title: "Space Shuttle" content: Space Shuttle The Space Shuttle was a partially reusable low Earth orbital spacecraft system operated by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program name was "Space Transportation System (STS)", taken from a 1969 plan for a system of reusable spacecraft of which it was the only item funded for development. The first of four orbital test flights occurred in 1981, leading to operational flights beginning in 1982. In addition to the prototype whose completion was cancelled, five complete Shuttle systems were built and used on a total of 135


title: "Space Shuttle" content: missions from 1981 to 2011, launched from the Kennedy Space Center (KSC) in Florida. Operational missions launched numerous satellites, interplanetary probes, and the Hubble Space Telescope (HST); conducted science experiments in orbit; and participated in construction and servicing of the International Space Station. The Shuttle fleet's total mission time was 1322 days, 19 hours, 21 minutes and 23 seconds. Shuttle components included the Orbiter Vehicle (OV) with three clustered Rocketdyne RS-25 main engines, a pair of recoverable solid rocket boosters (SRBs), and the expendable external tank (ET) containing liquid hydrogen and liquid oxygen. The Space Shuttle was launched vertically, like


title: "Space Shuttle" content: a conventional rocket, with the two SRBs operating in parallel with the OV's three main engines, which were fueled from the ET. The SRBs were jettisoned before the vehicle reached orbit, and the ET was jettisoned just before orbit insertion, which used the orbiter's two Orbital Maneuvering System (OMS) engines. At the conclusion of the mission, the orbiter fired its OMS to de-orbit and re-enter the atmosphere. The orbiter then glided as a spaceplane to a runway landing, usually to the Shuttle Landing Facility at Kennedy Space Center, Florida or Rogers Dry Lake in Edwards Air Force Base, California. After


title: "Space Shuttle" content: landing at Edwards, the orbiter was flown back to the KSC on the Shuttle Carrier Aircraft, a specially modified Boeing 747. The first orbiter, "Enterprise", was built in 1976, used in Approach and Landing Tests and had no orbital capability. Four fully operational orbiters were initially built: "Columbia", "Challenger", "Discovery", and "Atlantis". Of these, two were lost in mission accidents: "Challenger" in 1986 and "Columbia" in 2003, with a total of fourteen astronauts killed. A fifth operational (and sixth in total) orbiter, "Endeavour", was built in 1991 to replace "Challenger". The Space Shuttle was retired from service upon the conclusion


title: "Space Shuttle" content: of "Atlantis"s final flight on July 21, 2011. The U.S. has since relied primarily on the Russian Soyuz spacecraft to transport astronauts to the International Space Station. The Space Shuttle was a partially reusable human spaceflight vehicle capable of reaching low Earth orbit, commissioned and operated by the U.S. National Aeronautics and Space Administration (NASA) from 1981 to 2011. It resulted from shuttle design studies conducted by NASA and the U.S. Air Force in the 1960s and was first proposed for development as part of an ambitious second-generation Space Transportation System (STS) of space vehicles to follow the Apollo program


title: "Space Shuttle" content: in a September 1969 report of a Space Task Group headed by Vice President Spiro Agnew to President Richard Nixon. Nixon's post-Apollo NASA budgeting withdrew support of all system components except the Shuttle, to which NASA applied the STS name. The vehicle consisted of a spaceplane for orbit and re-entry, fueled from an expendable External Tank containing liquid hydrogen and liquid oxygen, with two reusable strap-on solid rocket boosters. The first of four orbital test flights occurred in 1981, leading to operational flights beginning in 1982, all launched from the Kennedy Space Center, Florida. The system was retired from service


title: "Space Shuttle" content: in 2011 after 135 missions, with "Atlantis" making the final launch of the three-decade Shuttle program on July 8, 2011. The program ended after "Atlantis" landed at the Kennedy Space Center on July 21, 2011. Major missions included launching numerous satellites and interplanetary probes, conducting space science experiments, and servicing and construction of space stations. The first orbiter vehicle, named "Enterprise", was used in the initial Approach and Landing Tests phase but installation of engines, heat shielding, and other equipment necessary for orbital flight was cancelled. A total of five operational orbiters were built, and of these, two were destroyed


title: "Space Shuttle" content: in accidents. It was used for orbital space missions by NASA, the U.S. Department of Defense, the European Space Agency, Japan, and Germany. The United States funded Shuttle development and operations except for the Spacelab modules used on D1 and D2sponsored by Germany. SL-J was partially funded by Japan. At launch, it consisted of the "stack", including the dark orange external tank (ET) (for the first two launches the tank was painted white); two white, slender solid rocket boosters (SRBs); and the Orbiter Vehicle, which contained the crew and payload. Some payloads were launched into higher orbits with either of


title: "Space Shuttle" content: two different upper stages developed for the STS (single-stage Payload Assist Module or two-stage Inertial Upper Stage). The Space Shuttle was stacked in the Vehicle Assembly Building, and the stack mounted on a mobile launch platform held down by four frangible nuts on each SRB, which were detonated at launch. The Shuttle stack launched vertically like a conventional rocket. It lifted off under the power of its two SRBs and three main engines, which were fueled by liquid hydrogen and liquid oxygen from the ET. The Space Shuttle had a two-stage ascent. The SRBs provided additional thrust during liftoff and


title: "Space Shuttle" content: first-stage flight. About two minutes after liftoff, frangible nuts were fired, releasing the SRBs, which then parachuted into the ocean, to be retrieved by NASA recovery ships for refurbishment and reuse. The orbiter and ET continued to ascend on an increasingly horizontal flight path under power from its main engines. Upon reaching 17,500 mph (7.8 km/s), necessary for low Earth orbit, the main engines were shut down. The ET, attached by two frangible nuts was then jettisoned to burn up in the atmosphere. After jettisoning the external tank, the orbital maneuvering system (OMS) engines were used to adjust the orbit.


title: "Space Shuttle" content: The orbiter carried astronauts and payloads such as satellites or space station parts into low Earth orbit, the Earth's upper atmosphere or thermosphere. Usually, five to seven crew members rode in the orbiter. Two crew members, the commander and pilot, were sufficient for a minimal flight, as in the first four "test" flights, STS-1 through STS-4. The typical payload capacity was about but could be increased depending on the choice of launch configuration. The orbiter carried its payload in a large cargo bay with doors that opened along the length of its top, a feature which made the Space Shuttle


title: "Space Shuttle" content: unique among spacecraft. This feature made possible the deployment of large satellites such as the Hubble Space Telescope and also the capture and return of large payloads back to Earth. When the orbiter's space mission was complete, it fired its OMS thrusters to drop out of orbit and re-enter the lower atmosphere. During descent, the orbiter passed through different layers of the atmosphere and decelerated from hypersonic speed primarily by aerobraking. In the lower atmosphere and landing phase, it was more like a glider but with reaction control system (RCS) thrusters and fly-by-wire-controlled hydraulically actuated flight surfaces controlling its descent.


title: "Space Shuttle" content: It landed on a long runway as a conventional aircraft. The aerodynamic shape was a compromise between the demands of radically different speeds and air pressures during re-entry, hypersonic flight, and subsonic atmospheric flight. As a result, the orbiter had a relatively high sink rate at low altitudes, and it transitioned during re-entry from using RCS thrusters at very high altitudes to flight surfaces in the lower atmosphere. The formal design of what became the Space Shuttle began with the "Phase A" contract design studies issued in the late 1960s. Conceptualization had begun two decades earlier, before the Apollo program


title: "Space Shuttle" content: of the 1960s. One of the places the concept of a spacecraft returning from space to a horizontal landing originated was within NACA, in 1954, in the form of an aeronautics research experiment later named the X-15. The NACA proposal was submitted by Walter Dornberger. In 1958, the X-15 concept further developed into a proposal to launch an X-15 into space, and another X-series spaceplane proposal, named X-20 Dyna-Soar, as well as variety of aerospace plane concepts and studies. Neil Armstrong was selected to pilot both the X-15 and the X-20. Though the X-20 was not built, another spaceplane similar


title: "Space Shuttle" content: to the X-20 was built several years later and delivered to NASA in January 1966 called the HL-10 ("HL" indicated "horizontal landing"). In the mid-1960s, the U.S. Air Force conducted classified studies on next-generation space transportation systems and concluded that semi-reusable designs were the cheapest choice. It proposed a development program with an immediate start on a "Class I" vehicle with expendable boosters, followed by slower development of a "Class II" semi-reusable design and possible "Class III" fully reusable design later. In 1967, George Mueller held a one-day symposium at NASA headquarters to study the options. Eighty people attended and


title: "Space Shuttle" content: presented a wide variety of designs, including earlier U.S. Air Force designs such as the X-20 Dyna-Soar. In 1968, NASA officially began work on what was then known as the Integrated Launch and Re-entry Vehicle (ILRV). At the same time, NASA held a separate Space Shuttle Main Engine (SSME) competition. NASA offices in Houston and Huntsville jointly issued a Request for Proposal (RFP) for ILRV studies to design a spacecraft that could deliver a payload to orbit but also re-enter the atmosphere and fly back to Earth. For example, one of the responses was for a two-stage design, featuring a


title: "Space Shuttle" content: large booster and a small orbiter, called the DC-3, one of several Phase A Shuttle designs. After the aforementioned "Phase A" studies, B, C, and D phases progressively evaluated in-depth designs up to 1972. In the final design, the bottom stage consisted of recoverable solid rocket boosters, and the top stage used an expendable external tank. In 1969, President Richard Nixon decided to support proceeding with Space Shuttle development. A series of development programs and analysis refined the basic design, prior to full development and testing. In August 1973, the X-24B proved that an unpowered spaceplane could re-enter Earth's atmosphere


title: "Space Shuttle" content: for a horizontal landing. Across the Atlantic, European ministers met in Belgium in 1973 to authorize Western Europe's manned orbital project and its main contribution to Space Shuttlethe Spacelab program. Spacelab would provide a multidisciplinary orbital space laboratory and additional space equipment for the Shuttle. The Space Shuttle was the first operational orbital spacecraft designed for reuse. It carried different payloads to low Earth orbit, provided crew rotation and supplies for the International Space Station (ISS), and performed satellite servicing and repair. The orbiter could also recover satellites and other payloads from orbit and return them to Earth. Each Shuttle


title: "Space Shuttle" content: was designed for a projected lifespan of 100 launches or ten years of operational life, although this was later extended. The person in charge of designing the STS was Maxime Faget, who had also overseen the Mercury, Gemini, and Apollo spacecraft designs. The crucial factor in the size and shape of the Shuttle orbiter was the requirement that it be able to accommodate the largest planned commercial and military satellites, and have over 1,000 mile cross-range recovery range to meet the requirement for classified USAF missions for a once-around abort from a launch to a polar orbit. The militarily specified


title: "Space Shuttle" content: cross range requirement was one of the primary reasons for the Shuttle's large wings, compared to modern commercial designs with very minimal control surfaces and glide capability. Factors involved in opting for solid rockets and an expendable fuel tank included the desire of the Pentagon to obtain a high-capacity payload vehicle for satellite deployment, and the desire of the Nixon administration to reduce the costs of space exploration by developing a spacecraft with reusable components. Each Space Shuttle was a reusable launch system composed of three main assemblies: the reusable OV, the expendable ET, and the two reusable SRBs. Only


title: "Space Shuttle" content: the OV entered orbit shortly after the tank and boosters are jettisoned. The vehicle was launched vertically like a conventional rocket, and the orbiter glided to a horizontal landing like an airplane, after which it was refurbished for reuse. The SRBs parachuted to splashdown in the ocean where they were towed back to shore and refurbished for later Shuttle missions. Five operational OVs were built: "Columbia" (OV-102), "Challenger" (OV-099), "Discovery" (OV-103), "Atlantis" (OV-104), and "Endeavour" (OV-105). A mock-up, "Inspiration", currently stands at the entrance to the Astronaut Hall of Fame. An additional craft, "Enterprise" (OV-101), was built for atmospheric testing


title: "Space Shuttle" content: gliding and landing; it was originally intended to be outfitted for orbital operations after the test program, but it was found more economical to upgrade the structural test article STA-099 into orbiter "Challenger" (OV-099). An additional test article, dubbed "Pathfinder" (OV-098), was built for form and fit tests, and is on display at the Alabama Space and Rocket Center in Huntsville, AL. "Challenger" disintegrated 73 seconds after launch in 1986, and "Endeavour" was built as a replacement from structural spare components. Building "Endeavour" cost about US$1.7 billion. "Columbia" broke apart over Texas during re-entry in 2003. A Space Shuttle launch


title: "Space Shuttle" content: cost around $450 million. Roger A. Pielke, Jr. has estimated that the Space Shuttle program cost about US$170 billion (2008 dollars) through early 2008; the average cost per flight was about US$1.5 billion. Two missions were paid for by Germany, Spacelab D1 and D2 (D for "Deutschland") with a payload control center in Oberpfaffenhofen. D1 was the first time that control of a manned STS mission payload was not in U.S. hands. At times, the orbiter itself was referred to as the Space Shuttle. This was not technically correct as the "Space Shuttle" was the combination of the orbiter, the


title: "Space Shuttle" content: external tank, and the two solid rocket boosters. These components, once assembled in the Vehicle Assembly Building originally built to assemble the Apollo Saturn V rocket, were commonly referred to as the "stack". Responsibility for the Shuttle components was spread among multiple NASA field centers. The Kennedy Space Center was responsible for launch, landing and turnaround operations for equatorial orbits (the only orbit profile actually used in the program), the U.S. Air Force at the Vandenberg Air Force Base was responsible for launch, landing and turnaround operations for polar orbits (though this was never used), the Johnson Space Center served


title: "Space Shuttle" content: as the central point for all Shuttle operations, the Marshall Space Flight Center was responsible for the main engines, external tank, and solid rocket boosters, the John C. Stennis Space Center handled main engine testing, and the Goddard Space Flight Center managed the global tracking network. The orbiter resembled a conventional aircraft, with double-delta wings swept 81° at the inner leading edge and 45° at the outer leading edge. Its vertical stabilizer's leading edge was swept back at a 50° angle. The four elevons, mounted at the trailing edge of the wings, and the rudder/speed brake, attached at the trailing


title: "Space Shuttle" content: edge of the stabilizer, with the body flap, controlled the orbiter during descent and landing. The orbiter's -long payload bay, comprising most of the fuselage, could accommodate cylindrical payloads up to in diameter. Information declassified in 2011 showed that these measurements were chosen specifically to accommodate the KH-9 HEXAGON spy satellite operated by the National Reconnaissance Office. Two mostly-symmetrical lengthwise payload bay doors hinged on either side of the bay comprised its entire top. Payloads were generally loaded horizontally into the bay while the orbiter was standing upright on the launch pad and unloaded vertically in the near-weightless orbital environment


title: "Space Shuttle" content: by the orbiter's robotic remote manipulator arm (under astronaut control), EVA astronauts, or under the payloads' own power (as for satellites attached to a rocket "upper stage" for deployment.) Three Space Shuttle Main Engines (SSMEs) were mounted on the orbiter's aft fuselage in a triangular pattern. The engine nozzles could gimbal 10.5 degrees up and down, and 8.5 degrees from side to side during ascent to change the direction of their thrust to steer the Shuttle. The orbiter structure was made primarily from aluminum alloy, although the engine structure was made primarily from titanium alloy. The operational orbiters built were


title: "Space Shuttle" content: OV-102 "Columbia", OV-099 "Challenger", OV-103 "Discovery", OV-104 "Atlantis", and OV-105 "Endeavour". The main function of the Space Shuttle external tank was to supply the liquid oxygen and hydrogen fuel to the main engines. It was also the backbone of the launch vehicle, providing attachment points for the two solid rocket boosters and the orbiter. The external tank was the only part of the Shuttle system that was not reused. Although the external tanks were always discarded, it would have been possible to take them into orbit and re-use them (such as a wet workshop for incorporation into a space station).


title: "Space Shuttle" content: Two solid rocket boosters (SRBs) each provided of thrust at liftoff, which was 83% of the total thrust at liftoff. The SRBs were jettisoned two minutes after launch at a height of about , and then deployed parachutes and landed in the ocean to be recovered. The SRB cases were made of steel about ½ inch (13 mm) thick. The solid rocket boosters were re-used many times; the casing used in Ares I engine testing in 2009 consisted of motor cases that had been flown, collectively, on 48 Shuttle missions, including STS-1. Astronauts who have flown on multiple spacecraft report


title: "Space Shuttle" content: that Shuttle delivers a rougher ride than Apollo or Soyuz. The additional vibration is caused by the solid rocket boosters, as solid fuel does not burn as evenly as liquid fuel. The vibration dampens down after the solid rocket boosters have been jettisoned. The orbiter could be used in conjunction with a variety of add-ons depending on the mission. This included orbital laboratories (Spacelab, Spacehab), boosters for launching payloads farther into space (Inertial Upper Stage, Payload Assist Module), and other functions, such as provided by Extended Duration Orbiter, Multi-Purpose Logistics Modules, or Canadarm (RMS). An upper stage called Transfer Orbit


title: "Space Shuttle" content: Stage (Orbital Science Corp. TOS-21) was also used once with the orbiter. Other types of systems and racks were part of the modular Spacelab system pallets, igloo, IPS, etc., which also supported special missions such as SRTM. A major component of the Space Shuttle Program was Spacelab, primarily contributed by a consortium of European countries, and operated in conjunction with the United States and international partners. Supported by a modular system of pressurized modules, pallets, and systems, Spacelab missions executed on multidisciplinary science, orbital logistics, and international cooperation. Over 29 missions flew on subjects ranging from astronomy, microgravity, radar, and


title: "Space Shuttle" content: life sciences, to name a few. Spacelab hardware also supported missions such as Hubble (HST) servicing and space station resupply. STS-2 and STS-3 provided testing, and the first full mission was Spacelab-1 (STS-9) launched on November 28, 1983. Spacelab formally began in 1973, after a meeting in Brussels, Belgium, by European heads of state. Within the decade, Spacelab went into orbit and provided Europe and the United States with an orbital workshop and hardware system. International cooperation, science, and exploration were realized on Spacelab. The Shuttle was one of the earliest craft to use a computerized fly-by-wire digital flight control


title: "Space Shuttle" content: system. This means no mechanical or hydraulic linkages connected the pilot's control stick to the control surfaces or reaction control system thrusters. The control algorithm, which used a classical Proportional Integral Derivative (PID) approach, was developed and maintained by Honeywell. The Shuttle's fly-by-wire digital flight control system was composed of 4 control systems each addressing a different mission phase: Ascent, Descent, On-Orbit and Aborts. Honeywell is also credited with the design and implementation of the Shuttle's Nose Wheel Steering Control Algorithm that allowed the Orbiter to safely land at Kennedy Space Center's Shuttle Runway. A concern with using digital fly-by-wire


title: "Space Shuttle" content: systems on the Shuttle was reliability. Considerable research went into the Shuttle computer system. The Shuttle used five identical redundant IBM 32-bit general purpose computers (GPCs), model AP-101, constituting a type of embedded system. Four computers ran specialized software called the Primary Avionics Software System (PASS). A fifth backup computer ran separate software called the Backup Flight System (BFS). Collectively they were called the Data Processing System (DPS). The design goal of the Shuttle's DPS was fail-operational/fail-safe reliability. After a single failure, the Shuttle could still continue the mission. After two failures, it could still land safely. The four general-purpose


title: "Space Shuttle" content: computers operated essentially in lockstep, checking each other. If one computer provided a different result than the other three (i.e. the one computer failed), the three functioning computers "voted" it out of the system. This isolated it from vehicle control. If a second computer of the three remaining failed, the two functioning computers voted it out. A very unlikely failure mode would have been where two of the computers produced result A, and two produced result B (a two-two split). In this unlikely case, one group of two was to be picked at random. The Backup Flight System (BFS) was


title: "Space Shuttle" content: separately developed software running on the fifth computer, used only if the entire four-computer primary system failed. The BFS was created because although the four primary computers were hardware redundant, they all ran the same software, so a generic software problem could crash all of them. Embedded system avionic software was developed under totally different conditions from public commercial software: the number of code lines was tiny compared to a public commercial software product, changes were only made infrequently and with extensive testing, and many programming and test personnel worked on the small amount of computer code. However, in theory


title: "Space Shuttle" content: it could have still failed, and the BFS existed for that contingency. While the BFS could run in parallel with PASS, the BFS never engaged to take over control from PASS during any Shuttle mission. The software for the Shuttle computers was written in a high-level language called HAL/S, somewhat similar to PL/I. It is specifically designed for a real time embedded system environment. The IBM AP-101 computers originally had about 424 kilobytes of magnetic core memory each. The CPU could process about 400,000 instructions per second. They had no hard disk drive, and loaded software from magnetic tape cartridges.


title: "Space Shuttle" content: In 1990, the original computers were replaced with an upgraded model AP-101S, which had about 2.5 times the memory capacity (about 1 megabyte) and three times the processor speed (about 1.2 million instructions per second). The memory was changed from magnetic core to semiconductor with battery backup. Early Shuttle missions, starting in November 1983, took along the Grid Compass, arguably one of the first laptop computers. The GRiD was given the name SPOC, for Shuttle Portable Onboard Computer. Use on the Shuttle required both hardware and software modifications which were incorporated into later versions of the commercial product. It was


title: "Space Shuttle" content: used to monitor and display the Shuttle's ground position, path of the next two orbits, show where the Shuttle had line of sight communications with ground stations, and determine points for location-specific observations of the Earth. The Compass sold poorly, as it cost at least US$8000, but it offered unmatched performance for its weight and size. NASA was one of its main customers. During its service life, the Shuttle's Control System never experienced a failure. Many of the lessons learned have been used to design today's high speed control algorithms. The prototype orbiter "Enterprise" originally had a flag of the


title: "Space Shuttle" content: United States on the upper surface of the left wing and the letters "USA" in black on the right wing. The name "Enterprise" was painted in black on the payload bay doors just above the hinge and behind the crew module; on the aft end of the payload bay doors was the NASA "worm" logotype in gray. Underneath the rear of the payload bay doors on the side of the fuselage just above the wing is the text "United States" in black with a flag of the United States ahead of it. The first operational orbiter, "Columbia", originally had the


title: "Space Shuttle" content: same markings as "Enterprise", although the letters "USA" on the right wing were slightly larger and spaced farther apart. "Columbia" also had black markings which "Enterprise" lacked on its forward RCS module, around the cockpit windows, and on its vertical stabilizer, and had distinctive black "chines" on the forward part of its upper wing surfaces, which none of the other orbiters had. "Challenger" established a modified marking scheme for the shuttle fleet that was matched by "Discovery", "Atlantis" and "Endeavour". The letters "USA" in black above an American flag were displayed on the left wing, with the NASA "worm" logotype


title: "Space Shuttle" content: in gray centered above the name of the orbiter in black on the right wing. The name of the orbiter was inscribed not on the payload bay doors, but on the forward fuselage just below and behind the cockpit windows. This would make the name visible when the shuttle was photographed in orbit with the doors open. In 1983, "Enterprise" had its wing markings changed to match "Challenger", and the NASA "worm" logotype on the aft end of the payload bay doors was changed from gray to black. Some black markings were added to the nose, cockpit windows and vertical


title: "Space Shuttle" content: tail to more closely resemble the flight vehicles, but the name "Enterprise" remained on the payload bay doors as there was never any need to open them. "Columbia" had its name moved to the forward fuselage to match the other flight vehicles after STS-61-C, during the 1986–88 hiatus when the shuttle fleet was grounded following the loss of "Challenger", but retained its original wing markings until its last overhaul (after STS-93), and its unique black wing "chines" for the remainder of its operational life. Beginning in 1998, the flight vehicles' markings were modified to incorporate the NASA "meatball" insignia. The


title: "Space Shuttle" content: "worm" logotype, which the agency had phased out, was removed from the payload bay doors and the "meatball" insignia was added aft of the "United States" text on the lower aft fuselage. The "meatball" insignia was also displayed on the left wing, with the American flag above the orbiter's name, left-justified rather than centered, on the right wing. The three surviving flight vehicles, "Discovery", "Atlantis" and "Endeavour", still bear these markings as museum displays. "Enterprise" became the property of the Smithsonian Institution in 1985 and was no longer under NASA's control when these changes were made, hence the prototype orbiter


title: "Space Shuttle" content: still has its 1983 markings and still has its name on the payload bay doors. The Space Shuttle was initially developed in the 1970s, but received many upgrades and modifications afterward to improve performance, reliability and safety. Internally, the Shuttle remained largely similar to the original design, with the exception of the improved avionics computers. In addition to the computer upgrades, the original analog primary flight instruments were replaced with modern full-color, flat-panel display screens, called a glass cockpit, which is similar to those of contemporary airliners. To facilitate construction of ISS, the internal airlocks of each orbiter except "Columbia"


title: "Space Shuttle" content: were replaced with external docking systems to allow for a greater amount of cargo to be stored on the Shuttle's mid-deck during station resupply missions. The Space Shuttle Main Engines (SSMEs) had several improvements to enhance reliability and power. This explains phrases such as "Main engines throttling up to 104 percent." This did not mean the engines were being run over a safe limit. The 100 percent figure was the original specified power level. During the lengthy development program, Rocketdyne determined the engine was capable of safe reliable operation at 104 percent of the originally specified thrust. NASA could have


title: "Space Shuttle" content: rescaled the output number, saying in essence 104 percent is now 100 percent. To clarify this would have required revising much previous documentation and software, so the 104 percent number was retained. SSME upgrades were denoted as "block numbers", such as block I, block II, and block IIA. The upgrades improved engine reliability, maintainability and performance. The 109% thrust level was finally reached in flight hardware with the Block II engines in 2001. The normal maximum throttle was 104 percent, with 106 percent or 109 percent used for mission aborts. For the first two missions, STS-1 and STS-2, the external


title: "Space Shuttle" content: tank was painted white to protect the insulation that covers much of the tank, but improvements and testing showed that it was not required. The weight saved by not painting the tank resulted in an increase in payload capability to orbit. Additional weight was saved by removing some of the internal "stringers" in the hydrogen tank that proved unnecessary. The resulting "light-weight external tank" was first flown on STS-6 and used on the majority of Shuttle missions. STS-91 saw the first flight of the "super light-weight external tank". This version of the tank was made of the 2195 aluminum-lithium alloy.


title: "Space Shuttle" content: It weighed 3.4 metric tons (7,500 lb) less than the last run of lightweight tanks, allowing the Shuttle to deliver heavy elements to ISS's high inclination orbit. As the Shuttle was always operated with a crew, each of these improvements was first flown on operational mission flights. The solid rocket boosters underwent improvements as well. Design engineers added a third O-ring seal to the joints between the segments after the 1986 Space Shuttle "Challenger" disaster. Several other SRB improvements were planned to improve performance and safety, but never came to be. These culminated in the considerably simpler, lower cost, probably


title: "Space Shuttle" content: safer and better-performing Advanced Solid Rocket Booster. These rockets entered production in the early to mid-1990s to support the Space Station, but were later canceled to save money after the expenditure of $2.2 billion. The loss of the ASRB program resulted in the development of the Super LightWeight external Tank (SLWT), which provided some of the increased payload capability, while not providing any of the safety improvements. In addition, the U.S. Air Force developed their own much lighter single-piece SRB design using a filament-wound system, but this too was canceled. STS-70 was delayed in 1995, when woodpeckers bored holes in


title: "Space Shuttle" content: the foam insulation of "Discovery"'s external tank. Since then, NASA has installed commercial plastic owl decoys and inflatable owl balloons which had to be removed prior to launch. The delicate nature of the foam insulation had been the cause of damage to the Thermal Protection System, the tile heat shield and heat wrap of the orbiter. NASA remained confident that this damage, while it was the primary cause of the Space Shuttle "Columbia" disaster on February 1, 2003, would not jeopardize the completion of the International Space Station (ISS) in the projected time allotted. A cargo-only, unmanned variant of the


title: "Space Shuttle" content: Shuttle was variously proposed and rejected since the 1980s. It was called the Shuttle-C, and would have traded re-usability for cargo capability, with large potential savings from reusing technology developed for the Space Shuttle. Another proposal was to convert the payload bay into a passenger area, with versions ranging from 30 to 74 seats, three days in orbit, and cost US$1.5 million per seat. On the first four Shuttle missions, astronauts wore modified U.S. Air Force high-altitude full-pressure suits, which included a full-pressure helmet during ascent and descent. From the fifth flight, STS-5, until the loss of "Challenger", one-piece light


title: "Space Shuttle" content: blue nomex flight suits and partial-pressure helmets were worn. A less-bulky, partial-pressure version of the high-altitude pressure suits with a helmet was reinstated when Shuttle flights resumed in 1988. The Launch-Entry Suit ended its service life in late 1995, and was replaced by the full-pressure Advanced Crew Escape Suit (ACES), which resembled the Gemini space suit in design, but retained the orange color of the Launch-Entry Suit. To extend the duration that orbiters could stay docked at the ISS, the Station-to-Shuttle Power Transfer System (SSPTS) was installed. The SSPTS allowed these orbiters to use power provided by the ISS to


title: "Space Shuttle" content: preserve their consumables. The SSPTS was first used successfully on STS-118. Orbiter (for "Endeavour", OV-105) External tank (for SLWT) Solid Rocket Boosters System Stack All Space Shuttle missions were launched from Kennedy Space Center (KSC). The weather criteria used for launch included, but were not limited to: precipitation, temperatures, cloud cover, lightning forecast, wind, and humidity. The Shuttle was not launched under conditions where it could have been struck by lightning. Aircraft are often struck by lightning with no adverse effects because the electricity of the strike is dissipated through its conductive structure and the aircraft is not electrically grounded.


title: "Space Shuttle" content: Like most jet airliners, the Shuttle was mainly constructed of conductive aluminum, which would normally shield and protect the internal systems. However, upon liftoff the Shuttle sent out a long exhaust plume as it ascended, and this plume could have triggered lightning by providing a current path to ground. The NASA Anvil Rule for a Shuttle launch stated that an anvil cloud could not appear within a distance of 10 nautical miles. The Shuttle Launch Weather Officer monitored conditions until the final decision to scrub a launch was announced. In addition, the weather conditions had to be acceptable at one


title: "Space Shuttle" content: of the Transatlantic Abort Landing sites (one of several Space Shuttle abort modes) to launch as well as the solid rocket booster recovery area. While the Shuttle might have safely endured a lightning strike, a similar strike caused problems on Apollo 12, so for safety NASA chose not to launch the Shuttle if lightning was possible (NPR8715.5). Historically, the Shuttle was not launched if its flight would run from December to January (a year-end rollover or YERO). Its flight software, designed in the 1970s, was not designed for this, and would require the orbiter's computers be reset through a change


title: "Space Shuttle" content: of year, which could cause a glitch while in orbit. In 2007, NASA engineers devised a solution so Shuttle flights could cross the year-end boundary. After the final hold in the countdown at T-minus 9 minutes, the Shuttle went through its final preparations for launch, and the countdown was automatically controlled by the Ground Launch Sequencer (GLS), software at the Launch Control Center, which stopped the count if it sensed a critical problem with any of the Shuttle's onboard systems. The GLS handed off the count to the Shuttle's on-board computers at T minus 31 seconds, in a process called


title: "Space Shuttle" content: auto sequence start. At T-minus 16 seconds, the massive sound suppression system (SPS) began to drench the Mobile Launcher Platform (MLP) and SRB trenches with of water to protect the Orbiter from damage by acoustical energy and rocket exhaust reflected from the flame trench and MLP during lift off. At T-minus 10 seconds, hydrogen igniters were activated under each engine bell to quell the stagnant gas inside the cones before ignition. Failure to burn these gases could trip the onboard sensors and create the possibility of an overpressure and explosion of the vehicle during the firing phase. The main engine


title: "Space Shuttle" content: turbopumps also began charging the combustion chambers with liquid hydrogen and liquid oxygen at this time. The computers reciprocated this action by allowing the redundant computer systems to begin the firing phase. The three main engines (SSMEs) started at "T"-6.6 seconds. The main engines ignited sequentially via the Shuttle's general purpose computers (GPCs) at 120 millisecond intervals. All three SSMEs were required to reach 90% rated thrust within three seconds, otherwise the onboard computers would initiate an RSLS abort. If all three engines indicated nominal performance by "T"-3 seconds, they were commanded to gimbal to liftoff configuration and the command


title: "Space Shuttle" content: would be issued to arm the SRBs for ignition at "T"-0. Between "T"-6.6 seconds and "T"-3 seconds, while the SSMEs were firing but the SRBs were still bolted to the pad, the offset thrust caused the entire launch stack (boosters, tank and orbiter) to pitch down measured at the tip of the external tank. The three second delay after confirmation of SSME operation was to allow the stack to return to nearly vertical. At "T"-0 seconds, the 8 frangible nuts holding the SRBs to the pad were detonated, the SSMEs were commanded to 100% throttle, and the SRBs were ignited.


title: "Space Shuttle" content: By "T"+0.23 seconds, the SRBs built up enough thrust for liftoff to commence, and reached maximum chamber pressure by "T"+0.6 seconds. The Johnson Space Center's Mission Control Center assumed control of the flight once the SRBs had cleared the launch tower. Shortly after liftoff, the Shuttle's main engines were throttled up to 104.5% and the vehicle began a combined roll, pitch and yaw maneuver that placed it onto the correct heading (azimuth) for the planned orbital inclination and in a heads down attitude with wings level. The Shuttle flew upside down during the ascent phase. This orientation allowed a trim


title: "Space Shuttle" content: angle of attack that was favorable for aerodynamic loads during the region of high dynamic pressure, resulting in a net positive load factor, as well as providing the flight crew with a view of the horizon as a visual reference. The vehicle climbed in a progressively flattening arc, accelerating as the mass of the SRBs and main tank decreased. To achieve low orbit requires much more horizontal than vertical acceleration. This was not visually obvious, since the vehicle rose vertically and was out of sight for most of the horizontal acceleration. The near circular orbital velocity at the altitude of


title: "Space Shuttle" content: the International Space Station is , roughly equivalent to Mach 23 at sea level. As the International Space Station orbits at an inclination of 51.6 degrees, missions going there must set orbital inclination to the same value in order to rendezvous with the station. Around 30 seconds into ascent, the SSMEs were throttled down—usually to 72%, though this varied—to reduce the maximum aerodynamic forces acting on the Shuttle at a point called Max Q. Additionally, the propellant grain design of the SRBs caused their thrust to drop by about 30% by 50 seconds into ascent. Once the Orbiter's guidance verified


title: "Space Shuttle" content: that Max Q would be within Shuttle structural limits, the main engines were throttled back up to 104.5%; this throttling down and back up was called the "thrust bucket". To maximize performance, the throttle level and timing of the thrust bucket was shaped to bring the Shuttle as close to aerodynamic limits as possible. At around "T"+126 seconds, pyrotechnic fasteners released the SRBs and small separation rockets pushed them laterally away from the vehicle. The SRBs parachuted back to the ocean to be reused. The Shuttle then began accelerating to orbit on the main engines. Acceleration at this point would


title: "Space Shuttle" content: typically fall to .9 "g", and the vehicle would take on a somewhat nose-up angle to the horizonit used the main engines to gain and then maintain altitude while it accelerated horizontally towards orbit. At about five and three-quarter minutes into ascent, the orbiter's direct communication links with the ground began to fade, at which point it rolled heads up to reroute its communication links to the Tracking and Data Relay Satellite system. At about seven and a half minutes into ascent, the mass of the vehicle was low enough that the engines had to be throttled back to limit


title: "Space Shuttle" content: vehicle acceleration to 3 "g" (29.4 m/s² or 96.5 ft/s², equivalent to accelerating from zero to in a second). The Shuttle would maintain this acceleration for the next minute, and main engine cut-off (MECO) occurred at about eight and a half minutes after launch. The main engines were shut down before complete depletion of propellant, as running dry would have destroyed the engines. The oxygen supply was terminated before the hydrogen supply, as the SSMEs reacted unfavorably to other shutdown modes. (Liquid oxygen has a tendency to react violently, and supports combustion when it encounters hot engine metal.) A few


title: "Space Shuttle" content: seconds after MECO, the external tank was released by firing pyrotechnic fasteners. At this point the Shuttle and external tank were on a slightly suborbital trajectory, coasting up towards apogee. Once at apogee, about half an hour after MECO, the Shuttle's Orbital Maneuvering System (OMS) engines were fired to raise its perigee and achieve orbit, while the external tank fell back into the atmosphere and burned up over the Indian Ocean or the Pacific Ocean depending on launch profile. The sealing action of the tank plumbing and lack of pressure relief systems on the external tank helped it break up


title: "Space Shuttle" content: in the lower atmosphere. After the foam burned away during re-entry, the heat caused a pressure buildup in the remaining liquid oxygen and hydrogen until the tank exploded. This ensured that any pieces that fell back to Earth were small. The Shuttle was monitored throughout its ascent for short range tracking (10 seconds before liftoff through 57 seconds after), medium range (7 seconds before liftoff through 110 seconds after) and long range (7 seconds before liftoff through 165 seconds after). Short range cameras included 22 16mm cameras on the Mobile Launch Platform and 8 16mm on the Fixed Service Structure,


title: "Space Shuttle" content: 4 high speed fixed cameras located on the perimeter of the launch complex plus an additional 42 fixed cameras with 16mm motion picture film. Medium range cameras included remotely operated tracking cameras at the launch complex plus 6 sites along the immediate coast north and south of the launch pad, each with 800mm lens and high speed cameras running 100 frames per second. These cameras ran for only 4–10 seconds due to limitations in the amount of film available. Long range cameras included those mounted on the external tank, SRBs and orbiter itself which streamed live video back to the


title: "Space Shuttle" content: ground providing valuable information about any debris falling during ascent. Long range tracking cameras with 400-inch film and 200-inch video lenses were operated by a photographer at Playalinda Beach as well as 9 other sites from 38 miles north at the Ponce Inlet to 23 miles south to Patrick Air Force Base (PAFB) and additional mobile optical tracking camera was stationed on Merritt Island during launches. A total of 10 HD cameras were used both for ascent information for engineers and broadcast feeds to networks such as NASA TV and HDNet. The number of cameras significantly increased and numerous existing


title: "Space Shuttle" content: cameras were upgraded at the recommendation of the Columbia Accident Investigation Board to provide better information about the debris during launch. Debris was also tracked using a pair of Weibel Continuous Pulse Doppler X-band radars, one on board the SRB recovery ship MV "Liberty Star" positioned north east of the launch pad and on a ship positioned south of the launch pad. Additionally, during the first 2 flights following the loss of "Columbia" and her crew, a pair of NASA WB-57 reconnaissance aircraft equipped with HD Video and Infrared flew at to provide additional views of the launch ascent. Kennedy


title: "Space Shuttle" content: Space Center also invested nearly $3 million in improvements to the digital video analysis systems in support of debris tracking. Once in orbit, the Shuttle usually flew at an altitude of , although the STS-82 mission reached . In the 1980s and 1990s, many flights involved space science missions on the NASA/ESA Spacelab, or launching various types of satellites and science probes. By the 1990s and 2000s the focus shifted more to servicing the space station, with fewer satellite launches. Most missions involved staying in orbit several days to two weeks, although longer missions were possible with the Extended Duration


title: "Space Shuttle" content: Orbiter add-on or when attached to a space station. STS-80 was the longest at almost 17 days and 16 hours. Almost the entire Space Shuttle re-entry procedure, except for lowering the landing gear and deploying the air data probes, was normally performed under computer control. However, the re-entry could be flown entirely manually if an emergency arose. The approach and landing phase could be controlled by the autopilot, but was usually hand flown. The vehicle began re-entry by firing the Orbital maneuvering system engines, while flying upside down, backside first, in the opposite direction to orbital motion for approximately three


title: "Space Shuttle" content: minutes, which reduced the Shuttle's velocity by about . The resultant slowing of the Shuttle lowered its orbital perigee down into the upper atmosphere. The Shuttle then flipped over, by pushing its nose down (which was actually "up" relative to the Earth, because it was flying upside down). This OMS firing was done roughly halfway around the globe from the landing site. The vehicle started encountering more significant air density in the lower thermosphere at about , at around Mach 25, . The vehicle was controlled by a combination of RCS thrusters and control surfaces, to fly at a 40-degree


title: "Space Shuttle" content: nose-up attitude, producing high drag, not only to slow it down to landing speed, but also to reduce reentry heating. As the vehicle encountered progressively denser air, it began a gradual transition from spacecraft to aircraft. In a straight line, its 40-degree nose-up attitude would cause the descent angle to flatten-out, or even rise. The vehicle therefore performed a series of four steep S-shaped banking turns, each lasting several minutes, at up to 70 degrees of bank, while still maintaining the 40-degree angle of attack. In this way it dissipated speed sideways rather than upwards. This occurred during the 'hottest'


title: "Space Shuttle" content: phase of re-entry, when the heat-shield glowed red and the G-forces were at their highest. By the end of the last turn, the transition to aircraft was almost complete. The vehicle leveled its wings, lowered its nose into a shallow dive and began its approach to the landing site. The orbiter's maximum glide ratio/lift-to-drag ratio varies considerably with speed, ranging from 1:1 at hypersonic speeds, 2:1 at supersonic speeds and reaching 4.5:1 at subsonic speeds during approach and landing. In the lower atmosphere, the orbiter flies much like a conventional glider, except for a much higher descent rate, over or


title: "Space Shuttle" content: 9,800 fpm. At approximately Mach 3, two air data probes, located on the left and right sides of the orbiter's forward lower fuselage, are deployed to sense air pressure related to the vehicle's movement in the atmosphere. When the approach and landing phase began, the orbiter was at a altitude, from the runway. The pilots applied aerodynamic braking to help slow down the vehicle. The orbiter's speed was reduced from , approximately, at touch-down (compared to for a jet airliner). The landing gear was deployed while the Orbiter was flying at . To assist the speed brakes, a drag chute


title: "Space Shuttle" content: was deployed either after main gear or nose gear touchdown (depending on selected chute deploy mode) at about . The chute was jettisoned once the orbiter slowed to . After landing, the vehicle stayed on the runway for several hours for the orbiter to cool. Teams at the front and rear of the orbiter tested for presence of hydrogen, hydrazine, monomethylhydrazine, nitrogen tetroxide and ammonia (fuels and by-products of the reaction control system and the orbiter's three APUs). If hydrogen was detected, an emergency would be declared, the orbiter powered down and teams would evacuate the area. A convoy of


title: "Space Shuttle" content: 25 specially designed vehicles and 150 trained engineers and technicians approached the orbiter. Purge and vent lines were attached to remove toxic gases from fuel lines and the cargo bay about 45–60 minutes after landing. A flight surgeon boarded the orbiter for initial medical checks of the crew before disembarking. Once the crew left the orbiter, responsibility for the vehicle was handed from the Johnson Space Center back to the Kennedy Space Center. If the mission ended at Edwards Air Force Base in California, White Sands Space Harbor in New Mexico, or any of the runways the orbiter might use


title: "Space Shuttle" content: in an emergency, the orbiter was loaded atop the Shuttle Carrier Aircraft, a modified 747, for transport back to the Kennedy Space Center, landing at the Shuttle Landing Facility. Once at the Shuttle Landing Facility, the orbiter was then towed along a tow-way and access roads normally used by tour buses and KSC employees to the Orbiter Processing Facility where it began a months-long preparation process for the next mission. NASA preferred Space Shuttle landings to be at Kennedy Space Center. If weather conditions made landing there unfavorable, the Shuttle could delay its landing until conditions are favorable, touch down


title: "Space Shuttle" content: at Edwards Air Force Base, California, or use one of the multiple alternate landing sites around the world. A landing at any site other than Kennedy Space Center meant that after touchdown the Shuttle must be mated to the Shuttle Carrier Aircraft and returned to Cape Canaveral. Space Shuttle "Columbia" (STS-3) once landed at the White Sands Space Harbor, New Mexico; this was viewed as a last resort as NASA scientists believed that the sand could potentially damage the Shuttle's exterior. There were many alternative landing sites that were never used. An example of technical risk analysis for a STS


title: "Space Shuttle" content: mission is SPRA iteration 3.1 top risk contributors for STS-133: An internal NASA risk assessment study (conducted by the Shuttle Program Safety and Mission Assurance Office at Johnson Space Center) released in late 2010 or early 2011 concluded that the agency had seriously underestimated the level of risk involved in operating the Shuttle. The report assessed that there was a 1 in 9 chance of a catastrophic disaster during the first nine flights of the Shuttle but that safety improvements had later improved the risk ratio to 1 in 90. Below is a list of major events in the Space


title: "Space Shuttle" content: Shuttle orbiter fleet. Sources: NASA launch manifest, NASA Space Shuttle archive On January 28, 1986, "Challenger" disintegrated 73 seconds after launch due to the failure of the right SRB, killing all seven astronauts on board. The disaster was caused by low-temperature impairment of an O-ring, a mission critical seal used between segments of the SRB casing. Failure of the O-ring allowed hot combustion gases to escape from between the booster sections and burn through the adjacent external tank, causing it to explode. Repeated warnings from design engineers voicing concerns about the lack of evidence of the O-rings' safety when the


title: "Space Shuttle" content: temperature was below 53 °F (12 °C) had been ignored by NASA managers. On February 1, 2003, "Columbia" disintegrated during re-entry, killing its crew of seven, because of damage to the carbon-carbon leading edge of the wing caused during launch. Ground control engineers had made three separate requests for high-resolution images taken by the Department of Defense that would have provided an understanding of the extent of the damage, while NASA's chief thermal protection system (TPS) engineer requested that astronauts on board "Columbia" be allowed to leave the vehicle to inspect the damage. NASA managers intervened to stop the Department


title: "Space Shuttle" content: of Defense's assistance and refused the request for the spacewalk, and thus the feasibility of scenarios for astronaut repair or rescue by "Atlantis" were not considered by NASA management at the time. NASA retired the Space Shuttle in 2011, after 30 years of service. The Shuttle was originally conceived of and presented to the public as a "Space Truck", which would, among other things, be used to build a United States space station in low earth orbit in the early 1990s. When the U.S. space station evolved into the International Space Station project, which suffered from long delays and design


title: "Space Shuttle" content: changes before it could be completed, the retirement of the Space Shuttle was delayed several times until 2011, serving at least 15 years longer than originally planned. "Discovery" was the first of NASA's three remaining operational Space Shuttles to be retired. The final Space Shuttle mission was originally scheduled for late 2010, but the program was later extended to July 2011 when Michael Suffredini of the ISS program said that one additional trip was needed in 2011 to deliver parts to the International Space Station. The Shuttle's final mission consisted of just four astronauts—Christopher Ferguson (Commander), Douglas Hurley (Pilot), Sandra


title: "Space Shuttle" content: Magnus (Mission Specialist 1), and Rex Walheim (Mission Specialist 2); they conducted the 135th and last space Shuttle mission on board "Atlantis", which launched on July 8, 2011, and landed safely at the Kennedy Space Center on July 21, 2011, at 5:57 AM EDT (09:57 UTC). NASA announced it would transfer orbiters to education institutions or museums at the conclusion of the Space Shuttle program. Each museum or institution is responsible for covering the cost of preparing and transporting each vehicle for display. Twenty museums from across the country submitted proposals for receiving one of the retired orbiters. NASA also


title: "Space Shuttle" content: made Space Shuttle thermal protection system tiles available to schools and universities for less than US$25 each. About 7,000 tiles were available on a first-come, first-served basis, limited to one per institution. On April 12, 2011, NASA announced selection of locations for the remaining Shuttle orbiters: In August 2011, the NASA Office of Inspector General (OIG) published a "Review of NASA's Selection of Display Locations for the Space Shuttle Orbiters"; the review had four main findings: The NASA OIG had three recommendations, saying NASA should: In September 2011, the CEO and two board members of Seattle's Museum of Flight met


title: "Space Shuttle" content: with NASA Administrator Charles Bolden, pointing out "significant errors in deciding where to put its four retiring Space Shuttles"; the errors alleged include inaccurate information on Museum of Flight's attendance and international visitor statistics, as well as the readiness of the Intrepid Sea-Air-Space Museum's exhibit site. Flight and mid-deck training hardware will be taken from the Johnson Space Center and will go to the National Air and Space Museum and the National Museum of the U.S. Air Force. The full fuselage mockup, which includes the payload bay and aft section but no wings, is to go to the Museum of


title: "Space Shuttle" content: Flight in Seattle. Mission Simulation and Training Facility's fixed simulator will go to the Adler Planetarium in Chicago, and the motion simulator will go to the Texas A&M Aerospace Engineering Department in College Station, Texas. Other simulators used in Shuttle astronaut training will go to the Wings of Dreams Aviation Museum in Starke, Florida and the Virginia Air and Space Center in Hampton, Virginia. Until another U.S. manned spacecraft is ready, crews will travel to and from the International Space Station (ISS) exclusively aboard the Russian Soyuz spacecraft. A planned successor to STS was the "Shuttle II", during the 1980s


title: "Space Shuttle" content: and 1990s, and later the Constellation program during the 2004–2010 period. CSTS was a proposal to continue to operate STS commercially, after NASA. In September 2011, NASA announced the selection of the design for the new Space Launch System that is planned to launch the Orion spacecraft and other hardware to missions beyond low earth-orbit. The Commercial Orbital Transportation Services program began in 2006 with the purpose of creating commercially operated unmanned cargo vehicles to service the ISS. The Commercial Crew Development (CCDev) program was started in 2010 to create commercially operated manned spacecraft capable of delivering at least four


title: "Space Shuttle" content: crew members to the ISS, to stay docked for 180 days, and then return them back to Earth. These spacecraft were to become operational in the 2010s. Space Shuttles have been features of fiction and nonfiction, from children's movies to documentaries. Early examples include the 1979 "James Bond" film, "Moonraker", the 1982 Activision videogame "Space Shuttle: A Journey into Space" (1982) and G. Harry Stine's 1981 novel "Shuttle Down". In the 1986 film "SpaceCamp", "Atlantis" accidentally launches into space with a group of U.S. Space Camp participants as its crew. A space shuttle named "Intrepid" is featured in the 1989


title: "Space Shuttle" content: film "Moontrap". The 1998 film "Armageddon" portrays a combined crew of offshore oil rig workers and U.S. military staff who pilot two modified Shuttles to avert the destruction of Earth by an asteroid. Retired American test pilots visit a Russian satellite in the 2000 Clint Eastwood adventure film "Space Cowboys". In the 2003 film "The Core", the "Endeavour"s landing is disrupted by the Earth's magnetic core, and its crew is selected to pilot a vehicle designed to restart the core. The 2004 Bollywood movie "Swades", where a Space Shuttle is used to launch a special rainfall monitoring satellite, was filmed


title: "Space Shuttle" content: at Kennedy Space Center in the year after the "Columbia" disaster that had taken the life of Indian-American astronaut KC Chawla. On television, the 1996 drama "The Cape" portrays the lives of a group of NASA astronauts as they prepare for and fly Shuttle missions. "Odyssey 5" was a short-lived sci-fi series that features the crew of a Space Shuttle as the last survivors of a disaster that destroys Earth. The 1997–2007 sci-fi series "Stargate SG-1" has a shuttle rescue written into an episode. The 2013 film "Gravity" features the fictional Space Shuttle "Explorer" during STS-157, whose crew are killed


title: "Space Shuttle" content: or left stranded after it is destroyed by a shower of high speed orbital debris. The 2017 Lego film "The Lego Batman Movie" features a hybrid between the Batmobile and a Space Shuttle, named "the Bat Space Shuttle" by Dick Grayson. It's clearly based on the Lego City set 3367 ("Space Shuttle"), but is black and weapon-equipped. The Space Shuttle has also been the subject of toys and models; for example, a large Lego Space Shuttle model was constructed by visitors at Kennedy Space Center, and smaller models have been sold commercially as a standard "LegoLand" set. A 1980 pinball


title: "Space Shuttle" content: machine "Space Shuttle" was produced by Zaccaria and a 1984 pinball machine "Space Shuttle: Pinball Adventure" was produced by Williams and features a plastic Space Shuttle model among other artwork of astronauts on the play field. The Space Shuttle also appears in a number of flight simulator and space flight simulator games such as "Microsoft Space Simulator", "Orbiter", "FlightGear", "X-Plane" and Space Shuttle Mission 2007. Several Transformers toys were modeled after the Space Shuttle. The U.S. Postal Service has released several postage issues that depict the Space Shuttle. The first such stamps were issued in 1981, and are on display


title: "Space Shuttle" content: at the National Postal Museum. Space Shuttle The Space Shuttle was a partially reusable low Earth orbital spacecraft system operated by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program name was "Space Transportation System (STS)", taken from a 1969 plan for a system of reusable spacecraft of which it was the only item funded for development. The first of four orbital test flights occurred in 1981, leading to operational flights beginning in 1982. In addition to the prototype whose completion was cancelled, five complete Shuttle systems were built and used


title: "Shot put" content: In the 16th century King Henry VIII was noted for his prowess in court competitions of weight and hammer throwing. The first events resembling the modern shot put likely occurred in the Middle Ages when soldiers held competitions in which they hurled cannonballs. Shot put competitions were first recorded in early 19th century Scotland, and were a part of the British Amateur Championships beginning in 1866. Competitors take their throw from inside a marked circle 2.135m (7.004593176 ft) in diameter, with a stopboard about high at the front of the circle. The distance thrown is measured from the inside of


title: "Rescue and recovery effort after the September 11 attacks on the World Trade Center" content: the Port Authority construction is not going as smoothly as planned. City officials are looking for better ways to lower the problems and delays. The World Trade Center completion of construction was scheduled for 2016. , four of seven planned buildings were completed, as were the transportation hub, 9/11 Memorial, and Liberty Park. Notes Bibliography New York Times: Other: Rescue and recovery effort after the September 11 attacks on the World Trade Center The local, state, federal and global reaction to the September 11 attacks on the World Trade Center was unprecedented. The equally unsurpassed events of that day elicited


title: "Strategic Air Command" content: and the perceived greater reliability of land-based and submarine-based ballistic missile systems. Although initially entering service in 1957, SAC's 2nd-generation aerial refueling aircraft, the KC-135 Stratotanker, had reached sufficient inventory numbers to allow SAC to begin divestiture of its KC-97 Stratofreighter tankers, transferring them to SAC-gained Air Force Reserve and Air National Guard units. As the KC-135 became the primary aerial tanker in active service, SAC employed the aircraft for several non-stop B-52 and KC-135 flights around the world, demonstrating that SAC no longer needed to depend on Reflex stations at air bases in Spain and Britain.) After the Secretary


title: "Scheme (programming language)" content: to implement advanced lazy evaluation constructs such as streams. In the R6RS standard, these are no longer primitives, but instead, are provided as part of the R5RS compatibility library (rnrs r5rs (6)). In R5RS, a suggested implementation of codice_38 and codice_39 is given, implementing the promise as a procedure with no arguments (a thunk) and using memoization to ensure that it is only ever evaluated once, irrespective of the number of times codice_39 is called (R5RS sec. 6.4). SRFI 41 enables the expression of both finite and infinite sequences with extraordinary economy. For example, this is a definition of the


title: "Sydney Harbour Bridge" content: Sydney Harbour Bridge The Sydney Harbour Bridge is a heritage-listed steel through arch bridge across Sydney Harbour that carries rail, vehicular, bicycle, and pedestrian traffic between the Sydney central business district (CBD) and the North Shore. The dramatic view of the bridge, the harbour, and the nearby Sydney Opera House is an iconic image of Sydney, and Australia itself. The bridge is nicknamed "The Coathanger" because of its arch-based design. Under the direction of Dr John Bradfield of the NSW Department of Public Works, the bridge was designed and built by British firm Dorman Long and Co Ltd of Middlesbrough


title: "Sydney Harbour Bridge" content: and opened in 1932. The bridge's design was influenced by the Hell Gate Bridge in New York City. It is the sixth longest spanning-arch bridge in the world and the tallest steel arch bridge, measuring from top to water level. It was also the world's widest long-span bridge, at wide, until construction of the new Port Mann Bridge in Vancouver was completed in 2012. The Sydney Harbour Bridge was added to the Australian National Heritage List on 19 March 2007 and to the New South Wales State Heritage Register on 25 June 1999. The southern end of the bridge is


title: "Sydney Harbour Bridge" content: located at Dawes Point in The Rocks area, and the northern end at Milsons Point in the lower North Shore area. There are six original lanes of road traffic through the main roadway, plus an additional two lanes of road traffic on its eastern side, using lanes that were formerly tram tracks. Adjacent to the road traffic, a path for pedestrian use runs along the eastern side of the bridge, whilst a dedicated path for bicycle use only runs along the western side; between the main roadway and the western bicycle path are two lanes used for railway tracks, servicing


title: "Sydney Harbour Bridge" content: the T1 North Shore Line for Sydney Trains. The main roadway across the bridge is known as the Bradfield Highway and is about long, making it one of the shortest highways in Australia. The arch is composed of two 28-panel arch trusses; their heights vary from at the centre of the arch to at the ends next to the pylons. The arch has a span of and its summit is above mean sea level; expansion of the steel structure on hot days can increase the height of the arch by . The total weight of the steelwork of the bridge,


title: "Sydney Harbour Bridge" content: including the arch and approach spans, is , with the arch itself weighing . About 79% of the steel was imported from England, with the rest being sourced from . On site, the contractors (Dorman Long and Co.) set up two workshops at Milsons Point, at the site of the present day Luna Park, and fabricated the steel into the girders and other required parts. The bridge is held together by six million Australian-made hand-driven rivets supplied by the McPherson company of Melbourne, the last being driven through the deck on 21 January 1932. The rivets were heated red-hot and


title: "Sydney Harbour Bridge" content: inserted into the plates; the headless end was immediately rounded over with a large pneumatic rivet gun. The largest of the rivets used weighed and was long. The practice of riveting large steel structures, rather than welding, was, at the time, a proven and understood construction technique, whilst structural welding had not at that stage been adequately developed for use on the bridge. At each end of the arch stands a pair of high concrete pylons, faced with granite. The pylons were designed by the Scottish architect Thomas S. Tait, a partner in the architectural firm John Burnet & Partners.


title: "Sydney Harbour Bridge" content: Some 250 Australian, Scottish, and Italian stonemasons and their families relocated to a temporary settlement at Moruya, NSW, south of Sydney, where they quarried around of granite for the bridge pylons. The stonemasons cut, dressed, and numbered the blocks, which were then transported to Sydney on three ships built specifically for this purpose. The Moruya quarry was managed by John Gilmore, a Scottish stonemason who emigrated with his young family to Australia in 1924, at the request of the project managers. The concrete used was also Australian-made and supplied from Railton, Tasmania and Kandos, New South Wales. Abutments at the


title: "Sydney Harbour Bridge" content: base of the pylons are essential to support the loads from the arch and hold its span firmly in place, but the pylons themselves have no structural purpose. They were included to provide a frame for the arch panels and to give better visual balance to the bridge. The pylons were not part of the original design, and were only added to allay public concern about the structural integrity of the bridge. Although originally added to the bridge solely for their aesthetic value, all four pylons have now been put to use. The south-eastern pylon contains a museum and tourist


title: "Sydney Harbour Bridge" content: centre, with a 360° lookout at the top providing views across the harbour and city. The south-western pylon is used by the New South Wales Roads and Traffic Authority (RTA) to support its CCTV cameras overlooking the bridge and the roads around that area. The two pylons on the north shore include venting chimneys for fumes from the Sydney Harbour Tunnel, with the base of the southern pylon containing the RMS maintenance shed for the bridge, and the base of the northern pylon containing the traffic management shed for tow trucks and safety vehicles used on the bridge. In 1942


title: "Sydney Harbour Bridge" content: the pylons were modified to include parapets and anti-aircraft guns designed to assist in both Australia's defence and general war effort.The top level of stonework was never removed. There had been plans to build a bridge as early as 1815, when convict and noted architect Francis Greenway reputedly proposed to Governor Lachlan Macquarie that a bridge be built from the northern to the southern shore of the harbour. In 1825, Greenway wrote a letter to the then "The Australian" newspaper stating that such a bridge would "give an idea of strength and magnificence that would reflect credit and glory on


title: "Sydney Harbour Bridge" content: the colony and the Mother Country". Nothing came of Greenway's suggestions, but the idea remained alive, and many further suggestions were made during the nineteenth century. In 1840, naval architect Robert Brindley proposed that a floating bridge be built. Engineer Peter Henderson produced one of the earliest known drawings of a bridge across the harbour around 1857. A suggestion for a truss bridge was made in 1879, and in 1880 a high-level bridge estimated at $850,000 was proposed. In 1900, the Lyne government committed to building a new Central railway station and organised a worldwide competition for the design and


title: "Sydney Harbour Bridge" content: construction of a harbour bridge. Local engineer Norman Selfe submitted a design for a suspension bridge and won the second prize of £500. In 1902, when the outcome of the first competition became mired in controversy, Selfe won a second competition outright, with a design for a steel cantilever bridge. The selection board were unanimous, commenting that, "The structural lines are correct and in true proportion, and... the outline is graceful". However due to an economic downturn and a change of government at the 1904 NSW State election construction never began. A unique three-span bridge was proposed in 1922 by


title: "Sydney Harbour Bridge" content: Ernest Stowe with connections at Balls Head, Millers Point, and Balmain with a memorial tower and hub on Goat Island. In 1914 John Bradfield was appointed "Chief Engineer of Sydney Harbour Bridge and Metropolitan Railway Construction", and his work on the project over many years earned him the legacy as the "father" of the bridge. Bradfield's preference at the time was for a cantilever bridge without piers, and in 1916 the NSW Legislative Assembly passed a bill for such a construction, however it did not proceed as the Legislative Council rejected the legislation on the basis that the money would


title: "Sydney Harbour Bridge" content: be better spent on the war effort. Following World War I, plans to build the bridge again built momentum. Bradfield persevered with the project, fleshing out the details of the specifications and financing for his cantilever bridge proposal, and in 1921 he travelled overseas to investigate tenders. On return from his travels Bradfield decided that an arch design would also be suitable and he and officers of the NSW Department of Public Works prepared a general design for a single-arch bridge based upon New York City's Hell Gate Bridge. In 1922 the government passed the Sydney Harbour Bridge Act No.


title: "Sydney Harbour Bridge" content: 28, specifying the construction of a high-level cantilever or arch bridge across the harbour between Dawes Point and Milsons Point, along with construction of necessary approaches and electric railway lines, and worldwide tenders were invited for the project. As a result of the tendering process, the government received twenty proposals from six companies; on 24 March 1924 the contract was awarded to British firm Dorman Long and Co Ltd, of Middlesbrough well known as the contractors who built the similar Tyne Bridge of Newcastle Upon Tyne, for an arch bridge at a quoted price of AU£4,217,721 11s 10d. The arch


title: "Sydney Harbour Bridge" content: design was cheaper than alternative cantilever and suspension bridge proposals, and also provided greater rigidity making it better suited for the heavy loads expected. Bradfield and his staff were ultimately to oversee the entire bridge design and building process, while Dorman Long and Co's Consulting Engineer, Sir Ralph Freeman of Sir Douglas Fox and Partners, and his associate Mr. G.C. Imbault, carried out the detailed design and erection process of the bridge. Architects for the contractors were from the British firm John Burnet & Partners of Glasgow, Scotland. The building of the bridge coincided with the construction of a system


title: "Sydney Harbour Bridge" content: of underground railways in Sydney's CBD, known today as the City Circle, and the bridge was designed with this in mind. The bridge was designed to carry six lanes of road traffic, flanked on each side by two railway tracks and a footpath. Both sets of rail tracks were linked into the underground Wynyard railway station on the south (city) side of the bridge by symmetrical ramps and tunnels. The eastern-side railway tracks were intended for use by a planned rail link to the Northern Beaches; in the interim they were used to carry trams from the North Shore into


title: "Sydney Harbour Bridge" content: a terminal within Wynyard station, and when tram services were discontinued in 1958, they were converted into extra traffic lanes. The Bradfield Highway, which is the main roadway section of the bridge and its approaches, is named in honour of Bradfield's contribution to the bridge. The building of the bridge was under the management of Bradfield. Three other people heavily involved in the bridge's design and construction were Lawrence Ennis, Edward Judge, and Sir Ralph Freeman. Ennis was the engineer-in-charge at Dorman Long and Co and the main on-site supervisor (Bradfield visited occasionally throughout the project and, in particular, at


title: "Sydney Harbour Bridge" content: many key stages of the project, to inspect progress and make managerial decisions), Judge was chief technical engineer of Dorman Long, and Freeman was hired by the company to design the accepted model in further detail. Later a bitter disagreement broke out between Bradfield and Freeman as to who actually designed the bridge. The official ceremony to mark the "turning of the first sod" occurred on 28 July 1923, on the spot at Milsons Point on the north shore where two workshops to assist in building the bridge were to be constructed. An estimated 469 buildings on the north shore,


title: "Sydney Harbour Bridge" content: both private homes and commercial operations, were demolished to allow construction to proceed, with little or no compensation being paid. Work on the bridge itself commenced with the construction of approaches and approach spans, and by September 1926 concrete piers to support the approach spans were in place on each side of the harbour. As construction of the approaches took place, work was also started on preparing the foundations required to support the enormous weight of the arch and loadings. Concrete and granite faced abutment towers were constructed, with the angled foundations built into their sides. Once work had progressed


title: "Sydney Harbour Bridge" content: sufficiently on the support structures, a giant "creeper crane" was erected on each side of the harbour. These cranes were fitted with a cradle, and then used to hoist men and materials into position to allow for erection of the steelwork. To stabilise works while building the arches, tunnels were excavated on each shore with steel cables passed through them and then fixed to the upper sections of each half-arch to stop them collapsing as they extended outwards. Arch construction itself began on 26 October 1928. The southern end of the bridge was worked on ahead of the northern end,


title: "Sydney Harbour Bridge" content: to detect any errors and to help with alignment. The cranes would "creep" along the arches as they were constructed, eventually meeting up in the middle. In less than two years, on Tuesday, 19 August 1930, the two halves of the arch touched for the first time. Workers riveted both top and bottom sections of the arch together, and the arch became self-supporting, allowing the support cables to be removed. On 20 August 1930 the joining of the arches was celebrated by flying the flags of Australia and the United Kingdom from the jibs of the creeper cranes. Once the


title: "Sydney Harbour Bridge" content: arch was completed, the creeper cranes were then worked back down the arches, allowing the roadway and other parts of the bridge to be constructed from the centre out. The vertical hangers were attached to the arch, and these were then joined with horizontal crossbeams. The deck for the roadway and railway were built on top of the crossbeams, with the deck itself being completed by June 1931, and the creeper cranes were dismantled. Rails for trains and trams were laid, and road was surfaced using concrete topped with asphalt. Power and telephone lines, and water, gas, and drainage pipes


title: "Sydney Harbour Bridge" content: were also all added to the bridge in 1931. The pylons were built atop the abutment towers, with construction advancing rapidly from July 1931. Carpenters built wooden scaffolding, with concreters and masons then setting the masonry and pouring the concrete behind it. Gangers built the steelwork in the towers, while day labourers manually cleaned the granite with wire brushes. The last stone of the north-west pylon was set in place on 15 January 1932, and the timber towers used to support the cranes were removed. On 19 January 1932, the first test train, a steam locomotive, safely crossed the bridge.


title: "Sydney Harbour Bridge" content: Load testing of the bridge took place in February 1932, with the four rail tracks being loaded with as many as 96 steam locomotives positioned end-to-end. The bridge underwent testing for three weeks, after which it was declared safe and ready to be opened. The construction worksheds were demolished after the bridge was completed, and the land that they were on is now occupied by Luna Park. The standards of industrial safety during construction were poor by today's standards. Sixteen workers died during construction, but surprisingly only two from falling off the bridge. Several more were injured from unsafe working


title: "Sydney Harbour Bridge" content: practices undertaken whilst heating and inserting its rivets, and the deafness experienced by many of the workers in later years was blamed on the project. Henri Mallard between 1930 and 1932 produced hundreds of stills and film footage which reveal at close quarters the bravery of the workers in tough Depression-era conditions. Interviews were conducted between 1982-1989 with a variety of tradesmen who worked on the building of the bridge. Among the tradesmen interviewed were drillers, riveters, concrete packers, boilermakers, riggers, ironworkers, plasterers, stonemasons, an official photographer, sleepcutters, engineers and draughtsmen. The total financial cost of the bridge was AU£6.25


title: "Sydney Harbour Bridge" content: million, which was not paid off in full until 1988. The bridge was formally opened on Saturday, 19 March 1932. Amongst those who attended and gave speeches were the Governor of New South Wales, Sir Philip Game, and the Minister for Public Works, Lawrence Ennis. The Premier of New South Wales, Jack Lang, was to open the bridge by cutting a ribbon at its southern end. However, just as Lang was about to cut the ribbon, a man in military uniform rode up on a horse, slashing the ribbon with his sword and opening the Sydney Harbour Bridge in the


title: "Sydney Harbour Bridge" content: name of the people of New South Wales before the official ceremony began. He was promptly arrested. The ribbon was hurriedly retied and Lang performed the official opening ceremony and Game thereafter inaugurated the name of the bridge as 'Sydney Harbour Bridge' and the associated roadway as the 'Bradfield Highway'. After they did so, there was a 21-gun salute and an RAAF flypast. The intruder was identified as Francis de Groot. He was convicted of offensive behaviour and fined £5 after a psychiatric test proved he was sane, but this verdict was reversed on appeal. De Groot then successfully sued


title: "Sydney Harbour Bridge" content: the Commissioner of Police for wrongful arrest, and was awarded an undisclosed out of court settlement. De Groot was a member of a right-wing paramilitary group called the New Guard, opposed to Lang's leftist policies and resentful of the fact that a member of the Royal Family had not been asked to open the bridge. De Groot was not a member of the regular army but his uniform allowed him to blend in with the real cavalry. This incident was one of several involving Lang and the New Guard during that year. A similar ribbon-cutting ceremony on the bridge's northern


title: "Sydney Harbour Bridge" content: side by North Sydney's mayor, Alderman Primrose, was carried out without incident. It was later discovered that Primrose was also a New Guard member but his role in and knowledge of the de Groot incident, if any, are unclear. The pair of golden scissors used in the ribbon cutting ceremonies on both sides of the bridge was also used to cut the ribbon at the dedication of the Bayonne Bridge, which had opened between Bayonne, New Jersey, and New York City the year before. Despite the bridge opening in the midst of the Great Depression, opening celebrations were organised by


title: "Sydney Harbour Bridge" content: the Citizens of Sydney Organising Committee, an influential body of prominent men and politicians that formed in 1931 under the chairmanship of the Lord Mayor to oversee the festivities. The celebrations included an array of decorated floats, a procession of passenger ships sailing below the bridge, and a Venetian Carnival. A message from a primary school in Tottenham, away in rural New South Wales, arrived at the bridge on the day and was presented at the opening ceremony. It had been carried all the way from Tottenham to the bridge by relays of school children, with the final relay being


title: "Sydney Harbour Bridge" content: run by two children from the nearby Fort Street Boys' and Girls' schools. After the official ceremonies, the public was allowed to walk across the bridge on the deck, something that would not be repeated until the 50th anniversary celebrations. Estimates suggest that between 300,000 and one million people took part in the opening festivities, a phenomenal number given that the entire population of Sydney at the time was estimated to be 1,256,000. There had also been numerous preparatory arrangements. On 14 March 1932, three postage stamps were issued to commemorate the imminent opening of the bridge. Several songs were


title: "Sydney Harbour Bridge" content: composed for the occasion. The bridge itself was regarded as a triumph over Depression times, earning the nickname "the Iron Lung", as it kept many Depression-era workers employed. In 2010, the average daily traffic included 204 trains, 160,435 vehicles and 1650 bicycles. From the Sydney CBD side, motor vehicle access to the bridge is normally via Grosvenor Street, Clarence Street, Kent Street, the Cahill Expressway, or the Western Distributor. Drivers on the northern side will find themselves on the Warringah Freeway, though it is easy to turn off the freeway to drive westwards into North Sydney or eastwards to Neutral


title: "Sydney Harbour Bridge" content: Bay and beyond upon arrival on the northern side. The bridge originally only had four wider traffic lanes occupying the central space which now has six, as photos taken soon after the opening clearly show. In 1958 tram services across the bridge were withdrawn and the tracks replaced by two extra road lanes; these lanes are now the leftmost southbound lanes on the bridge and are still clearly distinguishable from the other six road lanes. Lanes 7 and 8 now connect the bridge to the elevated Cahill Expressway that carries traffic to the Eastern Distributor. In 1988, work began to


title: "Sydney Harbour Bridge" content: build a tunnel to complement the bridge. It was determined that the bridge could no longer support the increased traffic flow of the 1980s. The Sydney Harbour Tunnel was completed in August 1992 and carries only motor vehicles. The Bradfield Highway is designated as a Travelling Stock Route which means that it is permissible to herd livestock across the bridge, but only between midnight and dawn, and after giving notice of intention to do so. In practice, owing to the high-density urban nature of modern Sydney, and the relocation of abattoirs and markets, this has not taken place for approximately


title: "Sydney Harbour Bridge" content: half a century. The bridge is equipped for tidal flow operation, permitting the direction of traffic flow on the bridge to be altered to better suit the morning and evening rush hours' traffic patterns. The bridge has eight lanes in total, numbered one to eight from west to east. Lanes three, four and five are reversible. One and two always flow north. Six, seven, and eight always flow south. The default is four each way. For the morning rush hour, the lane changes on the bridge also require changes to the Warringah Freeway, with its inner western reversible carriageway directing


title: "Sydney Harbour Bridge" content: traffic to the bridge lane numbers three and four southbound. The bridge has a series of overhead gantries which indicate the direction of flow for each traffic lane. A green arrow pointing down to a traffic lane means the lane is open. A flashing red "X" indicates the lane is closing, but is not yet in use for traffic travelling in the other direction. A static red "X" means the lane is in use for oncoming traffic. This arrangement was introduced in the 1990s, replacing a slow operation where lane markers were manually moved to mark the centre median. It


title: "Sydney Harbour Bridge" content: is possible to see odd arrangements of flow during night periods when maintenance occurs, which may involve completely closing some lanes. Normally this is done between midnight and dawn, because of the enormous traffic demands placed on the bridge outside these hours. The vehicular traffic lanes on the bridge are operated as a toll road. As of 27 January 2009 there is a variable tolling system for all vehicles headed into the CBD (southbound). The toll paid is dependent on the time of day in which the vehicle passes through the toll plaza. The toll varies from a minimum value


title: "Sydney Harbour Bridge" content: of $2.50 to a maximum value of $4. There is no toll for northbound traffic (though taxis travelling north may charge passengers the toll in anticipation of the toll the taxi must pay on the return journey). In 2017, the Bradfield Highway northern toll plaza infrastructure was removed and replaced with new overhead gantries to service all southbound traffic. And following on from this upgrade, in 2018 all southern toll plaza infrastructure was also removed. Only the Cahill Expressway toll plaza infrastructure remains. The toll was originally placed on travel across the bridge, in both directions, to recoup the cost


title: "Sydney Harbour Bridge" content: of its construction. This cost was recovered in the 1980s, but the toll has been kept (indeed increased) by the state government's Roads and Traffic Authority to recoup the costs of the Sydney Harbour Tunnel. After the decision to build the Sydney Harbour Tunnel was made in the early 1980s, the toll was increased (from 20 cents to $1, then to $1.50, and finally to $2 by the time the tunnel opened) to pay for its construction. The tunnel also had an initial toll of $2 southbound. After the increase to $1, the concrete barrier on the bridge separating the


title: "Sydney Harbour Bridge" content: Bradfield Highway from the Cahill Expressway was increased in height, because of the large numbers of drivers crossing it illegally from lane 6 to 7, to avoid the toll. The toll for all southbound vehicles was increased to $3 in March 2004. Originally it cost a car or motorcycle six pence to cross, a horse and rider being three pence. Use of the bridge by bicycle riders (provided that they use the cycleway) and by pedestrians is free. Later governments capped the fee for motorcycles at one-quarter of the passenger-vehicle cost, but now it is again the same as the


title: "Sydney Harbour Bridge" content: cost for a passenger vehicle, although quarterly flat-fee passes are available which are much cheaper for frequent users. In July 2008 a new electronic tolling system called e-TAG was introduced. The Sydney Harbour Tunnel was converted to this new tolling system while the Sydney Harbour Bridge itself had several cash lanes. The electronic system as of 12 January 2009 has now replaced all booths with E-tag lanes. In January 2017 work commenced to remove the southern toll booths. The pedestrian-only footway is located on the east side of the bridge. Access from the northern side involves climbing an easily spotted


title: "Sydney Harbour Bridge" content: flight of stairs, located on the east side of the bridge at Broughton St, Kirribilli. Pedestrian access on the southern side is more complicated, but signposts in the Rocks area now direct pedestrians to the long and sheltered flight of stairs that leads to the bridge's southern end. These stairs are located near Gloucester Street and Cumberland Street. The bridge can also be approached from the south by accessing Cahill Walk, which runs along the Cahill Expressway. Pedestrians can access this walkway from the east end of Circular Quay by a flight of stairs or a lift. Alternatively it can


title: "Sydney Harbour Bridge" content: be accessed from the Botanic Gardens. The bike-only cycleway is located on the western side of the bridge. Access from the northern side involves carrying or pushing a bicycle up a staircase, consisting of 55 steps, located on the western side of the bridge at Burton St, Milsons Point. A wide smooth concrete strip in the centre of the stairs permits cycles to be wheeled up and down from the bridge deck whilst the rider is dismounted. A campaign to eliminate the steps on this popular cycling route to the CBD has been running since at least 2008. On 7


title: "Sydney Harbour Bridge" content: December 2016 the NSW Roads Minister Duncan Gay confirmed that the northern stairway would be replaced with a 20 million ramp alleviating the needs for cyclists to dismount. At the same time the NSW Government announced plans to upgrade the southern ramp at a projected cost of 20 million. Both projects are expected to completed by late 2020. Access to the cycleway on the southern side is via the northern end of the Kent Street cycleway and/or Upper Fort Street in The Rocks. The bridge lies between Milsons Point and Wynyard railway stations, located on the north and south shores


title: "Sydney Harbour Bridge" content: respectively, with two tracks running along the western side of the bridge. These tracks are part of the North Shore railway line. In 1958 tram services across the bridge were withdrawn and the tracks they had used were removed and replaced by two extra road lanes; these lanes are now the leftmost southbound lanes on the bridge and are still clearly distinguishable from the other six road lanes. The original ramp that took the trams into their terminus at the underground Wynyard railway station is still visible at the southern end of the main walkway under lanes 7 and 8,


title: "Sydney Harbour Bridge" content: although around 1964, the former tram tunnels and station were converted for use as a carpark for the Menzies Hotel and as public parking. One of the tunnels was converted for use as a storage facility after reportedly being used by the NSW police as a pistol firing range. The Sydney Harbour Bridge requires constant inspections and other maintenance work to keep it safe for the public, and to protect from corrosion. Among the trades employed on the bridge are painters, ironworkers, boilermakers, fitters, electricians, plasterers, carpenters, plumbers, and riggers. The most noticeable maintenance work on the bridge involves painting.


title: "Sydney Harbour Bridge" content: The steelwork of the bridge that needs to be painted is a combined , the equivalent of sixty football fields. Each coat on the bridge requires some of paint. A special fast-drying paint is used, so that any paint drops have dried before reaching the vehicles or bridge surface. One notable identity from previous bridge-painting crews is Australian comedian and actor Paul Hogan, who worked as a bridge painter before rising to media fame in the 1970s. In 2003 the Roads & Traffic Authority began completely repainting the southern approach spans of the bridge. This involved removing the old lead-based


title: "Sydney Harbour Bridge" content: paint, and repainting the of steel below the deck. Workers operated from self-contained platforms below the deck, with each platform having an air extraction system to filter airborne particles. An abrasive blasting was used, with the lead waste collected and safely removed from the site for disposal. Between December 2006 and March 2010 the bridge was subject to works designed to ensure its longevity. The work included some strengthening. Since 2013, two grit-blasting robots specially developed with the University of Technology, Sydney have been employed to help with the paint stripping operation on the bridge. The robots, nicknamed Rosie and


title: "Sydney Harbour Bridge" content: Sandy, are intended to reduce workers' potential exposure to dangerous lead paint and asbestos and the blasting equipment which has enough force to cut through clothes and skin. Even during its construction, the bridge was such a prominent feature of Sydney that it would attract tourist interest. One of the ongoing tourist attractions of the bridge has been the south-east pylon, which is accessed via the pedestrian walkway across the bridge, and then a climb to the top of the pylon of about 200 steps. Not long after the bridge's opening, commencing in 1934, Archer Whitford first converted this pylon


title: "Sydney Harbour Bridge" content: into a tourist destination. He installed a number of attractions, including a café, a camera obscura, an Aboriginal museum, a "Mother's Nook" where visitors could write letters, and a "pashometer". The main attraction was the viewing platform, where "charming attendants" assisted visitors to use the telescopes available, and a copper cladding (still present) over the granite guard rails identified the suburbs and landmarks of Sydney at the time. The outbreak of World War II in 1939 saw tourist activities on the bridge cease, as the military took over the four pylons and modified them to include parapets and anti-aircraft guns.