Wednesday, January 24, 2018

Astronauts Replace Canadarm2 ‘Hand’ on ISS in First Spacewalk of 2018

Spacewalker Mark Vande Hei took his own photograph during the first spacewalk of 2018. These sky-high pictures are better known as “space-selfies.” Credit: NASA

The first spacewalk of 2018, U.S. EVA 47, is now in the history books after two NASA astronauts completed a nearly 7.5 hour extravehicular activity to replace an aging latching end effector on the International Space Station’s robotic Canadarm2.

Canadarm2 has a latching end effector, also called a LEE, on either side of the 58-foot (17-meter) robotic arm to either grab onto the exterior of the station, move objects around the outpost, or grab visiting spacecraft.

Launched in 2001 during Space Shuttle Endeavour’s STS-100 mission, the Canadian-built arm was designed to be serviced and refurbished in orbit. As such, in 2015, both end effectors, LEE-A and LEE-B, were lubricated during several spacewalks to extend the life of the “hands” of the outpost.

But with the LEEs more than 15 years in age, it was time to replace them. LEE-A was replaced over the course of three spacewalks in October 2017.

LEE-B was replaced during this spacewalk, U.S. EVA-47. LEE-B was originally planned to be replaced first, but a motor stall in the latches of LEE-A prompted NASA to switch the order.

The two Expedition 54 astronauts that performed this spacewalk were NASA’s Mark Vande Hei, who wore the spacesuit with red stripes and was designated EV-1, and Scott Tingle, who wore a space suit with no stripes and was designated EV-2.

After suiting up and squeezing inside the station’s Quest airlock, the chamber that leads to the exterior of the outpost, was sealed off from the rest of the lab with the duo inside and slowly depressurized.

U.S. EVA 47 began at 6:49 a.m. EST (11:49 GMT) Jan. 23, 2018, when Vande Hei and Tingle switched their spacesuits to battery power.

Not long after the start of the spacewalk, the first of several time-delaying issues cropped up. Vande Hei’s Display and Control Module on his suit locked up requiring him to completely reboot his suit.

Once it was verified his equipment was working, he and Tingle moved to External Stowage Platform 2 (ESP-2) to set up their work area. This involved placing two foot restraints on the platform so that the duo would be able to work on Canadarm2 with their feet attached to the station.

LEE-B was also at ESP-2. It was brought to the outpost during Space Shuttle Atlantis’ STS-129 mission in 2009.

The first order of business for the crew was to prepare the spare LEE for installation. This included removing insulation blankets and opening four launch locks to rotate the end effector upright allowing the astronauts to get to the ring where six bolts are holding it to the platform.

The first few bolts were released before the astronauts got onto their foot restraints to focus on the LEE-B attached to Canadarm2.

Just like on the spare, insulation blankets were removed to gain access to the ring attaching LEE-B to the arm’s wrist joint. The first two bolts were removed using the Pistol Grip Tool (PGT), a space-grade power tool. Once the bolts were released, Japanese astronaut Norishige Kanai, who was inside the station, commanded Canadarm2 to rotate LEE-B to give Vandi Hei access to the next set of bolts.

Written by: Derek Richardson
Original source: spaceflightinsider.com

2 comments:

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