The diary of an astronaut

To begin with, when you first reach space, all the blood from your legs pools up in your head because there is no pull of gravity. Your head actually becomes bigger and that is not due to the fact that you are now an astronaut, it is literal fluid shift. Due to this sudden pool of fluid in the upper body, the mind perceives this as excessive fluid and starts expelling through normal urination. The same mechanism quenches thirst as well. In effect, you lose 20 per cent of your body fluids. Another interesting concept is that since your heart does not have to pump blood against gravity, it actually shrinks in size. You may lose up to about 15 per cent of its size. I have spoken about space motion sickness but there is also space fog. A sense of confusion that slows you down initially. Even the things that you do know how to do, you become slow at them.

Then there is this concept of time itself. While orbiting Earth at 28,000 km per hour, the station laps the entire planet every 90 minutes. The sun rises and sets, not once, but sixteen times in a single 24-hour period. Sixteen sunrises. Sixteen sunsets. Each one, I should mention, more breathtaking than anything you will ever see from the ground, painting the curvature of Earth in colours that have no adequate names. If you allowed natural light to govern your body clock up here, your circadian rhythm would dissolve into something resembling madness within days. So instead, we run on GMT. Arbitrary, collective, entirely human, the decision that time is whatever we agree it is, enforced by a timetable of almost military precision. No Mondays. No Fridays. No weekends arriving like a rescue party at the end of a long week. Instead, the days are numbered with the unsentimental neutrality of mission elapsed time-GMT 175, GMT 176-one indistinguishable from the next except for what the schedule demands of each. And on your iPad, a thin red line moves with quiet, relentless authority across the day’s activities, marking exactly where you should be against where you actually are. Every astronaut aboard the ISS, regardless of experience and seniority, shares one universal condition: they are perpetually, desperately chasing the red line. It waits for no one. It offers no sympathy. It simply moves.

The day officially begins at 6.00. I preferred 5.45, a habit from Earth, and one of the few I managed to transport intact. Fifteen minutes before the red line begins its march. Fifteen minutes of quiet in a place that is, in almost every other respect, anything but quiet; the ventilation fans run constantly at a hum that registers at around 60 decibels, roughly equivalent to a conversation in a busy restaurant, necessary to prevent pockets of exhaled carbon dioxide from accumulating around sleeping crew. Silence, in space, is engineered. Those 15 minutes were mine.

The first task of the morning is one that ground-dwellers will find charmingly mundane-packing away your sleeping bag. Short-duration crew, which included me on Axiom Mission-4, entails that the mission pilot sleeps aboard the Dragon capsule. In the morning the bag must be rolled, secured and stowed according to safety protocols. It sounds like a small thing. In microgravity, small things have a way of demanding your full attention.

Then, and this was non-negotiable-coffee. Black, from a sealed pouch, sipped through a straw in the particular way that hot liquids must be consumed when they will otherwise float away from you in wobbling, scalding spheres.