And I heard in a presentation at the Cape some years ago that "We are so sure the solid rockets will ignite that we send the command to blow the hold down bolts before we send the solid rocket ignition command". Also I heard from somebody that the fractured hold down bolts are presented to the shuttle crew members as souvenirs after they return to Earth.
Dan Schultz N8FGV
A few years ago at the Amsat Colloquium University of Surrey we were
privilaged
to have astronaut Ron Parise (SK) as a guest speaker. He explained the
ignition
suquence for the shuttle in a very entertaining way, as best I remember it
went
like this
As the engines?come up to thrust the explosive bolts fire and away she goes.
If
one of the pyrotchnics?fails its no problem the bolt? just gets ripped out
of
the concrete
73 John G7HIA