The space shuttle's history in pictures

Nasa is approaching the end of an era with the retirement of the space shuttle.

The oldest craft in the fleet, Discovery, completed its final voyage in March, while Endeavour finished its career in April. The launch of Atlantis on Friday marks the 135th and final space shuttle mission.

For more than 30 years the space shuttle has been the workhorse of Nasa, carrying hundreds of astronauts into space, launching numerous satellites and helping to construct the International Space Station. Pictured above is Challenger in orbit in 1983.

The space shuttle's story began in 1969, months after the moon landing, when US officials began putting thought into a reusable spacecraft that would replace the Saturn rockets that had powered the Apollo missions.

Following on from designs tested by Nasa throughout the 1950s and 60s, the space shuttle had evolved by 1972 into an orbiter craft that was carried into space on rockets and returned to Earth unpowered, landing like a conventional glider — albeit one that weighs over 100 tons.

Above, the orbiter prototype Enterprise separates from the 747 shuttle carrier aircraft for its first flight without a protective tail cone, in 1977.

The prototype space shuttle was named after the USS Enterprise in Star Trek, following a letter-writing campaign by the TV show's fans.

Enterprise conducted numerous flight tests in the atmosphere in 1977, but was not equipped with engines or a heat shield, and was never intended to be sent into space.

It is currently on display at the Steven F Udvar-Hazy Center at Dulles Airport in Virginia.

Above, Columbia sits on the launch pad for the first shuttle flight into space on 12 April, 1981. John W Young and Robert L Crippen flew the shuttle into orbit for a two-day mission to test the orbiter's functionality.

The orbiter measures 78 feet in width and 122 feet in length, of which nearly half is the cargo bay.

The two narrow rockets on the side of the shuttle's body are solid-propellant rockets, a major innovation for the shuttle programme. Together they provide over 80 percent of the lift-off thrust. These rockets fall to Earth after two minutes, after which they are recovered from the sea, refurbished and reused for later missions.

The final component of the space shuttle design is the external booster tank, which provides fuel for the orbiter's three engines during launch. Around eight and a half minutes after blast-off, the external tank is jettisoned into the sea. It is the only component of the launch system not reused.

The external tank is usually orange; on the first two shuttle flights it was painted white as a precaution to help radiate heat. Nasa engineers later decided this was unnecessary. 

Discovery arcs into the sky after launching on a mission in 2009.

All shuttle missions launch from the Kennedy Space Center in Florida. Until 2007, Nasa avoided launching the craft in December-January time as it was feared its 1970s-era computers might suffer a glitch on New Year's Eve that would set the ship's clock back to zero.

On launch, the shuttle must hit a speed of almost 28,968 kph. After eight seconds, the craft is travelling at just 259kph; by the 60-second mark, it is speeding at 1,609kph. By the time the external tank has dropped away, the shuttle has burned more than 1.59 million kg of fuel. Once in orbit, it has a velocity of 17,500mph, making it the fastest winged vehicle in history.

Steven Lindsey, commander of Discovery's last mission, highlighted the shuttle's adaptability in an interview with CBS News. "It can't leave low Earth orbit, but it can do everything else," he said.

His opinions were echoed by Atlantis astronaut Sandra Magnus before the final mission. "It built the space station, it's done science missions that ranged from taking the Spacelab up, to the big radar missions we've done, it's done astronomy, it's done biological science, materials science and then it's done satellite deploy, repair and retrieve," she said. "It's an incredible legacy this vehicle has given us."

The shuttle features four onboard computers running the same software on different hardware, which together check each other's work. A fifth backup computer runs an entirely separate system in the event the other four fail.

In 1990, Nasa upgraded the computers, raising the memory 2.5 times to 1MB.

From 1999, 'glass cockpit' technology was added to the orbiters, providing more up-to-date display screens on the flight deck.

Discovery glides to a landing at Edwards Air Force base in 2008. 

The shuttle typically begins its return flight around half the world away from its landing site. It angles its nose up at 40 degrees, allowing the black tiling underneath to bear the brunt of the 1,600° C heat of re-entry.

When the craft drops below the speed of sound, at around 50,000 feet, the commander takes control. Despite the similarity of its shape to an ordinary aircraft, the shuttle makes its final approach to the runway 20 times faster than the average plane.

The shuttle was originally intended to have air-breathing jet engines to allow it to fly as an aircraft on re-entry; however, cost and weight considerations left it entirely unpowered during the descent, making it the heaviest and fastest glider in history.

On 28 January, 1986, Challenger exploded 73 seconds after launch at an altitude of nine miles. All six astronauts on board perished, including Christa McAuliffe, a teacher who had won a much-published competition to go into space.

The tragedy was blamed on the failure of an O-ring joint on one of the solid-fuel booster rockets, partly due to extremely cold weather conditions in Florida.

As a result of the inquiry that followed, Nasa tightened up safety procedures and the cost of shuttle missions soared, eradicating the notion of the space shuttle programme as a cost-effective route into space.

Nasa returned to space 32 months later with Discovery's Return to Flight mission, having made more than 400 changes to its orbiters and rockets.

A replacement shuttle, Endeavour, was commissioned in 1987 and made its first flight in 1992. 

The first American woman in space was Sally Ride on Challenger in 1983 (she flew on the same orbiter again in 1984).

In 1995, Eileen Collins became the first woman to pilot a space shuttle, on Discovery. She became the first female mission commander in 1999, on Columbia.

Senator John Glenn became the oldest man to go into space when he flew on Discovery in 1998 at the age of 77. In 1962, Glenn became the first American to orbit the Earth. 

The space shuttle programme completed nine dockings with the Russian space station Mir. It has docked with the International Space Station 36 times, prior to its final mission.

Excluding Atlantis's final flight, the programme has carried 355 individuals into space. It has racked up 20,830 orbits and 1,310 days of flight time.

On 1 February, 2003, Columbia was destroyed on re-entry during mission STS-107, resulting in the death of all seven crewmembers. A suitcase-sized block of insulating foam from the external tank had broken off during launch and punched a hole in the tiles on one wing, rendering it vulnerable to the super-heated gases of re-entry.

Pictured above, officials comb through the retrieved wreckage of Columbia.

The disaster spelled the beginning of the end of the shuttle programme. Discovery once again carried out the Return to Flight mission in 2005, but the programme was due to be wrapped up by 2010 (later extended to 2011), as Nasa cast about for new ways of travelling into space.

Critics of the shuttle said the design had been flawed from the very beginning. "The shuttle made America dependent on a fragile, expensive, risky launch system," space policy expert professor John Logsdon said in a Guardian interview. Logsdon noted that its design was influenced by the US Air Force, which insisted that the shuttle be able to fly at angle that would allow it to release spy satellites. While this never happened in practice, the shuttle was lumbered with a heavier heat shield than it needed.

As early as 1993, a Nasa report recommended replacing the already out-dated system by 2000. "The United States has advanced multiple proposals since at least the mid-1980s to build a space shuttle follow-on that would be less expensive and safer to operate," Nasa's chief historian, Roger Launius, wrote on his blog. "At the same time, the target date for space shuttle replacement shifted further into the future over the years." 

In 2004, then-President Bush announced the Constellation programme would develop new technology to replace the space shuttle. Budget overruns led to the project being cancelled by President Obama in 2010.

Some of Constellation's technology has, however, found its way into the Multi-Purpose Crew Vehicle, intended for journeys into deep space.

Concerns about the cost and purpose of manned spaceflight cloud Nasa's future. "There is every reason to believe that future human spaceflight vehicles will require an investment beyond the level normally granted to Nasa's programmes," said Roger Launius, citing a figure of around $240bn (£150bn).

Nasa continues to explore the idea of partnering with private companies to develop commercial manned spacecraft technology. In April, it advanced funding of $270m to four projects that could lead to working space taxis by 2015.

"I just don't know if we have that audacity now to build something nearly as ambitious as the shuttle," said astronaut Alvin Drew, following Discovery's last mission.

The space shuttle Discovery will be displayed near Washington at the Smithsonian National Air and Space Museum's Steven F Udvar-Hazy Center. Atlantis will remain at the Kennedy Space Center visitors' complex, while the Endeavour will be displayed at the California Science Center in Los Angeles.

The little-known Buran shuttle was the Russian equivalent of the US space shuttle. 

It began development in 1974 and was suspended in 1993, having made just one test flight in 1988, when it completed two orbits of the Earth with two cosmonauts on board.

Funding issues and the collapse of the Soviet Union put paid to the Buran project. The orbiter was retired to a hangar in Kazakhstan, where it was destroyed by a roof collapse in 2002.

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