An unflown Space Shuttle Power Transfer Unit (PTU) manufactured by Pratt & Whitney Rocketdyne for the STS-118 mission, which featured the first flight of the new Station‐to‐Shuttle Power Transfer System (SSPTS), a series of electrical converter units designed to provide additional power to the Space Shuttle while docked with the ISS, consequently allowing it to extend its missions and perform more complex tasks. The PTU, which measures 20″ x 7.5″ x 20″ and weighs 70 lbs, features a series of eight ports to the front and a Pratt & Whitney Rocketdyne label to the top: “Part Name: Power Transfer Unit - PTU, Part Number: MC409-0547-0010, Cage: 20602, Mfr. Part No.: R108230A1, Contract No.: 5H06865, Mfr. Name: Pratt & Whitney Rocketdyne Inc., Mfr. Serial No.: 9005091, Mfr’s Cage: 02602.” Also present to the top is a bar code label with parts information and an “XV” ITAR number, and a North American stamp that reads: “S/N 9003160, 02602-R108242-1, MFR 48458.” The right side bears a similar stamp: “S/N 9003149, 02602-R108233A2, MFR 48458.” In fine condition. Accompanied by its heavy-duty transportation case by Hardigg Cases / A&J Cases, with several affixed NASA “Critical Space Item” labels and a “U.S. Government Property, The Boeing Company” label. The case, 36″ x 30.5″ x 35″, also bears a KSC Form serviceable parts tag, a Pratt & Whitney Rocketdyne parts label, an uncontrolled hardware label, and a “Super Clean Pack” label, all of which feature numbers that match with the PTU.
The STS-118 mission featured the first flight of the new Station‐to‐Shuttle Power Transfer System (SSPTS), a series of electrical converter units in the shuttle that drew electricity from the ISS’s power system to supplement the normal electrical output from the shuttle’s three cryogenic fuel cells. The new capability is designed to extend the shuttle’s stay at the station to up to 12 days, if necessary, without depleting the finite electrical capability of the fuel cells themselves, thereby increasing the crew time available for scientific experiments, extravehicular activities, and remaining International Space Station assembly tasks. The SSPTS consisted of two Power Transfer Units (PTUs) in the shuttle, containing three converters per unit, two Orbiter Power Conversion Units (OPCUs), and one Assembly Power Conversion Unit (APCU). The STS-118 mission itself was significant for various reasons, including delivering and installing the S5 truss segment to the ISS, which extended the station's structural framework and provided additional support for solar arrays and other systems. The ability to draw power from the ISS through the SSPTS contributed to the success of the mission by allowing the Shuttle to perform these tasks and accomplish more objectives during its stay at the space station.
