Chamber training
Published on Jan 11, 2009 at 3:47 pm.
4 Comments.
Filed under NASA, microgravity flight.
Prior to our flight, we have to have training in a low pressure environment. The explanation given is two fold. First, we are not going to be in a normal commercial airliner. Yes, it is an airframe of a design that had been designed for commercial airliners, but it has been modified. There are no masks that drop down from overhead in the event of loss of cabin pressure. Rather, there are solid state personal oxygen generators stored on board for easy access. In the event of loss of cabin pressure, you have to make it to the oxygen generator, activate it, and put the hood over your head. It helps to know how you perform in an oxygen starved environment. Another reason for requiring the training is that NASA doesn’t carry passengers. So, in order to fly, you have to be crew, and crew are trained in this manner. At any rate, before we fly, we have to pass the training.
The training was done at NASA’s Sonny Carter Training Facility, located at the edge of Ellington Field. This is also the site of NASA’s Neutral Buoyancy Lab (NBL). The NBL is the home to what may be the world’s largest indoor pool. I will write more about that in a day or two. For safety, NASA has hyperbaric chambers available in case a diver gets into trouble. But, a hyperbaric chamber is just a large pressure vessel. If you use a vacuum pump instead of a compressor, then you can suck air out of the chamber. That would make it a hypobaric chamber. That is how we used it.
After an entire morning of lectures and briefings, those of us assigned to the afternoon chamber run went from the Johnson Space Center, where the briefings were located, to the Sonny Carter Training Facility. You can tell from the photo that it is a large building. The bulk of the building is for housing the NBL, an about 200 foot by 100 foot fresh water pool 40 feet deep. Just inside the entrance is the security station. Like many of the places that we’ve been, security is tight. We need to have our NASA passes plus current photo identification. Once inside, there is a classroom where we receive more briefings. We are each fitted with an oxygen mask, and we are briefed on how to use it and the oxygen regulators in the chamber. Then, we go to the chamber. I had been looking forward to the chamber run; however, all of the briefings in the morning about what could go wrong, however unlikely, got me to be a little apprehensive.
First, we pre-breathe pure oxygen for a while to purge some of the nitrogen in our bodies. At first, it was a bit uncomfortable. The regulator supplies oxygen on demand. So, when you inhale, the pressure in the mask drops and that triggers the regulator to supply oxygen. But, that means that you have to work a bit to get oxygen. It is a disconcerting feeling to have to work to breathe. However, over time, you get used to it. In fact, it becomes a bit comforting to see the indicator blinking showing oxygen flowing. You know that even if you don’t get a full breath you are still getting enough life giving oxygen because the air that you are breathing is 100% oxygen rather than being about 1/5 oxygen like normal air. The plan is to breathe the pure oxygen for about half an hour. During this time, the chamber’s operator is explaining what is going on and what we will be doing. But, after half an hour he announces that something is wrong. The electrical box for the vacuum pump was making a smell, so they called for electricians to come check on it. If we were to take the masks off and then the system declared OK, we’d have to pre-breathe oxygen again for a half hour. It doesn’t hurt us to breathe oxygen, so the decision is to keep breathing oxygen and wait for the electricians to give the all clear. Well, it took a while for them to get to the Sonny Carter facility. So, we wound up being on oxygen for nearly two hours. We did a few other things to keep busy, got to use the backup manual regulator, and experimented with pressure breathing. Finally, we got word that the electrical box checks out just fine. It had gotten dust in it was all. So, we finally got to close up the chamber and the vacuum pump engages to start pulling air out of the chamber.
The pump continued until nearly 2/3 of the air was removed from the chamber. This was the equivalent of the atmosphere at an altitude of about 25,000 feet. It only took a few minutes to reach that level. Once at the 25,000 foot equivalent level (they call these procedures “chamber flights”) we were given pencils and clipboards with worksheets. Then we turned off the oxygen regulators and took off our masks. Only half of us at a time did that, and there were chamber workers who did not take off their masks at all. Without our masks were given several tasks to perform. The idea was to see how long it took for us to develop recognizable symptoms of hypoxia (oxygen starvation). 
The instructions were to turn on the regulators, set them to the “emergency” setting providing a bit of overpressure of oxygen, and put our masks back on. As soon as I got to where I was pretty sure that I was experiencing the onset of hypoxia, I did just that. A number of other people had their masks off for about a minute longer, but I think that they may have been trying to see how long they could stand not having enough oxygen before they were incapacitated. I didn’t want to push it, so I followed directions and put the mask back on once I felt hypoxic.
So, everything went OK. That is, everything was OK until we started “down” from 25,000 feet. As the pressure increased, my ears did now equalize properly. We had to stop the descent and I needed a bit of help to clear my ears. Both ears still felt unequalized after the chamber was opened, and the right ear didn’t feel normal until the next morning. The left ear took quite a bit longer to equalize. I have occasionally had some ear problems flying, but nothing like this. Of course, commercial airliners normally pressurize at about a 6000 to 8000 foot level, not 25,000 feet. Hopefully, this won’t be a problem with the upcoming flight, since it will be pressurized.
-Astroprof
Posts about Home Security as of January 12, 2009 | TUI's Voice on January 12, 2009 at 1:35 am: 1
[…] New Orleans works to repair its broken school system, IDEA is contributing to the effort Chamber training - astroprofspage.com 01/11/2009 Prior to our flight, we have to have training in a low pressure […]
Sili on January 13, 2009 at 3:11 pm: 2
I know it sounds stupid and petty, but my I was rather happy to hear that they put the equipment to good use and only have one set of chambers for both high and low pressure.
Leon on January 14, 2009 at 2:55 am: 3
Hey, how are you doing? I just want to say, that your blog is awesome.
joe on February 23, 2009 at 11:54 pm: 4
http://www.cseti.org
aliens are alive and you’ve been lied to. seriously dude.