An array of spacewalk tasks completed via EVA-2

by Chris Bergin

Flight Day 6 of mission STS-120 has seen the completion of a challenging EVA-2, conducted by spacewalkers Scott Parazynski (EV1) and Dan Tani (EV2).

The six hour, 33 minute EVA set up the opening elements of the P6 solar array truss relocation, along with the inspection of the starboard S3/S4 SARJ (Solar Alpha Rotary Joint). The spacewalk also included outfitting requirements on the newly installed Node 2 “Harmony” module.

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Node 2 Hatch Opening:

Node 2 – currently berthed in its temporary location on the Node 1 ‘Unity’ portside dock, received its first ISS visitors during Saturday, after station commander Peggy Whitson, and Italian astronaut Paolo Nespoli opened the hatch at 7:24am Central time.

The gleaming white Italian-built ‘Harmony’ module is adding over 2500 cu.ft. (71 cubic meters) of living and working space to the ISS. It’ll eventually be moved to its permanent location after shuttle Discovery departs, allowing Node 2 to become the docking ports for new research laboratories from ESA (European Space Agency) and JAXA (Japanese Aerospace Exploration Agency) – set to arrive on upcoming shuttle missions.

‘Prior to ingressing Node-2, Whitson and Nespoli collected tools for configuring the ‘vestibule’ space between the Node-1 and Node-2 hatches, performing its outfitting necessary for the ingress (i.e., to provide power and data interfaces between the modules),’ noted Saturday’s ISS On Orbit Status Report.

‘Also before entering ‘Harmony’, FE-1 Yuri Malenchenko set up the Russian AK-1M adsorber and IPD-CO (carbon monoxide) Draeger tube air sampling equipment. Immediately after ingress, Yuri performed the air sampling, joined by Peggy and Paolo, who collected air samples with the CSA-CP (Compound Specific Analyzer-Combustion Products) and GSC (Grab Sample Container) equipment.

‘For the first 2.5 hrs after initiation of air ventilation (via a newly installed ventilation duct) between Node-1 and Node-2, crewmembers wore PPE (Personal Protective Equipment) surgical masks and goggles. For the PAO event from ‘Harmony’, the air inside Node-2 had to be renewed about five times.’

STS-120 EVA-2

A busy Sunday awaits the crew, with EVA-2 setting up the initial stages of the P6 solar array truss relocation, along with a multitude of tasks – now including an inspection of the starboard SARJ, which has been causing some concern to controllers on the ground, via observed vibrations and anomolies. Around one hour has been set aside for this additional task.

‘The CETA S1 handrail inspection and S3/S4 SARJ inspection for potential damage will be performed by Tani, while Parazynski will concentrate on the critical Node-2 outfitting,’ added the ISS On Orbit Status Report. ‘It is expected that Dan will subsequently be able to assist in the installation of the PDGF.

‘Background on SARJ: Starting on 9/2 the starboard SARJ has shown an increased current value to the drive motor (as high as 0.9A) whereas the portside SARJ has continued to operate nominally with a drive current around 0.3A. EVA-2 has been replanned to provide Dan (Tani) an opportunity to inspect the SARJ for obvious visible problems.’

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The full run-down of EVA-2 tasks are listed as: Disconnect Z1-to-P6 fluid umbilical QDs (Quick Disconnects); Detach P6 truss from Z1 truss element; Outfit Node-2 (handrails, trunnion/keel pin, covers, gap spanners, caps, CBM restraints, WIFs); CETA (Crew & Equipment Translation Aid) S1 handrail inspection for suspected MMOD (micrometeoroid/orbital debris) impacts.

Stbd SARJ (Solar Alpha Rotary Joint) inspection; Configure SFU (squib firing unit) on S1 truss to launch condition for radiator deployment; Reconnect MBSU (Main Bus Switching Unit) jumpers to support P6 start-up on P5; RPCM R&R (Remote Power Controller Module Removal & replacement); and the installation of the PDGF (Power & Data Grapple Fixture) on Node-2.

‘In preparation for EVA-2, FE-2 Clay Anderson prepared the DCS 760 digital still cameras for the spacewalk and charged the DCS batteries after their EVA-1 use,’ added the On Orbit Status Report. ‘Also working in the A/L, Scott and Dan prepared their EMU/spacesuits and the A/L EL (Equipment Lock), swapping EMU batteries, and checking out the REBA powered suit equipment and tools.

‘After completing A/L EL configuration for the first spacewalk tomorrow and conducting a joint one-hour review of EVA-2 timeline & procedures with all crewmembers, the two spacewalkers began their ‘campout’ in the ‘Quest’ A/L, starting with mask prebreathe, then closing hatches and initiating depressurization of the CL (Crewlock) from 14.7 to 10.2 psi.’

EVA-2 will begin at 5:58am EDT and last an estimated 6 hours 30min, nominally ending at 12:28pm. Nespoli and Whitson will again be IV-1 and IVA-2 (Intravehicular) crewmembers.

Flight Day 6 and EVA-2 will also involve some complex robotics, via the SSRMS (Space Station Remote Manipulator System). The arm will be used to transport the P6 solar array truss, after the spacewalkers release its bolts.

‘SSRMS starts off the day grappled to both the Lab PDGF and the MBS PDGF3 at WS4. SSRMS then ungrapples the Lab PDGF and grapples P6,’ noted the STS-120 Flight Plan walkthrough presentation. ‘Once all four P6 bolts are released and the spacewalkers are clear, SSRMS demates P6 and maneuvers to the handoff position where it remains overnight.’

Shuttle Discovery Status

Meanwhile, Discovery continues to perform without issue, with her own debuting of the SSPTS (Station-to-Shuttle Power Transfer System) performing without issue. The system made its first flight with an orbiter during STS-118 on Endeavour.

Boeing’s SSPTS provides electrical power to the orbiter main busses from the International Space Station (ISS), allowing the fuel cells to operate at lower power levels, thereby consuming less reactant from the PRSD (Power Reactant Storage and Distributation) storage tanks.

‘For the second time in history, the ISS is transferring power to the orbiter to allow it to remain docked longer. As per plan, three (of four) OPCUs (Orbiter Power Converter Units, 1A, 1B, & 2A) are currently active, transmitting up to 6.45 kW of power to the Shuttle PTUs (Power Transfer Units),’ added the ISS On Orbit Status Report.

This article will be updated as Flight Day 6 proceeds. See live threads for up-to-the-second live coverage.

L2 members: All documentation and quotes – from which the above article has quoted snippets – is available in full in the related L2 sections, updated live.

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