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From: rfc@calmasd.UUCP (Robert Clayton)
Newsgroups: net.columbia
Subject: Re: Columbia's Tiled Damaged by Rain
Message-ID: <521@calmasd.UUCP>
Date: Mon, 5-Aug-85 16:57:34 EDT
Article-I.D.: calmasd.521
Posted: Mon Aug  5 16:57:34 1985
Date-Received: Wed, 7-Aug-85 04:20:47 EDT
References: <4010@alice.UUCP> <199@mot.UUCP>
Organization: Calma Company, San Diego, CA
Lines: 32

> how interesting!  Columbia's tiles survive atmosphere re-entry only to get
> beat up by a rainstorm (which you'd think would be gentle) coming at it at
> a couple hundred mph.
> -- 
> << Generic disclaimer >>
> Fred Christiansen ("Canajun, eh?") @ Motorola Microsystems, Tempe, AZ
> UUCP:  ihnp4!{attunix, btlunix, drivax, sftig, ut-sally!oakhill}!mot!fred
> ARPA:  oakhill!mot!fred@ut-sally.ARPA             AT&T:  602-438-3472

Do not underestimate the power of any massive particles in a high
velocity fluid stream.  Commercial sand blasters operate at 60 mph and
are used to remove heavy corrosion from steel and to erode stone
surfaces in buildings.  Shotblasters operate at 100 mph and are used
for shotpeening metal parts - a work hardening process used to
strengthen steel castings and forgings.  In the last century, hydraulic
mining was used to wash away mountain slopes to expose pay dirt in
California's gold country.  These hydraulic cannons can be seen today
along the roadside set up as historical monuments.  They are the size
of field artillery pieces.   From the look of them, it is unlikely they
would have operated above 50 mph.  Extensive flumes and aquaducts were
built to channel the water to them.  Hydraulic mining is used today to
mine iron ores.

A several hundred mph blast of water is extremely destructive.
Fortunately in a storm the water is dispersed, but I suspect it compares
to a sand blaster in terms of destructive potential.

Today, commercially available cutting tools use high pressure water
jets to cut steel plates 6 inches thick.  Water is not harmless.

Bob Clayton
GE Calma, San Diego R&D
(619) 458-3400