This morning, I was awakened at 6am by the alarm on my astronaut watch. It's certified for space flight.
I was an astronaut for 21 years, and flew into space three times, the last time for six months, so let's talk about a day on the International Space Station (ISS).
First, you have to choose which time zone you are in, because you are going around the world every 92 minutes. So when is morning? We chose Greenwich Mean Time.
On the ISS, you can sleep anywhere you want. You go around the world every 92 minutes, so that means you have a sunrise and sunset at least every 46 minutes. You don't want to be any place where the sun is coming up or going down, because that will disturb your sleep. So you need some place that is dark. I liked the sleep pod best, because it is the quietest place.
You're in a foetal position - with your arms floating and your knees bent and your head tipped a little forward. That's the natural relaxed state of the human body. It's the most comfortable sleep you could imagine.
Often there is a bit of a line-up for the bathrooms, as there are only two for six people. On Earth, we count on gravity for toilets, but in space, we use airflow instead. As the waste comes out of you, it gets pulled away from you.
Water is in extremely short supply in a spaceship and we recycle about 92pc of our water up there, including our urine. Showers are very water wasteful, so you just get a wash cloth and wipe yourself. It's like a sponge-bath in hospital, and it works fine. We keep ourselves very clean. In the six months up there, I never smelled any other human smell. It was actually the least smelly toilet of any I've ever used. The air purification system works great.
There is no kitchen on the ISS - just a hot-water and ambient-water dispenser, and an easy-bake oven where you can warm up a package. You get a packet of dehydrated scrambled eggs and add water, push hot, and wait for it to hydrate.
Then we have a formal briefing with all the mission controls. You have a digital schedule that tells you what you are doing for the whole six months you are up there. Every five minutes is delineated. Many of the things that you are doing are tag-timed with someone on Earth - scientific research teams in Philadelphia or Tokyo - so you need to be working at their time.
Then you get to work. We are running about 200 experiments in the space station. Some of them are looking at the universe and we are trying to see other stars, to see if there is life somewhere else. We are trying to understand our atmosphere, and the natural cycle of the world. When we look at the pollutants of the world, it's instructive about what we need to be doing. Most of the world is doing great, and it's beautiful.
We run experiments inside, like how flames behave without gravity, because heat doesn't rise in space. And how does water behave? We look at how space life affects the human body. Your heart shrinks when you are in space because it doesn't have to be a weight-lifting heart.
There are two hours in there for exercise, because if you don't exercise, your body wastes away. We have a stationary bike with no seat and a treadmill with a harness that pulls down on your shoulders and hips, so that you can run. And there is a resistive exercise machine where you are pushing against the vacuum of space.
You have strong productive work to do every day. It's a very purpose-driven, satisfying life. To be selected as an astronaut is extremely rigorous. Twenty-and-a-half years of my life were training, and that's not like taking a course. I spent years developing the relationships and the way to deal with problems together, so that we wouldn't manifest ourselves differently when we got to space. You can deliberately be a jerk or deliberately be a good person to be with - it's totally your choice. I worked really hard, both as a crew member and as a commander, to build the environment that would maximise on our chances for group success. I tried to do one nice thing for every crew mate each day without being asked.
We try to have dinner together, but normally everyone is too busy and you don't want to interrupt other people's private time. Then in the evening, you are studying for the next day. Normally people would steal an hour or two of their sleep time to do the personal things - play music or take pictures, write a diary or talk to their family .
Mostly, I took pictures and I recorded music. And I made a lot of videos so that people could share in the experience. The videos consisted of anything that made me smile or laugh.
I've led dangerous professions as a fighter pilot and test pilot and annual ski racer and astronaut, and I've seen lots of friends die young, brutally, violently and instantly, so that's been a reminder. Don't wait for some other point in your life to enjoy what you are doing. There are no guarantees that you are going to see them.
You better enjoy your life today. Make a deliberate choice to notice the beautiful things that are happening to you today, and integrate that into who you are.
When people ask me if I miss being in space, I say, no. I was in space. I don't miss it. It's who I am, but I'm not going to dwell on my past. I'm really interested in the present and the future.
Chris Hadfield was in Dublin as part of Electric Ireland Brighter Energy
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