Date: 23 Aug 93 16:09:28 GMT
From: Dani Eder <eder@hsvaic.boeing.com>
Subject: DC-X Questions about NBC clip on clipper
Newsgroups: sci.space

In article <252n7d$j9m@access.digex.net> mheney@access.digex.net (Michael
K. Heney) writes:
 
>How much advantage would there be to having a shallow pool at the
>take-off and landing points?  For take-off, the pool woulde be integral 
>to the launch stand; at landing, the target area could be a 100ft 
>diameter pool a foor or two deep, gently sloping to 0 depth.  If
>DC-n regularly lands as accurately as Wednesday's tests, this would
>give protection during optimum landings, possibly reducing maintenance in
>the long run.  Yes?  No?
 

This is such a common practice with existing rockets that it has a
name.  It's called a flame trench.  In the case of the Shuttle, it
is a slot in the launch pad 500 feet long, 60 feet wide and 40 feet
deep.  Flame trenches commonly have some water in them to protect
the concrete or steel from the rocket exhaust.  Water is cheap
and safe, and has a high heat of vaporization, so it can absorb
a lot of heat.  The shuttle also has large sprinklers on the launch
platform (the steel deck the shuttle actually rests on).  They
stand 11 feet high.  And the holes in the launch platform that
the rocket engines fire through are surrounded by water nozzles
(roughly a fire hose nozzle every foot around the perimeter of
the holes.  So, to a first approximation, every exposed surface
on the pad that gets rocket exhaust on it has a water coating
thrown on it for protection.  All this is fed from a half-million
gallon tank that empties in about 20 seconds.

Dani Eder


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