External stowage platforms (ESPs) are key components of the International Space Station (ISS). Each platform is made from steel and serves as an external pallet that can hold spare parts, also known as orbital replacement units (ORUs), for the space station. As a platform it is not pressurized, but does require electricity to power the heaters of some of the stored equipment. ORUs are attached to the ESP via Flight Releasable Attachment Mechanisms (FRAMs), matching witness plates that mate the ORU to the platform. While ESP-1 is unique in shape, ESP-2 and ESP-3 were based on the deployable version of the Integrated Cargo Carriers (ICC), which were designed to transport unpressurized cargo inside the Space Shuttle's cargo bay. ESP-1 was transported to the International Space Station on STS-102, ESP-2 flew on mission

STS-114 STS-114 was the first "Return to Flight" Space Shuttle mission following the Space Shuttle Columbia disaster, Space Shuttle ''Columbia'' disaster. Space Shuttle Discovery, ''Discovery'' launched at 10:39 Eastern Time Zone, EDT (14:39 Coordinated ...

'Return to Flight' and ESP-3 on mission STS-118. FRAM breakdown

Locations and components

ESP-1

The first of the external stowage platforms, called ESP-1, was installed on the port side trunnion pin on the outer hull of the ''Destiny'' Laboratory Module on March 13, 2001 during the second EVA of the STS-102 Space Shuttle mission. It is powered by the Unity Module and has two attach points to store ORUs. ESP-1 was carried into orbit on the underside of an Integrated Cargo Carrier. It is smaller than the other ESPs and ELCs, with dimensions approximately wide by long, and is differently shaped. ESP-1 holds the following ORUs: * FRAM-1 Pump Flow Control System (PFCS) nicknamed 'Leaky' from ITS-P6 was swapped out during an EVA on Exp. 55 May 18, 2018 with the PFCS nicknamed 'Frosty' originally added here by the STS-102 crew * FRAM-2 Direct-Current Switching Unit (DCSU) added by STS-100 crew Image:STS-102 EVA ORUs.png, ESP-1 and hardware installation locations on the Destiny during STS-102 Image:ESP-1 s115e05689.jpg, ESP-1 attached to the Destiny portside trunnion pin, PFCS on the left File:STS-129 EVA1 Michael Foreman 4.jpg, Another view of ESP-1 File:S108e5594.jpg, ESP-1 attached to the Destiny portside trunnion pin on the right File:PFCS STS-114 ref 115.png, PFCS attach points

ESP-2

ESP-2 was detached from its Keel Yoke Assembly (which remained in the Orbiter) and installed with the assistance of Space Shuttle Discovery's robotic arm and two spacewalkers during the

mission. It is much larger than ESP-1 with eight FRAM sites creating room for up to eight spare parts (ORUs). Like ESP-1, it is powered by the Unity Module. However, unlike ESP-1, ESP-2 is attached to the Quest Joint Airlock using a specialized ESP Attachment Device (ESPAD). ESP-2 and ESP-3 are deployable versions of the integrated cargo carrier and have the same dimensions, approximately long and wide. The ORUs on ESP-2 are: * FRAM-1 (top side) Pump Module SN0005. Moved here robotically from ELC-2 on 6 March 2015 in a swap with failed Pump Module SN0004, which had been relocated here by the ISS-41 US EVA-27 crew in Oct. 2014 * FRAM-2 (top side) Direct Current Switching Unit (DCSU) (added by

STS-123 STS-123 was a Space Shuttle mission to the International Space Station (ISS) which was flown by Space Shuttle ''Endeavour''. STS-123 was the 1J/A ISS assembly mission. The original launch target date was 14 February 2008 but after the delay of ...

crew) FRAM formerly held the VSSA * FRAM-3 (top side) CTC-3 container moved here via SPDM. DCSU added by

crew) had been relocated via SPDM Jan. 30, 2013 to ELC-2. * FRAM-4 (top side) Latching End Effector Support Equipment moved here via SPDM from ELC1.)Main Bus Switching Unit (MBSU) launched on ESP-2 moved to truss to replace a degraded unit which was brought inside and returned to earth on SpaceX CRS-12. * FRAM-5 (keel side) Pitch/Roll Joint (P/R-J) added by

crew FRAM formerly held a CMG * FRAM-6 (keel side) Main Bus Switching Unit (MBSU) added by STS-120 crew This unit was swapped with a failed unit MBSU #1 from the SO truss, by the Exp 32 crew in late 2012. * FRAM-7 (keel side) Flex Hose Rotary Coupler (FHRC SN1003) launched on ESP-2 * FRAM-8 (keel side) Utility Transfer Assembly (UTA) launched on ESP-2 Notes: *Video Stanchion Support Assembly (VSSA) launched on ESP-2 at FRAM-2 was jettisoned overboard on July 23, 2007 (the video stanchions were placed on the truss during EVAs). *Pump Module (PM) (SN0004), initially installed on FRAM-1 during STS-121, was removed on August 17, 2010 by the Exp 24 crew and installed on S1 Truss, replacing the original (failed) PM SN0002. The failed unit had been temporarily stored on an ORU site on the MBS, then moved to ESP-2 by the STS-133 crew, then returned to earth by the STS-135 crew July 13, 2011. *A failed Control Moment Gyroscope was installed on FRAM-5 from August 13, 2007 during STS-118 until February 13, 2008 when it was returned by STS-122. *MBSU was moved to the truss during Expedition 52 and the Latching End Effector was moved to ESP2 to prepare for the spacewalk on January 23, 2018. The failed MBSU was returned to earth on Space X CRS12. Image:ESPAD mount on QUEST.png, ESPAD mount used to secure ESP-2 to Quest Image:ESP-2 iss011e11344.jpg, ESP-2 in the payload bay of STS-114 Image:STS-114 External Storage Platform 2 crop.jpg, ESP-2 can be seen highlighted and under the Quest Joint Airlock Image:STS-118 ESP-2.jpg, ESP-2 viewed during STS-118 EVA to remove a failed CMG for return to earth Image:S133e010583.jpg, ESP-2 viewed by the departing STS-133 crew

ESP-3

ESP-3 was detached from its Keel Yoke Assembly (which remained in the Orbiter) and installed on the P3 Truss at UCCAS-1 on August 14, 2007 during the Space Shuttle STS-118 mission. It has seven attachment sites for ISS spare parts and assemblies, called Orbital Replacement Units (ORUs). The platform also has handrails and attachment points for tethers and foot restraints that astronauts can use while working with the ORUs on the ESP-3. ESP-3, as with ESP-2 are deployable versions of the Integrated Cargo Carrier and have the same dimensions, approximately 8.5 feet long and 14 feet wide. ESP-3 has two grapple fixtures to aid deployment. ESP-3 was the first major station element to be installed completely by robotics, using only the shuttle and station's robotic arms, an external berthing camera system (BCS) and a

Photovoltaic Radiator Grapple Fixture Photovoltaics (PV) is the conversion of light into electricity using semiconducting materials that exhibit the photovoltaic effect, a phenomenon studied in physics, photochemistry, and electrochemistry. The photovoltaic effect is commerci ...

(PVRGF). Astronauts robotically installed the platform onto the station's P3 truss segment during the STS-118 mission's seventh day. On January 12, 2010, the station's robotic arm was used again to move ESP-3 from the P3 truss segment UCCAS-1 site. It was grappled by the arm and then transferred down the station's backbone on the mobile transporter. ESP-3 was then attached to its new location on the lower part of S3 truss segment at the PAS-3 site. Moving the storage platform cleared the way for ExPRESS Logistics Carrier-3 to be installed during STS-134. The ORUs (currently) installed on ESP-3 are: * FRAM-1 (top side) Pitch/roll joint (P/R‐J) launched on ESP-3 * FRAM-2 (top side) Flex Hose Rotary Coupler (FHRC SN1004) added by

STS-126 STS-126 was the one hundred and twenty-fourth NASA Space Shuttle mission, and twenty-second orbital flight of the ''Space Shuttle Endeavour'' (OV-105) to the International Space Station (ISS). The purpose of the mission, referred to as ULF2 by ...

crew * FRAM-3 (top side) empty * FRAM-4 (top side) Linear Drive Unit (LDU) added by

STS-127 STS-127 ( ISS assembly flight 2J/A) was a NASA Space Shuttle mission to the International Space Station (ISS). It was the twenty-third flight of . The primary purpose of the STS-127 mission was to deliver and install the final two components of t ...

crew * FRAM-5 (keel side) Space-to-Ground Antenna (SGANT) added by

crew * FRAM-6 (keel side) Battery Charge/Discharge Unit (BCDU) launched on ESP-3 * FRAM-7 (keel side) ATA Flight Support Equipment (FSE) added by STS-118 crew. Notes: FRAM-2 originally hosted NTA tank (SN0005) that was launched on ESP-3, it was swapped for the depleted NTA (SN0002) from the S1 truss during

STS-124 STS-124 was a Space Shuttle mission, flown by Space Shuttle ''Discovery'' to the International Space Station. ''Discovery'' launched on 31 May 2008 at 17:02 EDT, moved from an earlier scheduled launch date of 25 May 2008, and landed safely at t ...

.NASA.gov
/ref> That failed unit was later returned on

when the FHRC was placed here. FRAM-3 hosted Pump Module (PM) SN0006 that was added by the

crew. The ISS Exp 38 crew swapped PM SN0006 with the failed PM SN0004 from the S1 Truss during 2 EVAs Dec. 21 and 24, 2013, leaving PM SN0004 on the MBS ORU POA for later storage. It was eventually (in Oct. 2014) stored on ESP-2 FRAM-1, rather than ESP-3 FRAM-3. FRAM-4 hosted a CMG & frame and both were removed Aug. 13, 2007 during STS-118. Support frame was placed on ESP-2, CMG was installed in the Z1. The failed CMG was placed on the CMG frame on ESP-2 FRAM-5 and later returned to earth by

. File:03 NTA.jpg, Nitrogen tank assembly (NTA) preflight Image:ESP-3 iss015e21711.jpg, ESP-3 in the payload bay of STS-118 File:ESP-3_s118e07098.tiff, ESP-3 in the payload bay Image:STS-118 ESP-3.jpg, ESP-3 being installed by

Canadarm2 The Mobile Servicing System (MSS), is a robotic system on board the International Space Station (ISS). Launched to the ISS in 2001, it plays a key role in station assembly and maintenance; it moves equipment and supplies around the station, supp ...

. Image:ESP-3 s133e011051.jpg, ESP-3 view from the departing STS-133 crew. ESP-3 has the SGANT antenna, note ELC-4 on the left and ELC-2 above Truss breakdown

Notes

External links

NASA videos related to ESP-2Astrium North America, Inc.
{{Use American English, date=January 2014 Components of the International Space Station