Highlight: The Shuttle Era
The Space Transportation System (STS) was NASA’s Space Shuttle Program for 30 years, spanning from 1981 to 2011. As the Space Transportation System program represents a critical portion of NASA’s rich history, an overview of this mission has been provided below to highlight its accomplishments and contributions to NASA’s current mission.
The Space Transportation System, otherwise known as the Space Shuttle Program, comprised American spacecraft operated by NASA for orbital human spaceflight missions. According to NASA, the Shuttle is the most complex machine ever built, with over 2.5 million moving parts. 
Major missions of the Shuttle have included conducting space science experiments, launching satellites and interplanetary probes, and aiding in the construction and servicing of the largest space structure, the International Space Station. 
As the first ever orbiter designed for reuse, the space shuttle fleet—Columbia, Challenger, Discovery, Atlantis, and Endeavour—flew a total of 135 missions. 
Each shuttle is comprised of three main assemblies: the reusable orbital vehicle, the expendable external tank, and the two reusable solid rocket boosters. 
The Shuttle is designed to reach orbit heights ranging from 115 to 400 miles high, and flies at a velocity of 17,500 mph. The longest the Shuttle has stayed in orbit, on any single mission, is 17.5 days (Columbia’s STS-80, November 1996). Typical missions lasted 5-16 days. The smallest crew ever to fly on the Shuttle included two people, during the first few missions. The largest crew included eight people. Normal crew sizes ranged from five to seven people. 
Enterprise: The Enterprise never flew in space but was used for approach and landing tests and launch pad studies in the late 1970s.
Columbia: In March 1979, Colombia was the first Space Shuttle orbiter to be delivered to NASA’s Kennedy Space Center and fly into orbit on STS-1. Columbia and the STS-107 crew were lost during re-entry on February 1, 2003. Further information on the Columbia shuttle is available via NASA’s Columbia (OV-102) Overview.
Challenger: In July 1982, the Orbiter Challenger was delivered to NASA’s Kennedy Space Center. In January 1986, the shuttle was destroyed during ascent by an explosion when a seal failed on one of its boosters. Further information on the Challenger shuttle is available via NASA’s Challenger (OV-099) Overview.
Discovery: Discovery completed its final mission, STS-133, in early 2011. Discovery conducted more missions than any other shuttle. Of those 39 missions, several major events occurred including the delivery of the Hubble Space Telescope into orbit; sending the Ulysses robotic probe to the sun; conducting the first shuttle rendezvous with the Russian Mir Space Station; and, delivering the Japanese Kibo Laboratory to the International Space Station. Discovery has flown more than 5,600 trips around the Earth carrying 180 people – including the first female shuttle pilot and the first female shuttle commander (Eileen Collins), the first African American spacewalker (Bernard Harris) and the first sitting member of congress to fly in space (Jake Garn). 
Further information on the Discovery shuttle is available via NASA’s Discovery (OV-103) Overview.
Endeavour: Built as a replacement following the Challenger accident, Endeavour was delivered in May 1991. Endeavor remained in operation until its final mission, STS-134, in May 2011. Further information on the Endeavour shuttle is available via NASA’s Endeavour (OV-105) Overview.
Atlantis: Delivered in April 1985, Atlantis completed its final mission, STS-135, in July 2011. Atlantis was the final shuttle to launch from the Kennedy Space Center’s seaside launch complex, after a 30-year shuttle era. Further information on the Atlantis shuttle is available via NASA’s Atlantis (OV-104) Overview.
United Space Alliance
In August 1995, NASA announced its intention to consolidate 12 Space Shuttle program contracts under a single prime contractor. More than 40 companies responded to the request for proposals. At that time, Rockwell International and the Lockheed Martin Space Operations formed United Space Alliance (USA), which was then selected as the single prime contractor for Shuttle operations in November 1995. USA and NASA signed the Space Flight Operations Contract (SFOC) the following September, which became effective in October 1996. In December of that year, The Boeing Company purchased the aerospace and defense components of Rockwell, which included its role in USA. In September 2001, NASA exercised the first two-year option of the SFOC, keeping USA as the prime contractor through 2004. In 2004, the second two-year option of the SFOC was exercised, and NASA again kept USA as the prime contractor. When the SFOC ended in 2006, NASA awarded USA the new Space Program Operations Contract (SPOC). The SPOC was a four-year contract through September 2010 in which USA continued as the prime contractor for space operations, as well as continuing related support for the International Space Station and Exploration Program. As of September 30, 2014, USA no longer holds active contracts and will not pursue future contracts. As of December 20, 2019, USA was dissolved and is no longer an operating entity 
Lockheed Martin Space Systems
Lockheed Martin Space Systems Company’s Michoud Operations was responsible for the production of the Space Shuttle’s external tank (ET) at NASA’s Michoud Assembly Facility in New Orleans, LA. The ET is the largest single component of the shuttle system at 154 feet long and 28 feet in diameter and the largest single component of the Space Shuttle system. Michoud also works on experimental space vehicles and related projects and is currently working under the Orion program to produce the Multi-Purpose Crew Vehicle. 
The Boeing Company
The Space Shuttle Orbiter became a Boeing program in 1996, when the company purchased the aerospace and defense assets of Rockwell International. In 1972, Rockwell International had won a $2.6 billion contract to build the Space Shuttle Orbiter. The first shuttle—the Enterprise—rolled out in 1976. In 1996, Boeing and Lockheed Martin created United Space Alliance (USA), which served as NASA’s primary industry partner for human space operations. USA was responsible for the management of the Space Shuttle fleet, as well as planning, training, and operations for 55 shuttle missions. As the major subcontractor to USA, Boeing was responsible for integrating shuttle system elements and payloads, as well as providing operations support services and ongoing engineering support. 
Alliant Techsystems Inc.
Alliant Techsystems (ATK) manufactured the Space Shuttle Reusable Solid Rocket Motor (RSRM). Each Space Shuttle launch required two RSRMs to lift the shuttle vehicle. From ignition to end of burn, each of the two RSRMs generate an average thrust of 2.6 million pounds while burning for about 123 seconds. The RSRM was the largest ever to fly. It is the only solid rocket motor that was rated for human flight and the first designed for reuse. The two motors provided 90% of the thrust required to launch the Space Shuttle. 
While the tragedies of the Colombia and Challenger shuttles were felt around the world, it is important to note that the shuttle has the most reliable launch record of any rocket now in operation. Since 1981, more than 600 crew members have flown shuttle missions, boosting more than 1.36 million kilograms (3 million pounds) of cargo into orbit.
The Shuttle constantly evolved throughout its more than 20 years of operation, and ultimately became a significantly different platform than the first shuttles launched. Over operational time, NASA made major and minor modifications to the original design thousands of times. This resulted in safer, more dependable and capable shuttles. 
Since 1992, NASA has made engine and systems improvements that tripled shuttle safety, decreased the number of problems experienced in flight by 70%, and increased cargo capacity by 7.3 metric tons. While undergoing these changes, since 1992, the cost of operating the shuttle has decreased by $1.25 billion annually: a reduction of more than 40% of the previous operational cost. 
STS-135: FINAL SHUTTLE LAUNCH, AND THE END OF AN ERA
On July 8, 2011, Atlantis launched from the Kennedy launch complex as the final shuttle to fly after a rich 30-year history of missions. Crewed by four veteran astronauts, Atlantis delivered supplies and spare parts in the 37th and final shuttle mission to the International Space Station. Atlantis returned to Earth on July 21, 2012, landing on a runway at the Kennedy Shuttle Landing facility in the early hours of morning, for the last time. As the shuttle era ends, its heritage thrives with the continued pursuit of space exploration. 
SHUTTLE RETIREMENT AND EXHIBITION
Each of the shuttles are spending their retirement on exhibit in a different location across the United States:
- Enterprise: Intrepid Sea, Air & Space Museum (New York City, NY)
- Discovery: Steven F. Udvar-Hazy Center (Chantilly, VA)
- Atlantis: Kennedy Space Center Visitor Complex (Orsino, FL)
- Endeavor: California Science Center (Los Angeles, CA) 
In addition to the shuttles, hundreds of shuttle artifacts have been allocated to museums and educational institutions. Some of these are highlighted below:
- A variety of shuttle simulators have been allocated to the following locations:
- Adler Planetarium (Chicago, IL)
- Evergreen Aviation & Space Museum (McMinnville, OR)
- Texas A&M’s Aerospace Engineering Department (College Station, TX)
- A full fuselage trainer is located at the Museum of Flight (Seattle, WA)
- A nose cap assembly and crew compartment trainer can be found at the National Museum of the U.S. Air Force at Wright-Patterson Air Force Base (WPAFB, OH)
- Flight deck pilot and commander seats were allocated to NASA’s Johnson Space Center (Houston, TX)
- Orbital maneuvering system engines can be found at the following locations:
- S. Space and Rocket Center (Huntsville, AL)
- National Air and Space Museum (Washington, D.C.)
- Evergreen Aviation & Space Museum (McMinnville, OR)