat faster than
any other color.

	So if a second generation shuttle was made of titanium, you would
also have to design in expansion factors for titanium, and insulate
everything on the inside from the extreme heat. The tiles are a perfect
choice for heat insulation. You can hit a tile with a blowtorch until it
starts to turn orange, and then after removing the torch, 30 seconds later
you can handle it safely. Also (depending on the thickness) the heat would
not travel through the tile. This is because the tile is almost like pumice:
it has many little air pockets and is extremely light. But the cost of
insulation and lightness is in its being brittle and soft. Water particles
travelling at high speed can easily fracture the surface of the tile and
slowly cause it to wear down.

Peter Barada
{ihnp4!inmet|{harvard|cca}!ima}!pbear!peterb