This year will see both the end of space flights by NASA’s Shuttle fleet and the thirtieth anniversary of the first orbital mission by this historic spacecraft. Our coverage of these milestones begins with an overview of the project’s chequered history.
In the glory days of the Space Race, the public avidly followed the exploits of astronauts. Heroic rocket jockeys were strapped into tiny capsules mounted on rockets, often converted nuclear missiles, and blasted into the wild blue yonder on live TV. Things were different in the early 1970s; through hard work, brains and guts NASA astronauts were walking on the moon in what seemed like an effortless Space Race victory yet nobody cared. NASA’s budget was savagely cut down and earlier and costly plans forbases on the Moon and flights to Mars were shelved. The space programme was going into terminal decline.
Management at NASA saw a way forward. Satellites were proving vital for all manner of tasks, from predicting the weather to relaying TV around the world. It was very expensive to place a satellite into orbit as their launch vehicles, expensively crafted rockets, were thrown away in the course of each flight. Imagine how expensive air travel would be if the whole airliner was thrown away after its first landing! What if a reusable vehicle for carrying cargoes to orbit could be developed? It could fly into space many times, massively cutting costs in the process. Once established, these craft would be shuttling between Earth and space several times per month, and would open a much wider range of possible space projects, including giant space telescopes, space stations, moonbases and Mars landings. Within a couple of decades, a flight to low earth orbit by Shuttle would cost much the same as a first-class ticket on a transatlantic flight
In 1969 NASA asked four industrial contractors to supply concepts for a Space Transportation System or Space Shuttle (note that this never received a proper name from mythology like the preceding Mercury, Gemini and Apollo projects: NASA wanted to show that this was a hard-headed piece of necessary infrastructure, not some flight of fancy). Money was tight and this forced compromises with effects which had lasting effects. Early shuttle concepts were completely reusable, two similarly-shaped but differently-sized winged craft would have been launched connected together piggy-back fashion. Each would have been piloted by astronauts. The larger one, the booster (about the size of a Boeing 747) would have carried the smaller orbiter halfway to orbit before separating to fly home for a runway landing. Although potentially very economical to run, this concept was unaffordable with the development budget at hand. A complete Space Shuttle as eventually developed comprises four components, a large disposable (but cheap) External Tank (ET) for propellants, two reusable Solid Rocket Boosters (SRBs) and the aeroplane-like Orbiter.
At launch the shuttle Orbiter is attached to the 47m (154 ft) tank which carries 720 tonnes of liquid hydrogen and oxygen for the three main engines at the rear of the Orbiter. These fuels must be kept very cold so the tank is coated in a 2.5 cm (1 inch) thick coat of spray-on foam insulation. Unbelievably use of this this foam later led to the Columbia tragedy. The Orbiter’s engines are not sufficient to push the craft into orbit, so two 45m (147 ft) long solid-fuel rocket boosters are attached to the side of the tank.
All shuttle missions are launched from the Kennedy Space Center in Florida. There are two Shuttle launch pads, Complex 39A and 39B, built originally for the Apollo Moon missions. At launch the 4.5 million lb (2040 tonne) spacecraft rises skyward on seven million lb (31MN) of rocket thrust. Two minutes after launch, the SRBs are discarded at an altitude of 45 km, descending under parachutes to the sea to be recovered and reused. The ET is discarded about 70 miles (113 km) above the Earth, falling on a planned trajectory to a fiery fate. Within 8 minutes from take-off, the Orbiter has reached its orbital speed of 17 500 mph (7.8 km/s).
Approved in 1972, the project initially made rapid progress. On 17 September 1976, NASA’s first Space Shuttle Orbiter was unveiled to the public. Originally to be named Constitution, when the gleaming white spaceplane was rolled out of the hangar it bore the name Enterprise on its wings and side. This was the result of a campaign by Star Trek fans to bombard the White House with letters demanding the name change. Actors Deforest Kelly, George Takei, James Doohan, Nichelle Nichols and Leonard Nimoy plus Star Trek creator Gene Rodenberry were among the VIPs in the crowd.
When rolled out, Enterprise was not fitted with engines or Thermal Protection System (TPS) tiles as they were not ready yet. Both TPS and Space Shuttle Main Engine (SSME) proved more difficult to develop and maintain than anyone expected. The SSME design still represents the pinnacle of liquid fuelled rocket engine technology. There have been bigger engines of higher thrust (the Saturn 5’s F1 comes to mind) but for its weight, the SSME’s performance is superlative. Most importantly, every other rocket engine is designed to be used once and discarded. The SSME is the only large liquid fuel motor that can be used over and over again. Sadly this reusability relies on extensive and costly technical support. Each engine (originally intended to fly ten times before major servicing) must be disassembled and rebuilt after every mission. This is so costly that it would probably be cheaper to discard the engine after every flight. Then there were the infamous tiles. Each Shuttle Orbiter is protected during re-entry to Earth’s atmosphere (when its skin temperature can exceed 1250° C) by typically 21 801 heat-resistant tiles and 1977 thermal blankets. Each tile is unique and identified by number. During the Shuttle’s development process these displayed an embarrassing tendency to fall off the craft’s airframe.
Enterprise was used for many tests including a series of gliding flights. Originally when this testing was complete, Enterprise was to be made space-worthy and flown along side her sister ships. However so much was learned while Enterprise was being built, that the other later Orbiters were very different in detail. Upgrading Enterprise to the same standard was too difficult so Enterprise never flew into space. The project used a lot of new technology, and developing the TPS and Shuttle Main Engines took longer than expected. The first Shuttle flight was pencilled in for 1979 but this was delayed by nagging technical faults.
Columbia was successfully launched for the first time on 12 April 1981 from the Kennedy Space Center in Florida. This was the first Shuttle flight into space and the first American manned spaceflight in nearly six years. It was also the 20th anniversary of Yuri Gagarin’s flight. Columbia’s crew was veteran astronaut John Young (one of the twelve men to have walked on the Moon) and space-newbie Bob Crippen. After orbiting the Earth 36 times, Columbia made a triumphant return on 14 April landing on the dry lakebed runway at Edwards Air Force Base in California.
Columbia’s successful maiden flight was followed by more missions. Three more Orbiters, Challenger, Discovery and Atlantis, joined the fleet. Everything looked rosy. Shuttle flights quickly became routine with nine missions in 1985. The Shuttle competed with Europe’s Ariane launch vehicle to deploy satellites for private companies. NASA was so confident in their new spacecraft’s reliability that VIPs were allowed to fly in ‘spare’ seats on missions, an extreme case of political junketing. These worthies included US senators Jake Garn and Bill Nelson and a Saudi price, Sultan bin Salman bin Abdulaziz Al Saud. Astronauts from Canada and various European Space Agency nations worked on board Shuttle missions. To encourage students to study science, school teachers were selected to fly on some missions, they would broadcast live science lessons from space.
On 28 January 1986, Challenger was ripped apart 73 seconds into its flight, leading to the deaths of its seven crew members. Investigators discovered that a seal between joints in its right SRB failed, causing a blowtorch-like jet of white hot gas from inside the booster’s rocket motor to cut through the connector linking it to the External Tank and even into the tank itself. The ET broke apart, causing a catastrophic structural failure of the whole vehicle. The crew, the first US astronauts to perish on a mission, were Michael J. Smith, Dick Scobee, Ronald McNair, Ellison Onizuka, Christa McAuliffe, Gregory Jarvis and Judith Resnik.
Making the loss even more poignant was the sad fact that Christa McAuliffe was the first teacher to be part of a Shuttle crew. Thousands of students witnessed the loss of Challenger as the launch was being shown live in classrooms across the US.
After the Challenger disaster, it was two and a half years before the next Shuttle mission. NASA had been harshly but fairly criticised for a corner-cutting and reckless safety culture by the investigation into the accident. A new and more serious atmosphere was established. There would be no more commercial satellite launches, teachers in space or joyrides for politicians.
A new Orbiter, Endeavour, was constructed to replace Challenger. For it and the other surviving Orbiters, the period between the losses of Challenger and Columbia was the most productive time of the Shuttle era. The Shuttle fleet sent probes into interplanetary space and deployed science satellites. Shuttles were used as ‘mini-space stations’ for weeks at a time when the European Spacelab (or the very similar US Spacehab) was installed in the cavernous cargo bay. Eventually the Orbiters began to visit a destination unthinkable just a few years earlier. US astronauts were invited to live and work on the Russian Mir space station, and the Shuttles carried crews and cargo to and from the pioneering orbital habitat.
Some of the notable spacecraft carried into space by Space Shuttles are the Magellan Venus probe, the Galileo Jupiter probe and the Chandra X-ray observatory. Most famous of all Shuttle payloads is the amazing Hubble Space Telescope (HST). The Shuttle turned out to be vital for this important science mission. The ability to service it in orbit by spacewalking astronauts made it possible to rectify the infamous manufacturing fault which made the HST virtually useless. Just think of all the classic Hubble images of the wonders of the Universe we would have missed out on without the Shuttle!
In 1998, Endeavour carried the first US module to the International Space Station (ISS). In a venture straight from science fiction, this was the first of dozens of flights to add components to the eventually vast complex.
On its 28th mission in January 2003, Columbia was destroyed during re-entry. The crew (Rick D. Husband, William C. McCool, David Brown, Laurel Blair Salton Clark, Michael P. Anderson, Ilan Ramon, and Kalpana Chawla) all perished. An investigation determined that a suitcase-sized chunk of insulating foam had been torn off the ET 82 seconds after take-off and struck the Orbiter, damaging the heat shielding. This disaster led to much stricter safety rules for Shuttle missions and the decision to retire the surviving Orbiters as soon as it was practical to do so. After the Columbia disaster, ISS assembly and servicing missions became the Shuttle’s main raison d’etre.
Unless something unexpected happens, the Space Shuttle project will end with the final flight of Atlantis in the summer. This will be the last flight of an American manned spacecraft for some years. Until a new spacecraft is put in service (and it is not yet clear what this will be, SpaceX’s Dragon capsule is the most likely candidate), NASA astronauts will travel as passengers on Russian Soyuz vehicles. The Shuttle program never lived up to the hopes that it would make spaceflight more affordable. In hindsight the NASA engineers were naive to think making a spaceship in the shape of an aeroplane would automatically lead to airliner running costs.
It is true that the Space shuttle did not revolutionize access to space as originally hoped. However people have predicted personal jetpacks or flying cars for years and we don’t have those yet either. In its thirty year history, the Shuttle fleet has still made many landmark missions. More people have flown into space on the Shuttle than any other vehicle. Vital lessons have been learned into how a space program should (and sometimes not) be run during the Shuttle experience. Space Shuttle achievements include many science missions, servicing of Mir and the assembly of the ISS and launching and repairing many satellites.
One day travel into orbit will be as routine as air travel but that day still lies in the unforeseen future. The Shuttle will then remembered as an important pioneer from the heroic first days of space exploration.
(Article by Colin Johnston, Science Communicator)