April 2011 marked 30 years since NASA’s main spacecraft’s first mission. July 2011 marked its retirement. Take a look at this marvelous space machine and discover how it works.
In January 1972, the US president Richard Nixon announced a plan to create the first reusable spacecraft. Ten years later, on the 20th anniversary of the first human space flight, NASA had its first successful mission with the orbiter Columbia. This flight demonstrated that the space transportation system (STS) was viable. The space transportation system was designed by Maxime Faget, the same American engineer who designed all of NASA’s previous spacecraft systems. Since then the program had 135 launches, experiencing some significant successes, not to mention some devastating losses and setbacks.
Although we think of the winged, plane-like spacecraft as the shuttle, it is actually the orbiting part of the entire space shuttle system. The spacecraft’s design came about in part because of the need for a large payload capacity, from which satellites could be deployed. Its unique design means that it launches and flies like a rocket, but lands like a plane. The orbiter and solid rocket boosters are recovered and reused, making it more efficient than the previous spacecraft systems.
Originally the first orbiter was going to be named the Constitution, but fans of the cult television show Star Trek staged a write-in campaign and convinced NASA to change its name to that of the sci-fi show’s spaceship, the Enterprise. This orbiter was not designed to fly into space, but NASA intended to upgrade it to do so as needed after testing. However, enough significant design changes were made between test flights and the first fully functional launch to require the building of a new orbiter, the Columbia. The Enterprise is still on display at the United States National Air and Space Museum in Washington DC.
NASA’s space shuttle programme ended in July 2011. Potential replacement spacecraft, such as NASA’s Orion, are in progress with targets of completing a lunar mission by the early-2020s. However, with funding always a concern, there could still be a gap of several years before the US is fully re-engaged in space travel and exploration.
The shuttle’s main parts
At launch, the space shuttle system, or ‘stack’ comprises three main components: a black-and-white orbital vehicle (OV) containing payload and crew, as well as the space shuttle main engines (SSMEs) and orbital manoeuvring engines (OMEs), two white solid rocket boosters (SRBs) and an orange external tank (ET) carrying liquid fuel oxidizer and liquid hydrogen.
Orbiter – The orbiter is the only part of the space shuttle system that actually goesintospace.lt transports a crew of up to seven astronauts as well as payloads, including satellites, ISS components and experiments.
Fuel tank – The external fuel tank stores fuel for the orbiter’s main engines. It contains more than 700,000 kilograms of liquid oxygen and liquid hydrogen, separated into two separate tanks. The tank is insulated with foam to shield the fuels from heat.
Rocket boosters – The solid rocket boosters provide nearly 75 per cent of the thrust required to lift the rest of the shuttle system off the launch pad. They have a jointed structure and contain solid rocket fuel, a catalyst, instruments, a parachute and explosive charges.
Crawler transporters – NASA uses these tracked vehicles to move the space shuttle from the assembly building to the shuttle launch pad. They travel on a special pathway called the ‘crawlerway’ and have been in use since 1965. Each crawler transporter weighs nearly 3,000 tons.
Launching the space shuttle
The space shuttle launch is a multi-step process that begins on the launch pad at the Kennedy Space Center in Cape Canaveral, Florida
The first step of the launch is controlled by computers on the orbiter. They ignite the space shuttle main engines (SSME) one at a time, then fire the solid rocket boosters (SRB). As the shuttle begins its ascent, it rolls 180” to the right. Once the shuttle reaches about 45km (28 miles), the SRBs then separate. They deploy parachutes and fall into the ocean for retrieval by ships. The space shuttle continues travelling horizontally towards Earth orbit.
About five minutes into the flight, the SSMEs are turned off and the external tank is released. It typically burns up upon re-entry into the atmosphere, although small pieces may reach the ocean. Then the shuttle fires its orbital manoeuvring engines (OMEs) to orient it vertically and provide the final push into low Earth orbit. They fire again to get into orbit 400km (250 miles) above the Earth. The orbiter typically flies upside down and nose first.
Before the orbiter can land, its crew must perform several operations for a safe and smooth re-entry!
When the orbiter ends a mission, the first step is to close the payload bay doors. Then the RCS thrusters are fired to turn the orbiter so that it is tail first. The pilot slows the orbiter down by firing the OMEs, then fires more RCS thrusters to orient it in a nose-first position with its underside facing the atmosphere at an attitude of 40”. The forward RCS thrusters are fired to burn off any excess fuel, since the front of the orbiter encounters the most heat.
Once it is inside Earth’s atmosphere, the orbiter flies like an aeroplane via computer controls, making S-shaped turns to help slow it down as it approaches the runway. When the orbiter is about 40 kilometres (25 miles) from the runway and 600 metres (2,000ft) from the ground, the commander lines it up and pulls up the nose. He deploys the landing gear and a parachute to cause drag and eventually stop the orbiter.