STORY WRITTEN FOR CBS NEWS USED WITH PERMISSION
After a bit of a onslaught with a refractory bolt, space hire commander Peggy Whitson transposed a unsuccessful outmost mechanism during a short, hurriedly designed spacewalk Tuesday while crewmate Jack Fischer commissioned a span of antennas to urge wireless communications during destiny excursions.
The comparatively brief two-hour 46-minute spacewalk was a tenth for Whitson, already a world’s many gifted womanlike spacewalker, and it changed her adult from fifth to third in a universe with a accumulative EVA time of 60 hours and 21 minutes.
Only cosmonaut Anatoly Solovyev and late wanderer Mike Lopez-Alegria have some-more spacewalk time than Whitson, who also is NASA’s many gifted wanderer altogether with 564 days in space, as of Tuesday, over her 3 hire stays. Her sum time in space will mount during 666 days when she earnings to Earth Sept. 3.
Tuesday’s spacewalk was systematic when an outmost mechanism famous as a multiplexer-demultiplexer unsuccessful Saturday. Two such avionics boxes are used to control a far-reaching accumulation of hire systems and while one can lift a bucket on a own, NASA managers wanted to get a deputy commissioned as shortly as probable to revive full redundancy.
The spacewalk began during 7:20 a.m. EDT (GMT-4) when Whitson and Fischer switched their spacesuits to battery power. After withdrawal a station’s Quest airlock, a astronauts separate up, with Whitson creation her approach to a lab’s energy constrict where a unsuccessful MDM was located and Fischer relocating to a Earth-facing side of a Destiny laboratory module.
“Oh my gosh, so beautiful!” Fischer pronounced looking down on a Earth 250 miles below.
He had no problems installing a wireless antennas while Whitson private a unsuccessful MDM. But when attempting to implement a deputy box, she felt a executive primary shaft holding it in place was not as secure as she expected. She afterwards private a MDM and reported tiny shavings or waste floating from a closeness of a executive shaft hole.
Fischer retrieved a cleaning apparatus from a airlock and helped Whitson mist dense nitrogen into a primary shaft hole and dual delegate equipment to purify out any debris.
Whitson re-installed a MDM and while dual of a 3 bolts did not expostulate in as many turns as expected, engineers motionless a box was resolutely in place.
“All right, Peggy, good news,” called wanderer Jessica Meir from goal control in Houston “We have a good install, everybody’s happy with those.”
After plugging in an ethernet cable, Whitson stood by while moody controllers activated a deputy MDM for initial tests and checkout. A few mins after they reported a box seemed to be in good figure and operative normally.
Whitson and Fischer afterwards collected their collection and done their approach behind to a Quest airlock. Repressurization started during 10:06 p.m., strictly bringing U.S. EVA-43 to a close.
It is not nonetheless famous what caused a MDM to malfunction Saturday. Whitson, inspecting a unsuccessful section after she private it from a energy truss, reported no apparent signs of repairs to any of a electrical connectors. What competence have left wrong inside a box is not nonetheless known.
The space hire uses 44 MDM computers, operative in 3 “tiers,” to control probably all aspects of a lab’s operation.
Three top-level tier 1 MDMs are tied together, with one actively estimate information and promulgation commands, one in a “warm” backup mode estimate information though not autocratic and one that is powered adult though in standby mode. The tier 1 MDMs are double-fault tolerant, definition a hire can work with dual failures.
The MDM that unsuccessful and an matching section are partial of a tier 2 authority design and send commands to a accumulation of vicious hire systems, including a station’s guidance, navigation and control system, a lab’s stabilizing gyros, a environmental control system, a station’s cooling complement and others.
Both tier 2 computers were commissioned during spacewalks Mar 30 and Mar 24 respectively, replacing dual comparison units with models featuring upgraded information estimate cards. It is not nonetheless famous either a problem with MDM-1 concerned a upgraded components or some other electronics or software.