EVA success for STS-115

by Chris Bergin

STS-115 Astronauts Heidemarie Stefanyshyn-Piper and Joe Tanner have concluded the final spacewalk of the mission, carrying out maintenance and final preparation on the new P3/P4 truss on the International Space Station (ISS).

The conclusion of Flight Day 7’s EVA marks another successful milestone for Shuttle Atlantis’ mission, ahead of next week’s return to Earth.

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STS-115: Full EVA Mission Overview (326 pages, 56 meg) STS-116: EVA Outline and Checklist (80meg – 433 pages). STS-116 Full Flight Plan – all available to download on L2.

Three spacewalks have been carried out by the spacewalkers, mainly in aid of the new solar arrays that now stand proud in the new configuration of the ISS, in what has been a highly successful mission so far.

While some mass media columnists continue to fall over themselves to find any excuse to use negative sound bytes in relation to anything relating to the Shuttle and Station, the facts of this missions goals should not be overlooked or dismissed.

STS-115 is the first assembly mission in four years, re-starting an ambitious swansong for the Shuttle before retirement in 2010.

The three EVAs bring the ISS’ totals up to 72 spacewalks, for a total nearing 440 hours. EVA-1 saw the release of launch restraint pins (seven each) on the four SABBs (Solar Array Blanket Boxes), installed four AJIS (Alpha Joint Interface Structure) struts, prepared spring clamps for SARJ (Solar Alpha Rotary Joint) rotation, and connected 13 data and power umbilicals to allow operation of internal “keep alive” heaters until the new solar arrays were deployed today.

The EVA managed to keep below its scheduled timeline, thus allowing some of EVA-2’s work to be completed, which included the removal of two of 16 solar array joint launch locks, deployment of all four SARJ braces, removal of two avionics thermal shrouds, and retrieval of a QD (quick disconnect) vent tool from the Z1 tray to the interior.

A few items were lost during the first two EVAs, with the inboard bolt, spring and washer of SARJ thermal Cover 21 drifting away on EVA-1.

EVA-2 began at 5:05am EDT, lasting 7h 11m. During the spacewalk, Shuttle Mission Specialists Dan Burbank (EV3) and Canadian Steve MacLean (EV4) completed pre-activation work on the massive SARJ (Solar Alpha Rotary Joint) by removing 14 (of 16) launch locks, after temporarily unbolting 14 thermal covers, and six launch restraints.

During removal of cover #8 with the PGT (Pistol Grip Tool), another bolt was lost overboard, indicating the need for improved bolt design in the future. A partially loose thermal cover on the P3 outboard bulkhead was reattached with Velcro.

Get-ahead work from EVA-3 on FD7 involved clearing the ‘railroad’ path of the MT on the P3 segment (by removing and stowing a P1 MT (Mobile Transporter) stop, the P3 truss keel pin and drag link, the P3 truss robotic vision target, and a P3 truss tether shuttle stop. Also accomplished were installation of a temporary rail stop, removal of a pair of avionics thermal shrouds, and relocation of a pair of foot restraints.

Friday’s EVA-3 is finalising all of the required work for both ISS maintenance and P3/P4 electrical connections. Work included:

Installing BGA (Beta Gimbal Assembly) shoulder bolt retainers on the P6 truss;
Releasing cinches and winch bars to deploy the new PVR (Photovoltaic Radiator);
Reconfiguring the foot restraint (APFR) at P4-20 and relocating a second APFR as get-ahead for 12A.1;
Releasing IEA MMOD ((Integrated Electronic Assembly Micrometeoroid/Orbital Debris) cover bolts on P4;
Clearing the rail path for MT relocation to WS-8 by removing the obstructing safety tether cable;
Removing & replacing the string 1 BSP (Baseband Signal Processor) and transponder on the S1 truss;
Installing the Ku-band AGIT (Antenna Group Interface Tube) heat shield;
Installing an EWIS (External Wireless Instrumentation System) antenna on the Lab for tracking docking loads (P4 carries six quarter-size three-axis-sensitive EWIS RSU {Remote Sensor Unit} accelerometers placed around the outboard integrated truss structure);
Retrieving MISSE-5 (Materials ISS Experiment 5);
Removing & replacing the SASA (S-band Antenna Support Assembly) on the S1 truss with a spare unit (failed SASA to be relocated to the Z1 truss, protected with shrouds).
Taking infrared imagery of the Orbiter leading edge and, if time permits, of an ISS PVR radiator.

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