Rosemary Coogan was pushed, pulled, squeezed and squeezed by a group of people.

It takes about 45 minutes to secure all the gear to her head before the helmet is carefully lowered.

The British astronaut is about to face her most difficult challenge yet - assessing whether she is ready for a spacecraft. The test will be held in one of the world's largest pools: NASA's Neutral Buoyancy Laboratory is located at the Johnson Space Center in Houston, Texas.

The pool is 12m (40 feet) deep - contains a life-sized replica of the International Space Station (ISS), where "space walks" are as close to the level of weightlessness imitating the Earth.

“It’s a big day,” Rosemary said before the dive, which will last for more than six hours. “It’s very nervous physically – very intense psychologically.”

But rosemary doesn't seem too confused. She smiled and waved as she slowly dropped into the water on the platform she stood.

She said that becoming an astronaut was Dr. Rosemary Coogan who dreamed from a young age. But it seems like a distant dream.

"You don't meet astronauts on career days in school," Rosemary said. "You don't meet people who did, you really don't hear their stories."

So she decided to study stars and instead chose a career in astrophysics. But when the European Space Agency (ESA) announced that it was looking for new recruits to go to space, Rosemary applied and selected from more than 22,000 people.

ESA's goal is to bring rosemary to the International Space Station (ISS) by 2030. She will follow in the footsteps of British Helen Sharman, who visited the Soviet Mir space station in 1991 and ISS in 2015.

Rosemary conducted six months of training at the Johnson Space Center. In addition to exploring the exterior of the flooded International Space Station, she can also advance to the orbital laboratory in another life-sized model located in a huge hangar.

She took us to the modules in which the labs are interconnected. It feels very cramped, especially considering the astronauts usually spend months on board. But rosemary reminds us of spectacular views.

“It’s an isolated environment, but I think it helps with this connection to the outside to alleviate the feeling of claustrophobia.”

Rosemary’s training covers all aspects of the journey to the space – including learning how to use the onboard toilet.

"The lower part is where you place solid waste," she said, pointing to the toilet in a small compartment that looks like something you might find in a very old camp. “The funnel here is actually attached to the air suction system, which is where you place the liquid waste.”

Rosemary said female astronauts can choose to use drugs to suppress their period, but also choose not to.

“Essentially, you put a filter on the top of the cone of your urine, which is to block any particles, any blood from entering the urine system.”

The urine needs to be separated because it is purified and considered reused as drinking water, she explained.

Back in the pool, divers are constantly adjusting the buoyancy of rosemary in the water to make the experience as close to microgravity as possible.

She worked hard to walk around to make sure she always attached to the submerged structure using two hooks.

Each manual is carefully selected along the rod outside each module. Their location is exactly the same as the real thing, and if she can walk 200 miles (322 kilometers) above the earth, their muscle memory is crucial.

It's slow and difficult work that requires a lot of upper body strength and physical labor in the hot, bulky spacesuits.

"You're doing a lot of mental preparation - you're really thinking through every move," Rosemary explained. "You have to be very effective with energy. You don't want to do something, realize that it's not exactly right, you have to do it again."

Rosemary is working with another astronaut to complete a list of space station repairs and test maintenance. Her every move was monitored by a team in the control room overlooking the pool. They kept communicating with her when she finished her mission.

Aki Hoshide, former space station commander from Japan Aerospace Exploration Agency, is seeking advice. He has completed four spacewalks and says it is a steep learning curve for new astronauts.

“When we first started, there was so much information to you that you had to learn, show and show a lot of skills,” he said. “It’s the baby’s step, but they’re moving forward – and every time they come here and jump into the pool, I see their excitement.”

Rosemary takes us to see Saturn V - a rocket that brought Apollo astronauts to the moon in 1969. For more than 50 years, NASA plans to return to the moon's surface through its Artemis program. European astronauts will join future missions. With an expected 35-year space career, Rosemary may one day have the chance to be the first British man to walk on the moon.

"As humans, we're back to the moon and of course, I can be a part of it, and I'm definitely very excited. I think it's absolutely exciting," she said.

After six tough hours underwater, Rosemary approached the end of her aerospace test-but then she threw a curveball.

In the control room, we hear her conducting communications checks with her astronaut partners who work in another part of the space station. But she was silent.

On the video screen, we can see him motionless. Rosemary didn't know, but he was asked to pretend to be unconscious. Rosemary’s job is to arrive at him, check his condition-and then drag him back to the air lock.

After so long underwater, we can see how exhausted she is - but in a slow and steady work she brings him safely to the airlock.

“Rosemary has the stamina of champions. “We were very happy with where she was – she performed great. ”

The space walk is finally over. Rosemary’s platform hangs next to the pool and the support team can help her get rid of her clothes. When her helmet was removed, we could see that she was obviously tired but was still smiling.

"It was really a challenging rescue, and it was a challenging rescue, but it was a very pleasant day," she told us.

Rosemary's hard work brought her closer and closer to her dream of reaching space.

"It's amazing, if I could do that for a real space station - you can look at the stars here and see the stars at the same time, that's the cherry on the top," Rosemary said.