Why has the Axiom-4 mission been delayed? | Explained Premium

Axiom-4 mission to ISS postponed indefinitely due to LOX leak, delaying historic Indian astronaut's journey.

The story so far: On June 10, Axiom Space announced that the launch of its Axiom-4 mission to the International Space Station (ISS) would be postponed indefinitely. The mission crew included India’s astronaut-designate Shubhanshu Shukla, who — if the rocket had lifted off as planned — would have become the first Indian in earth orbit after 40 years and the first Indian onboard the ISS.

The Axiom-4 mission is the fourth mission planned by US-based spaceflight company Axiom Space to the ISS. It consists of a crew of four people — Peggy Whitson, Shubhanshu Shukla, Sławosz Uznański-Wiśniewski, and Tobir Kapu — plus cargo.

To facilitate the mission, NASA had contracted Axiom, which in turn had contracted the Falcon 9 rocket and the Dragon crew capsule for the mission from SpaceX. The mission is commercial in nature and isn’t part of the regular resupply missions NASA undertakes to the ISS.

Following an announcement to strengthen India-US ties in 2023, the Indian Space Research Organisation (ISRO) spent more than Rs 500 crore for Mr. Shukla to fly on the mission. Mr. Shukla is one of the four astronaut-designates for ISRO’s forthcoming Gaganyaan human spaceflight mission. His compatriot Prasanth Nair is part of the Axiom-4 backup crew.

Ahead of Thursday’s flight, SpaceX had tested one of the rocket’s engines as a matter of procedure and discovered it was leaking liquid oxygen (LOX). LOX is a cryogenic fuel, meaning it needs to be stored at an extremely low temperature. If LOX is exposed to warmer conditions, the oxygen will turn into gas and not be usable as fuel (since it’s very difficult to pump gases).

Falcon 9 engines combust a mix of rocket-grade kerosene and LOX to generate thrust, meaning a LOX leak is a serious issue. The Axiom-4 mission had first been scheduled for liftoff on May 29 but had to be postponed to June 8, June 10, and June 11. There was a back-up launch window on June 12. The delays were a result of a combination of unfavourable conditions related to the weather and the launch vehicle.

The crew thus continues its wait.