Throughout National Science and Technology Week (October 17–26), we're celebrating new Canadian books on science and technology. Today's pick is Canadian Spacewalkers, in which celebrated science journalist Bob McDonald compiles perspectives of the three Canadians who have walked in space (astronauts Chris Hadfield, Steve MacLean, and Dave Williams). The book includes an extensive interview transcription—a one-on-one with spacewalkers who tell tales of training underwater in the world's largest swimming pool; recount how they learned to use power tools in zero gravity while wearing bulky gloves; and describe the moment when they opened the hatch and stepped outside.

In this excerpt, McDonald shares his own experience with simulated spacewalking, and speaks with Steven MacLean about the feeling of being head over heels. 

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One of the great joys of being a science journalist is getting to play with big toys. Over the years I’ve managed to get myself into many different types of torture devices—I mean training equipment—used on pilots and astronauts. Often a simple phone call asking if I can do a story on the subject gives me a ride in an aerobatic airplane, a zero-g flight or a chance to experience a wide assortment of very clever machinery designed to simulate different aspects of spaceflight.

Twice I’ve been strapped into centrifuges and spun up to more than three times my weight, which is the force space shuttle astronauts feel during launch. While your arms feel heavy to lift under three g, it’s not really that bad. You can still perform all the necessary functions; it just takes a little more effort.

The most interesting devices are those that try to disorient your sense of up and down by confusing your organs of balance. It’s a serious issue that astronauts have to deal with as soon as they arrive in space. While weightlessness looks like a lot of fun, and it is, many space flyers feel motion sickness because of the confusion in their brains between what their eyes are seeing and what their body is sensing.

One device at the Defence Research Labs in Toronto is a flight simulator mounted on a rotating platform. As I sat in the pilot’s seat with a control stick in my hand and a computer screen in front of me, the door to the cabin was closed so I could not see out. As the cabin began to rotate I had a slight sense of motion but it turned so smoothly and steadily that the feeling went away after a few seconds. As far as I was concerned I was flying straight and level, which was my task. Just keep the horizon on the computer screen steady.

At first the flying was so simple I wondered why they’d bothered to build this device. The spinning was having no effect on me at all. Then the instructor asked me to tilt my head quickly to the side and touch my ear to my shoulder. Instantly I got a powerful sensation that I was heading upward. I push the control stick forward to compensate.

“Okay, straighten your head.”

As I rotate my head back upright I get another powerful sensation, this time of diving down. I pull up on the stick. The simulated horizon in front of me is moving all over the place. I’m barely in control.

“Now tilt your head in the opposite direction.”

Now I’m suddenly going down again. This time I don’t move the stick and I realize the sensation is entirely in my head. The horizon remains steady but that’s not what I feel. When my head comes back upright it feels like I’m looping upward. I try to ignore the sensation but I find it extremely difficult. The sense of upward motion is so powerful I want to believe it, but my eyes are telling me otherwise. A little knot begins to form in my stomach.

The final part of the exercise is to tilt my head up. The world suddenly turns on its side. I bow my head down and everything tilts the other way. It was very hard to keep flying the simulator straight and level. In fact, I crashed and burned. My brain was telling me the world was tilting in all different directions every time I moved my head when in fact it was not.

These powerful motion cues were coming to me though my semi-circular canals, little tubes filled with liquid that are part of the inner ear. When you move your head, fluids in the tubes slosh around, telling you your head is moving, but they only detect a change of motion—when your head starts to turn and when it stops. If you turn continuously, the fluids catch up and stop sending their signals to the brain, which is why I didn’t sense the constant spinning of the flight simulator.

Each ear contains a group of three tubes, and they are oriented to the three axes of motion we experience every day. One set of tubes is positioned to be activated when you nod your head up and down when saying yes. The second detects side to side motion when you say no, and the third is activated when you tilt your head from side to side.

Usually only one set of tubes is activated at a time and your eyes confirm what the tubes are sensing. You know you’re turning your head because your view of the world changes.

When I tilted my head to the side in the simulator, my up and down semi-circular canals, which had not been activated up to that point, suddenly started spinning and my brain got the cue I was tilting up, even though I actually wasn’t. My eyes could see the flat horizon but because I was supposed to be flying it really felt as if I were rising. All the other motion cues I got when I tilted my head in different directions were just as powerful and convincing.

Whenever there is a conflict in the brain between signals from the organs of balance and information from the eyes, a common reaction is to empty the contents of the stomach because, coincidentally, poisoning can affect balance in the same way.

In space, astronauts’ heads are moving in all directions at once as they float around in weightlessness. Their organs of balance, which depend on gravity, are constantly sending false cues to the brain that have to be ignored. That’s why many astronauts feel nauseous when they first arrive in orbit. Eventually the brain just stops listening to the balance system and relies totally on the eyes, which means astronauts must consciously choose which directions are up and down, because in reality those directions are meaningless in space.

Imagine working on a giant assembly project in an environment where you are constantly floating freely and where up and down don’t exist at all.

Choosing your personal sense of up and down

Question: Did you have any problems with disorientation, the fact that sometimes the Earth is over your head and sometimes it’s under your feet? How did you deal with disorientation in space where there is no up or down?

Steven MacLean: There is a phenomenon that occurs when you go floating in the mid-deck of the space shuttle, for example, and you turn upside down. You have to change your frame of reference, so how fast can you shift from being a shuttle-centred reference to a head-centred reference?

On your very first flight, on your first day, you tend to have your feet on the floor and your head toward the ceiling. You tend to float that way around the entire vehicle. You keep a shuttle frame of reference. As CAPCOM, when you watch somebody float you know what framework they’re in, and there are several possibilities. You’ve got the Earth as a reference that you can use, or the shuttle as a reference, or your own head. You can decide that wherever your head is pointed is up.

Let’s suppose you’re in the zero-g aircraft. You hit zero g and you’re floating up. Everything looks normal to you. If I take you and spin you around so your head is down, how long does it take for you to switch out of the aircraft reference system? How quickly can you feel that your head is up? You may not be able to do it at all. I can do it right away, but some guys take three or four days to get that adaptation. I think that’s part of the reason we do EVAs on the fourth day. By then you have all of the adaptation syndrome stuff and you’re settling down. When it’s your second flight, it doesn’t take long at all—maybe about an hour—but it varies for everybody.

The question is, can you float with your head, using the frame of your suit, and just go where you want or are you using one of the other standard frames—the frame of the Earth or the station itself? What I found was that I could shift between them depending on what I wanted to do.

I’ve thought about this a lot. The guys who get the death grip, what happens to them is they have separated from those three frames and they don’t know which one they’re in. You have all of that going on and when you’re outside you just have to pick which one you’re going to use. Once you’ve picked one, there is no issue at all.

I found that when I was translating—moving from one place to another—I would use the frame of the station, but then if I was working on a task I’d use the frame of my suit so that wherever I was working my head was up. It’s an awareness that, okay, that frame is over there, this frame is over here; which frame am I in and which one do I use? I might start out being upside down relative to the Earth but when I start working I’m head up.

If you are in the wrong frame you can easily set off in one direction, take one step, and realize that it’s the wrong direction, but you figure all of that out in the first five or ten minutes after you go outside.

From the book Canadian Spacewalkers: Hadfield, MacLean and Williams Remember the Ultimate High Adventure, by Bob McDonald, ©2014. Published by Douglas & McIntyre. Reprinted with permission of the publisher. 

Photos courtesy of NASA except where otherwise noted.