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Steven F. Udvar-Hazy Center: SR-71 Blackbird and Space Shuttle Enterprise in the distance
Image by Chris Devers
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Details, quoting from Smithsonian National Air and Space Museum | Lockheed SR-71 Blackbird:
No reconnaissance aircraft in history has operated globally in more hostile airspace or with such complete impunity than the SR-71, the world's fastest jet-propelled aircraft. The Blackbird's performance and operational achievements placed it at the pinnacle of aviation technology developments during the Cold War.
This Blackbird accrued about 2,800 hours of flight time during 24 years of active service with the U.S. Air Force. On its last flight, March 6, 1990, Lt. Col. Ed Yielding and Lt. Col. Joseph Vida set a speed record by flying from Los Angeles to Washington, D.C., in 1 hour, 4 minutes, and 20 seconds, averaging 3,418 kilometers (2,124 miles) per hour. At the flight's conclusion, they landed at Washington-Dulles International Airport and turned the airplane over to the Smithsonian.
Transferred from the United States Air Force.
Manufacturer:
Lockheed Aircraft Corporation
Designer:
Clarence L. "Kelly" Johnson
Date:
1964
Country of Origin:
United States of America
Dimensions:
Overall: 18ft 5 15/16in. x 55ft 7in. x 107ft 5in., 169998.5lb. (5.638m x 16.942m x 32.741m, 77110.8kg)
Other: 18ft 5 15/16in. x 107ft 5in. x 55ft 7in. (5.638m x 32.741m x 16.942m)
Materials:
Titanium
Physical Description:
Twin-engine, two-seat, supersonic strategic reconnaissance aircraft; airframe constructed largley of titanium and its alloys; vertical tail fins are constructed of a composite (laminated plastic-type material) to reduce radar cross-section; Pratt and Whitney J58 (JT11D-20B) turbojet engines feature large inlet shock cones.
Long Description:
No reconnaissance aircraft in history has operated in more hostile airspace or with such complete impunity than the SR-71 Blackbird. It is the fastest aircraft propelled by air-breathing engines. The Blackbird's performance and operational achievements placed it at the pinnacle of aviation technology developments during the Cold War. The airplane was conceived when tensions with communist Eastern Europe reached levels approaching a full-blown crisis in the mid-1950s. U.S. military commanders desperately needed accurate assessments of Soviet worldwide military deployments, particularly near the Iron Curtain. Lockheed Aircraft Corporation's subsonic U-2 (see NASM collection) reconnaissance aircraft was an able platform but the U. S. Air Force recognized that this relatively slow aircraft was already vulnerable to Soviet interceptors. They also understood that the rapid development of surface-to-air missile systems could put U-2 pilots at grave risk. The danger proved reality when a U-2 was shot down by a surface to air missile over the Soviet Union in 1960.
Lockheed's first proposal for a new high speed, high altitude, reconnaissance aircraft, to be capable of avoiding interceptors and missiles, centered on a design propelled by liquid hydrogen. This proved to be impracticable because of considerable fuel consumption. Lockheed then reconfigured the design for conventional fuels. This was feasible and the Central Intelligence Agency (CIA), already flying the Lockheed U-2, issued a production contract for an aircraft designated the A-12. Lockheed's clandestine 'Skunk Works' division (headed by the gifted design engineer Clarence L. "Kelly" Johnson) designed the A-12 to cruise at Mach 3.2 and fly well above 18,288 m (60,000 feet). To meet these challenging requirements, Lockheed engineers overcame many daunting technical challenges. Flying more than three times the speed of sound generates 316° C (600° F) temperatures on external aircraft surfaces, which are enough to melt conventional aluminum airframes. The design team chose to make the jet's external skin of titanium alloy to which shielded the internal aluminum airframe. Two conventional, but very powerful, afterburning turbine engines propelled this remarkable aircraft. These power plants had to operate across a huge speed envelope in flight, from a takeoff speed of 334 kph (207 mph) to more than 3,540 kph (2,200 mph). To prevent supersonic shock waves from moving inside the engine intake causing flameouts, Johnson's team had to design a complex air intake and bypass system for the engines.
Skunk Works engineers also optimized the A-12 cross-section design to exhibit a low radar profile. Lockheed hoped to achieve this by carefully shaping the airframe to reflect as little transmitted radar energy (radio waves) as possible, and by application of special paint designed to absorb, rather than reflect, those waves. This treatment became one of the first applications of stealth technology, but it never completely met the design goals.
Test pilot Lou Schalk flew the single-seat A-12 on April 24, 1962, after he became airborne accidentally during high-speed taxi trials. The airplane showed great promise but it needed considerable technical refinement before the CIA could fly the first operational sortie on May 31, 1967 - a surveillance flight over North Vietnam. A-12s, flown by CIA pilots, operated as part of the Air Force's 1129th Special Activities Squadron under the "Oxcart" program. While Lockheed continued to refine the A-12, the U. S. Air Force ordered an interceptor version of the aircraft designated the YF-12A. The Skunk Works, however, proposed a "specific mission" version configured to conduct post-nuclear strike reconnaissance. This system evolved into the USAF's familiar SR-71.
Lockheed built fifteen A-12s, including a special two-seat trainer version. Two A-12s were modified to carry a special reconnaissance drone, designated D-21. The modified A-12s were redesignated M-21s. These were designed to take off with the D-21 drone, powered by a Marquart ramjet engine mounted on a pylon between the rudders. The M-21 then hauled the drone aloft and launched it at speeds high enough to ignite the drone's ramjet motor. Lockheed also built three YF-12As but this type never went into production. Two of the YF-12As crashed during testing. Only one survives and is on display at the USAF Museum in Dayton, Ohio. The aft section of one of the "written off" YF-12As which was later used along with an SR-71A static test airframe to manufacture the sole SR-71C trainer. One SR-71 was lent to NASA and designated YF-12C. Including the SR-71C and two SR-71B pilot trainers, Lockheed constructed thirty-two Blackbirds. The first SR-71 flew on December 22, 1964. Because of extreme operational costs, military strategists decided that the more capable USAF SR-71s should replace the CIA's A-12s. These were retired in 1968 after only one year of operational missions, mostly over southeast Asia. The Air Force's 1st Strategic Reconnaissance Squadron (part of the 9th Strategic Reconnaissance Wing) took over the missions, flying the SR-71 beginning in the spring of 1968.
After the Air Force began to operate the SR-71, it acquired the official name Blackbird-- for the special black paint that covered the airplane. This paint was formulated to absorb radar signals, to radiate some of the tremendous airframe heat generated by air friction, and to camouflage the aircraft against the dark sky at high altitudes.
Experience gained from the A-12 program convinced the Air Force that flying the SR-71 safely required two crew members, a pilot and a Reconnaissance Systems Officer (RSO). The RSO operated with the wide array of monitoring and defensive systems installed on the airplane. This equipment included a sophisticated Electronic Counter Measures (ECM) system that could jam most acquisition and targeting radar. In addition to an array of advanced, high-resolution cameras, the aircraft could also carry equipment designed to record the strength, frequency, and wavelength of signals emitted by communications and sensor devices such as radar. The SR-71 was designed to fly deep into hostile territory, avoiding interception with its tremendous speed and high altitude. It could operate safely at a maximum speed of Mach 3.3 at an altitude more than sixteen miles, or 25,908 m (85,000 ft), above the earth. The crew had to wear pressure suits similar to those worn by astronauts. These suits were required to protect the crew in the event of sudden cabin pressure loss while at operating altitudes.
To climb and cruise at supersonic speeds, the Blackbird's Pratt & Whitney J-58 engines were designed to operate continuously in afterburner. While this would appear to dictate high fuel flows, the Blackbird actually achieved its best "gas mileage," in terms of air nautical miles per pound of fuel burned, during the Mach 3+ cruise. A typical Blackbird reconnaissance flight might require several aerial refueling operations from an airborne tanker. Each time the SR-71 refueled, the crew had to descend to the tanker's altitude, usually about 6,000 m to 9,000 m (20,000 to 30,000 ft), and slow the airplane to subsonic speeds. As velocity decreased, so did frictional heat. This cooling effect caused the aircraft's skin panels to shrink considerably, and those covering the fuel tanks contracted so much that fuel leaked, forming a distinctive vapor trail as the tanker topped off the Blackbird. As soon as the tanks were filled, the jet's crew disconnected from the tanker, relit the afterburners, and again climbed to high altitude.
Air Force pilots flew the SR-71 from Kadena AB, Japan, throughout its operational career but other bases hosted Blackbird operations, too. The 9th SRW occasionally deployed from Beale AFB, California, to other locations to carryout operational missions. Cuban missions were flown directly from Beale. The SR-71 did not begin to operate in Europe until 1974, and then only temporarily. In 1982, when the U.S. Air Force based two aircraft at Royal Air Force Base Mildenhall to fly monitoring mission in Eastern Europe.
When the SR-71 became operational, orbiting reconnaissance satellites had already replaced manned aircraft to gather intelligence from sites deep within Soviet territory. Satellites could not cover every geopolitical hotspot so the Blackbird remained a vital tool for global intelligence gathering. On many occasions, pilots and RSOs flying the SR-71 provided information that proved vital in formulating successful U. S. foreign policy. Blackbird crews provided important intelligence about the 1973 Yom Kippur War, the Israeli invasion of Lebanon and its aftermath, and pre- and post-strike imagery of the 1986 raid conducted by American air forces on Libya. In 1987, Kadena-based SR-71 crews flew a number of missions over the Persian Gulf, revealing Iranian Silkworm missile batteries that threatened commercial shipping and American escort vessels.
As the performance of space-based surveillance systems grew, along with the effectiveness of ground-based air defense networks, the Air Force started to lose enthusiasm for the expensive program and the 9th SRW ceased SR-71 operations in January 1990. Despite protests by military leaders, Congress revived the program in 1995. Continued wrangling over operating budgets, however, soon led to final termination. The National Aeronautics and Space Administration retained two SR-71As and the one SR-71B for high-speed research projects and flew these airplanes until 1999.
On March 6, 1990, the service career of one Lockheed SR-71A Blackbird ended with a record-setting flight. This special airplane bore Air Force serial number 64-17972. Lt. Col. Ed Yeilding and his RSO, Lieutenant Colonel Joseph Vida, flew this aircraft from Los Angeles to Washington D.C. in 1 hour, 4 minutes, and 20 seconds, averaging a speed of 3,418 kph (2,124 mph). At the conclusion of the flight, '972 landed at Dulles International Airport and taxied into the custody of the Smithsonian's National Air and Space Museum. At that time, Lt. Col. Vida had logged 1,392.7 hours of flight time in Blackbirds, more than that of any other crewman.
This particular SR-71 was also flown by Tom Alison, a former National Air and Space Museum's Chief of Collections Management. Flying with Detachment 1 at Kadena Air Force Base, Okinawa, Alison logged more than a dozen '972 operational sorties. The aircraft spent twenty-four years in active Air Force service and accrued a total of 2,801.1 hours of flight time.
Wingspan: 55'7"
Length: 107'5"
Height: 18'6"
Weight: 170,000 Lbs
Reference and Further Reading:
Crickmore, Paul F. Lockheed SR-71: The Secret Missions Exposed. Oxford: Osprey Publishing, 1996.
Francillon, Rene J. Lockheed Aircraft Since 1913. Annapolis, Md.: Naval Institute Press, 1987.
Johnson, Clarence L. Kelly: More Than My Share of It All. Washington D.C.: Smithsonian Institution Press, 1985.
Miller, Jay. Lockheed Martin's Skunk Works. Leicester, U.K.: Midland Counties Publishing Ltd., 1995.
Lockheed SR-71 Blackbird curatorial file, Aeronautics Division, National Air and Space Museum.
DAD, 11-11-01
• • • • •
See more photos of this, and the Wikipedia article.
Details, quoting from Smithsonian National Air and Space Museum | Space Shuttle Enterprise:
Manufacturer:
Rockwell International Corporation
Country of Origin:
United States of America
Dimensions:
Overall: 57 ft. tall x 122 ft. long x 78 ft. wing span, 150,000 lb.
(1737.36 x 3718.57 x 2377.44cm, 68039.6kg)
Materials:
Aluminum airframe and body with some fiberglass features; payload bay doors are graphite epoxy composite; thermal tiles are simulated (polyurethane foam) except for test samples of actual tiles and thermal blankets.
The first Space Shuttle orbiter, "Enterprise," is a full-scale test vehicle used for flights in the atmosphere and tests on the ground; it is not equipped for spaceflight. Although the airframe and flight control elements are like those of the Shuttles flown in space, this vehicle has no propulsion system and only simulated thermal tiles because these features were not needed for atmospheric and ground tests. "Enterprise" was rolled out at Rockwell International's assembly facility in Palmdale, California, in 1976. In 1977, it entered service for a nine-month-long approach-and-landing test flight program. Thereafter it was used for vibration tests and fit checks at NASA centers, and it also appeared in the 1983 Paris Air Show and the 1984 World's Fair in New Orleans. In 1985, NASA transferred "Enterprise" to the Smithsonian Institution's National Air and Space Museum.
Transferred from National Aeronautics and Space Administration
• • •
Quoting from Wikipedia | Space Shuttle Enterprise:
The Space Shuttle Enterprise (NASA Orbiter Vehicle Designation: OV-101) was the first Space Shuttle orbiter. It was built for NASA as part of the Space Shuttle program to perform test flights in the atmosphere. It was constructed without engines or a functional heat shield, and was therefore not capable of spaceflight.
Originally, Enterprise had been intended to be refitted for orbital flight, which would have made it the second space shuttle to fly after Columbia. However, during the construction of Columbia, details of the final design changed, particularly with regard to the weight of the fuselage and wings. Refitting Enterprise for spaceflight would have involved dismantling the orbiter and returning the sections to subcontractors across the country. As this was an expensive proposition, it was determined to be less costly to build Challenger around a body frame (STA-099) that had been created as a test article. Similarly, Enterprise was considered for refit to replace Challenger after the latter was destroyed, but Endeavour was built from structural spares instead.
Service
Construction began on the first orbiter on June 4, 1974. Designated OV-101, it was originally planned to be named Constitution and unveiled on Constitution Day, September 17, 1976. A write-in campaign by Trekkies to President Gerald Ford asked that the orbiter be named after the Starship Enterprise, featured on the television show Star Trek. Although Ford did not mention the campaign, the president—who during World War II had served on the aircraft carrier USS Monterey (CVL-26) that served with USS Enterprise (CV-6)—said that he was "partial to the name" and overrode NASA officials.
The design of OV-101 was not the same as that planned for OV-102, the first flight model; the tail was constructed differently, and it did not have the interfaces to mount OMS pods. A large number of subsystems—ranging from main engines to radar equipment—were not installed on this vehicle, but the capacity to add them in the future was retained. Instead of a thermal protection system, its surface was primarily fiberglass.
In mid-1976, the orbiter was used for ground vibration tests, allowing engineers to compare data from an actual flight vehicle with theoretical models.
On September 17, 1976, Enterprise was rolled out of Rockwell's plant at Palmdale, California. In recognition of its fictional namesake, Star Trek creator Gene Roddenberry and most of the principal cast of the original series of Star Trek were on hand at the dedication ceremony.
Approach and landing tests (ALT)
Main article: Approach and Landing Tests
On January 31, 1977, it was taken by road to Dryden Flight Research Center at Edwards Air Force Base, to begin operational testing.
While at NASA Dryden, Enterprise was used by NASA for a variety of ground and flight tests intended to validate aspects of the shuttle program. The initial nine-month testing period was referred to by the acronym ALT, for "Approach and Landing Test". These tests included a maiden "flight" on February 18, 1977 atop a Boeing 747 Shuttle Carrier Aircraft (SCA) to measure structural loads and ground handling and braking characteristics of the mated system. Ground tests of all orbiter subsystems were carried out to verify functionality prior to atmospheric flight.
The mated Enterprise/SCA combination was then subjected to five test flights with Enterprise unmanned and unactivated. The purpose of these test flights was to measure the flight characteristics of the mated combination. These tests were followed with three test flights with Enterprise manned to test the shuttle flight control systems.
Enterprise underwent five free flights where the craft separated from the SCA and was landed under astronaut control. These tests verified the flight characteristics of the orbiter design and were carried out under several aerodynamic and weight configurations. On the fifth and final glider flight, pilot-induced oscillation problems were revealed, which had to be addressed before the first orbital launch occurred.
On August 12, 1977, the space shuttle Enterprise flew on its own for the first time.
Preparation for STS-1
Following the ALT program, Enterprise was ferried among several NASA facilities to configure the craft for vibration testing. In June 1979, it was mated with an external tank and solid rocket boosters (known as a boilerplate configuration) and tested in a launch configuration at Kennedy Space Center Launch Pad 39A.
Retirement
With the completion of critical testing, Enterprise was partially disassembled to allow certain components to be reused in other shuttles, then underwent an international tour visiting France, Germany, Italy, the United Kingdom, Canada, and the U.S. states of California, Alabama, and Louisiana (during the 1984 Louisiana World Exposition). It was also used to fit-check the never-used shuttle launch pad at Vandenberg AFB, California. Finally, on November 18, 1985, Enterprise was ferried to Washington, D.C., where it became property of the Smithsonian Institution.
Post-Challenger
After the Challenger disaster, NASA considered using Enterprise as a replacement. However refitting the shuttle with all of the necessary equipment needed for it to be used in space was considered, but instead it was decided to use spares constructed at the same time as Discovery and Atlantis to build Endeavour.
Post-Columbia
In 2003, after the breakup of Columbia during re-entry, the Columbia Accident Investigation Board conducted tests at Southwest Research Institute, which used an air gun to shoot foam blocks of similar size, mass and speed to that which struck Columbia at a test structure which mechanically replicated the orbiter wing leading edge. They removed a fiberglass panel from Enterprise's wing to perform analysis of the material and attached it to the test structure, then shot a foam block at it. While the panel was not broken as a result of the test, the impact was enough to permanently deform a seal. As the reinforced carbon-carbon (RCC) panel on Columbia was 2.5 times weaker, this suggested that the RCC leading edge would have been shattered. Additional tests on the fiberglass were canceled in order not to risk damaging the test apparatus, and a panel from Discovery was tested to determine the effects of the foam on a similarly-aged RCC leading edge. On July 7, 2003, a foam impact test created a hole 41 cm by 42.5 cm (16.1 inches by 16.7 inches) in the protective RCC panel. The tests clearly demonstrated that a foam impact of the type Columbia sustained could seriously breach the protective RCC panels on the wing leading edge.
The board determined that the probable cause of the accident was that the foam impact caused a breach of a reinforced carbon-carbon panel along the leading edge of Columbia's left wing, allowing hot gases generated during re-entry to enter the wing and cause structural collapse. This caused Columbia to spin out of control, breaking up with the loss of the entire crew.
Museum exhibit
Enterprise was stored at the Smithsonian's hangar at Washington Dulles International Airport before it was restored and moved to the newly built Smithsonian's National Air and Space Museum's Steven F. Udvar-Hazy Center at Dulles International Airport, where it has been the centerpiece of the space collection. On April 12, 2011, NASA announced that Space Shuttle Discovery, the most traveled orbiter in the fleet, will be added to the collection once the Shuttle fleet is retired. When that happens, Enterprise will be moved to the Intrepid Sea-Air-Space Museum in New York City, to a newly constructed hangar adjacent to the museum. In preparation for the anticipated relocation, engineers evaluated the vehicle in early 2010 and determined that it was safe to fly on the Shuttle Carrier Aircraft once again.
Steven F. Udvar-Hazy Center: Space exhibit panorama (hang glider, Space Shuttle Enterprise)
Image by Chris Devers
Quoting Smithsonian National Air and Space Museum | Gemini Paraglider Research Vehicle 1-A with wing:
Manufacturer:
NASA - Dryden Flight Research Center
Country of Origin:
United States of America
Dimensions:
Overall: 11 ft. 3 in. tall x 7 ft. 5 in. wide x 8 ft. deep, 485 lb. (342.9 x 226.1 x 243.8cm, 220kg)
Materials:
Tubular steel; Dacron wing; rubber wheels
From 1962 to 1964, NASA used the Paresev to develop the technology for landing the two-man Gemini capsule on land, instead of parachuting into the ocean, as had been done in Project Mercury. The astronauts would release an inflatable paraglider wing based on the work of Francis Rogallo, and maneuver to a runway or dry lake bed. Astronauts "Gus" Grissom and Neil Armstrong were among those who piloted the Paresev during several hundred flights at Edwards Air Force Base in California. The Paresev was towed by a ground vehicle or a small aircraft and released at an altitude between 5,000 and 12,000 feet. It was tested with three different wings; the 1-A is the first configuration. Before the paraglider concept could be fully developed for the Gemini program, NASA decided to stick with the proven technology of parachutes and water landing.
NASA transferred the Paresev to the Smithsonian in 1968.
Transferred from the National Aeronautics and Space Administration
• • • • •
See more photos of this, and the Wikipedia article.
Details, quoting from Smithsonian National Air and Space Museum | Space Shuttle Enterprise:
Manufacturer:
Rockwell International Corporation
Country of Origin:
United States of America
Dimensions:
Overall: 57 ft. tall x 122 ft. long x 78 ft. wing span, 150,000 lb.
(1737.36 x 3718.57 x 2377.44cm, 68039.6kg)
Materials:
Aluminum airframe and body with some fiberglass features; payload bay doors are graphite epoxy composite; thermal tiles are simulated (polyurethane foam) except for test samples of actual tiles and thermal blankets.
The first Space Shuttle orbiter, "Enterprise," is a full-scale test vehicle used for flights in the atmosphere and tests on the ground; it is not equipped for spaceflight. Although the airframe and flight control elements are like those of the Shuttles flown in space, this vehicle has no propulsion system and only simulated thermal tiles because these features were not needed for atmospheric and ground tests. "Enterprise" was rolled out at Rockwell International's assembly facility in Palmdale, California, in 1976. In 1977, it entered service for a nine-month-long approach-and-landing test flight program. Thereafter it was used for vibration tests and fit checks at NASA centers, and it also appeared in the 1983 Paris Air Show and the 1984 World's Fair in New Orleans. In 1985, NASA transferred "Enterprise" to the Smithsonian Institution's National Air and Space Museum.
Transferred from National Aeronautics and Space Administration
• • •
Quoting from Wikipedia | Space Shuttle Enterprise:
The Space Shuttle Enterprise (NASA Orbiter Vehicle Designation: OV-101) was the first Space Shuttle orbiter. It was built for NASA as part of the Space Shuttle program to perform test flights in the atmosphere. It was constructed without engines or a functional heat shield, and was therefore not capable of spaceflight.
Originally, Enterprise had been intended to be refitted for orbital flight, which would have made it the second space shuttle to fly after Columbia. However, during the construction of Columbia, details of the final design changed, particularly with regard to the weight of the fuselage and wings. Refitting Enterprise for spaceflight would have involved dismantling the orbiter and returning the sections to subcontractors across the country. As this was an expensive proposition, it was determined to be less costly to build Challenger around a body frame (STA-099) that had been created as a test article. Similarly, Enterprise was considered for refit to replace Challenger after the latter was destroyed, but Endeavour was built from structural spares instead.
Service
Construction began on the first orbiter on June 4, 1974. Designated OV-101, it was originally planned to be named Constitution and unveiled on Constitution Day, September 17, 1976. A write-in campaign by Trekkies to President Gerald Ford asked that the orbiter be named after the Starship Enterprise, featured on the television show Star Trek. Although Ford did not mention the campaign, the president—who during World War II had served on the aircraft carrier USS Monterey (CVL-26) that served with USS Enterprise (CV-6)—said that he was "partial to the name" and overrode NASA officials.
The design of OV-101 was not the same as that planned for OV-102, the first flight model; the tail was constructed differently, and it did not have the interfaces to mount OMS pods. A large number of subsystems—ranging from main engines to radar equipment—were not installed on this vehicle, but the capacity to add them in the future was retained. Instead of a thermal protection system, its surface was primarily fiberglass.
In mid-1976, the orbiter was used for ground vibration tests, allowing engineers to compare data from an actual flight vehicle with theoretical models.
On September 17, 1976, Enterprise was rolled out of Rockwell's plant at Palmdale, California. In recognition of its fictional namesake, Star Trek creator Gene Roddenberry and most of the principal cast of the original series of Star Trek were on hand at the dedication ceremony.
Approach and landing tests (ALT)
Main article: Approach and Landing Tests
On January 31, 1977, it was taken by road to Dryden Flight Research Center at Edwards Air Force Base, to begin operational testing.
While at NASA Dryden, Enterprise was used by NASA for a variety of ground and flight tests intended to validate aspects of the shuttle program. The initial nine-month testing period was referred to by the acronym ALT, for "Approach and Landing Test". These tests included a maiden "flight" on February 18, 1977 atop a Boeing 747 Shuttle Carrier Aircraft (SCA) to measure structural loads and ground handling and braking characteristics of the mated system. Ground tests of all orbiter subsystems were carried out to verify functionality prior to atmospheric flight.
The mated Enterprise/SCA combination was then subjected to five test flights with Enterprise unmanned and unactivated. The purpose of these test flights was to measure the flight characteristics of the mated combination. These tests were followed with three test flights with Enterprise manned to test the shuttle flight control systems.
Enterprise underwent five free flights where the craft separated from the SCA and was landed under astronaut control. These tests verified the flight characteristics of the orbiter design and were carried out under several aerodynamic and weight configurations. On the fifth and final glider flight, pilot-induced oscillation problems were revealed, which had to be addressed before the first orbital launch occurred.
On August 12, 1977, the space shuttle Enterprise flew on its own for the first time.
Preparation for STS-1
Following the ALT program, Enterprise was ferried among several NASA facilities to configure the craft for vibration testing. In June 1979, it was mated with an external tank and solid rocket boosters (known as a boilerplate configuration) and tested in a launch configuration at Kennedy Space Center Launch Pad 39A.
Retirement
With the completion of critical testing, Enterprise was partially disassembled to allow certain components to be reused in other shuttles, then underwent an international tour visiting France, Germany, Italy, the United Kingdom, Canada, and the U.S. states of California, Alabama, and Louisiana (during the 1984 Louisiana World Exposition). It was also used to fit-check the never-used shuttle launch pad at Vandenberg AFB, California. Finally, on November 18, 1985, Enterprise was ferried to Washington, D.C., where it became property of the Smithsonian Institution.
Post-Challenger
After the Challenger disaster, NASA considered using Enterprise as a replacement. However refitting the shuttle with all of the necessary equipment needed for it to be used in space was considered, but instead it was decided to use spares constructed at the same time as Discovery and Atlantis to build Endeavour.
Post-Columbia
In 2003, after the breakup of Columbia during re-entry, the Columbia Accident Investigation Board conducted tests at Southwest Research Institute, which used an air gun to shoot foam blocks of similar size, mass and speed to that which struck Columbia at a test structure which mechanically replicated the orbiter wing leading edge. They removed a fiberglass panel from Enterprise's wing to perform analysis of the material and attached it to the test structure, then shot a foam block at it. While the panel was not broken as a result of the test, the impact was enough to permanently deform a seal. As the reinforced carbon-carbon (RCC) panel on Columbia was 2.5 times weaker, this suggested that the RCC leading edge would have been shattered. Additional tests on the fiberglass were canceled in order not to risk damaging the test apparatus, and a panel from Discovery was tested to determine the effects of the foam on a similarly-aged RCC leading edge. On July 7, 2003, a foam impact test created a hole 41 cm by 42.5 cm (16.1 inches by 16.7 inches) in the protective RCC panel. The tests clearly demonstrated that a foam impact of the type Columbia sustained could seriously breach the protective RCC panels on the wing leading edge.
The board determined that the probable cause of the accident was that the foam impact caused a breach of a reinforced carbon-carbon panel along the leading edge of Columbia's left wing, allowing hot gases generated during re-entry to enter the wing and cause structural collapse. This caused Columbia to spin out of control, breaking up with the loss of the entire crew.
Museum exhibit
Enterprise was stored at the Smithsonian's hangar at Washington Dulles International Airport before it was restored and moved to the newly built Smithsonian's National Air and Space Museum's Steven F. Udvar-Hazy Center at Dulles International Airport, where it has been the centerpiece of the space collection. On April 12, 2011, NASA announced that Space Shuttle Discovery, the most traveled orbiter in the fleet, will be added to the collection once the Shuttle fleet is retired. When that happens, Enterprise will be moved to the Intrepid Sea-Air-Space Museum in New York City, to a newly constructed hangar adjacent to the museum. In preparation for the anticipated relocation, engineers evaluated the vehicle in early 2010 and determined that it was safe to fly on the Shuttle Carrier Aircraft once again.
