Space Shuttle Enterprise

Space Shuttle Enterprise (Orbiter Vehicle Designation: OV-101) is the first orbiter of the Space Shuttle system. Rolled out on September 17, 1976, it was built for NASA as part of the Space Shuttle program to perform atmospheric test flights after being launched from a modified Boeing 747. It was constructed without engines or a functional heat shield. As a result, it was not capable of spaceflight. Originally, Enterprise had been intended to be refitted for orbital flight to become the second space-rated orbiter in service. However, during the construction of Space Shuttle Columbia, details of the final design changed, making it simpler and less costly to build Challenger around a body frame that had been built 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. Enterprise was restored and placed on display in 2003 at the Smithsonian's new Steven F. Udvar-Hazy Center in Virginia. Following the retirement of the Space Shuttle fleet, Discovery replaced Enterprise at the Udvar-Hazy Center, and Enterprise was transferred to the Intrepid Museum in New York City, where it has been on display since July 2012.

Differences between Enterprise and future shuttles The design of Enterprise was not the same as that planned for Columbia, the first flight model; the aft fuselage 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 Enterprise, but the capacity to add them in the future was retained, as NASA originally intended to refit the orbiter for spaceflight at the conclusion of its testing. Instead of a thermal protection system, its surface was primarily covered with simulated tiles made from polyurethane foam. Fiberglass was used for the leading edge panels in place of the reinforced carbon–carbon ones of spaceflight-worthy orbiters. Only a few sample thermal tiles and some Nomex blankets were real. Enterprise used fuel cells to generate its electrical power, but these were not sufficient to power the orbiter for spaceflight.

Enterprise also lacked reaction control system thrusters and hydraulic mechanisms for the landing gear; the landing gear doors were simply opened through the use of explosive bolts and the gear dropped down solely by gravity. As it was only used for atmospheric testing, Enterprise featured a large nose probe mounted on its nose cap, common on test aircraft because the location provides the most accurate readings for the test instruments, being mounted out in front of the disturbed airflow. Enterprise was equipped with Lockheed-manufactured zero-zero ejection seats like those its sister Columbia carried on its first four missions.

Construction milestones

Service

Construction began on Enterprise on June 4, 1974. Designated OV-101, it was originally planned to be named Constitution and unveiled on Constitution Day, September 17, 1976. Fans of Star Trek asked US President Gerald Ford, through a letter-writing campaign, to name the orbiter after the television show's fictional starship, USS Enterprise. In an official memo, White House advisors cited "hundreds of thousands of letters" from Trekkies, "one of the most dedicated constituencies in the country", as a reason for giving the shuttle the name. Although Ford did not publicly mention the campaign, the president said that he was "partial to the name" Enterprise because his naval unit had serviced the aircraft carrier USS Enterprise (the ship for which Star Trek's fictional craft was named) during World War II, and directed NASA officials to change the name. 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)

On January 31, 1977, Enterprise 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 uncrewed 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 crewed to test the shuttle flight control systems. On August 12, 1977, Enterprise flew on its own for the first time. Enterprise underwent four more 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 used to carry out several aerodynamic and weight configurations. The first three flights were flown with a tailcone placed at the end of Enterprise's aft fuselage, which reduced drag and turbulence when mated to the SCA. The final two flights saw the tailcone removed and mockup main engine nozzles installed. On the fifth and final glider flight, pilot-induced oscillation problems were revealed, which had to be addressed before the first orbital launch occurred.

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