ISS finishes out eventful third quarter of 2024 with Expedition 71 giving way to Expedition 72

by Justin Davenport

The International Space Station (ISS) has spent the last three months with a larger crew complement than usual following the Starliner Crew Flight Test (CFT) docking with the ISS on June 6. However, the Station’s crew complement is about to return to its normal number of astronauts with the imminent departure of Crew-8 and Crew Dragon Endeavour after the handover with the CFT and two Crew-9 astronauts.

August began with Starliner Calypso still docked to ISS and ended with a large change in plans due to returning Calypso without the CFT crew. Crew-9 was changed from the usual four astronauts to just two, with the CFT crew, Butch Wilmore and Suni Williams, forming the other half of the crew that Crew-9 commander Nick Hague and Roscosmos’ Aleksandr Gorbunov will spend six months with. Former Crew-9 commander Zena Cardman and mission specialist Stephanie Wilson are now available for future assignments.

While the CFT crewmembers were working with the Crew-8 members assigned to Expedition 71 on experiments and Station upkeep, a Northrop Grumman Cygnus cargo ship launched to the Station on Aug. 4. The Cygnus, S.S. Francis R. “Dick” Scobee, named after the commander of the ill-fated STS-51L mission, was berthed to the Station two days after its launch. It is to stay berthed to the ISS Unity module’s nadir common berthing mechanism until sometime around January 2025.

Cygnus cargo ship S.S. Francis R. “Dick” Scobee approaches ISS for the Canadarm2’s 50th berthing of a spacecraft. (Credit: NASA)

In addition, Roscosmos was preparing for its own crew handover on the Russian segment of the ISS. Soyuz MS-26 launched successfully on Sept. 11 at 16:23 UTC, with Roscosmos commander Aleksey Ovchinin, Roscosmos flight engineer Ivan Vagner, and NASA’s Don Pettit docking with the ISS Russian segment’s Rassvet module just over three hours later.

After a 12-day handover period, Expedition 71 officially ended with the undocking of Soyuz MS-25 from the Russian segment’s Prichal module on Sept. 23 at 08:36 UTC. Roscosmos crew commander Oleg Kononenko, Roscosmos flight engineer Nikolai Chub, and NASA’s Tracy C. Dyson landed safely in Kazakhstan aboard Soyuz MS-25 on Sept. 23 at 11:58 UTC.

Kononenko and Chub spent 374 days in space due to a crew reshuffle necessitated by the Soyuz MS-22 on-orbit coolant leak and the need to launch Soyuz MS-23 uncrewed to bring back the Soyuz MS-22 crew. Soyuz MS-24, which Kononenko and Chub launched aboard, was then needed to bring home Roscosmos’ Oleg Novitskiy and Belarus’ Marina Vasilevskaya, who launched aboard Soyuz MS-25.

Expedition 71 NASA astronaut Tracy Dyson, Roscosmos cosmonaut Oleg Novitskiy, and Belarus spaceflight participant Marina Vasilevskaya are seen in quarantine, behind glass, during a press conference on Wednesday, March 20, 2024. They launched aboard Soyuz MS-25 just a few days later. (Credit: NASA/Bill Ingalls)

NASA’s Loral O’Hara, who launched with Kononenko and Chub, landed with Novitskiy and Vasilevskaya on Soyuz MS-24, while Tracy C. Dyson launched aboard Soyuz MS-25 with Novitskiy and Vasilevskaya. O’Hara and Dyson were the only crew members who launched and landed aboard the same spacecraft.

Kononenko and Chub, having set the record for the longest continuous stay aboard the ISS, now join their compatriots Mikhail Kornienko, Sergey Prokopyev, Dmitry Petelin, and Pyotr Dubrov, along with NASA’s Frank Rubio, Mark Vande Hei, Christina Koch, and Scott Kelly, as crew members who have spent over 300 consecutive days in space aboard the Station. In addition, Kononenko has spent 1,111 days cumulatively in orbit and is the current record holder for most cumulative days in space.

These orbital stays exceed the roughly nine months it would take a crew to get from Earth to Mars one-way using the lowest-energy trajectory possible — a Hohmann transfer orbit — and have greatly increased human knowledge on the effects of long-term exposure to microgravity.

Oleg Kononenko, Nikolai Chub, and Tracy C. Dyson returned to Earth aboard Soyuz MS-25. (Credit: NASA)

While Kononenko and Chub spent over a year in orbit, Dyson spent nearly 184 days in orbit. NASA usually assigns crews to ISS stays for six months, though Wilmore and Williams will have spent nine months in orbit before returning to Earth aboard Crew-9 early next year.

As a result of the CFT mission ending without its crew, the Crew-9 mission not only had its crew complement reduced but was also pushed back from mid-August to late September. Crew-9’s launch is now set for Saturday, Sept. 28, at 1:17 PM EDT (17:17 UTC) after a delay from Sept. 24 due to unsettled tropical weather in the Gulf of Mexico.

Once Crew-9 and the Crew Dragon Freedom dock with ISS on the Harmony module’s forward port, the handover period between Crew-8 and Crew-9 will commence. Crew-9’s vehicle will become the spacecraft the CFT astronauts will use for their normal return and any emergencies, while Crew-8 and Crew Dragon Endeavour will be prepared for departure.

Closeup of Crew Dragon Endeavour during its relocation to the zenith port of Harmony. (Credit: NASA)

Crew-8’s undocking from Harmony’s zenith port is scheduled for Sunday, Oct. 6, at 12:00 UTC with NASA’s Matthew Dominick, Michael Barratt, and Jeanette Epps along with Roscosmos’ Alexander Grebenkin aboard.

Crew Dragon Endeavour is scheduled to splash down in the Atlantic or the Gulf of Mexico off Florida, and looks likely to be one of the last Crew Dragons to do so. Next year, SpaceX is moving Crew Dragon recoveries to the west coast of the U.S. so that debris from the expendable “trunk” of the spacecraft does not fall over populated areas. Endeavour’s splashdown is subject to weather being acceptable at one or more splashdown sites, and tropical weather could have a say in when Crew-8 comes back to Earth.

After Crew-8’s return to Earth, the Station will be left with the two Crew-9 astronauts, the two CFT astronauts, and the three Soyuz MS-26 crew members on board, with Suni Williams having now become the Station’s commander upon Soyuz MS-25’s undocking.

Current visiting vehicle complement on ISS as of September 25, 2024. (Credit: NASA)

They will have a busy few months during the Expedition 72 increment that started with MS-25’s undocking. Astronauts Wilmore and Williams not only have prior ISS expedition experience but also training in conducting spacewalks and any other tasks they may need to perform. The Expedition 72 crew has not only the usual Station maintenance tasks and science experiments to perform but also could be tasked with resuming EVAs from the ISS following technical issues that have kept U.S. segment EVAs from being completed since November 2023.

The last successful EVA from the US segment occurred on Nov. 1, 2023. On ISS EVA-89, Jasmin Moghbeli and Loral O’Hara prepared the Station’s S4 truss segment for the installation of a new solar array. They also replaced a trundle bearing on the port solar alpha rotary joint and secured a cable on Camera 8. They could not complete the retrieval of the S-band Antenna Sub-Assembly (SASA) from the External Stowage Platform-2.

Astronaut Tracy C. Dyson in her spacesuit during the shortened spacewalk on June 24, 2024. (Credit: NASA)

The latter task was supposed to be performed on the next EVA from the US segment. However, it still has not been completed due to repeated issues with the aging Extravehicular Mobility Units (EMU) aboard the Station. These Shuttle-era suits have been used for Station EVAs from the US segment ever since the first U.S. element was launched in December 1998, and the EMU was designed in the late 1970s before first being used in April 1983.

On June 24, after earlier delays and a change of spacewalkers, Tracy C. Dyson and Michael Barratt donned their spacesuits for EVA-90. Their tasks were to perform the SASA retrieval, collect samples from the Station’s hull for examination of possible microorganisms, and prepare the Canadarm2 robotic manipulator arm for a future wrist joint replacement. However, the EVA lasted for only half an hour due to a service and cooling umbilical water leak on Dyson’s spacesuit.

The only successful EVA completed on ISS so far in 2024 was the spacewalk on April 25 performed by Russian cosmonauts Kononenko and Chub. They donned their Orlan suits and completed several tasks on the Russian segment. These included gathering microbial and hydrazine samples from handrails, releasing launch locks on a radar unit, retrieving a Biorisk canister, and installing a payload adapter.

Matthew Dominick (to left) and Don Pettit checking a camera aboard ISS. (Credit: NASA)

When EVAs resume from the US segment, the SASA retrieval will be one of the crew’s tasks. Other tasks included sample collection from the ISS exterior, wrist joint replacement preparation on the Canadarm2, replacement of rate gyros from the S0 truss section, installation of struts for a future solar array upgrade, and the replacement of Camera 9, among others.

The Expedition 72 crew has already started work on various experiments. This includes a colloid gel experiment examining the relationship between particle sizes and gel structure. Ivan Vagner assisted departing cosmonaut Alexander Grebenkin with testing a new Roscosmos lower body negative pressure suit, while Don Pettit worked out on the advanced resistive exercise device while a motion capture system monitored his form. This could inform new exercises to sustain crew health on long-duration space missions.

During the past few months, the Station crew has performed many experiments. Some of these include experiments with a free-flying artificial intelligence assistant known as CIMON, vein scans with an ultrasound device, and an orthostatic intolerance garment designed to help astronauts adapt more quickly to Earth’s gravity after returning from space.

Aurora seen over the Indian Ocean as the ISS flies overhead. The Nauka and Prichal modules and Soyuz MS-25 spacecraft can be seen. (Credit: NASA)

Ultra-high-resolution photography experiments have also occurred, with new cameras being tested. Photography is one of the activities that crew members routinely perform on the Station, and the Cupola module was designed to facilitate this. Don Pettit, along with Matthew Dominick, are veteran photographers who have documented the Earth from the ISS, and many parts of the world have been photographed over two decades of ISS occupancy.

Over the next few months, the Station will be visited by the Progress MS-29 cargo ship in November and the CRS-31 Cargo Dragon mission no earlier than October. CRS-32 is another Cargo Dragon mission scheduled for no earlier than this coming December. While these missions bring needed cargo, the Expedition 72 crew will continue to stay busy with maintenance tasks, experiments, and perhaps the resumption of EVAs.

(Lead image: Soyuz MS-26 is seen in the foreground docked to the Rassvet module, while Soyuz MS-25 is docked to the Prichal module in the background. Credit: NASA)

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