NASA Primes Retired Test Shuttle Enterprise For One Last Flight

Enterprise, NASA's first space shuttle prototype, which in 1985 was delivered to the Smithsonian as a museum piece after proving that a winged spacecraft could land safely as a glider, is now being readied by the space agency for what is planned to be its final ferry flight atop a modified Boeing 747 jetliner.

Enterprise's upcoming flight comes as a result of NASA's plan to retire the three space-worthy shuttles remaining in its fleet later this year. All three are expected to be placed on public display, with one, Discovery, heading for the Smithsonian's Stephen F. Udvar-Hazy Center, the annex to the National Air and Space Museum in Chantilly, Va., where Enterprise has been exhibited since 2003.

"If we indeed receive a flown orbiter as expected, we can't be greedy and have two of them here so we'll need to look for a new home for Enterprise," explained curator Valerie Neal in an interview with collectSPACE.com.

Though the Smithsonian and NASA have yet to choose a new museum for OV-101 (the space agency's designation for Enterprise), or whether it will be placed on permanent loan from the national collection or provided outright to its new home, the two organizations recognized the need now to make sure that Enterprise could be safely moved.

"The people who are starting to work on the logistics for flying the orbiters to their different new homes decided that they better take a good look at Enterprise and just validate that it is ferry-worthy after all these years," said Neal. "The assumption all along is that it is and a quick look assessment had indicated that yes, it is intact." Now that they're getting really serious about the possibility of a ferry flight, they wanted to take a very close look ? a microscope look ? at the critical features and junctures."

So an eleven-person team from NASA's shuttle operations contractor United Space Alliance (USA) was sent from the Kennedy Space Center in Florida to the Smithsonian's Udvar-Hazy Center to "shake down" Enterprise and make sure it is ready to go.

"They have been here for two weeks and have worked their way pretty methodically all around the vehicle," Neal described. "So far, they've found everything to be in good order."

Just enough different

"There does not appear to be any type of big problem or show-stopper or anything like that," reported Neal. "This is really kind of a confidence building exercise just to make sure, because Enterprise is just enough different from the vehicles that remain that they're concerned [if] everything will fit with the equipment we're using today or is there any kind of anomaly here that we need to be aware of that will affect what our standard procedure is."

Built between 1974 and 1976 by Rockwell (now Boeing) in California, Enterprise was used for NASA's Approach and Landing Test (ALT) program, making 13 flights between February and October 1977 while attached to the modified 747 Shuttle Carrier Aircraft (SCA). During the last five of those flights, Enterprise separated from the jet at altitude and was then piloted by two NASA astronauts to a landing at Edwards Air Force Base.

The prototype orbiter was later used for vibration and "fit" checks, the latter to make sure that the support facilities and launch pad was properly configured for the shuttle.

Originally, Enterprise was to be refitted for spaceflight but design changes during the construction of OV-102, named Columbia, made it impractical. Still the two shared more in common than what separated them.

"This vehicle very much closely matches the real airframe on the spacecraft," said Klint Combs, USA's manager for orbiter handling and mechanisms, who has led the team of USA technicians working on Enterprise. "They were going through the design process and they wanted to make sure that what they were designing for a spacecraft to land as a glider, they were testing what they were going to fly."

"She does resemble inside a lot like Columbia," described Martin Boyd, who as NASA's lead structures engineer for the orbiter fleet has been overseeing the work by Combs and his team. "It is unique because [Enterprise] doesn't exactly look like ours. It is structurally, but because it doesn't have all the plumbing and all the hyper-systems and all the stuff in there, we get to kind of get in there and say, 'Wow, that's what it really looks like behind all of that other stuff.'"

As similar as Enterprise may be to the other space shuttles from the inside, its tiles on the outside were different enough to provide a concern for flight.

"We were somewhat concerned about the adherence of the foam," explained Combs to collectSPACE.com, referring to the polyurethane foam blocks that were used to replicate the appearance of the thermal heat shield tiles on the real orbiters, "so we did a bunch of pull tests to verify the bond of the foam to the aluminum skin of the vehicle. We were particularly concerned in the aft, where hydraulic systems have leaked out over the decades. The foam back there is saturated, so we were concerned that may have affected the bond but those areas passed as well."

Continue reading at collectSPACE.com about the problems found with Enterprise and view two exclusive photo galleries, including "How to display a retired space shuttle" and "Preparing Enterprise for flight."

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• Stunning Space Photo Shows Shuttle in Silhouette
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