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From: fiddler%concertina@Sun.COM (Steve Hix)
Newsgroups: sci.military
Subject: Re: SR-71 Blackbird question
Message-ID: <1990Oct2.235417.24001@cbnews.att.com>
Date: 2 Oct 90 23:54:17 GMT
References: <1990Sep27.031756.7889@cbnews.att.com> <1990Sep29.155328.7880@cbnews.att.com>
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From: fiddler%concertina@Sun.COM (Steve Hix)

> From: deichman@cod.nosc.mil (Shane D. Deichman)

> I seem to recall hearing something about the properties of the "skin"
> of the Blackbird.  If memory serves correct, the plane was covered 
> with a polymeric composite which, due to the friction of high speed
> flight in a resistive medium (even at high altitude), would essentially
> melt -- i.e., become amorphous -- and recongeal as it cooled.

Sorry, the SR-71's skin is less of a chemical engineer's fantasy than
a high-tech cast iron stove.

The skin is titanium alloy.  One major problem is that heating causes so
much expansion that the aircraft would have severe buckling problems 
during operations.

One of the design team happened upon curious-looking cast-iron stove,
having parallel grooves formed in the stove's sides.  He asked, and
found it was a way to avoid buckling...the grooves allowed for the
expansion and contraction while allowing the side to stay flat.

Sort of like a steel bridge's expansion joints.

On the other hand, when they first went looking for a hydraulic fluid,
the hydraulics manufacturer offered something with perfect specs for
the cruise phase of flight.  Unfortunately, the hydraulic fluid was
a powder at room temperature.

--
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  The only drawback with morning is that it comes 
    at such an inconvenient time of day.
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