What's worse than fiddling with cables? Trying to do it in vacuum, wearing gloves, with the sun setting every hour. Astronauts Butch Wilmore and Tery Virts spent nearly seven hours to run just over 100 meters of cable reconfiguring the space station for the commercial crew program.
Astronaut Terry Virts running cabling on the outside of the International Space Station, as seen from the cupola. Image credit: NASA/Samantha Cristoforetti
Today, Commander Barry Wilmore and Flight Engineer Terry Virts put in nearly seven hours as the cable guys for the International Space Station. The astronauts ran 103 meters of cable as part of reconfiguring the station to install new docking adapters for commercial crew vehicles. This was the first of three spacewalks within the next month all dedicated to the remodelling program, the first step in preparing the station of the arrival of space taxis starting in 2017.
Astronaut Terry Virts is an inverted reflection in Butch Wilmore's visor. Image credit: NASA/Butch Wilmore
Proving that cable repair windows are universally unreliable, the extravehicular activity got off to a late start when astronauts Wilmore and Virts exited the station at 7:45 a.m EST, nearly a half-hour behind schedule. They immediately got to work on rerouting cables around the Harmony module, and attaching power and data cables to the Pressurized Mating Adapter-2 (PMA2). Today's To Do list sounds dreadfully boring — routing cables, whoohoo! — but is notoriously fiddly work for astronauts to accomplish in their not-so-dexterous gloves.
Fiddling with cables is not easy in bulky, tough, insulated, pressurized gloves. Image credit: NASA/Terry Virts
To make the ambitious task of moving around ten cables with a total of 21 leg-ends even more obnoxious, some of the rerouted cables were never designed to be unplugged and manipulated in orbit so lack the standard semi-astronaut-friendly EVA connectors. Not only did Wilmore and Virts make it through their entire list, but by extending the EVA a few extra minutes until 2:26 p.m. EST, they were even able to get an extra chore completed ahead of schedule. (The extra chore was another dull-but-necessary task: moving around supplies to pre-stage for the next spacewalk, saving time getting started on the next batch of chores.)
Animation of planned spacewalk activities.
All this work is being done in preparation for a pair of new docking adapters manufactured by Boeing for the commercial crew transport program that will be delivered to the station later this year. The new docking adapters are specifically designed to be compatible with the two spacecraft selected for NASA's commercial crew transport program: Boeing's CST-100 and SpaceX's Crew Dragon. The spacecraft are currently being built and flight-tested in anticipation of being crew-certified in 2017, taking on crew transportation duties in the years ahead.
Space cable guy Terry Hurts with his safety tether glittering in the sunshine. Image credit: NASA/Butch Wilmore
The station needs to be reconfigured with new docking ports because the current setup was designed for the space shuttles, and because we're trying to be gentler on our aging station to extend its lifespan.
The problem with having a shuttle-friendly layout gets into the difference between docking and berthing. Berthing is when a spacecraft gets within reach of the station, gets grappled by the Canadarm, pulled in close, then astronauts intercede to manually hook, tug, plug, and seal everything into place. While functional for the many cargo tugs that ferry supplies to the station, this process is neither graceful nor quick, and doesn't meet the emergency-escape requirements of a crew vehicle. Instead, crew vehicles need to dock with the station: flying directly up to the station and attaching via a capture ring.
Wilmore (left) and Virts (right) plugging in cables at PMA2 on the Harmony module. Screenshot from NASATV
The space shuttles used to dock with the space station at Pressurised Mating Adapter-2 (PMA-2). Since only one shuttle ever came to the station at a time, only one docking adapter was needed. The backup, PMA-3, was tucked away in an inaccessible storage module with insufficient clearance from other station structures to allow clean entries and exits. A backup system that is totally nonfunctional is no backup at all, and is not acceptable for the higher-traffic future we envision for the station. Therefore, PMA-3 is being shuffled to a new module and a new orientation, taking the spot of port currently used as a backup for cargo vehicles, and that backup port will be slipped off to a new location.
Virts (right) dives headlong into his work while Wilmore (left) rigs cables in a more traditional orientation. Screenshot from NASATV
It's also time for a technology upgrade on the ports. The original connectors use the Androgynous Peripheral Attachment System (APAS), a capture ring that requires smashing into the station to engage properly. While functional, repeatedly smashing into the station is causing problems for structural integrity, triggering microcracking that isn't necessarily a problem yet but will definitely shorten the lifespan of the aging station. To fix this, Boeing has designed Soft Impact Mating Attenuation Concept (SIMAC), a docking system that uses electromagnets instead of kinetic impact to make a solid seal between spaceship and space station. The new system is integrated into a pair of International Docking Adapters (IDAs) that will be shipped up to the station later this year to convert both PMA ports to the new system.
Before heading on the EVA, astronauts Wilmore and Virts breathed pure oxygen to remove nitrogen from their bloodstreams.
For the 185th spacewalk supporting the space station's construction and maintenance, the astronauts are colour-coded for easier identification. Out on his second spacewalk, Wilmore (EV1) is in a spacesuit with red stripes, and his helmet camera is number 18. Stepping outside for the first time, Virts (EV2) is wearing an unstriped spacesuit with helmet camera number 20.
This spacewalk was the first of three for Wilmore and Virts as they work on reconfiguring the station. The next venture outside the station will be on February 25th to deploy two more cables and to lubricate a robotic arm. The final spacewalk in the sequence is currently scheduled for March 1st.