Space Shuttle Atlantis Nears Finish Of Stellar Mission

Chemical Leak On Space Station Is Contained

The Space Shuttle Atlantis, undocked from the International Space Station (ISS), looked fine in last-minute checks for exterior damage, and is poised for reentry Wednesday.

But after Atlantis left the ISS, a chemical leak of potassium hydroxide sent fumes through parts of the space station. The leak later today was cleaned up, and NASA doesn’t see any serious safety problem here.

The Atlantis mission has sparkled with a series of perfect tasks completed, echoing the brilliant performance of the last voyage of Space Shuttle Discovery. The Atlantis crew completed every item on their jobs list, and more, ahead of time.

After repeated pre-launch snags and delays that included a near-hit by lightning and a passing hurricane, Atlantis scored a brilliant if last-minute ascent and soared heavenward to resume a years-delayed resumption of construction on the ISS.

The undocking and final checks for damage to the orbiter cap a mission that seemed to see everything go wrong while Atlantis was on the ground, only to see so much go right once the 4.5 million-pound shuttle lifted off Pad 39-B at Kennedy Space Center, Fla., on Sept. 9, some two weeks after its planned launch date.

It was a critical mission for NASA, because Atlantis carried aloft a vital component for the ISS, a massive 17.5-ton P3/P4 truss assembly costing $372 million that is required before the space station can receive other additions such as two laboratories for space research, one built in Europe, one in Japan.

Then massive solar arrays were deployed from the newly-installed truss, with a wingspan of 240 feet, to provide a huge boost in electrical generating power for the station that will be needed as more components are added to it in future shuttle missions, such as those new laboratory buildings.

In the Atlantis mission, a series of three extra vehicular activities (EVAs), or spacewalks, saw four shuttle crew members sweat and wrestle with balky parts, but in each case the spacewalkers completed their assigned tasks and even managed to do get-ahead work that had been scheduled for later EVAs. Aside from some bolts drifting away to form space junk, the EVAs were a perfect run through checkoff lists.

The Atlantis crew was Commander Brent Jett, Pilot Chris Ferguson, and mission specialists Joe Tanner, Dan Burbank, Heide Stefanyshyn-Piper and Canadian Space Agency astronaut Steve MacLean.

The first EVA, to attach the truss to the space station, and the third spacewalk were performed by Tanner and Stefanyshyn-Piper, aided by crew members inside operating the robotic arms.

The second spacewalk was handled by Burbank and MacLean.

But getting up to the space station to perform the critical tasks was a weeks-long series of disappointments and delays, where the Atlantis mission seemed on the verge of being scrubbed for the time being.

In a cliff-hanger, the Sept. 9 launch was the last day for liftoff soon. If Atlantis had been delayed yet again, it would have been weeks before the shuttle could begin the mission in daylight, the preferred time for safety reasons, likely postponing liftoff well into next month unless NASA had decided to drop its preference for a daytime, “lit” launch. (Please see Space & Missile Defense Report, Monday, Aug. 28, 2006, page 1.)

The Atlantis mission to the space station had to be coordinated so as not to interfere with the Russian spacecraft Soyuz that launched today on a mission to arrive Wednesday at the space station. (Please see page 6.) The Russian spacecraft will bring back to Earth two ISS crew members who have spent months in space, U.S. astronaut Jeff Williams and Russian cosmonaut Pavel Vinogradov.

As well, the Russian craft carried aloft, and is to bring back to Earth, a wealthy Iranian American entrepreneur, the fourth civilian and first woman to pay some $20 million for a ride into space. Anousheh Ansari is to conduct some experiments while in the space station.

Detailed Inspection

Also today, the shuttle underwent a meticulous, exhaustive examination of its protective heat tiles, including the leading edges of the wings, the large carbon area over the nose, and tiles on the underbelly, searching for any type of damaged or missing heat shielding that could threaten the shuttle crew during their fiery reentry

This inspection is part of the NASA response to the disastrous loss of Space Shuttle Columbia more than three years ago. Because a hefty chunk of foam insulation ripped loose from the external fuel tank and hit the Columbia orbiter vehicle, a hole was opened in the leading edge of a wing.

Then, during re-entry, blistering hot gases entered the wing and heated structural components until they failed, and the orbiter disintegrated as it traveled at thousands of miles per hour through the atmosphere. The orbiter and crew were lost.

NASA reworked the shuttle fleet, removing foam insulation from some areas of the external fuel tank, applying foam in different ways, removing the protuberance air load ramp over some external lines, and adjusting the ice frost ramp.

The fix worked.

During the July 4 launch of Space Shuttle Discovery, little foam broke loose, and even then it occurred so late in the ascent there was little air outside the shuttle to accelerate any foam to lethal speeds.

And the same was true of the Atlantis launch, providing a thumbs-up for engineers who designed the safety fixes for the shuttle fleet.

A minute inspection of the Atlantis orbiter vehicle upon its arrival at the space station showed no visible significant damage. Flipping upside down so the space station crew could check the belly, there also was final painstaking examination of all the heat shielding areas prior to reentry.