SpaceX, along with Axiom Space, had been preparing to launch the fourth private Dragon mission to the International Space Station (ISS). The mission has since been postponed, however, following leaks that have been discovered on both the launch vehicle and subsequently on the Station’s Zvezda module.
A Falcon 9 rocket was due to launch the mission from Launch Complex 39A (LC-39A) at the Kennedy Space Center (KSC) on Wednesday, June 11. SpaceX indefinitely delayed the mission on Tuesday evening after discovering a liquid oxygen leak in the engine bay of the first stage, B1094, during post-test inspections that followed a brief 7-second static fire on the pad. A leak had previously been detected following the booster’s maiden flight and was believed to have been addressed during refurbishment.
NASA subsequently reported on Thursday, June 12, that the mission will be postponed while it investigates another leak – this time on the ISS in the aft most segment of the Zvezda service module. The agency is working with Roscosmos to evaluate the situation and determine whether any additional troubleshooting is necessary, it reported.
Falcon 9 on the pad at LC-39A ahead of the Axiom-4 launch (Credit: SpaceX)
Axiom-4 (Ax-4) will include the American astronaut with the most time in space and members from three different countries, each marking that country’s first journey to the Station. The mission is expected to spend up to 14 days docked to the ISS.
Mission overview
The Ax-4 mission has the slogan “realize the return,” which is meant to symbolize the return of three different nations to spaceflight. Poland, Hungary, and India have each sent one human to space previously in 1978, 1980, and 1984, respectively. This flight will see each nation have an astronaut onboard.
All three nations have also never had a human presence aboard the ISS throughout its more than 25 years in orbit prior to this flight.
The Ax-4 crew started familiarizing themselves with the SpaceX Dragon spacecraft. (Credit: SpaceX)
The primary objective of the mission is to complete as much research as possible during the two weeks onboard the station. With nearly 60 scientific studies from 31 different countries — including the United States of America (USA), India, Poland, Hungary, Saudi Arabia, Brazil, Nigeria, the United Arab Emirates (UAE), and more — this will be the most research conducted on any Axiom mission launched to date.
Docking to the Station was due to take place approximately 12 hours after launch, with research able to begin shortly after.
The crew
The mission will be commanded by Peggy Whitson, piloted by Shubhanshu Shukla, with mission specialists Sławosz Uznański-Wiśniewski and Tibor Kapu.
Peggy Whitson, who was inducted into the US Astronaut Hall of Fame just weeks before the flight, currently holds the record for the most time spent in space by an American with 675 total days in orbit.
Ax-4 mission commander Peggy Whitson. (Credit: Axiom Space)
With more than 38 years of NASA experience, Whitson has held the roles of chief of the Astronaut Office, chair of NASA’s Astronaut Selection Board, chief of NASA’s Operations Branch, and deputy division chief for both Medical Sciences and the Astronaut Office.
She has flown on four different missions to space, all of them to the ISS. She first flew on Expedition 5, where she was named NASA’s first science officer, and also flew on Expeditions 16 and 50/51/52. During that time, she performed 10 spacewalks, setting the record for the most spacewalks by a female.
Whitson then assumed the position of director of human spaceflight for AxiomSpace and becoming the first woman to command a private space mission during Ax-2.
She grew up on a farm outside the town of Beaconsfield, Iowa, before obtaining degrees in biology and chemistry from Iowa Wesleyan and a doctoral degree in biochemistry from Rice University.
Group Captain Shubhanshu Shukla was born on October 10, 1985, in Lucknow, Uttar Pradesh, India. He joined the Indian Air Force in 2006 as part of their fighter wing. He has more than 2,000 hours of flight experience flying the Su-30 MKI, MiG-21, MiG-29, Jaguar, Hawk, Dornier, and An-32.
Ax-4 mission pilot Shubhanshu Shukla. (Credit: Axiom Space)
In 2019, Shukla took part in a year-long training event at the Yuri Gagarin Cosmonaut Training Center in Star City, Russia. In February 2024, Indian Prime Minister Narendra Modi unveiled him as one of four astronauts selected to train for human spaceflight, including eventual flights as part of the Indian Gaganyaan human spaceflight missions. This will be his first spaceflight.
Sławosz Uznański-Wiśniewski is joining the crew as a European Space Agency (ESA) project astronaut. He began his higher education in Łódź, Poland, where he earned a Master of Science with honors at the University of Technology in 2008. The same year, he also obtained another master’s from the Université de Nantes in France.
He completed his doctoral dissertation at the University of Aix-Marseille in 2011, focusing on hardening electronic devices against radiation during spaceflight.
Ax-4 mission specialist Sławosz Uznański-Wiśniewski. (Credit: Axiom Space)
Sławosz then lent his expertise to the European Organization for Nuclear Research (CERN) in Geneva, where he became Engineer in Charge for the famous Large Hadron Collider.
Uznański-Wiśniewski was selected as part of the ESA Astronaut Reserve Class of 2022.
Tibor Kapu was born November 5, 1991, in Nyíregyháza, Hungary. He would go on to earn a degree in mechanical engineering from the Budapest University of Technology and Economics before completing his master’s, specializing in polymer technology.
He contributed to the pharmaceutical and logistical industries and worked on hybrid car battery development in the automotive industry during his career, before working on studying space radiation protection.
Ax-4 mission specialist Tibor Kapu. (Credit: Axiom Space)
Kapu was selected as one of four for the Hungarian to Orbit (HUNOR) astronaut program in 2023.
While not studying or working, he is an avid recreational skydiver, having completed 38 successful jumps as well as 21 half marathons.
Vehicles
This flight will mark the debut of the fifth and final Crew Dragon capsule to enter SpaceX’s active rotation. C213 has yet to receive an official name and is expected to receive one from its crew once it has arrived in orbit. This would join Endeavour, Endurance, Freedom, and Resilience to complete the fleet.
The capsule has already faced issues. The vehicle was originally intended to launch the Crew-10 mission, which at the time was scheduled for February 2025. Following issues with the propulsion and environmental control systems onboard, it was instead replaced by Endurance, the capsule originally assigned to Ax-4, which then launched to the ISS in March.
Crew Dragon C213 rolling out to LC-39A prior to its inaugural flight. (Credit: SpaceX)
Prior to the delays caused by leaks, the Ax-4 launch had also been delayed slightly to allow for “spacecraft readiness,” pushing the mission from May 29 to the most recent launch windows in early June. A revised launch date has yet to be announced.
The booster scheduled for this flight is B1094-2. This will mark the vehicle’s second flight into space following the launch of the Starlink 12-10 mission on April 28. Had it launched as planned on June 11 that would mean a turnaround of just over a month and a half.
The booster was expected to perform a Return to Launch Site (RTLS) landing at LZ-1, located just a few miles from the KSC launch site on the nearby Cape Canaveral Space Force Station.
Zero-G indicator
Since the return of crew flight to US soil in 2020, missions now contain an item that will float as an indicator that the spacecraft and its crew have entered weightlessness. This flight will include Joy, a plush baby swan symbolizing grace and elegance.
“Joy” the Bay Swan will be the Ax-4 zero-g indicator. (Credit: Axiom Space)
According to Axiom Space, “Joy embodies the shared pursuit of ISRO, ESA, and HUNOR to soar high above our home planet. The swan, known for its grace and elegance, carries allegorical meanings across cultures. In India, it symbolizes wisdom and purity, representing the pursuit of truth. In Poland, the swan stands for purity, loyalty, and resilience, while in Hungary, it epitomizes loyalty, grace, and the beauty of nature. By choosing a swan as the zero-g indicator, the Ax-4 crew celebrates the diversity of their cultures, united in the shared human experience of space exploration.”
Science experiments
With nearly 60 experiments, this mission will have a full slate of experiments to complete. This includes a study to investigate whether astronauts with insulin-dependent diabetes can be supported for short-duration stays in microgravity. This will include the study of astronauts’ blood glucose levels to check for data accuracy and eventual viability of insulin in cooperation with a UAE-based healthcare provider.
A joint NASA/ISRO study will see if it’s possible to regrow muscle fibers in space. The Myogenesis-ISRO investigation uses muscle stem cell cultures to examine the muscle repair process and test chemicals known to support mitochondrial function. The hope is to not only use it as a way to combat deterioration on long-duration spaceflights but also help athletes or those with age-related muscle loss and muscle-wasting diseases.
Immunofluorescent image of human muscle fibers for Myogenesis-ISRO, showing nuclei (blue) and proteins (red). (Credit: Institute for Stem Cell Science and Regenerative Medicine, India)
Other experiments include testing the effectiveness of “wearables,” such as smart watches, on spaceflight. A Polish Space Agency (POLSA)/ESA experiment will study ways to extend the shelf life of medicine during long-duration spaceflights, as their effectiveness can be weakened by cosmic radiation. The study will hopefully find ways to extend the life of medicines here on Earth.
The END-SANS project from HUNOR will test whether a contact lens with active pharmaceutical ingredients can help prevent changes in shape to the eyes, something experienced by most astronauts during spaceflight. The actual ingredients will be tested without a human. However, an astronaut will wear the “eye inserts” once a day for at least five days. If they can help stabilize the eyes during spaceflight, it could also have significant impacts on patients on Earth with diseases such as macular edema.
A full list of all research objectives on this flight can be found on Axiom’s website.
(Lead image: B1094 and C213 vertical at LC-39A ahead of the Ax-4 launch. Credit: Axiom Space)
