The International Space Station is in the midst of a transitional period, with the crew of the privately-operated Axiom Mission 4 aboard for a multi-week stay as Crew-11 prepares for liftoff in late July. The Progress MS-31 cargo vehicle is also set to launch to the Station on Thursday, with the older Progress MS-29 vehicle having departed for a destructive reentry on Tuesday.
Progress MS-31 which is loaded with 2,625 kg of cargo for the Station, is scheduled to launch on Thursday, July 3, at 19:32 UTC from Site 31/6 at the Baikonur Cosmodrome in Kazakhstan. Progress MS-31 will fly on a trajectory that will take it to a rendezvous and docking with the Russian segment’s Poisk module on July 5, approximately 48 hours after liftoff.
Progress MS-31’s cargo includes 1,205 kg of dry cargo — including food, clothing, and equipment for several science experiments — along with 950 kg of fuel for the Station’s thrusters, 420 kg of drinking water for the crew, and 50 kg of nitrogen to help replenish the Station’s atmosphere.
The Progress MS-31 spacecraft during processing. (Credit: Roscosmos)
The ISS uses both oxygen and nitrogen to pressurize its crew modules, unlike earlier crewed spacecraft, such as Mercury, Gemini, or Apollo, which used pure oxygen at partial pressure. The Soyuz and Crew Dragon spacecraft also use a similar two-gas pressurization system.
The Soyuz-2-1a rocket that is to fly Progress MS-31 is painted in an unusual blue and white scheme, as it was originally intended for a Glavkosmos commercial launch. It is also sporting a logo commemorating the 50th anniversary of the Apollo-Soyuz mission in July 1975.
In preparation for the new craft’s arrival, Progress MS-29 undocked from the Poisk module on Tuesday, July 1, at 18:43 UTC after over 220 days docked to the Station. The spacecraft deorbited later that evening at 22:30 UTC, carrying trash deposited by the crew to a fiery end in the atmosphere. Its departure cleared the way for Progress MS-31 to launch.
NASA maintains separate designations for Progress missions under the ISS program. Under this system, Progress MS-31 is designated Progress 92, while the recently-departed Progress MS-29 was Progress 90, and the still-on-orbit Progress MS-30 is Progress 91.
ISS visiting vehicles as of July 1, 2025 after Progress MS-29’s undocking. (Credit: NASA)
The Russian segment’s current visiting vehicle complement includes Soyuz MS-27, docked to the Prichal module at the end of the Nauka science module, and Progress MS-30, docked to the Zvezda module’s aft port. However, cracks in the aft docking port area and pressure leaks could force Roscosmos to order the port sealed off, prohibiting further use by visiting vehicles if the situation worsens.
These leaks also caused delays to the launch of the latest crewed flight to the US segment of the Station: the privately funded Axiom Mission 4 aboard Crew Dragon Grace. This mission finally launched on June 25 at 2:31 am EDT (06:31 UTC), docking to the zenith port of the Harmony module at 10:31 UTC on June 26.
The Axiom-4 crew after arrival aboard the ISS. (Credit: NASA)
Axiom-4’s crew: commander and former NASA astronaut Peggy Whitson, Indian astronaut Shubhanshu Shukla, Polish and ESA astronaut Slawosz Uznanski-Wisniewski, and Hungarian Tibor Kapu are now aboard the ISS, joining the Expedition 73 astronauts for up to two to three weeks on orbit, during which time they will conduct a number of experiments aboard the outpost. The Expedition 73 crew arrived aboard the Crew-10 and Souyz MS-27 missions earlier this year.
Crew Dragon Endurance, Crew-10’s spacecraft, is docked at the forward port of Harmony. Astronauts Anne McClain, Nichole Ayers, JAXA’s Takuya Onishi, and Roscosmos’ Kirill Peskov have been aboard the Station since March 16 and have about one more month aboard the Station before their return to Earth.
NASA astronaut Jonny Kim along with Roscosmos’ Sergey Ryzhikov and Alexey Zubritsky launched on April 8 aboard Soyuz MS-27 and will remain at the ISS until December. Russia is making its crew rotations longer – eight months instead of six – reducing the frequency of Soyuz missions from twice a year to three missions every two years.
The current Expedition 73 crew members posing inside the Zvezda service module in the Russian segment of ISS. (Credit: NASA)
The 11 crew members aboard the ISS, from six different nations, are busy with experiments and maintenance tasks. Recent science conducted aboard the Station includes measuring blood flow in the brain in microgravity, brain activity for brain-computer interfaces, high-resolution eye scans, and optic nerve scans.
Researchers are exploring using vitamin B supplements to protect astronauts’ vision in space; astronauts and scientists have reported vision degradation as a side effect of long stays in space. Besides the brain and eye experiments, electrical muscle stimulation as a supplement to exercise, hyperspectral imagery of landmarks in Mexico and Central America, and a host of other experiments also were conducted in the last few weeks.
Expedition 73 is scheduled to last until Soyuz MS-27 leaves the Station on Dec. 8. Anne McClain and Nichole Ayers completed the first extravehicular activity (EVA) of this expedition, EVA-93, on May 1. They are expected to conduct another spacewalk before they return home.
Anne McClain conducting the EVA-93 spacewalk. (Credit: NASA)
EVA-94, which does not currently have a scheduled date, will finish tasks left incomplete after EVA-93. The astronauts were unable to install telescoping booms for two side struts of the ISS Roll Out Solar Array modification kit attached to the 2B side of the P4 port truss during the previous spacewalk, so they will use EVA-94 to attempt to finish this work.
In addition, other EVA-94 tasks include removing H fixtures on the S6 starboard truss, replacing Camera 9 and bringing it back inside the Station, replacing a light, installing a router, and installing a DC to DC converter unit jumper cable.
Crew-11 is the next scheduled crewed flight to ISS, with a no earlier than (NET) launch date of this month. It will use Crew Dragon Endeavour, which was the first Crew Dragon to fly with astronauts aboard, and is expected to lift off sometime after Axiom Mission 4 has departed the Station.
The official Crew-11 portrait. (Credit: NASA)
Crew-11 will be commanded by NASA’s Zena Cardman, who had been scheduled to command Crew-9 before that mission’s crew size had to be reduced due to the situation with the Starliner Crewed Flight Test and its uncrewed return to Earth. Her fellow NASA astronaut Mike Fincke is the mission pilot. This will be Cardman’s first space mission, while Fincke is a veteran astronaut making his fourth flight.
JAXA’s Kimiya Yui is one of Crew-11’s two mission specialists. This will be his second spaceflight, while Roscosmos’ Oleg Platonov is making his first. Following a handover period, Crew-10 will return to Earth with a splashdown off the US West Coast.
While the Station and its crew continue their activities, the program’s future is being considered on the ground. Besides the ongoing issues with cracks and leaks in the Zvezda module, NASA budget deliberations in Congress continue which could see the program’s research and crew visits cut in the near future. The program is entering its last few years before the Station’s scheduled deorbit in the 2030-31 timeframe.
(Lead image: Progress MS-31 on the launch pad before its scheduled launch on Thursday, July 3, 2025. Credit: Ivan Timoshenko and Roscosmos)
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