Orbital replacement unit

ORUs are parts of the main systems and subsystems of the external elements of the ISS, none are intended to be installed inside the pressurised modules.All are stored on the three external stowage platforms (ESPs) or the four ExPRESS Logistics Carriers (ELCs) mounted on the Integrated Truss Structure (ITS).While spare parts/ORUs were routinely brought up and down during the ISS life-time via Space Shuttle resupply missions, there was a heavy emphasis[clarification needed] once the Station was considered complete.Other modes of ORU delivery included: Payload bay sidewall mounted ORUs, such as BCDUs, were regularly carried and transported to the ISS via EVAs.As well as storage tanks for oxygen as part of the station Environmental Control and Life Support System (ECLSS).ORUs can be hardware such as radiators, or simply batteries or communication antennas, essentially any element that can readily be removed and replaced when required.ORUs to be handled by Dextre have attachments designed to be gripped with the ORU/Tool Changeout Mechanisms (OTCM) on the end of each arm.A Modified Truncated Cone (MTC) Target is used to visually line up Dexter's arm to grab a fixture.The LDU provides drive and stopping forces for the mobile transporter along the integrated truss structure rail.
Location of ESPs and ELCs on the International Space Station .
ISS Integrated Truss Structure detailing all Orbital Replacement Units in situ
Orbital replacement unit (HST)International Space StationDextreexternal stowage platformsExPRESS Logistics CarriersIntegrated Truss StructureSTS-102External Stowage PlatformSTS-114STS-118STS-129ExPRESS Logistics CarrierSTS-133STS-134Integrated Cargo CarrierSTS-105STS-121STS-122STS-127STS-132STS-126STS-128STS-131STS-135External Active Thermal Control SystemEnvironmental Control and Life Support Systemgrapple fixtureCanadarm2STS-124STS-120Expedition 32SpaceX CRS-19SpaceX CRS-14Latching End EffectorSpecial-purpose dextrous manipulatorElectrical system of the International Space StationIntegrated cargo carriersScientific research on the International Space Station