Axiom-4 Mission: A chronicle of Shubhanshu Shukla’s historic space odyssey

The Axiom Mission 4 (Ax-4) crew, comprising Commander Peggy Whitson, Pilot Shubhanshu Shukla, and Mission specialists Sławosz Uznański-Wiśniewski and Tibor Kapu, is set to return to Earth on Tuesday (July 15).

They successfully docked with the International Space Station (ISS) on June 26 at 4:30 PM Indian Standard Time (IST) on their first day.

Also read: Shubhanshu Shukla to undergo 7-day rehab after returning to Earth

The crew officially boarded the ISS at 8:23 a.m. ET, starting their mission. This occurred after the 28-hour orbital phasing period following their launch from the Kennedy Space Centre on June 25, 2025, at 12:01 PM IST.

Settling into life in Space

On the second day, Shubhanshu and the crew focused on adjusting to their new microgravity environment. They set up their sleeping quarters, with Shubhanshu assigned to the Dragon spacecraft. The team did handover tasks with the Expedition 73 crew already aboard the ISS, unpacked important cargo, and went over emergency procedures to familiarise them with the space station.

Also read: India looks full of ambition from space: Shubhanshu Shukla in ISS farewell speech

The crew was completely integrated with the ISS team by the third day. They practised emergency drills, moved important scientific equipment and safety gear, and learnt the rules for the station. Shubhanshu began preparing for upcoming research experiments by setting up the necessary equipment and placing biological samples in the designated lab modules.

Commencement of key experiments

The fourth day was particularly significant for Shubhanshu. He conducted the Myogenesis experiment inside the Life Sciences Glovebox, studying muscle degradation in microgravity — a crucial concern for long-duration space missions. Additionally, he participated in the Cerebral Hemodynamics study, using ultrasound scans to analyse brain blood flow in weightlessness. Shubhanshu engaged in a live conversation with Prime Minister Narendra Modi, which was live telecast.

Also read: 'Microgravity', 'gajar halwa': What Shubhanshu Shukla, PM Modi discussed in chat

On the fifth day, Shubhanshu deployed microalgae samples as part of research into sustainable food sources for future deep-space missions. The study, conducted with the assistance of ISRO (Indian Space Research Organisation), ICGEB (International Centre for Genetic Engineering and Biotechnology), and NIPGR (National Institute of Plant Genome Research), examines the impact of microgravity and space radiation on the growth, metabolism, and genetic activity of three edible microalgae strains in comparison to their Earth-based controls.

Microalgae are ideal for space missions due to their ability to produce oxygen through photosynthesis, serve as a nutrient-rich food source, generate biofuels, and recycle waste in closed-loop systems. During the mission, Shubhanshu deployed culture bags containing microalgae on the ISS, monitored their growth through imaging, and analysed key biological parameters, including transcriptomic, proteomic, and metabolic changes.

The crew also contributed to the Neuro Motion VR project, examining how microgravity affects cognitive and motor functions. Another key study, Telemetric Health AI, used advanced analytics to monitor cardiovascular health in space, providing valuable insights for astronaut well-being.

Advancing muscle and brain-computer interface studies

The sixth day saw Shubhanshu continuing his work on the Myogenesis experiment, analysing muscle cell behaviour under microgravity conditions. Proposed by India’s Institute for Stem Cell Science and Regenerative Medicine (InStem), with support from ISRO, this study addressed critical astronaut health challenges by examining muscle stem cell behaviour in weightlessness using 3D tissue chips in the ISS’s Life Sciences Glovebox. Shubhanshu meticulously monitored cellular changes, comparing space-grown samples with Earth-grown controls to isolate the effects of microgravity on myogenesis — the process of muscle formation. Findings from this study promise dual benefits: developing countermeasures for astronaut muscle preservation during future Moon/Mars missions, and advancing treatments for terrestrial muscle-wasting disorders.

He also tested the PhotonGrav brain-computer interface, a cutting-edge technology that could transform how astronauts interact with spacecraft systems. This innovation holds potential applications for neurorehabilitation and assistive devices on Earth.

Cyanobacteria growth

On the seventh day, Shubhanshu documented the growth of cyanobacteria for an ISRO-led experiment. The crew also participated in the Voyager Displays project, studying how microgravity impacts eye movement and coordination to improve spacecraft interface designs.

The eighth day was packed with multiple research activities. Shubhanshu examined muscle cell development for the Myogenesis study and commenced the Tardigrades experiment, which explores how microscopic organisms survive in space. In this experiment designed by IISc Bengaluru, Shubhanshu used Tardigrades, tiny half-millimetre creatures called Water Bears, known to survive extreme conditions like heat, cold, oceans, and even volcanoes. Before space travel, they were hibernated, needing no food with zero metabolism. At the ISS, Shubhanshu revived them in microgravity using water. When Axiom-4 returns, the samples will reach Earth for Indian scientists to study how these amazing creatures survive harsh environments. The crew also tested new materials for space suits that would help maintain stable temperatures and worked on the Voice in Space study, which examined how speech patterns change in microgravity.

Rest and reflection

After a busy week, the ninth day provided a much-needed break. Shubhanshu and his crewmates used this time to rest, reconnect with their families, and reflect on the progress of their mission.

On the 10th day, Shubhanshu resumed his research on muscle atrophy, analysing molecular mechanisms in the Myogenesis study. He redeployed microalgae samples and contributed further to the Voyager Displays project, refining spacecraft control systems for future missions.

The 11th day focused on botany. Shubhanshu irrigated seeds for the Sprouts experiment, studying germination in space, and continued microalgae research, which could one day provide food and oxygen for astronauts on long-duration missions.

Developed in collaboration

This research was conducted with the assistance of Indian agricultural and technical institutes, as well as ISRO. Its goal was to improve space farming for future missions to the Moon and Mars while also helping farming on Earth. The experiment examined how seeds germinated, how plants developed in the early stages, and how plants altered their genetic makeup in the absence of gravity. Shubhanshu nurtured seeds in petri dishes, documenting root/shoot orientation anomalies caused by absent gravity cues. Samples were preserved at -80°C for post-mission analysis of microbial ecosystems and nutritional changes across multiple generations. Successful space-grown sprouts could supplement astronaut diets with fresh food while reducing the payload's dependence on external sources. Earth applications include developing stress-resistant crops for arid regions and vertical farming systems.

Muscle and cardiovascular health studies

By the 12th day, Shubhanshu collected cellular samples for the Myogenesis study and supported the Telemetric Health AI project, which uses ultrasound scans to monitor heart health in space.

The 13th day involved centrifuging cyanobacteria samples and redeploying microalgae cultures. The crew also gathered more data for the Voyager Displays experiment, analysing eye movement in microgravity.

On the 14th day, Shubhanshu preserved plant samples for future analysis, photographing Sprouts seeds and storing them in a -80°C freezer. He also redeployed microalgae cultures and contributed further to the Voyager Displays project.

By the 15th day, the crew had completed approximately 230 Earth orbits, covering over 6 million miles. They reviewed their progress and prepared for the mission’s final phase.

On the 16th day, Shubhanshu continued microalgae research. At the same time, the crew advanced the Voyager Displays study, refining insights into human-machine interaction.

Preparation for return

The 17th day involved centrifuging and freezing microalgae cultures for safe return to Earth. The crew also participated in the Voice in Space study and the Acquired Equivalence Test, examining learning adaptations in the microgravity environment.

On the 18th day, the crew tested Continuous Glucose Monitors (CGMs) to assess their accuracy in space — a step toward allowing insulin-dependent astronauts to participate in future missions.

The 19th day was spent getting ready to leave. Shubhanshu and the crew packed samples for experiments, including seeds that had sprouted and algae cultures. They took part in the farewell ceremony with the ISS crew.

The crew closed the hatches and got ready to undock on the last day, the twentieth. This was the end of their 20-day mission.

Undocking and splashdown

The Ax-4 Crew Dragon spacecraft began its return on Monday (July 14) by undocking from the ISS. It will take approximately 22-24 hours before splashdown. After separation, the capsule will perform calculated phasing burns to lower its orbit. About 30-60 minutes before landing, a critical deorbit burn initiates re-entry. The craft will zip through the atmosphere. Due to the friction, the temperature surrounding the craft will go as high as 1,900°C. The specially made heat shield will protect the crew during this phase. After entering the atmosphere, parachutes will be deployed at 5.5 km, ensuring a safe splashdown off the coast of California. The entire process takes 20-24 hours, depending on orbital conditions.

Post-splashdown recovery

Recovery teams will approach the capsule within 30 minutes of splashdown to conduct safety checks. The spacecraft will then be hoisted onto a recovery ship for crew extraction. After two weeks in microgravity, astronauts may require assistance to adjust to the effects of gravity. Medical teams will conduct preliminary health checks and offer food and water before transporting them to a California facility for detailed evaluations. Extended quarantine is unlikely unless new health concerns arise. In a few days after the splashdown, Shubhanshu is expected to return to India.