The problem was with re-using the seals. All of the boost phase assembly
is retrieved from the water after launch and re-used. Your documentary
and/or your understanding of its content is flawed.
From:
http://en.wikipedia.org/wiki/Space_Shuttle_Challenger_disaster
<quote>
The disaster resulted in a 32-month hiatus in the shuttle program and the
formation of the Rogers Commission, a special commission appointed by United
States President Ronald Reagan to investigate the accident. The Rogers
Commission found that NASA's organizational culture and decision-making
processes had been a key contributing factor to the accident. NASA managers
had known that contractor Morton Thiokol's design of the SRBs contained a
potentially catastrophic flaw in the O-rings since 1977, but they failed to
address it properly.
They also ignored warnings from engineers about the
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
dangers of launching on such a cold day and had failed to adequately report
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
these technical concerns to their superiors. The Rogers Commission offered
NASA nine recommendations that were to be implemented before shuttle flights
resumed.
<end quote>
<quote>
Forecasts for January 28 predicted an unusually cold morning, with
temperatures close to 31 °F (?0.5 °C), the minimum temperature permitted for
launch. The low temperature had prompted concern from engineers at Morton
Thiokol, the contractor responsible for the construction and maintenance of
the shuttle's SRB. At a teleconference which took place on the evening of
January 27, Thiokol engineers and managers discussed the weather conditions
with NASA managers from Kennedy Space Center and Marshall Space Flight
Center. Several engineers?most notably Roger Boisjoly, who had voiced
similar concerns previously?expressed their concern about the effect of the
temperature on the resilience of the rubber O-rings that sealed the joints
of the SRBs. They argued that if the O-rings were colder than 53 °F
(approximately 11.7 °C), there was no guarantee the O-rings would seal
properly. This was an important consideration, since the O-rings had been
designated as a "Criticality 1" component?meaning their failure would
destroy Challenger and its crew. They also argued that the low overnight
temperatures would almost certainly result in SRB temperatures below their
redline of 40 °F. However, they were overruled by Morton Thiokol management,
who recommended that the launch proceed as scheduled.[4]
<end quote>
