Technicians had worn them for decades as they prepared the space shuttles for their move from Kennedy Space Center’s three Orbiter Processing Facilities to the towering Vehicle Assembly Building, and eventually the launch pad. “Bunnysuits,” those white coveralls with floppy hoods and rubber-banded booties, were designed to keep dirt and debris from contaminating the orbiter interiors.

But on this summer day in one Orbiter Processing Facility, technicians working inside Discovery’s crew module wore street clothes. No need to worry about contamination: Discovery would not be returning to space.

After flying 148 million miles and orbiting Earth 5,830 times, Discovery, first flown in August 1984, was being decommissioned and readied for its trip to the National Air and Space Museum’s Steven F. Udvar-Hazy Center in northern Virginia, where it will arrive in mid-April. The three main engines had been removed from the shuttle’s aft end, which was now covered by a tightly fitted mask with three white discs the size of the engine bells. Clear plastic stretched across the crater in the orbiter’s nose, where the forward reaction control system—small thrusters that maneuvered the spacecraft in orbit—had been removed. And this harvesting of the orbiter’s components was only the beginning.

In late autumn of last year, more than six months after Discovery landed for the final time, NASA crews began peeling back the orbiter’s skin, clipping wires, and pulling hydraulics. They removed and analyzed propellant tanks and valves and scrutinized electronics, looking for evidence of deterioration the way coroners look for signs of illness during autopsies.

“ ‘Autopsy’ is a sad way of putting it—these vehicles are almost like our friends—but it’s what we are doing,” says Joyce M. Seriale-Grush, orbiter chief engineer at NASA’s Johnson Space Center in Houston, Texas. “We have been evaluating this hardware with nondestructive tests throughout their history. Now we can actually tear some of this hardware down.”

The orbiter autopsies can determine whether the best estimates and educated guesses NASA engineers relied on to keep the shuttle flying for three decades were trustworthy. The results could improve the understanding of shuttle failures and guide the design of future spacecraft.

Before the autopsies could begin, however, workers in the Orbiter Processing Facility had to “safe” each vehicle, removing toxic propellants and hydraulic fluids as they had done hundreds of times before. Crews, shrunk by layoffs, attended first to Discovery, then Endeavour, and finally Atlantis.

“You think you want to do something that you normally would do, and they say it’s not required for where this shuttle is going,” says Terry White, project lead for the orbiter thermal protection system and a 32-year shuttle program veteran. Some habits die hard. On the aft end of Endeavour, the ports for purging nitrogen from the reaction control thrusters on the orbital maneuvering system pod are covered with cloth sporting a notice reminding workers to “remove before flight.”

Orbiter Processing Facility 2 is all about warnings. The blue metal door leading inside bears two against unauthorized entry, a third about electrical hazards, and a caution against unfastened objects.

Once inside today, the orbiter processing team will remove one of Endeavour’s two orbital maneuvering system pods, which bookend the vertical stabilizer. As the drone of ventilators fills the building, a technician wearing a “Lucky’s Bar” T-shirt thumbs a manual detailing the steps for excising the orbital maneuvering systems. Held by a latticework of steel beams, the pod rotates out and into the free-hang position, ready for the next day’s crew to winch it into retirement.