NASA astronauts Chris Williams and Jessica Meir spent 7 hours and 20 minutes outside the International Space Station on Monday, removing a malfunctioning wrist joint from the Canadarm2 robotic arm and installing a replacement that was already stored aboard the orbiting laboratory. The repair, designated U.S. Spacewalk 95, restored full range of motion to the 17-meter arm that handles cargo transfers, visiting vehicle captures, and crew support on a daily basis. The fact that a spare joint was already on station allowed the crew to act roughly five weeks after the malfunction first appeared on May 27, avoiding the months-long wait that a resupply mission would have required.
How a spare part turned five weeks of downtime into a same-day fix
On May 27, ground controllers detected elevated motor current and unexpected motion behavior in one of Canadarm2’s wrist joints. The arm remained operational but with restricted capability, limiting the station’s ability to move external payloads and reposition hardware. NASA and the Canadian Space Agency analyzed the telemetry and concluded that a spacewalk was required to swap the component. Because a replacement joint was already aboard, mission planners could schedule the repair for June 30 rather than waiting for a cargo vehicle to deliver one from Earth.
That timeline tells a practical story about how the station manages risk. Resupply missions to the ISS typically fly on schedules set months in advance, and adding an unplanned payload to a cargo manifest involves engineering reviews, packaging, and launch-window coordination. Keeping a spare wrist joint in the station’s inventory compressed the response from what could have been a quarter-year gap into just over a month of reduced arm operations. For a system that supports nearly every external maintenance task and visiting vehicle berthing, each week of limited capability carries a cost in deferred work and schedule pressure on other station systems.
What Williams and Meir did during 7 hours outside the station
Williams and Meir began their spacewalk at approximately 8:35 a.m. EDT, with live coverage starting at 7 a.m. ET. Their primary task was straightforward in description but physically demanding in execution: unbolt and remove the failed wrist joint, then install the spare in its place. Spacewalk flight director Fiona Antkowiak participated in a preview briefing before the event, outlining the planned steps and contingencies.
The EVA ran 40 minutes longer than the roughly 6 hours and 40 minutes that NASA had originally estimated, ending at 3:40 p.m. EDT. Extended spacewalk durations are not unusual when crews encounter tight bolt connections or need extra time to verify that a replacement component is properly seated and electrically connected. The additional time suggests the crew took care to confirm the new joint was fully functional before closing out the work, though NASA’s post-mission account did not detail the specific cause of the overrun.
The completed repair restores Canadarm2 to full operational status. That matters because the arm is not a backup system or a secondary tool. It is the station’s primary means of grappling cargo vehicles, repositioning external equipment, and supporting astronauts during other spacewalks. Any period of reduced arm capability forces mission planners to defer tasks or find workarounds, and those delays ripple through a station schedule that is already tightly packed.
Open questions after the Canadarm2 wrist joint swap
Several details remain absent from NASA’s public accounts. The agency has not released raw motor current telemetry or motion logs from the May 27 malfunction, so outside engineers cannot independently assess how close the joint was to total failure or whether the elevated current indicated a mechanical, electrical, or software root cause. Post-EVA inspection data and torque measurements from the removed joint have not been published either. Those measurements would help determine whether the failure mode could affect the other joints on Canadarm2, which share the same basic design and have accumulated similar hours of use in the harsh thermal and radiation environment of low Earth orbit.
Neither Williams nor Meir has been quoted in any of the official NASA releases about the repair, an unusual gap given that astronaut commentary typically accompanies high-profile spacewalks. The absence of direct crew observations leaves a hole in the public record about what the damaged joint looked like up close and whether the crew noticed any external signs of wear or damage during removal.
The most immediate question for station operations is whether NASA and CSA will send a replacement spare to the station. The inventory now has zero backup wrist joints aboard. If a second joint fails before a new spare arrives, the station would face the exact months-long delay that the pre-positioned part avoided this time. How quickly the agencies move to restock that inventory will signal whether the lesson of this repair, that targeted spares cut downtime far more effectively than faster resupply cycles, has been absorbed into planning. Readers tracking ISS operations should watch for manifest updates on upcoming cargo missions for any mention of Canadarm2 hardware.
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*This article was researched with the help of AI, with human editors creating the final content.
