From: ederd@bcstec.ca.boeing.com (Dani Eder)
Subject: Re: What do rockets rest on?
Date: May 02 1996
Newsgroups: sci.space.tech

Frank Alvaro <franka@acay.com.au> writes:

>I've wondered about this for a long time, and I'm constantly reminded of 
>it whenever I see footage of a Shuttle or Saturn V lift off...

>When these craft are sitting on the launch pad prior to liftoff, what 
>part of the craft are they resting on? It can't be the engine's nozzles, 
>because surely they couldn't bear the enormous weight (and besides, in 
>close-up footage of Shuttle liftoffs you can see the nozzles clearly from 
>below).  Can anyone enlighten me???

>Thanks,

In the case of the Shuttle, the Solid Rocket Boosters support the
entire vehicle.  At the back end of the SRBs is a conical pieces
of structure which is around the nozzle proper, and that cone is
beefed up at four places on the edge, so the Shuttle rests on 8
spots on these SRB cones.  It is bolted to the launch pad with
one 3" diameter high strength steel bolt per spot, to keep the
Shuttle from falling over while driving it out to the pad or when
the wind blows.   The same signal that starts the SRBs sets off
shaped charges that fracture the bolts

In theory, you could support a rocket partly on the nozzle and
the back of the combustion chamber, since that is where the thrust
of the engines is applied and the thrust is more than the weight of
the rocket.  It is not done probably because the support structure
under the rocket would then be in the way of the exaust.

Dani Eder

Newsgroups: sci.space.shuttle
From: henry@spsystems.net (Henry Spencer)
Subject: Re: Question: How Is The Shuttle Supported?
Date: Fri, 26 Nov 1999 03:42:02 GMT

In article <81kpa8$s6u$1@fir.prod.itd.earthlink.net>,
Randy Bird <randybird@earthlink.net> wrote:
>Does the entire stack rest on the skirts of the SRB's...

Yes.  The orbiter hangs on the ET, the ET hangs on the SRBs, and the SRBs
are supported via their skirts.

>...and is there any contact of the shuttle itself on any
>surfaces of the crawler?

There are umbilical connections -- power, fuel, various fluids -- through
the Tail Service Masts on either side of the orbiter's tail, but they do
not carry any structural loads.
--
The space program reminds me        |  Henry Spencer   henry@spsystems.net
of a government agency.  -Jim Baen  |      (aka henry@zoo.toronto.edu)

Newsgroups: sci.space.shuttle
From: henry@spsystems.net (Henry Spencer)
Subject: Re: Question: How Is The Shuttle Supported?
Date: Sun, 28 Nov 1999 05:01:33 GMT

In article <Tj004.18574$n3.247684@news1.telusplanet.net>,
Richard Thomas <rbthomas@planet.eon.net> wrote:
>...what would happen to the shuttle should one of these pyro
>bolts happen to fail and and SRB is actually held down at launch...

If one of the pyro nuts failed to fire, the SRB would rip it out, the
flight would proceed normally, and the cost of refurbishing the pad before
the next launch would be a bit higher than usual.

Holding one SRB down while the other flies would be very bad news -- it
would probably total the pad, the ET, the orbiter, and the crew -- and so
the system is quite carefully designed so it won't happen.

In any case, the nuts have never failed to fire.  There are two separate
charges in each nut, fired by separate circuits, either one sufficient.
--
The space program reminds me        |  Henry Spencer   henry@spsystems.net
of a government agency.  -Jim Baen  |      (aka henry@zoo.toronto.edu)