||[Apr. 20th, 2004|09:33 pm]
Hey all, this is Brian, and I'm going to be replacing your usual blogger today for a bit of information about the training we've been undergoing. On Friday, the four flyers, our alternate, and our journalist (Me, Rebecca, George, Cyrus, Whitney, and John) had our physiological training.|
For starters, we had 4 hours of lectures, beginning at 7 am (quite early for us, even after everyone but Whitney had slept through their alarms). The first was basic information on the atmosphere--how pressure gets lower as you go higher, the oxygen content of the air, etc--and respiration and circulation. We learned about how your lungs process the air you breathe, and why you can't just stick your head out the window above 10,000 feet and breathe in the air. If you do, you won't get enough oxygen--the gas that keeps you going--and will start to experience various symptoms (more on that later).
Next, we had a lecture on hypoxia and hyperventilation. Hypoxia is where your body does not receive enough oxygen, and your cells aren't able to do work. It can be caused by high altitude (which is what we were learning it for), drowning, carbon monoxide, and a host of other nasty things. The second, hyperventilation, is when you breathe too fast for your lungs to extract the oxygen from the air. It can be caused by emotional stress or as a symptom of hypoxia. We learned about the symptoms of both of these, and how to treat them – put on your oxygen mask, and breathe in 100% oxygen (as opposed to the 21% oxygen you normally get from the air).
Ok, still two more lectures to go (hey, be happy, you’re getting the abridged version here). The third one was on trapped gas and decompression sickness. So what does that mean? Well, as you go higher and higher in the atmosphere, any gas that’s trapped—-say in a balloon, your stomach, or in your ears—-expands. If you’ve ridden on an airplane, you know this effect, where your ears pop as you go takeoff and climb, and again as you land. This is because your ear is actually two parts: one which goes in from your ear canal on the side of your head, and the second which leads from the back of your throat. These are separated by your eardrum. If one of these tunnels has higher pressure than the other, there’s the chance that your eardrum will burst. We learned about how to clear out our ears and how to protect against this. Unfortunately, not only does the gas in your ears expand, but so does that in your stomach and intestine. So if you had Mexican the night before….well, at least we’d all be wearing oxygen masks. Decompression sickness is also known as the “bends”, and is something usually experienced by divers. In it, the nitrogen in your blood will come out of solution (think of a shaken up soda) and gather in gas pockets in your joints. This is very painful and quite dangerous. We learned how to recognize it, and how to treat it. The biggest thing to do is to breathe pure oxygen for at least 30 minutes first. This forces out all of the nitrogen (78% of the atmosphere) from your blood, and reduces the risk.
Finally, our last lecture (well, for now). This one was all about spatial disorientation – motion sickness. In the KC-135, we won’t have gravity to help us determine which way is up. Our inner ear—-our personal gyroscopes and orientation devices—-get fooled by this and will start to panic. Our brains can’t handle this, and it often leads to nausea and vomiting. To counteract this, we learned how to trust our eyes instead, and to understand how our inner ear works, so we can avoid doing things that really upset it.
We had to learn about all of this because of the possibility that the Weightless Wonder—-the plane we’re riding on-—might lose cabin pressure. Remember the safety briefings you receive on a commercial airliner, when they say that the captain will tell you to put on your oxygen masks, which fall from the ceiling, if they lose pressure in the aircraft? Because of the layout of the KC-135, we have to go back to our seats and pull out the equipment ourselves. To do this, everyone needs to know what it feels like to not get enough oxygen. It’s kind of hard to do that just sitting here on the ground, but we can simulate it by taking a “chamber flight.”
All right, this is the good stuff. No more lectures, just some experiencing. Ok, I lied, one more lecture. This one was on oxygen equipment, and how to use emergency equipment on the aircraft. Simple masks coming out of the ceiling doesn’t cut it for NASA; no, you have to do it all yourself. We were shown how to use the emergency hoods on the KC, and the regulators that we would use in our chamber flight.
And now, it’s the moment of truth. After our last briefing, we moved out to NASA’s Neutral Buoyancy Lab (NBL). This building contains the giant (and I mean really really big) 6.2 million gallon pool that they train the astronauts in. Inside the tank, there are mockups of most of the International Space Station, the Space Shuttle cargo bay, and anything else astronauts will work on. The astronauts put on real space suits and will get in the water to practice procedures and experience the work they will do in space. It is as close to weightlessness as one can get, unless you’re on the KC. I’ll post pictures of it soon!
Also in the NBL are the hyperbaric chamber and the altitude chamber. The first makes it seem like you are below ground level, and increases the pressure, while the second is for lowering the pressure to make it feel like you are at a higher altitude. Our chamber flight would take us up to 25,000 feet by lowering the pressure to roughly one-third of what it was on the ground. Once there, we would remove our oxygen masks and begin to feel the effects of hypoxia. Then, we’d slowly raise the pressure again until we reached ground level.
First, we were all fitted with oxygen masks. These masks would make sure that we would receive all of the oxygen we needed for the flight. Next, we pre-breathed oxygen for 30 minutes to get all of the nitrogen out of our systems. Now, we were ready to climb. The chamber operators “flew” us up to 25,000 feet in 5 minutes, during which time we all felt a bit uncomfortable as the remains of lunch shifted in our stomachs and the gas expanded. As repeatedly expressed by our trainers, good manners were left at the door, and we were encouraged to expel the gas through either of the two ends nature provides.
After reaching altitude, we alternated pulling off our masks. At 25,000 feet, most people have a time of useful consciousness (TUC) of 3-5 minutes. This means that you will be able to do something helpful to yourself for only a couple of minutes before you are beyond caring—not quite passed out, but essentially useless to you or anyone else. Almost immediately, everyone would start experiencing symptoms of hypoxia. For me, this was tunnel vision, where I lost my peripheral (side) vision and couldn’t concentrate. My judgment was affected too, since I thought the generally fuzziness of the world was just my glasses fogging up – but things got much clearer as soon as I began to breathe from the oxygen again. Rebecca had a major case of the giggles (euphoria is a common side-effect), while John became very very intent on the quiz we were working on.
Once everyone put their masks back on (failure to do so yourself and making the three former fighter pilots we had with us do it was worth a case of beer to the instructors), we started our descent. This was the most uncomfortable part of the whole flight, as our ears were big problems. If the area behind your eardrums contains low-pressure air, and the surrounding air raises in pressure, they’re liable to hurt, a lot. We constantly valsalva-ed (pinch nose, blow hard), but for one girl on our ride, it wasn’t enough. We had to “bounce”—-going up 2,000 feet quickly and holding there-—to relieve her pain. This happened four times, and at least twice, they had to use a special air “gun” to clear her ears. As she swallowed water, the device would shoot air up her nose to pop her ears. Finally, we reached ground level, pulled off our masks, and were able to hop out. Up and down to 25,000 feet without going anywhere? Not too bad of a trip.