Orbiter Payload
Space shuttle Discovery will carry a variety of payloads. The flight will carry 29,725 pounds of equipment and supplies in its cargo bay to the International Space Station (ISS). When Discovery lands, it will return with 25,121 pounds of equipment in its cargo bay. Additional items will be carried on the space shuttle mid-deck, which include supplies, food, water and clothing for the crew.
The cargo bay measures 60 feet long and by 15 feet diameter and can carry the cargo equivalent to the size of a school bus. Under the Space Flight Operations Contract with United Space Alliance, Boeing performs the form, fit and function of any cargo that goes into the payload bay. The addition of the 50-foot boom and its suite of sensors called the Orbiter Boom Sensor System are considered to be part of the orbiter and are not considered part of the payload weight listed above.
The primary payload for this flight is the Italian-built Multi-Purpose Logistics Module (MPLM), named Raffaello. The MPLM is a pressurized cargo container used to transport racks, equipment and supplies to the International Space Station. The MPLM is removed from the space shuttle cargo bay using the station's arm and connected to the ISS using the Common Berthing Mechanism, which locks it in place with an airtight seal on the nadir side of the Station's Unity Module. The MPLM has a length of 22.4 feet and a diameter of 14.8 feet.
Another item carried in the payload bay is the External Stowage Platform-2 (ESP-2). ESP-2 is an external pallet that can securely hold up to eight critical spare parts or Orbital Replacement Units (ORUs) for the Station. ESP-2 is a cross-bay carrier since it spans the width of the cargo bay and is used primarily to transport items to the Station. The astronauts will install ESP-2 during a spacewalk on the ninth day of the mission.
A third item carried in the payload bay is called the Lightweight Multipurpose Experiment Support Structure Carrier (LMC), which will be used to transport a replacement Control Moment Gyroscope (CMG) and the failed CMG on orbit back to Earth. The LMC also will carry a large box with a lid, called a Detailed Test Objective (DTO), that astronauts will open up to conduct several tile and Reinforced Carbon-Carbon (RCC) panel repair experiments while on orbit. The experiment will check the proof of concept of one tile and one RCC panel repair method. The LMC is a cross-the-bay carrier as well. Astronauts will temporally park the old CMG on the side of the LMC via a tether, remove the new one and install it, and then put the old CMG in the same spot as the new CMG when launched.
All three payloads will have electrical power drawn from the space shuttle for heaters to maintain the proper thermal environment while on orbit. A switch removes MPLM power electronically causing Remotely Operated Electrical Umbilical to disconnect, while the crew will have to physically disconnect power connectors to the ESP-2 and LMC.
