Just days after installing a new grapple fixture on the International Space Station’s robotic Canadarm2, NASA is working on a plan to re-install the old latching end effector on an upcoming spacewalk after a problem was found with the new mechanism.
U.S. EVA-48 was already planned for Monday, Jan. 29, 2018, less than a week after the previous spacewalk installed the new LEE. Now with an issue NASA says is preventing the grapple fixture from “transitioning to an operational state on one of two redundant sets of communications strings,” the space agency will send two astronauts outside to undo the work done on U.S. EVA-47.
Hints of an issue cropped up during the previous spacewalk when two of the six Expedition 54 astronauts—NASA’s Mark Vande Hei and Scott Tingle—replaced the end effector, called LEE-B, but ground teams were unable to communicate with the mechanism.
“The spacewalking crew demated and remated the connectors and ground teams were able to power up the arm to an operational state on its secondary communications sting leaving the arm operational but without a redundant communications string,” a NASA statement reads.
After several days of troubleshooting, NASA and the Canadian Space Agency—which built the 17-meter long Canadarm2—said the decision was made to use the upcoming spacewalk to re-install the old LEE-B to restore the redundant capability with the arm. The space agency said if Canada and its robotics specialists find a way to solve the issue, the Jan. 29 spacewalk could be delayed.
On Jan. 23, 2018, Vande Hei and Tingle performed the first spacewalk of 2018. The 7.5 hour extravehicular activity only involved replacing the old LEE-B. LEE-A had already been replaced during a trio of spacewalks in October of 2017 and continues to operate nominally. The spare LEE-B had been brought to the outpost in 2009 and remained in storage on the stations exterior since.
Canadarm2 has been in orbit since 2001 when Space Shuttle Endeavour’s STS-100 crew brought the remote manipulator system to the outpost. NASA managers said replacing the two LEEs would enable the arm to continue to operate during the remainder of the outposts expected lifespan.
The Jan. 29 spacewalk will see Vande Hei leave the station again, this time with Japan Aerospace Exploration Agency astronaut Norishige Kanai. It will be the former’s fourth spacewalk and the latter’s first.
Originally, the duo were to move the old LEE-B, currently in temporary storage on External Stowage Platform-2, to the station’s Mobile Base System on the outposts large truss assembly. LEE-A, which is currently on the MBS, was expected to be brought inside the outpost to be returned to Earth inside a future SpaceX Dragon capsule.
It is unclear if, when, or how many spacewalks will be planned to finish the job of replacing LEE-B and to move LEE-A inside. Additionally, a Russian segment-based spacewalk is expected to be performed Feb. 2, 2018, by the two Expedition 54 Russian cosmonauts, Alexander Misurkin and Anton Shkaplerov. They are slated to retrieve external science samples and install a high gain antenna on the Zvezda service module, according to NASA.
NOTE: While this article was written by Derek Richardson, it was originally published at SpaceFlight Insider. Feel free to head over there to read all the stuff they write about!