The private space mission Axiom Mission 4 (Ax-4), bound for the International Space Station (ISS), faces a new delay due to a propellant leak in SpaceX’s Falcon 9 rocket. The announcement, issued by Axiom Space in a statement and by SpaceX via a post on X, follows a prior postponement from June 10 to June 11 caused by adverse weather conditions. The new launch date has not yet been disclosed.

The issue, a liquid oxygen (LOx) leak—one of the two propellants used by the rocket’s engines—was already detected during static fire tests conducted on Sunday, June 8, at the Kennedy Space Center in Florida. Although the Falcon 9 first stage had exhibited a similar problem during its sole previous flight (a Starlink mission), specifically a defect identified during re-entry, SpaceX teams are currently working on repairs. As indicated by Bill Gerstenmaier, SpaceX Vice President, the leak might not have been fully resolved or correctly identified in the past.

The Ax-4 mission, Axiom Space’s fourth, plans to carry a crew of four to the ISS for about 10 days, with the objective of conducting over 60 scientific experiments and demonstrations focusing on human research, Earth observation, and biological, materials, and life sciences. Leading the team is NASA veteran Peggy Whitson. Her crewmates include Shubhanshu Shukla from India, Slawosz Uznanski-Wisniewski of the European Space Agency (Poland), and Tibor Kapu from Hungary. For these three countries, it marks the first time their astronauts have visited the ISS, making this mission a significant milestone for global space collaboration.

The Dragon spacecraft supporting this mission is on its maiden flight, while the Falcon 9 first stage booster, as mentioned, is on its second use. After stage separation, the Falcon 9 first stage will attempt landing on Landing Zone 1 (LZ-1) at Cape Canaveral Space Force Station in Florida. SpaceX has confirmed that teams are dedicating additional time to the necessary repairs while awaiting launch pad availability to set a new date.