Shuttle hardware

The orbiter is the key part of the Space Shuttle system. It is ingeniously designed to be part rocket, part spacecraft and part aircraft, and it performs all these functions well. A fleet of four orbiters was originally planned: Columbia, Challenger, Discovery and Atlantis.

On making its second flight into orbit in November 1981, Columbia became the first launch vehicle ever to return to space. Challenger met a tragic end on its tenth flight in January 1986, when it exploded 73 seconds after lift-off, killing its crew of seven. Shuttle operations were suspended until September 1988 to allow modifications of the hardware and of management procedures to take place. A replacement orbiter, Endeavour, was commissioned for operation in 1993.

The crew of up to seven ride in the forward fuselage of the orbiter, pressurized with air at normal pressure. Two astronauts fly the craft from a cockpit at the front of the upper deck . The cockpit looks much like that of a modern airliner, but has more switches, instruments and controls. It also incorporates three video display units connecting with the orbiter's powerful computer system.

A close-up of the instrument console in the cockpit of the Space Shuttle orbiter,(left) showing the three cathode-ray tube displays. They are tied into the powerful computer system that operates the orbiter. The pilot and commander can call up all kinds of data on to the screens via computer keyboards.

The orbiter carries its payload (cargo) in the huge payload bay, which measures 18 m long and 4.5 m across. Because it is so large, the bay can accommodate two or more satellites at the same time. On some missions it carries a single large payload, such as the European-built Spacelab, a fully equipped scientific laboratory. Around the major payloads, the bay also has room for so-called Getaway Specials. These are experiments by small research teams that can "hitch a ride" into space at low cost.

The tail pod houses the three main engines and the two engines of the orbital manoeuvring system (OMS). The OMS engines fire to inject the orbiter into orbit and to brake the craft prior to re-entry. The pod also carries sets of thrusters for the reaction control system (RCS), by which the pilots can change the position, or attitude, of the craft in space.

To prevent the aluminium airframe of the orbiter overheating when re-entering the atmosphere, it is covered with insulation. Much of the orbiter is covered with a layer of ceramic tiles made of silica. Over 30,000 tiles are required, each one individually tailored for a particular location. On the nose and wing edges, where temperature can soar to over 1,500'C, a carbon refractory material is used.

click to enlarge A replacement main engine being manoeuvred into position in the tail pod of orbiter Discovery in preparation for Space Shuttle mission STS-26. The mission, which eventually took place in September 1988, was the first since Challenger exploded in the Florida skies just after 1ift-off on 28 January 1986. That tragedy, in which seven astronauts died, forced a complete rethink of Shuttle design and operational procedures to ensure greater safety in the future.

The delta-winged Space Shuttle arbiter is about the size of a medium-sized airliner, with a length of 37m and a wingspan of nearly 24 m. On the launch pad it weighs about 90 tonnes. The biggest part of the Shuttle stack is the external tank, which measures 47 m long. It holds some 2 million litres of liquid hydrogen and liquid oxygen, the propellants for the orbiter's three main engines. Strapped to the tank are two boosters which burn solid propellants, a mixture of powdered aluminium (fuel) and ammonium perchlorate (oxidizer). The solid rocket boosters (SRBs) are 45.5 m long and nearly 4 m in diameter. They are made up of thick steel segments, locked together by pins. The joints are sealed by sets of rings.

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