From: Henry Spencer <henry@zoo.toronto.edu>
Newsgroups: sci.space.science
Subject: Re: space related Q`s.
Date: Wed, 15 Oct 1997 14:18:36 GMT

In article <3447d34d.20101341@nntp.ix.netcom.com>,
Christopher P. Winter <cpwinter@ix.netcom.com> wrote:
>I don't know a whole lot about vacuum welding myself.  But I do recall
>that the experiments on LDEF found very little evidence for it.

The incidence of cold welding, aka vacuum welding, is greatly exaggerated.
It afflicts only some metals and rarely occurs unless other problems are
also present (e.g., inadequate lubrication for sliding surfaces).  The
Lockheed Space Materials Handbook (1969) says that as of its publication
date, there were no known cases of *unintentional* cold welding in space.
--
If NT is the answer, you didn't                 |     Henry Spencer
understand the question.  -- Peter Blake        | henry@zoo.toronto.edu

From: henry@spsystems.net (Henry Spencer)
Newsgroups: sci.space.tech
Subject: Re: No MPL Transmissions During Landing?
Date: Sat, 11 Dec 1999 02:18:36 GMT

In article <82rmlr01min@news1.newsguy.com>, Tom Neff <tneff@bigfoot.com> wrote:
> * The stage flanges cold-weld in space...
>All of these failure modes have been documented on previous space flights at
>one time or another.

Small quibble here:  I'd like to see the documentation on that one.  The
discussions of cold-welding that I've seen tend to emphasize that there
have been *no* confirmed cases of unintentional cold-welding in space.
Ever.  It's much less of a problem than was once thought; all confirmed
cases have involved deliberate attempts at it, and in fact, many of the
deliberate attempts have been unsuccessful.  The handful of early problems
which were *blamed* on cold-welding are now thought to have been galling
(inadequate lubrication of materials which don't deal well with that).
--
The space program reminds me        |  Henry Spencer   henry@spsystems.net
of a government agency.  -Jim Baen  |      (aka henry@zoo.toronto.edu)