"Pat Flannery" wrote:

snip

and indeed film of the Shuttle on the pad showed a jet of smoke emerging
from the the field joint that would later burn through on SRB ignition and
prior to lift-off. This was due to the O-rings on that field joint being
unseated by the "twang" and unable to reseat themselves due to their low
temperatures making them inflexible.

Kind of like this unreleased STS 51-L video where the smoke, uh stops at
3.375 seconds?

http://www.challengerdisaster.info/s..._m-2_mpg_i.mpg

Daniel