The Space Shuttle is the United States’ manned space vehicle. The External Tank (ET) component of the Shuttle system is the large brownish colored structure on which the orbiter and solid rocket boosters are mounted. The External Tank is constructed by Martin Marietta Manned Space Systems in New Orleans, Louisiana, which has produced ETs for over fifteen years. The function of the ET is to supply the Shuttle main engines (located in the orbiter) with liquid oxygen and hydrogen fuel. After about eight minutes of flight, the fuel from the tank has been expended and the ET is jettisoned. The orbiter ascends to orbital altitude while the ET falls, burning up as it reenters die atmosphere. Because the ET is disposed of in this way, each Shuttle launch requires a new ET.