A space shuttle is a space craft designed for transporting humans and cargo into space. The space shuttle system is called the Space Transportation System (STS). The space shuttle uses two solid rocket boosters (SRBs) to carry it into space. When the space shuttle takes off the solid rocket boosters take the shuttle to an altitude of 28 mi (45 km), at a speed of 3,094 miles per hour (4973 km/h). The solid rocket boosters will only last for eight minutes during each flight. After the rocket boosters fall off, the three main engines start up to give the space shuttle thrust. All of the space shuttles’ engines are attached at the bottom of the ship. The space shuttles’ rocket engines were the first rocket engines that were reusable. The three main engines are the fastest engines ever built. When the space shuttle takes off it is vertical, and when it lands it is horizontal. To get the ship traveling fast enough to escape earths, gravitational pull an external fuel tank is attached to the ship. The external fuel tank is154ft (47m) long, 27.5ft (8.4m) in diameter. The external fuel tank is the largest piece of equipment on the space shuttle. The fuel that the external fuel tanks hold is made up of liquid hydrogen fuel and liquid oxygen oxidizer. This fuels the three main engines in the space shuttle. During the first 8.5 minutes of liftoff all 526,000 gallons (1.99 million liters) of fuel is used. The first five space shuttles used external fuel tanks made of aluminum alloys that weighed about 77,000 lb (35,000 kg) when empty. In 1983 NASA made a new design that reduced that weigh to 66,000 lb (30,000kg), when empty. The new design is made of aluminum lithium. The space shuttle is also used to take astronauts to and from the International Space Station.