Sunday, March 26, 2000
As the oxygen runs out, the mind runs slower
Inside the test chamber, a new attitude to altitude
This Online Bonus story did not appear in the print edition.
BY TIM BONFIELD
The Cincinnati Enquirer
The voice coming over the headset was sharp, loud and seemingly unmistakable. “Number 11! Number 11! Put on your mask!” the instructor ordered. “Do you remember what to do first?”
The young woman at seat No. 11 simply grinned as her oxygen mask dangled from the left side of her face. All she had to do was flip a single switch and swing the mask over her nose and mouth.
If this were a real aircraft that had really lost all cabin pressure at 24,000 feet, this woman would soon lose consciousness, then die. Just like what our instructors said must have happened to professional golfer Payne Stewart.
The young woman, and all the rest of us, suffered absolutely real cases of hypoxia (a loss of oxygen that impairs mental and physical ability). But the risk of death was nil because the whole thing happened inside a NASA altitude test chamber, as part of a two-week student reduced gravity flight program.
Instead of a tragic ending, an instructor simply put the mask back over her face. She felt better instantly and a half-hour later she was laughing along with me and a room full of other chamber flight survivors at how silly we looked on the videotape.
While taking a ride on NASA's KC-135 airplane is the big highlight of the trip, the altitude chamber experience is just as unforgettable.
The chamber offers a first-hand demonstration of what can happen when humans fly into the upper levels of the atmosphere and ultimately into space. In the chamber, those boring old terms from high school physics class, like Boyle's law and Dalton's law, become immediately relevant to your life.
After a day-long refresher course in aerospace physiology, I became “Number 2” of 16 fellow journalists and college students to be fitted with a military-issue oxygen mask and communication head gear.
The rectangular chamber stands inside a much larger building. It had thick white walls with windows along the sides and the end. From outside one end, a NASA staff member “pilots” the chamber by controlling the air pressure. Another talks to the passengers through the comm links. A flight surgeon stands by.
Hooking up the oxygen gear was simple enough. But I found breathing through an oxygen mask to be disconcerting.
It was difficult to talk and catch a breath. It got even harder when we switched to “pressure breathing,” which causes the mask to blast oxygen down your throat.
After reaching the equivalent of 8,000 feet, we jumped suddenly to 24,000 feet to simulate sudden loss of pressure in the cabin. If this happened in a commercial jetliner, the oxygen masks would drop from overhead. But we were instructed to remove our masks.
The first demonstration of Boyle's law occurred when the two balloons hung inside the chamber swelled to triple their size. The exact same thing was happening to any and all gasses inside our stomachs and intestinal tract.
“This is one situation where social graces go out the window. It's OK to pass gas in the altitude chamber,” said physiological training officer Mike Fox.
People can't help but belch and pass gas.
To my surprise, breathing the low-pressure air felt normal. There just wasn't enough oxygen — and we couldn't tell.
With our masks off, we were told to answer various questions on a form:
• Name the past six presidents.
• Write your name backwards.
• Do a few math problems.
I was doing fine for three, maybe four minutes, until I had to write out what NASA stood for. I thought I knew what I was doing. But I wrote total gibberish.
In the video, I looked totally focused on the test. I was actually too focused, a common problem with people suffering hypoxia.
While looking at the paper, I could not hear voice instructions. If I had been a pilot and the radio had been barking “Pull up!” I would have crashed.
A few moments later, I did manage to flip my own oxygen switch and put my mask back on, but only after an instructor waved at me.
In the chamber, other people reacted in different ways. One person's face turned beet red. Another's turned ash gray. I felt tingles in my fingers, like my hand was going to sleep. Another passenger said his hand clenched into a claw he could not relax.
After the chamber “flight,” I had a whole new attitude about altitude. I found myself noticing that the plane that flew me to Houston traveled as high as 29,000 feet. Inside, it felt like about 8,000 feet because the cabin was pressurized.
Now, I know exactly why the flight attendants do that oxygen mask demonstration that so many passengers ignore. The NASA trainers called it “time of useful consciousness.”
If an airplane window blew out (what the experts call explosive decompression) at less than 10,000 feet, it would get extremely windy inside but people could breathe.
But at 25,000 feet, the average person without an oxygen mask can breathe for only about three minutes before they become non-responsive and helpless. At 35,000 feet, the useful consciousness time drops to 30 seconds. Above 43,000 feet, it drops to five seconds.
Now, the freaky story of Payne Stewart's plane flying along with everyone dead inside seems much more understandable.
In the chamber, all we had to do was put on our mask and flip a switch. But at high altitude, that simple act wasn't simple at all.
Photo gallery
Zero G is the ride of a lifetime
InfoGraphic: How plane gets Zero G
Weightless ride churns reporter's stomach, but thrill is worth it
As the oxygen runs out, the mind runs slower
NASA needs to go boldly, hero of moon program says
Students get a look behind the scenes
How to be an astronaut
