However, the problem-free appearance of the flight so far was deceptive. Scientifically, STS-40 was already proving itself to be a great success - ''The
mission has exceeded our expectations,'' exulted Arnauld Nicogossian, the head of NASA's space life sciences division - but a potentially dangerous problem with some of Columbia's thermal insulation cropped up soon after the crew reached orbit. Within minutes of opening the payload bay doors on the afternoon of 5 June, cameras revealed that several thermal 'blankets' attached to the aft bulkhead had become unfastened. Moreover, part of the payload bay door seal strip was displaced.
The danger, of course, was that the seal and the insulation could hamper the successful closure of the Shuttle's payload bay doors prior to re-entry. Lead Flight Director Randy Stone told the press there was no cause for alarm. ''We don't believe this to be any issue with respect to safety or mission duration,'' he said. ''The latches on these doors are very strong and we believe that, even if the seal was in the way, we could collapse the seal and close the doors safely with no problem.''
Nonetheless, it was decided to ship a section of seal to JSC where astronaut Kathy Sullivan simulated a spacewalk to evaluate the procedures and tools needed to remove it manually. Encased in a bulky spacesuit, she was immersed in a huge water tank called the Weightless Environment Training Facility (WETF) and verified managers' beliefs that, despite the loose seal, the doors could close properly without requiring a spacewalk. If Bagian and Jernigan did need to venture outside their spacecraft, it was considered straightforward to either cut off the broken seal or push it back into its retainer.
By 8 June, Mission Control told the crew they did not believe a spacewalk would be necessary, and were surprised by a rare note of disagreement. O'Connor was
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worried that the seal might snarl on a mechanical 'fork' that assists in the closure of the payload bay doors. However, after several discussions during the day and the transmission of a printed explanation of the procedures to the Shuttle, he seemed to acquiesce, telling them, ''If you've been through this and you still think there's a pretty good chance of the door latching, then you've answered our big questions.''
In the meantime, the mission was proceeding so smoothly that, on the evening of 9 June, a relaxed Bagian - an amateur magician - decided to play a trick on Capcom Marsha Ivins and Flight Director Al Pennington. With the assistance of apprentice Gutierrez, Bagian asked Pennington to pick a card from a new deck. He also had a deck of cards in space and said before the flight that he had selected a card and turned it opposite to the other cards. Bagian predicted that the card he had selected before launch would match the one Pennington chose on the ground.
The flight director picked the four of spades, as did Bagian. ''Truly incredible,'' was all Ivins could say as she then succumbed to the same trick.
After a highly productive mission, O'Connor, Gutierrez and Jernigan began preparing Columbia's systems for re-entry on 13 June. Then came the moment of truth early the following morning: the closure of the payload bay doors. To play things safe, for the last half-hour before the closure, the Shuttle's nose and the troublesome seal were oriented towards the Sun to 'thermally condition' the seal. Meanwhile, Bagian entered the Spacelab module for the last time, partly to store the last few blood and urine sample bags and also to videotape the payload bay door closure.
The port-side door was satisfactorily closed and latched at 11:20 am with no ill effects for the seal, followed by the starboard door at 12:08 pm. ''We see both doors closed and latched,'' Jernigan, stationed on the flight deck, told Mission Control. ''Roger Tammy. We see both doors closed and latched,'' replied Capcom Steve Oswald. ''Nice job.'' Then, at 2:37 pm, Columbia's OMS engines ignited for two-and-a-half minutes to begin the descent back to Earth.
An hour later, at 3:39:11 pm, O'Connor and Gutierrez guided their spacecraft crisply onto Runway 22 at Edwards, wrapping up a mission of just over nine days -eclipsing STS-35 to become the third-longest Shuttle flight to date. ''Congratulations on a super flight,'' Oswald radioed the crew. More than 7,500 people had gathered at the California landing site to watch Columbia's return, but they would not - unlike previous missions - see the seven astronauts disembark. On this occasion a specially designed airport-style 'people mover', known as the Crew Transport Vehicle (CTV), had been commissioned to whisk them away for medical checks.
''It's like a big trailer house on high that can be jacked-up,'' spacesuit technician Jean Alexander said of the new vehicle. ''They [the astronauts] come inside and take the suits off and kind of get their land legs back and the doctors check them out. If there's any medical experiments that have to be done after landing, there's gurneys and stuff in there. They do blood draws [and] whatever [else] they require for that particular mission.''
The rats, too, were quickly taken away, but to a somewhat different fate; 10 of the RAHF occupants and five of the AEM occupants, together with their ground-based 'control' counterparts, were killed and dissected about a week later for detailed analysis of their inner ear mechanisms. Their first flight had proved a remarkable success and would blaze the trail expected to be set on the SLS-2 mission some time in 1993 which, as well as lasting for almost two weeks, would controversially involve the first dissections of rats in space.
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