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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Shuttle Carrier Aircraft | 1/2 | https://en.wikipedia.org/wiki/Shuttle_Carrier_Aircraft | reference | science, encyclopedia | 2026-05-05T13:22:22.332194+00:00 | kb-cron |
The Shuttle Carrier Aircraft (SCA) are two extensively modified Boeing 747 airliners that NASA used to transport Space Shuttle orbiters. One (N905NA) is a 747-100 model, while the other (N911NA) is a short-range 747-100SR. Both are now retired. The SCAs were used to ferry Space Shuttles from landing sites back to the Shuttle Landing Facility at the Kennedy Space Center. The orbiters were placed on top of the SCAs by Mate-Demate Devices, large gantry-like structures that hoisted the orbiters off the ground for post-flight servicing then mated them with the SCAs for ferry flights. In approach and landing test flights conducted in 1977, the test shuttle Enterprise was released from an SCA during flight and glided to a landing under its own control.
== Design and development == The Lockheed C-5 Galaxy was considered for the shuttle-carrier role by NASA but rejected in favor of the 747. This was due to the 747's low-wing design in comparison to the C-5's high-wing design, and also because the U.S. Air Force would have retained ownership of the C-5, while NASA could own the 747s outright. Lockheed had also proposed a heavily modified twin body C-5, to counter the Conroy Virtus concept.
The first aircraft, a Boeing 747-123 registered N905NA, was originally manufactured for American Airlines. With a decline in air traffic and failure to fill their 747s, American Airlines sold it to NASA. It still wore the visible American cheatlines while testing Enterprise in the 1970s. It was acquired in 1974 and initially used for trailing wake vortex research as part of a broader study by NASA Dryden, as well as Shuttle tests involving an F-104 flying in close formation and simulating a release from the 747. The aircraft was extensively modified for NASA by Boeing in 1976. While first-class seats were kept for NASA passengers, its main cabin and insulation were stripped, and the fuselage was strengthened. Mounting struts were added on top of the 747, located to match the fittings on the Shuttle that attach it to the external fuel tank for launch. With the Shuttle riding on top, the center of gravity was altered. Vertical stabilizers were added to the tail to improve stability when the Orbiter was being carried. The avionics and engines were also upgraded. An internal escape slide was added behind the flight deck in case of catastrophic failure mid-flight. In the event of a bail-out, explosives would be detonated to make an opening in the fuselage at the bottom of the slide, allowing the crew to exit through the slide and parachute to the ground. The slide system was removed following the Approach and Landing Tests because of concerns over the possibility of escaping crew members being ingested into an engine. Flying with the additional drag and weight of the Orbiter imposed significant fuel and altitude penalties. The range was reduced to 1,000 nautical miles (1,900 km; 1,200 mi), compared to an unladen range of 5,500 nautical miles (10,200 km; 6,300 mi), requiring an SCA to stop several times to refuel on a transcontinental flight. Without the Orbiter, the SCA needed to carry ballast to balance its center of gravity. The SCA had an altitude ceiling of 15,000 feet (4,600 m) and a maximum cruise speed of Mach 0.6 with the orbiter attached. A crew of 170 took a week to prepare the shuttle and SCA for flight.
Studies were conducted to equip the SCA with aerial refueling equipment, a modification already made to the U.S. Air Force E-4 (modified 747-200s) and 747 tanker transports for the IIAF. However, during formation flying with a tanker aircraft to test refueling approaches, minor cracks were spotted on the tailfin of N905NA. While these were not likely to have been caused by the test flights, it was felt that there was no sense taking unnecessary risks. Since there was no urgent need to provide an aerial refueling capacity, the tests were suspended.By 1983, SCA N905NA no longer carried the distinct American Airlines tricolor cheatline. NASA replaced it with its own livery, consisting of a white fuselage and a single blue cheatline. That year, after secretly being fitted with an infrared countermeasures system to protect it from heat-seeking missiles, it was also used to fly Enterprise on a tour in Europe, with refueling stops in Goose Bay, Canada; Keflavik, Iceland; England; and West Germany. It then went to the Paris Air Show.
In 1988, in the wake of the Challenger accident, NASA procured a surplus 747SR-46 from Japan Airlines. Registered N911NA, it entered service with NASA in 1990 after undergoing modifications similar to N905NA. It was first used in 1991 to ferry the new shuttle Endeavour from the manufacturers in Palmdale, California to Kennedy Space Center. Based at the Dryden Flight Research Center within Edwards Air Force Base in California the two aircraft were functionally identical, although N911NA has five upper-deck windows on each side, while N905NA has only two.
The rear mounting points on both aircraft were labeled with humorous instructions to "attach orbiter here" or "place orbiter here", clarified by the precautionary note "black side down". Shuttle Carriers were capable of operating from alternative shuttle landing sites such as those in the United Kingdom, Spain, and France. Because Shuttle Carrier's range is reduced while mated to an orbiter, additional preparations such as removal of the payload from the orbiter may have been necessary to reduce its weight. Boeing transported its Phantom Ray unmanned combat aerial vehicle (UCAV) demonstrator from St. Louis, Missouri, to Edwards on a Shuttle Carrier Aircraft on December 11, 2010.
== Approach and Landing Tests ==