EMMA: I’VE LOST all sense of time. It could have been hours. Maybe a day. Two, even.

I’m sure of one thing: I have decompression sickness. Not bad enough to kill me, but bad enough that I feel it every second. I’d really like to vomit right now, but it’s not a good time for that.

The science of decompression sickness goes like this. The ISS and space shuttle are pressurized to 14.7 psi-the same atmospheric pressure you’d feel on Earth at sea level. The EVA suits are pressurized to 4.3 psi- the same atmospheric pressure as on the summit of Mount Everest. So in a matter of seconds, I was blasted from sea level to the summit of Everest. Why is that bad? A rapid decrease in pressure causes nitrogen in the body, which is usually dissolved in blood and tissues, to break out and form bubbles. It’s like opening a can of soda. The contents of the can are at high pressure. When it’s opened, the contents are exposed to dramatically lower pressure. The result? Fizzy bubbles. Carbon dioxide released from the liquid. That’s what’s happened to me: fizzy bubbles of nitrogen are racing around my body. I’m like a human can of soda that was at high pressure and has just been opened and is bubbling away.

Scuba divers have known about decompression sickness for a long time and take steps to avoid it. So does the ISS: we have a protocol we follow before EVAs to prevent decompression sickness. But there wasn’t time. In this case, it was decompression sickness or death.

And at the moment, I feel bad enough to second-guess my choice.

I hurt all over. I feel exhausted, but I don’t dare fall asleep. I’m scared I’ll never wake up.

I cling to life, every second of it. I realize now just how much I want to live. That’s what ultimately matters in a survival situation: the will to live.

Except there’s not much for me to do with that will to live right now. I just watch the debris from the station, searching for clues that there are any other survivors-or any move for me to make.

Every now and then a piece of the station falls into the atmosphere and burns up. They’re like glowing pieces of sand falling through an hourglass, counting down to my doom.

I’m in a decaying orbit. It’s only a matter of time before I, along with the piece of the station I’m tethered to, fall into the atmosphere and burn up as well.

There’s another brilliant flash of light. I assume it’s more debris burning up. But this light gets brighter, not darker. Something is coming up.

A rocket. Barreling toward me.

A capsule disconnects, and its thrusters fire.

It’s coming toward me.

For me.

I watch in wonder. Tears stream down my face. I’m going to be rescued.