NASA is mandated to complete the International Space Station's construction before the Space Shuttle fleet is retired/decommissioned in 2010. There are 12 to 16 Shuttle flights scheduled to meet that requirement, and we have had a one year launch delay between the first (
STS-114 on July 26, 2005) and second (
STS-121, today's scheduled launch) "Return to Flight" missions.
If anything catastrophic or even remotely so occurs during this launch, the Space Shuttle program is doomed as is the International Space Station's completion because no other, comparable launch vehicle exists to transport the size and types of material the Shuttle's payload bay can carry.
You are right that there are unresolved issues NASA is gambling are not "showstoppers" likely to endanger the crew and vehicle. You are right that there are dissenters (people who's jobs are to ensure the safety of the crew and orbiter); specifically, NASA's Chief Engineer Christopher Scolese and NASA's Chief Safety and Mission Assurance Officer, Bryan O'Connor, who served as pilot on STS-61-B and commanded STS-40 are both on record as being "No Go" for this launch due to the foam/debris-shedding problem that continues to plague all Space Shuttle flights and only became noteworthy in NASA's eyes after the catastrophic loss of Space Shuttle
Columbia during re-entry in 2003.
The views of Scolese and O'Connor are on record in NASA's
Flight Readiness Review document. Both chose not to appeal to NASA's Administrator,
Mike Griffin and thus both tacitly support the launch. Reason? The International Space Station is seen as a "safe harbor" for the astronauts, should their craft fail in some way after getting on-orbit; it would get very crowded in the ISS if all 7 crewmembers on STS-121 had to evacuate to the Station, but it is possible. I think it's a gamble, because they're assuming some risks -- if they couldn't dock with the ISS for some reason, their "safe haven" is not accessible.
The astronauts do have a vote in the "Go/No Go" decisions, but I would imagine it's career suicide to buck the administration and utter a dissenting word in a "Go/No Go" decision. It would be interesting to see if Scolese and O'Connor get reassigned after this mission, assuming it is all a success.
I suspect the launch will go off as scheduled today. I suspect we will see more debris shed during lift-off, due to the amount and quality of cameras (still and video) that are now used to monitor the Shuttle during ascent (a byproduct of the
Columbia accident investigation). What this all means for future missions, I do not know. They can't keep calling every mission from now to the end of program a "test flight", and as such they ought to address the debris/foam shedding issue. It was one of the primary criterion that came out of the
Columbia accident investigation, and that is why it's worrisome NASA has opted to forego resolving it (they thought they had, with STS-114, and the voila --
foam debris shedding caught on tape.)
On another note, check out Flickr for various
photos of STS-121, many of which were taken by various employees associated with the Space Shuttle program.
STS-121 Shuttle Launch
Linear Mode
