India’s Shubhanshu Shukla is set to return to Earth within the next 22 hours, following an 18-day journey aboard the International Space Station (ISS) as part of the historic Axiom-4 (Ax-4) private mission.
Flying the spacecraft ‘Grace’ as pilot, Shukla — also called “Shux” — was accompanied by Commander Peggy Whitson, Mission Specialist Sławosz “Suave” Uznański-Wiśniewski, and Mission Specialist Tibor Kapu.
The hatch has been closed, and the spacecraft has undocked from the ISS, marking the end of a mission that saw the astronauts complete over 230 orbits, covering more than 6 million miles and witnessing more than a hundred sunrises and sunsets from orbit.
During his time on the ISS, Shukla carried out a range of microgravity experiments aligned with India’s aspirations for future human spaceflight missions, notably Gaganyaan.
Here is a detailed day-wise account of his work.
Day 6 (June 30): Myogenesis & mental health study
Shukla led the Myogenesis Experiment inside the Life Sciences Glovebox (LSG), focusing on how microgravity affects skeletal muscle formation and regeneration. The goal was to map molecular pathways responsible for muscle loss to help develop therapies for astronauts.
The team also documented activities for the Astronaut Mental Health study, which contributes to research on cognitive well-being in space. NASA notes the technology involved could later assist in neurorehabilitation and assistive devices on Earth.
Day 7 (July 1): Microalgae and Photosynthetic Bacteria study
Shukla grew three strains of microalgae aboard the ISS, studying how they behave in microgravity — focusing on growth, metabolism, and genetic activity.
He also compared two strains of photosynthetic bacteria to observe their functional changes in space.
The crew completed the second session of the Cerebral Hemodynamics study, using ultrasound tech to monitor blood flow in the brain under microgravity.
Day 8 (July 2): Tardigrades, Microalgae, Bone health & Suit fabric
Shukla continued the Space Micro Algae experiment, examining how edible algae grow in space to support future life-support systems through food, oxygen, and biofuel production.
As part of the Voyager Tardigrade microgravity experiment, Shukla carried a “Bengaluru‑strain” tardigrade (Paramacrobiotus species) to the ISS. These microscopic critters are renowned for their abilities to withstand extreme conditions—deep space radiation, vacuum, and severe temperature fluctuations—by entering a cryptobiotic “tun” state, reported The Indian Express.
The experiment, designed by researchers from the Indian Institute of Science (IISc), focused on how tardigrades survive and revive from cryptobiosis in space, reproduce under microgravity and deploy molecular-level protective mechanisms (e.g., specific genes/proteins) in response to space stressors.
Within the first week aboard the ISS, Shukla successfully completed the tardigrade microgravity experiment, reported The Times of India. ISRO confirmed that the study “focused on tardigrades’ survival, revival, and reproductive behaviour in space,” marking it a success during those initial days.
Participated in Bone on ISS, tracking markers related to bone breakdown and recovery, helping build digital skeletal twins for future astronaut health modeling.
Took part in the Suit Fabric Study, a tech demonstration exploring how future spacewear materials perform in microgravity.
Day 9 (July 3): Rest and recharge
The Ax-4 crew was granted an off-duty day. Shukla and his fellow astronauts reconnected with their families and enjoyed Earth views from orbit.
Day 10 (July 4): Voyager Displays & Radiation monitoring
The objective of this study was to investigate how astronauts interact with screen-based interfaces in microgravity — specifically, measuring pointing tasks, gaze fixation, and rapid eye movements — while also evaluating associated cognitive stress and well-being.
Understanding these interactions under zero‑gravity conditions aims to inform the design of intuitive and stress‑reducing cockpit, spacecraft, and remote‑operation interfaces for future missions .
Throughout the mission, Shukla conducted repeated sessions, gathering data on:
Eye movement metrics: gaze patterns, fixation points, and saccades (rapid eye movements).
Pointing accuracy: tasks involving touchscreens or cursor control.
Stress and cognitive load: correlated through physiological markers and self-reports.
He also measured ambient radiation using the Rad Nano Dosimeter, essential for refining radiation shielding and safety protocols for future lunar, Martian, and Gaganyaan missions.
Day 11 (July 5): Seeds in space & Cancer research
Shukla worked on the Sprouts–ISRO experiment, germinating green gram (moong) and fenugreek (methi) seeds in microgravity.
He documented their germination, microbial ecosystems, and nutritional profiles, storing samples in the ISS freezer.
Shukla also revisited the Myogenesis experiment and stowed further samples for the Micro Algae study.
Day 12 (July 6): Wearable health-tech
Shukla tested a sensor-equipped acoustic vest as part of the Wireless Acoustics project. The wearable monitored sound aboard the ISS, evaluating its comfort, usability, and performance compared to fixed station sensors.
Day 13 (July 7): Sustaining food systems
Shukla expanded his research in food, photosynthesis, and microorganisms, continuing work on methi and moong sprouts. He also supported the ongoing Cerebral Hemodynamics study, a vital experiment for understanding cardiovascular adaptations in microgravity.
Day 15 (July 9): Earth views from orbit
As the crew wrapped up over 230 orbits, they spent the day capturing images and video of Earth, taking in its breathtaking views.
According to Axiom Space, the off-duty time provided a rare pause in their otherwise demanding schedule, allowing the astronauts to reconnect with their thoughts and loved ones.
Other key experiments:
Cyanobacteria in Microgravity
Throughout the mission, Shukla led this experiment, exploring cellular behavior, genomic stability, and biomanufacturing potential under microgravity — vital for future air regeneration and waste recycling systems.
Zero-gravity water surface tension demo
In a captivating outreach session, Shukla conducted a water surface tension demonstration in zero gravity, forming a floating water bubble.
“I've become a water bender here in the station,” he quipped. Commander Whitson further showcased how water clings to plastic, behaving like a liquid lens.
As he prepares to re-enter Earth’s atmosphere, Shubanshu Shukla leaves behind a remarkable trail of experiments that will directly inform India’s Gaganyaan mission, and contribute to the global body of space research.