He’s been there, done that, and is raring to get back into space, humankind’s final frontier. Shubhanshu Shukla, India’s first man on the International Space Station (ISS), says he is drawing from his background as a IAF test pilot in his training for the Gaganyaan mission.

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Fly any new aircraft that comes in and prove that it has safe operational limits is the principle he followed then, and now too, said Group Captain Shukla, called “Shux” by his friends, describing Indian Space Research Organisation (ISRO)’s first human spaceflight programme as a developmental or 'prototype' mission.

“Globally, there is a lot of respect for the Indian space community, specifically ISRO… transitioning to a human space mission is a change of magnitude — it is a big shift from what we have been doing and what we are going to do,” Mr. Shukla told PTI Videos.

He said Gaganyaan will position India uniquely in the global race for space exploration.

Last June, Mr. Shukla was one of the four astronauts who travelled to space and spent 18 days aboard the ISS as part of NASA's Axiom-4 mission. It marked the return of an Indian to space after 41 years — Wing Commander Rakesh Sharma was the first to do so in 1984.

Exactly a year later, Mr. Shukla is now based in Bengaluru, as one of the four astronaut-designates selected for the ISRO's Gaganyaan mission. He lives with his family in Bengaluru at the Human Space Flight Centre as he prepares for a second space voyage.

Tentatively scheduled for mid-2027, the mission aims to demonstrate India's capability of human spaceflight by launching a team of three members to a low-Earth orbit of 400 kilometres for three days and bringing them back safely by landing in Indian sea waters.

Comparing Axiom-4 — an international, commercial collaboration — and Gaganyaan — India's indigenous, flagship programme — Mr. Shukla said, “I think in terms of outcomes, they're quite different, and especially, when India pursues this [Gaganyaan] and we are able to do it successfully, it will give a lot of courage to other nations who are looking at doing something like this, because it feels possible. You're not able to relegate it to, OK, this is for somebody else.”

The astronaut, who was at the Ashoka University in Sonepat to talk to students, is involved in the design and refinement of the design of the system that will carry the astronauts to space. Once finalised and frozen, mission-specific training will commence.

In April, ISRO successfully conducted the second Integrated Air Drop Test (IADT-02) for Gaganyaan at the Satish Dhawan Space Centre in Sriharikota. IADT-02 is one of the precursor, unmanned missions through which safety and reliability will be proven.

If successful, India will be only the fourth nation in the world to have shown a capability of doing manned space missions, after the U.S., Russia, and China.

"I think it is monumental in terms of capability that we as a country will possess when we are able to execute Mission Gaganyaan because it involves [the] development of a lot of new technologies which are otherwise not existing, with nations who do not pursue these missions," the Lucknow-born astronaut said.

New technologies comprising engineering and human centric systems are being developed and realised for ensuring human safety, which is of paramount importance in Gaganyaan mission, ISRO said in a factsheet.

This is a crucial juncture for space missions, said Mr. Shukla. “… especially as you see, there is a kind of race that is happening right now [of] going back to space and back to the moon and onwards.”

In January, the 40-year-old was awarded the Ashoka Chakra, India's highest peacetime gallantry award.

Discussing his unforgettable 18 days in space last year, Mr. Shukla said scientific experiments from India conducted during the Axiom-4 mission, including researching stem cells for preventing muscle damage in space or looking at the growth of microalgae in microgravity, were all curated with "a basic theme in mind that we want to execute our own human space missions in the future".

"Living in space is exactly like going to school. You follow a timetable," he said. A typical day aboard the ISS started at 6 a.m. The first briefing of the day was at 7.30 a.m. Activities would start at 8 a.m. and continue through the day till 6 p.m. Evenings, sometimes after a 13-hour workday, usually involved sipping tea in a pouch and looking outside the window, next to where Mr. Shukla slept.

He described the experience of seeing both the Earth and Moon as "surreal". Mr. Shukla said that while there are people on board the space station to talk to and things to do, sometimes not being able to communicate exactly — the unique, first-time experience of spaceflight — to his loved ones made him feel lonely.

"Very few people have gotten a chance to see or feel that kind of perspective that you are getting to witness, and there is no good way to communicate it to your loved ones back home. You can just talk, you can just speak to them, but it doesn't even come close to doing the justice of communicating of what it is exactly," he said.

Ever so often, the immensity of what is happening would hit him.

"It's unbelievable, you know, after 41 years that we were able to send an Indian to space, and you happen to be that person who's going to space, so there are definitely emotional moments.

"There are times I tried to suppress them so that I could keep functioning normally and keep doing what I'm supposed to do, because sometimes the weight of emotions can be crushing, can cripple you, the weight that comes with just the sheer understanding of what is happening," said Mr. Shukla.

The fantastic crew helped a lot, he added. "... the conversations, talking to each other because you know it is a very similar place that they are also in, from their own side, so it was very easy to communicate, talk to them about things, figure it out, and then move on and do things," he said.