Payload Changeout Room Supports Last Shuttle Cargo
After 29 years of supporting space shuttle missions, the payload changeout room, or PCR, at NASA Kennedy Space Center's Launch Pad 39A has been used for the last time to install cargo into a shuttle's payload bay.
The canister containing the Raffaello multi-purpose logistics module, or MPLM, was hoisted into the PCR on June 17 and the MPLM transferred into space shuttle Atlantis on June 20.
As part of the rotating service structure, or RSS, the PCR is an enclosed, environmentally controlled area that supports payload delivery and servicing at the pad and mates to the shuttle's cargo bay for vertical payload installation. Clean-air purges help ensure that payloads being transferred from a payload canister into the PCR are not exposed to the open air.
Although there was a PCR on both Launch Complex 39 pads, the first 24 shuttle missions lifted off from pad A while pad B was being transitioned from an Apollo to a shuttle pad.
The payload for the STS-4 mission was the first shuttle cargo to be installed from a PCR, arriving at the pad May 22, 1982, a few days before shuttle Columbia's rollout on May 26.
Greg Henry, United Space Alliance, or USA, deputy director of solid rocket booster manufacturing operations, was the pad's first payload move director and supported the first payload transfer from the PCR, which was for the STS-4 mission.
"STS-4 carried a primary Department of Defense payload, DoD 82-1," Henry recalled, "which was a classified instrumentation pallet."
The STS-4 cargo manifest also included the first university student experiments, known as Get Away Specials, and the first commercial experiment, which utilized the Continuous Flow Electrophoresis System, or CFES.
"At the pad, the payload canister is lifted and mated to the PCR," Henry explained. "The PCR and canister doors then are opened and the payload is transferred to the payload ground-handling mechanism, or PGHM, a movable payload handling mechanism that is supported by overhead rails in the PCR."
The PGHM has platforms positioned at five levels to provide access to the payload when it is installed on the mechanism and the orbiter payload bay. Each platform has extendible planks that can be configured to accommodate a particular payload.
"That first transfer was the only one done using the original configuration of the PGHM," Henry said. "The original design proved to be operationally impractical for larger multi-payload transfers."
Henry said a major redesign was required of the PGHM front support beams and support fittings that replaced mechanical jack screw operated J-hooks with the current hydraulic cylinder actuated hooks and control panels.
"The design was completed prior to STS-4 pad flow and the actual modification to the PCR and PGHM was accomplished between launch of STS-4 on June 27 and arrival of the STS-5 payloads on Oct. 12," Henry said. "In less than four months, the team replaced the old PGHM payload support beams with stronger beams and support hardware."
They also installed an all new hydraulic system, including pump package control panels, hydraulic lines and J-hook fittings, completed a system proofload, and conducted a validation transfer using payload mass simulators.
"It was an incredible accomplishment in a very short period of time," Henry said.
Richard Jacques, USA lead payload technician for advanced systems, has supported work in the PCR since 1989.
"Since 25 to 30 technicians are needed to transfer the payloads into the orbiter, the payload shop utilizes technicians from the entire launch pad," Jacques said.
"The Hubble Space Telescope launch and servicing missions were the most difficult because the clean room criteria was stricter. We put in many more hours than usual, cleaning every nook and cranny. More attention was paid to anything that would be touched. We even used 'clean-room' paper for any documents needed in the PCR and Kapton tape designed to reduce the tape's outgassing."
Pete Reutt, USA payload mechanical engineer, also started in 1989 and recalled the challenges of payload processing for the Hubble missions.
"Although these were highly sensitive clean missions and we had to go above-and-beyond normal cleaning procedures, it was rewarding to see the telescope filling the payload bay, all by itself, enclosed in its shiny silver blankets and panels. It was an especially beautiful payload," Reutt said.
"Support for STS-125, the last Hubble servicing mission, was particularly complex. The fluid lines and cables had to be connected in the PCR the whole time the payload was undergoing testing, right up until closeout."
Not all of the excitement in the PCR came as a result of normal payload processing operations, Jacques recalled: "After 9/11, a public announcement was made that an inbound aircraft had been spotted in the vicinity of the pad, requiring a complete pad evacuation. We had to safe the systems, get people out of their body harnesses and egress out of the clean room quickly, still wearing our bunny suits (clean-room attire). As it turned out, the alarm was caused by a small aircraft flying down the coastline with its radio turned off. That was a day to remember!"
Following Atlantis' final launch on the STS-135 mission, the fixed and rotating service structures on pad A will be dismantled. The pad surface, though, is planned to be used to support the liftoff of future rockets carrying NASA astronauts into space.
NASA's John F. Kennedy Space Center