Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!cwjcc!hal!nic.MR.NET!shamash!nis!ems!srcsip!orion!rogers
From: rogers@orion.SRC.Honeywell.COM (Brynn Rogers)
Newsgroups: sci.space.shuttle
Subject: Re: "Walking"
Message-ID: <10897@srcsip.UUCP>
Date: 27 Oct 88 14:21:41 GMT
References: <665@sas.UUCP>
Sender: news@src.honeywell.COM
Reply-To: rogers@orion.UUCP (Brynn Rogers)
Organization: Honeywell Systems & Research Center, Camden, MN
Lines: 15


 In Ben Baily's artical he commented on walking.

I have heard it called Twang.  It happens on every launch when
the MAIN engines are ignited. since the main engines are not on the 
centerline of the spacecraft they produce offset thrust.
When they are ignited the whole STS twists (in relation to the pad,
I think the orbiter is pretty ridged) in its mounting and springs back
to close to its original position before SRB ignition, which balances
out the thrust so it is centerline and not offset.
The top of the ET moves something like 1 or 2 feet (a guess) during
this period.   The Clamps holding the SRBs down apparently absorb this
torque. (another guess)

Brynn Rogers      rogers@src.honeywell.com