Spaceflight Now

NASA mulls changes for next space shuttle flight
Posted: August 25, 2003

The addition of a time-consuming tile inspection on the next shuttle flight, a spacewalk to test new tile repair equipment and techniques and lack of a third space station crew member to assist in equipment transfer work is forcing NASA managers to consider major changes to reduce the crew's workload.

While a variety of options is under study, it does not appear likely the STS-114 shuttle crew, commanded by Eileen Collins, will be able to accomplish its original objectives, including transfer of a fresh three-person crew and all associated equipment and supplies to the space station. NASA managers are considering the possibility of off-loading the crew transfer to a later flight, either to an additional shuttle mission or, possibly, to a Russian Soyuz flight later next year, and adding non-station crew members to the STS-114 mission to assist with logistics and equipment transfer work.

In addition, some of the mission's scientific objectives may be deferred as well because of weight limitations resulting from the expected addition of tile repair equipment and a long robot arm extension boom needed for post-launch inspection of the shuttle's thermal protection system.

Crew transfer issues depend in large part on when Atlantis can be ready for flight. A new two-person station crew is scheduled for launch aboard a Soyuz ferry craft in mid October. They will return to Earth next spring aboard Atlantis or, if the shuttle is not ready in time, aboard a Soyuz.

Most insiders, including several sources who discussed the issues last week, believe NASA will be hard pressed to get Atlantis off the ground before next summer. In that case, the October station crew likely would be replaced by two fliers launching aboard a Soyuz next April. Whether Atlantis then would take another crew up later that summer, or whether the April station crew would remain aloft until a fresh Soyuz crew arrives in Oct. 2004 - carrying either two or three station fliers - is part of the current debate about Atlantis' mission.

Any option off-loading crew rotation to the Soyuz, obviously, would require Russian concurrence. The Russians have not yet booked, or sold, a Soyuz seat for the October 2004 mission and that flight could, in theory, carry up a fresh three-person station crew. But that remains to be seen.

In the meantime, NASA managers are assessing a variety of options to alleviate the STS-114 crew timeline shortfall. The additional weight of a robot arm tile inspection camera boom, the tile repair demonstration kit and other items mean Atlantis cannot carry the originally planned complement of scientific equipment, the research gear needed to make the shuttle flight a space station "utilization" mission as originally envisioned.

"There is growing impetus, within both the shuttle and the station programs, to request (NASA) headquarters add a shuttle flight, a logistics flight, that would offload the strain of return-to-flight tasks from 114," said one NASA official familiar with the discussions.

Before Columbia's destruction Feb. 1, NASA was readying Atlantis for launch around March 1 to carry a fresh three-man crew to the space station along with supplies and research equipment stowed in a pressurized module known as an MPLM.

In addition, STS-114 features three spacewalks by astronaut Stephen Robinson and Japanese astronaut Soichi Noguchi. The objectives are to install a new control moment gyroscope, or CMG; to mount an external stowage platform, or ESP, on the outside of the station for use during upcoming solar array reconfigurations; and to mount TV camera gear and other equipment on the station's exterior.

In the wake of the Columbia tragedy, the station's three-man crew was replaced with two fliers, Yuri Malenchenko and Ed Lu. Because of limitations on fresh water, NASA and the Russian space agency will continue to staff the station with two-person crews until shuttle flights resume, leaving the STS-114 crew with a shortage of manpower in orbit to unloaded the pressurized logistics module.

The Columbia Accident Investigation Board, which will release its final report Tuesday, already has released five preliminary recommendations, including one requiring NASA to carry out extensive on-orbit tile inspections and another requiring development of an in-flight tile repair capability.

Since then, engineers have developed a lengthy tile inspection procedure expected to be carried out on the second day of the mission, in which cameras mounted on a long boom will be maneuvered about the orbiter by the shuttle's robot arm to look for signs of damage. The procedure will involve two astronauts and take up to seven hours or more to complete, throwing a wrench of sorts into normal flight-day two equipment check-out activity.

Areas of the shuttle that cannot be seen by the camera boom will be inspected by the station crew during Atlantis' final approach when Collins performs a pitch maneuver to expose the underside of the orbiter to view from the station above. She already is practicing the maneuver in flight simulators at the Johnson Space Center in Houston.

Once docked, the MPLM will have to be unloaded with one less station astronaut than usual. NASA managers are evaluating a variety of options to lighten the load, in some cases literally, by deferring some transfer items to later missions.

Agency officials hope to carry out at least two spacewalks. The CMG replacement and the tile repair demonstration. The ESP installation also is a top priority because it includes equipment that will be needed by an upcoming assembly crew. Whether it can be accommodated during Atlantis' mission is not yet clear.

The tile repair kit will be located at the back of the shuttle's cargo bay and feature a panel of deliberately damaged heat shield tiles. The spacewalkers will attempt to repair the tiles using materials and procedures currently in the development stage.

The work does not yet include any sort of repair demonstration for reinforced carbon carbon panels making up the orbiter's wing leading edges. While promising procedures are under study, it's not yet clear whether any repair techniques can be developed in time for a flight next spring.

NASA planners hope to refine the requirements of STS-114 in the next few weeks.

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