NASA successfully transported the space shuttle Discovery from Florida to Virginia yesterday on its way to the Smithsonian. But how do you get a 68,000kg space vehicle off a 70m aeroplane without dropping it?
The shuttle is affixed to the 747, known as the Shuttle Carrier Aircraft, with three struts — one on the nose, the other two at the base of the wings. After those struts are disconnected, a pair of cranes perform a tandem lift of the shuttle. The smaller crane will lift Discovery's nose, while the larger crane will hoist the rear of the craft. The cranes will then hold the shuttle while the SCA backs out and set the shuttle on the tarmac.
Unfortunately, it's not quite as simple setting up the piggyback to begin with. At the Kennedy Space Center, NASA employs the Mate-Demate Device (MDD). It's a $US1.7 million structure consisting of two 30m towers with work platforms every 6m and equipped with triple 45,000kg hoists capable of raising the shuttle into place atop the SCA or upright for transport to the launch pad.
According to NASA:
Two of the hoists are connected to the aft portion of the lift beam and one hoist is attached to the beam's forward section. The three hoists operate simultaneously in the hoisting process. Each of the three hoists has a 100,000-pound lift capability. Operating together, the total lifting capacity of the three units is 240,000 pounds (120 tons).