Shuttle Atlantis Leaves Space Station, Heads Home

19 July 2011

Astronaut Mike Fossum hitched a ride on the station's external robotic arm as he took the final spacewalk of the shuttle era.

The shuttle Atlantis undocked from the International Space Station July 19 to complete final inspections and journey back to Earth, the last of the shuttle craft ever to do so, as this era of manned space flight comes to a close.

Atlantis is the last of the shuttle craft to travel on a mission, and like the other craft already retired, will take up a new educational mission as a museum exhibit.

Until then, the craft and its crew still have work to do. Somewhere over New Zealand, the first task after undocking required pilot Doug Hurley to maneuver the shuttle into position to see the longitudinal axis of the station, never before seen by a shuttle crew in a fly-around. Mission specialists Rex Walheim and Sandy Magnus took photos of the station and its unseen angles for review back on the ground. About two hours after the initial separation, the pilot fired the shuttle’s thrusters and the journey away from the station and back to Earth began in earnest.

Atlantis spent about eight and a half days paired up with the station on this trip. Atlantis and the other shuttle craft built the station, ferrying every piece into space and assembling them, creating a larger and larger human outpost in space on each trip. Thirty-seven shuttle missions were devoted to that construction project, and, cumulatively, shuttles and station were joined a total of almost 40 weeks. NASA recorded the time down to the minutes: 276 days, 11 hours and 23 minutes.

Neither craft nor crew could indulge in sentimentality at this parting, however. A critical part of the mission came next: inspection of the shuttle’s thermal protection system. NASA briefing materials say the crew will use the 15.24-meter-long Orbiter Boom Sensor System to get in close on this inspection, producing a high-fidelity, three-dimensional scan of Atlantis’ exterior, especially those areas of the craft that are subject to the highest heating as the ship comes tearing through the Earth’s atmosphere on its return.

Neglect of this inspection led to tragedy in a shuttle flight of 2003. The shuttle Columbia disintegrated upon its reentry and seven crew members were killed because a chunk of the thermal protection system’s outer covering was ripped from the spacecraft during the forces of takeoff. Upon return, the extreme heat generated by the high-speed reentry penetrated that breach in the protection system and the craft shattered in midair, leaving pieces scattered across two states.

Like the earlier shuttle explosion in 1986, the disaster broke the heart of the nation, but did not break the spirit at NASA. An exhaustive investigation revealed not just the engineering problem that damaged the TPS, but also internal decisionmaking processes that created pressure to launch and reluctance to raise problems that would delay launch.

So today, NASA reports that managers and engineers are taking the data from the ship scan “to validate the heat shield’s integrity.”

Even though Atlantis’ landing, set for July 20, will close a chapter in human space flight, nothing is forgotten. Each journey, each success and each failure have taught NASA leaders, crews and technicians more about space flight. That accumulated knowledge will be pushed to its limits and beyond as NASA sets a course for the next goal in U.S. space exploration: a trip to Mars.

President Obama laid down that challenge on the first day of this last shuttle flight: “And I have tasked the men and women of NASA with an ambitious new mission: to break new boundaries in space exploration, ultimately sending Americans to Mars. I know they are up to the challenge — and I plan to be around to see it.”

President Obama celebrates his 50th birthday August 4.