Astronauts aboard the International Space Station completed a six-hour and 49-minute spacewalk on Sept. 1, installing a new retroreflector on the Harmony module's forward port to help guide visiting vehicles and replacing a high-definition camera on the station's truss assembly. Sophie Adenot, serving as EV1, and Jessica Meir, as EV2, also swabbed the station's exterior for microorganism samples and began routing jumper cables for electrical systems, work that will be finished on a future spacewalk.
The excursion, designated US EVA-99, was the 248th spacewalk in support of the orbiting laboratory. It marked Meir's seventh spacewalk and Adenot's third. Meir now ranks as NASA's third most experienced female spacewalker, behind only Peggy Whitson and Suni Williams. During the spacewalk, Adenot experienced mobility problems in her left shoulder that were traced to a joint heater harness caught in the shoulder joint; Meir unzipped the joint and the issue appeared to be resolved. The aging shuttle-era suits have repeatedly delayed station spacewalks and forced repairs on various components, some of which can be returned to Earth aboard Cargo Dragon spacecraft for evaluation.
Two more spacewalks are planned for Expedition 75 to install iROSA solar arrays on the 3B and 2A power channels, though NASA has not yet announced a schedule for that work. The new arrays are part of ongoing efforts to maintain the station's power supply as it continues to operate more than a quarter-century after its first elements launched.
In the Russian segment, the Progress MS-33 cargo ship undocked from the Poisk module to clear the way for its successor. Loaded with trash, MS-33 burned up on reentry on Sept. 7. Progress MS-35 launched Sept. 16 after a hydraulic issue with its rocket forced a delay from an earlier Sept. 9 target, and it docked with the Poisk module on Sept. 19 at 13:44 UTC. The freighter, also designated Progress 96 by NASA, delivered roughly 2,600 kilograms of cargo for the station and its crew. As of Sept. 24, five visiting vehicles were attached to the station: Progress MS-34 and MS-35, Soyuz MS-29, Dragon Freedom on the Crew-12 mission, and the NG-24 Cygnus S.S. Steven R. Nagel.
NASA also announced that the Crew-13 flight would be delayed because of an oxidizer leak on the Crew Dragon Grace spacecraft. The mission is now set for Oct. 1, and the Crew-13 astronauts entered quarantine on Sept. 17. When they arrive, NASA astronauts Jessica Watkins and Luke Delaney, Canada's Joshua Kutryk, and Roscosmos' Sergey Teteryatnikov will relieve their Crew-12 counterparts after a short handover period. Expedition 75 will continue until spring 2027 and the planned departure of Soyuz MS-29.
Science work has continued alongside the logistics and spacewalk activity. NASA's Anil Menon set up a work area in the Harmony module and soldered components on a circuit board as part of a lead-free soldering experiment. The board will be returned to Earth for comparison with another soldered on the ground. Demonstrating in-flight soldering could reduce reliance on resupply flights during future missions by enabling more repairs to be carried out in place. Other recent highlights included a 3D colloidal crystal experiment that observed particles suspended in liquids, with possible applications for space-based manufacturing. Adenot set up the Kubik research incubator and centrifuge for remote operation by scientists on the ground, a common way experiments aboard the station are controlled.
Adenot has also worked extensively with the Advanced Resistive Exercise Device in the Tranquility module, recording her workouts with a motion capture system, and is evaluating the European Enhanced Exploration Exercise Device in the Columbus science module, including rope-pulling exercises that had never been performed in space. Astronauts must exercise at least two hours per day to counter microgravity's effects on the body, such as muscle atrophy and bone weakening. Cosmonauts Andrey Fedyaev and Anna Kikina have been evaluating a Russian lower-body negative pressure suit designed to force blood back toward the lower body and feet, reversing the fluid shift toward the head that occurs in weightlessness. Future crews may use such suits to help adapt to Earth's gravity before returning home.
Meanwhile, NASA signed a contract modification with SpaceX to fly the upcoming Crew-15, Crew-16, and Crew-17 missions, with readiness dates in 2027 and 2028.
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