Two Russian spacewalks in Orlan spacesuits are to take place at long last – the previous one was just over a year ago (6 June 2007). James Oberg gives an overview in “Next spacewalk will have an explosive twist”, MSNBC.com, 2/7.
Two Russian cosmonauts on the international space station practiced Thursday for a dramatic spacewalk planned in July, which will involve taking an explosive bolt from the exterior of a docked Soyuz spacecraft and bringing it into the station itself. The risky operation is aimed at figuring out why similar bolts on earlier Soyuz spaceships misfired, leading to two rugged, off-course landings over the past year. The cosmonauts hope to avoid similar problems when they use the currently docked Soyuz to return to Earth at the end of their mission in October.
The 2/7 ISS Daily Report provides an outline of both spacewalks (20A and 20):
EVA-20A Timeline Preview: Orlan EVA-20a by Volkov/EV1 & Kononenko/EV2 is scheduled to begin at ~2:18 p.m. EDT [18:18 UTC] (DC1 EV hatch open) on 10/7, to last an estimated 6 hrs. During the spacewalk, EV2 will be riding on the DC1-based Strela 1 crane, operated via hand crank by EV1, who will then join EV2. Main objective is the inspection of the Soyuz TMA-12 spacecraft at its first separation plane (Plane I) followed by removal of one pyrobolt for return to Earth. Before removing the separation bolt, EV2 will install temporary protective covers on the spacecraft’s DPO attitude control thrusters, open up the MLI (Multi-Layer Insulation), demate the pyrobolt’s electrical connector and cut the wiretie between the pyrobolts. MLI will then be reattached and the covers removed again. If enough time remains after the Soyuz activity, the spacewalkers will also install a docking target (for the new MLM/Multipurpose Laboratory Module) in the SM PkhO (Transfer Compartment) area for zenith port docking. [Background: Before their separation, Descent Module (SA) & Instrumentation Compartment (AO) are connected by five locks, each “zamok” containing two pyrobolts with individual electrical connection, of which only one needs to fire to release the lock. The locks are equally spaced around the 360-degree circumference of the separation plane, i.e., 72 deg apart. After the five locks have released, five pushers, also equally spaced, separate the two modules by pre-loaded spring force. Each lock and pusher is located at the apex (node) of two triangularly arranged aluminum pipes, i.e., altogether 20 inclined pipes, which make up the open truss structure between the modules.]
EVA-20 Timeline Preview (preliminary): The Orlan EVA-20 by Volkov (EV1) & Kononenko (EV2) on 7/15 is scheduled to begin at ~1:14 p.m. EDT [17:14 UTC] (DC1 EV hatch open), to last an estimated 5 hrs 30 min, i.e., concluding at approximately 6:44 p.m. [22:44 UTC] Part of the EVA will be supported by the DC1-based Strela 1 crane, operated via hand crank. Main objectives of the Russian spacewalk are:
- Closeout ops on Soyuz TMA-12 Plane I inspection/pyrobolt removal (if not completed during EVA-20A);
- Installation of a new docking target on SM PkhO (Transfer Compartment), Plane IV, for MLM (if not completed during EVA-20A);
- Post-installation photography of the new docking target;
- Inspection of mounting holes for an adapter of a Kurs antenna (4AO-VKA) on PkhO-RO (SM Working Compartment, small diameter section);
- Transferring one “Yakor” foot restraint (of two) from the DC1 EVA ladder to the SM and installing it in an attachment socket at a PkhO handrail (two Yakors were installed on DC1 ladder during EVA-17A on 2/22/07);
- Installing the VSPLESK (“Burst”) science payload on the SM RO (large diameter section); and
- Removing the BIORISK-MSN (BIO-2) experiment container 1 from the DC1 for return to the station (BIORISK-MSN #1 was installed with two other BIO-2 containers during EVA-19 on 6/6/07).
