S3 / S4 truss assembly |
International |
Launch, orbit data:
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The newly installed S3/S4 truss assembly during the first EVA of mission STS-117 on June 11, 2007 |
 S3/S4 truss at KSC |
The P3/P4 truss assembly was installed by the Space Shuttle AtlantisSTS-115 mission, launched September 9, 2006, and attached to the P1 segment. The P3 and P4 segments together contain a pair of solar arrays, a radiator and a rotary joint that will aim the solar arrays, and connects P3 to P4. Upon its installation, no power was flowing across the rotary joint, so the electricity generated by the P4 solar array wings was only being used on the P4 segment, and not the rest of the station. Then in December of 2006 a major electrical rewiring of the station by STS-116 routed this power to the entire grid. The S3/S4 truss assembly -- a mirror-image of P3/P4 -- was installed on June 11, 2007 also by Space ShuttleAtlantis during flight STS-117, mission 13A and mounted to the S1 truss segment.
Major P3 and S3 subsystems include the Segment-to-Segment Attach System (SSAS), (SARJ), and Unpressurized Cargo Carrier Attach System (UCCAS). The primary functions of the P3 truss segment are to provide mechanical, power and data interfaces to payloads attached to the two UCCAS platforms; axial indexing for solar tracking, or rotating of the arrays to follow the sun, via the SARJ; movement and work site accommodations for the Mobile Transporter. The P3/S3 primary structure is made of a hexagonal shaped aluminum structure and includes four bulkheads and six longerons. The S3 truss also supports EXPRESS Logistics Carrier locations, first to be launched and installed in the 2009 time frame.
Major subsystems of the P4 and S4 Photovoltaic Modules (PVM) include the two Solar Array Wings (SAW), the Photovoltaic Radiator (PVR), the Alpha Joint Interface Structure (AJIS), and Modified Rocketdyne Truss Attachment System (MRTAS), and Beta Gimbal Assembly (BGA).