It’s difficult to decide what Mark Kelly is most famous for these days: being an astronaut or a husband.

Four times, between 2001 and 2011, he flew into space. Twice he commanded missions. His responsibilities included delivering and installing equipment worth billions of dollars for the International Space Station (ISS). Among his payloads were everything from the $2-billion (Dh7.3 billion) Alpha Magnetic Spectrometer – which attempts to trace dark matter – to replacement parts for a malfunctioning toilet.

Yet he has also faced challenges of a very different nature on Earth. In 2011, his wife, former American congresswoman Gabrielle Giffords, was shot in an assassination attempt in Arizona. She survived, and the couple has campaigned to reform gun laws in the US ever since.

As both spaceman and her other half, Mark, 51, has been called an American hero; and he wears the title well. He looks like one. He’s broad, bald and blunt. When we first meet – in the back of a taxi in Nevada – he has a handshake like a bear and a glance that says he won’t take fools lightly. I quickly decide to dispense with small talk and ask him straight up about the big issues.

On being a spaceman

Mark – a one-time US Navy pilot – has spent 50 nights in space during four different missions. ‘It’s a lot of fun,’ he says. ‘Very challenging but exciting. Launching a rocket, travelling through space, then rendezvousing and docking at the ISS – it’s kind of a hard thing to do. You’re delivering payloads worth billions so there’s pressure.

‘The flight has a lot of vibrations, much more than in the simulator. I remember my first flight; on take-off the vibrations were much higher than I thought they’d be. I looked over to my commander, and he seemed OK, so I figured it must be normal.

‘Then you’re working constantly. These missions are expensive – about $500 million to a billion per flight – so we try and get the most out of them. Basically, you work very, very hard.’

Each astronaut on a two-week mission is given just half a day off, he adds. ‘That’s when you take pictures. The opportunity to see Earth as an island, just floating there in this vast blackness – it’s pretty incredible.’

On the risks of the job

It’s testament to Nasa’s dedication and tenacity that in 2016, space travel can almost seem routine to outsiders. It isn’t. Astronauts are told ahead of every mission there is roughly a one-in-55 chance they won’t make it back.

‘Those odds are like pulling a card out of a deck,’ says Mark. ‘It’s a high risk. Your life is on the line. But for me, it’s about weighing the risk against the reward. If I take this risk, potentially it kills me, yeah. So, what’s the best benefit? Not so much to me personally, but what are the benefits to society and country? And they’re huge: for our economy, innovation and technology. If these benefits weren’t there, I wouldn’t do it. Then it would just be foolish. But I think it’s worth it.’

On being weightless

This is the question, he says, which all astronauts are most asked. What’s it like to be weightless? ‘It makes some things easier to do, for sure,’ he says. ‘I was able to move and install a science rack that on earth weighs around 272kg and would have taken about five people to do.

‘At the same time, you can’t put anything down. There is no down. You let something go and it drifts away. It can be difficult to keep track of things. You’ll have stuff floating past you.’

Going to the toilet causes issues too. ‘It’s hard,’ he says. ‘There’s a suction system, but you also need to use your hand and coax things in the right direction.’

On helping Nasa put men on Mars

Mark retired from Nasa in 2011, but he’s helping with an experiment, which could one day lead to humans stepping on the 
Red Planet. His twin, Scott, is spending a year at ISS. By monitoring changes in the brothers, scientists hope to discover the effects of long-term stay in space.

‘Being in space – the radiation, [fluctuating] gravity – has significant negative effects on the body, DNA and molecular structure,’ explains Mark. ‘So there are about 10 different studies looking at that, using my brother as the subject and me as control here on the ground. They’re taking data from both of us: blood and urine samples, ultrasounds, MRIs, etc.

‘The idea is to figure out how we can negate or medicate some of the effects of long-term space travel if we want to send people to Mars, for example. A mission like that might be two years long so you need that data to make sure it goes smoothly.’

On the assassination attempt on his wife

On January 8, 2011, Gabrielle, along with a district court judge and a nine-year-old girl, was shot by Jared Lee Loughner while she was meeting constituents at a supermarket in Tucson, Arizona. Six people died but she survived, despite a bullet lodging in her brain. Her injuries were so severe that she had to learn to speak again. For half an hour on the day itself, Mark was in a state of panic because of TV reports stating that she had died.

‘What happened that day is certainly the biggest challenge we’ve ever faced,’ he says.

‘But my faith in my wife was unshakeable. I thought, “If anybody can take this on and overcome it, it’s Gabby”.’

She proved her husband right. Barely four months after nearly losing her life, Gabrielle flew to Florida to watch her husband lead space shuttle Endeavour’s final voyage. A couple of months later, she insisted on being in Congress to vote on a bill to raise the debt ceiling.

‘I couldn’t be more proud of Gabby,’ says Mark, who was constantly by her side during the months of rehab.

Since the attack, she has undergone multiple surgeries and physical therapy to relearn how to walk and talk.

Looking back, how did it feel? ‘You know, I don’t recommend it to anyone,’ he says. ‘It was tough.

‘My personality is one to look at things like: “OK, what problems do we need to solve right now to get through this?” So that’s what we did all the way through. We focused on what needed to be done. And there was a lot of stuff to handle. You just get through it.’

On curbing gun violence in the US

Two years after the shooting in Tucson, Mark and Gabrielle launched Americans for Responsible Solutions, a campaign aiming To reduce gun violence.

‘As gun owners ourselves,’ the mission statement declared, ‘we know we must protect the rights of Americans to own guns for collection, recreation, and protection. But we also agree with the majority of Americans that common-sense solutions can prevent shootings.

‘President Obama has taken some very positive steps, which should have a serious impact on reducing the number of criminals and people who are dangerous, mentally ill, or domestic abusers having easy access to guns,’ says Mark of some legislation passed in January. ‘So it should save lives. But there are things we could do about further prosecuting people who break gun laws, and increase restrictions on people guilty of domestic abuse or convicted of a misdemeanour, stalking and such crimes.’

Plenty of people in the US are opposed to these suggestions, though. ‘I think it’s because they hear messaging from a very powerful lobby over and over again,’ says Mark. ‘And that messaging is very effective. It’s not logical, it’s just rhetoric. But rhetoric is a powerful thing.’

On being a gun owner himself

‘It’s written in our constitution that you should be able to own a gun for whatever reason you want and, if you’re a responsible person, you should be able to do that,’ says Mark.

‘The first gun I owned was when I was in the Navy. I was flying combat missions over Iraq. I’ve also owned guns to go hunting. I’ve a gun in my house to protect myself. If there was an attempt to make gun ownership illegal, I would stand against that very strongly.’

On sending tourists to space

Since retiring from Nasa, Mark has joined a space tourism company called World View. Based in Arizona, it plans to use high-altitude balloons to take people 20 miles above Earth.

‘We’ve started flights already, but the first test flights with people will maybe happen in about a year. And then, the first flights with paying passengers will probably be in about two years’ time. We’re looking at $90,000 per person per flight, and people will get to see the planet like I did as an astronaut. They will get to see this round ball floating in the blackest of space. It’s a pretty crazy place to visit.’

On being associated with Breitling

Speaking to Friday in his role as ambassador for Breitling, the renowned Swiss watchmaker, Mark says: ‘I’ve worn a Breitling on three of my four Nasa flights. Timekeeping is absolutely critical throughout the missions so you need the best.’