Space Shuttle Discovery Mission To Test Thermal Tile Repairs
Atlantis May Not Retire Next Year
Spacewalking astronauts on the upcoming Space Shuttle Discovery STS-120 Mission to the International Space Station (ISS) likely will test making repairs to damaged thermal tile samples, using a goo-spurting device like a caulk gun, Wayne Hale, the space shuttle program manager, told journalists.
A final decision on this spacewalk will be made later today.
The spacewalk will mean the mission involves a challenging five extravehicular activities, and the repair test also means that the mission will be extended by a day to 13 days,beginning with the scheduled liftoff Oct. 23.
Discovery later this week will be moved into the Vehicle Assembly Building at Kennedy Space Center.
NASA needs a viable, workable means of repairing damage to crucial thermal tiles that protect the shuttle orbiter vehicle and its crew from the searing heat of reentry.
Just how critical the tiles are was demonstrated tragically in 2003 when Space Shuttle Columbia launched on a mission to the space station, and a chunk of insulating foam ripped loose from the external fuel tank and punched an undetected hole in the leading edge of an orbiter vehicle wing.
Later, as Columbia attempted to return to Earth, the searing hot gases of reentry rushed into the wing, heating structural components until they failed. The ship and crew were lost.
Since then, NASA has made changes to the external fuel tank such as switching to titanium materials on some parts because that metal has better insulating properties than the old aluminum components, so that less foam insulation must be applied. Also, the agency is making changes to the foam insulation applied to the tank, to lessen chances of foam breaking loose.
But insulation loss continues, including a piece of foam in the last liftoff, on Aug. 8, that gashed thermal tiling on the bottom of Space Shuttle Endeavour.
While NASA leaders correctly decided that the shuttle could survive reentry without first performing repairs in space, they decided as well that foam insulation hits on orbiter vehicles still constitute a threat of serious damage, and thus the space agency must devise new and better repair capabilities.
"We will probably always lose foam," Hale predicted, even though NASA redesigned external lines on the external fuel tanks and reduced or eliminated the amount of insulation applied to various areas of the tanks.
For example, just recently, NASA technicians discovered cracks in ablative insulation on the external fuel tank of Space Shuttle Discovery, raising fears that the cracks might lead to serious loss of insulation. (Please see Space & Missile Defense Report, Monday, Aug. 27, 2007.)
Therefore, NASA must be prepared for foam losst to occur, and be able to respond with repairs, he said.
While NASA has tested the goo gun and other repair methods on the ground, that doesn’t answer just how well such repairs would work in space. The only way to answer that question is to head to orbit and perform repairs there.
In orbit, for example, when the shuttle is on the side of the Earth in sunlight, it may warm the orbiter vehicle tiles and make repairs easier (the warmth means the repair material is easier to spread or form), while in the frigid dark and cold above the night side of Earth, repair materials may not spread easily. It’s also unknown whether the goo may bubble in space the way it does on the ground.
Therefore, test repairs to deliberately damaged tile will be performed in space, so that NASA can "go forward with a higher degree of confidence" that should serious damage occur to protective tiles, it can be repaired.
The space agency wants to know more about any possible hazards in its space shuttle fleet, whether it involves foam or other materials, Hale said,
To that end, he said NASA is encouraging its employees to speak out if they see possible dangers.
However, he added, despite that, most tips about problems still are being made anonymously, for fear of retribution. Hale emphasized that NASA policy is that it wants employees to be open, and encourages that.
A pre-flight mission review involving lower-level program manager personnel will be held, running a day and a half to two days, and then the executive-level review will commence about a week later, to ensure that more points of view are aired, he said.
"I think this will make a better review," he said. "I am particularly interested in dissenting opinions."
Assuming this format works well, it will be continued for the duration of the space shuttle program, Hale said.
Atlantis Life Extended?
Separately, Hale said that Space Shuttle Atlantis still is on schedule for launch Dec. 6 on the STS-122 Mission to the ISS, and for its mission to the Hubble Space Telescope to provide servicing for it in July or August.
While Hale said the official plan remains to retire Atlantis then to save money, NASA instead might keep the shuttle in operation to provide more mission flexibility.
If NASA in coming months sees a need for more margin for delays and problems in the space shuttle fleet mission schedule, the agency then would consider whether to keep Atlantis flying, he said.
IF Atlantis is retired after the Hubble mission, it would be scavenged, picked over for spare parts to help keep other shuttles flying.
As far as the plan for Atlantis to launch Dec. 6, Hale said while he is optimistic that will come off on schedule, if there are lengthy delays, then the approach would be to forego a launch around the end of the year, because of computer dating concerns, and to launch instead in January. That might involve, however, NASA employees having to work through the holiday season.
Under current orders, NASA must retire the shuttle fleet by 2010. That creates some pressure, because only the shuttles have the size and muscle to hoist huge structural components into space to finish construction of the space station.
But the next-generation U.S. space vehicle, the Orion-Ares asset being developed in the Constellation Program, won’t be ready to fly with astronauts on board until 2015, unless Congress supplies more money to hasten work on the new spaceship. (Please see related story in this issue.)
That shuttle fleet retirement and much later emergence of Orion-Ares will create a half-decade-long gap, during which the United States — the nation that put men on the moon – – will be unable to so much as transport an astronaut into low Earth orbit.
Many NASA leaders have worried that when the United States loses the ability to fly to space, interest in the space program will wane, just when NASA and its contractors face an enormous number of retirements of senior personnel. As well, other, younger personnel may drift off to other pursuits they find more challenging, or to ensure that they don’t find their jobs being abolished.
Hale said that an effort may be initiated to pull some personnel in the old shuttle program into the Constellation Program work, "to show them they still have a future in the … industry," he said.
The Discovery Mission
When Discovery heads aloft, it will be a busy mission to help continue construction of the space station, including installing a node on the ISS, a sort of vestibule onto which other components will be attached.
Discovery crew members are Cdr.Pam Melroy, Pilot George Zamka and mission specialists Scott Parazynski, Stephanie Wilson, Douglas Wheelock, Dan Tani and Paolo Nespoli of the European Space Agency.
Tani will remain aboard the station for several months and return with the STS-122 crew. Current station Flight Engineer Clayton Anderson will return to Earth aboard Discovery.
Discovery’s crew will add the node that serves as a port for installing additional international laboratories.
The Harmony module will be the first expansion of the living and working space on the complex since the Russian Pirs airlock was installed in 2001. The mission also will move the first set of solar arrays installed on the station to a permanent location on the complex and redeploy them.
That may be a tricky part. Prior missions have seen astronauts physically wrestling to get balky solar arrays to retract into the stowed position, after long deployment in the fully opened electrical generating position.