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MDD: Mate/Demate Device Key To Shuttle Prep For Return To Kennedy
October 18, 2011

Technicians begin preparations for Atlantis' attachment on the back of a 747 Shuttle Carrier Aircraft for the ferry flight back to Kennedy Space Center, Fla., following the STS-44 landing at Edwards in December 1991. Post-flight servicing of the orbiter and mating operations were carried out at Dryden in the Mate/Demate Device, the large gantry-like structure used in hoisting the spacecraft during post-spaceflight processing. (NASA Photo by Jim Ross) › View Larger Image


The most extensive overhaul in the 29-year history of Dryden's Mate/Demate Device was completed in 2004, and involved replacing the mammoth structure's original coating of lead-based paint with a fresh coat of non-toxic paint.


Contractors and NASA personnel collaborated to develop a way of disposing of the lead-based paint removed from the structure by recycling it into commercial cement. The alternative was sending it to a landfill as hazardous waste - all 240 tons of it. The MDD had not been repainted since it was first built, though it had been retouched.


The structure has served NASA well, as Dryden was the primary landing site during the early days of the space shuttle program. About a year before it would hoist prototype shuttle Enterprise onto the NASA 747 Shuttle Carrier Aircraft for the first time, the gargantuan steel frame had been erected and stood ready to do the heavy lifting.


Dryden remained the primary backup landing site when clouds rolled in at Kennedy Space Center, Fla., and the weather wasn't good enough for a landing there. In all, 54 shuttle landings took place at Dryden, including those of the first nine orbiter flights minus STS-3, in which Columbia landed at White Sands, N.M. That 54-flight total includes all of the first landings of new orbiters as each joined the fleet.


The MDD consists of two 100-foot towers with stationary platforms every twenty feet from 20 to 80 feet on each tower, and a horizontal structure mounted at the 80-foot level between the two towers. The horizontal unit cantilevers 70 feet out from the main tower units, guiding and controlling a large lift beam that attaches to the orbiters to raise and lower them.


Three large hoists are used to raise and lower the lift beam. Two of the hoists are connected to the aft portion of the lift beam and one is attached to the beam's forward section. The three hoists operate simultaneously. As a unit they can lift 120 tons, or 240,000 pounds; space shuttles weighed in at about 231,000 pounds. Joe D'Agostino was originally hired as a shuttle security officer and served for decades as the Dryden space shuttle manager before his retirement in 2007. He recalled the first time the MDD was used.


"We had a technical problem [mating Enterprise]. The operation lasted almost 14 hours. We got it to the point where we were ready to lower Enterprise onto the 747, and then we learned the orbiter didn't fit. To make it fit we moved the forward strut on the 747. It was nerve-wracking," he said.


The second time Enterprise was lifted was much more streamlined and the effort took about eight hours, he said. Shuttle landings later required changing work schedules in order to keep staff on site around the clock until the orbiter was safely mated to the NASA 747 and winging its way back to Kennedy Space Center.


Dryden and Kennedy are home to NASA's two MDDs. Dryden's MDD is more complex than the one at Cape Canaveral, D'Agostino said, because the one here is used as a work site for tasks that, when they are necessary in Florida, are undertaken at Kennedy's Orbiter Processing Facility. Dryden's structure is similar to its Florida twin, but the Dryden MDD has elevators and had extra equipment built into it that were required in the early days of the shuttle program.


What was essentially one of the world's largest Erector sets became a permanent structure at Dryden as the needs of the space shuttle program changed and required welds, concrete and additional work platforms and heavier lift capability in the MDD. Modifications since the MDD's completion in 1976 have cemented the device into Dryden history - not just physically but metaphorically as well.

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