Being an astronaut is one of those jobs where you're guaranteed perspective in life. As we take off, I imagine I'll be thinking about the newness of all the sounds and sights. I've spoken to a lot of fellow astronauts about what it's like going into space; I remember NASA's Gregory Chamitoff describing what it felt like to space walk. He said he remembered being surrounded by the deepest black you can think of. I've always had strange dreams of being in nothingness, just floating in complete darkness or going through the matrix. Soon, it will no longer be a dream.

Space-walk training is one of the coolest parts of my job. NASA operates a Neutral Buoyancy Laboratory (NBL) at the Sonny Carter Training Facility in Houston, Texas; it's a huge pool that's 40ft 6in deep, 102ft wide and 202ft long. There are mock-ups of the International Space Station (ISS) there. We have to get into the space-walk suit, which weighs about 140kg, and then they lower us into the water to simulate what it will be like in space by making us neutrally buoyant, so we neither sink nor float.

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Jeanette taking part in a water landing simulation

We can be training underwater for six hours, which is pretty draining. At some point, you start feeling the weight of the suit. It's also mentally exhausting, because you have to figure out how to make the suit work. When you spacewalk, you don't actually use your legs very much – you mainly use your upper body, so you need to be able to operate tools and work wearing gloves, which feel like oven mitts. If something breaks while I'm on the ISS I might have to do a space walk to fix it. I'll be one of the flight engineers, so my main duties will be conducting science experiments and maintaining the ISS systems.

I've always had strange dreams of just floating in complete darkness. Soon it will no longer be a dream.

As a child, I wanted to go into aerospace engineering and work for NASA, but I never thought I'd be selected as an astronaut. Growing up in Syracuse, New York, my twin sister Janet and I were always interested in science and maths. We were the youngest of seven children; my mother Luberta, who worked as a keypunch operator for a local computer company, was very protective of us and always stressed how important education was.

When we were nine years old, my older brother Michael came home from university and saw our school grades on our report cards. I remember being surprised by how proud he was. He said we could become scientists, aerospace engineers or even astronauts. At the time, Sally Ride, who would become the first American woman in space, had just been selected by NASA. I guess his encouragement planted a seed in my mind.

I decided I wanted to study engineering when I was 16-years-old. I was doing an internship in pathology at the New York Health Science Center to figure out what it was I wanted to do. The only reason I didn't continue down that path was because one of the doctors invited me into the autopsy room. When he started taking out the intestines, it was the worst thing I'd ever seen, and I knew I would be more suited to engineering.

As a graduate student at the University of Maryland with my sister Janet, I worked all the time. My adviser always told a story about how he had been out of town and stopped by the lab late on Sunday evening, and Janet (who later went into genetics) and I were there collecting data. We worked constantly, but we didn't think it was strange; we thought it was a good way to spend our time. After grad school, I went to work at Ford Motor Company in their scientific research laboratory as a Technical Specialist.

Sexism and racism are always present, and I've had some pretty negative experiences, both at university and in my career. One of the questions young women often ask me is whether I've had any problems being a black woman working in engineering. I always tell them I have no problem with it, but other people may have and that's their problem. If I make it mine, it stops me from moving forward. The intention [of their negativity] is to stop you from progressing and limit your creative thinking.

Sexism and racism are always present, and I've had some pretty negative experiences, both at university and in my career.

In 2003, I went to Iraq as a Technical Operations Officer with the CIA to look for weapons of mass destruction. As a lab geek, making the decision to go to Iraq was daunting, but I told myself, "I have to do this." I had to do something different and gain a new perspective. I was there for four months and it was an amazing, life-changing experience, but it's not for everyone. As a scientist I'd spent most of my time doing design work and trying to create things, so going to Iraq, helping to solve a national issue and really getting a sense of what was happening, fuelled my desire to know and to understand.

I get very excited when I think about being up in space, partly because I compare it to going into a war zone. Both are very dangerous but, for me, it's a no-brainer: I would rather face the dangers in space than go back to a war zone. I'll never forget the night when we were in the airport in Iraq and a young man had just come back from a convoy; he looked totally different to when I had seen him the previous week. He showed me the rounds that had struck his body armour that day. He was just sitting there thinking about how he was nearly killed. Seeing him and realising that our wars are fought by people's children, people's husbands and wives, had a real impact on me.

I constantly think about work, but when I get home I like to have a domestic life. Once a month, I'll go out to a happy hour, just chat with friends and try not to talk about work. I don't have any kids and I'm one of those people who seems to always have a boyfriend or something romantic going on. I don't know if men are intimidated, but it's hard to keep a relationship going when I'm preoccupied with work.

The earth from spacepinterest
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I'll be one of six living on the ISS and the only woman. I'm not too worried about that, though. I completed the underwater NASA Extreme Environment Mission Operations (NEEMO), which places trained astronauts in an underwater laboratory off the coast of Florida for up to three weeks. I was the only female out of six people and we had close quarters, sleeping in bunks.

When you're living 50ft underwater, your blood becomes saturated with nitrogen, so it's one of the closest equivalents to space; you can't just get up and leave. You have to do a 17-hour acclimatisation to purge the nitrogen out of your blood, otherwise it can be dangerous. NEEMO was one of my favourite training exercises. It was tough, but it was so much fun living and working underwater.

I'll be one of six living on the International Space Station and the only woman. I'm not too worried about that though.

The space suits look strange from the outside because they appear as though you're squashed in, but they're more comfortable than they look. We're allowed to pick some of the clothes that will be shipped up to the ISS before we arrive. There are polo shirts, cargo trousers and a couple of uniforms, some of which have Velcro on them so you can attach tools for when you're going about the space station doing maintenance work. We also get to choose home comforts to take. I love woolly sweaters, so I'll pick some of my own; I like that they make it relatively comfortable and you can make the ISS your home.

I'm healthier and stronger now than I was when I was 20. On the ISS, they have an exercise device that helps load your bones so you don't lose any density; there's also a bicycle and treadmill. I'm not a long-distance runner, but I do like putting on my headphones, going for a run and forgetting about the world. There will be iPads and laptops up there so we can watch movies while we run.

When people come back from space, I see how much they want to go again. I suspect I will be one of those people. I'd find myself at the back of the queue, but it's worth the wait – or at least that's what I think I'll come back saying.

This feature originally appeared in the March issue of ELLE UK, on sale now