Mark Shuttleworth - March 31, 2002: Under pressure - Log for 15 March:
Our visits to Zvezda, the company that manufactures the Soyuz space suits, have come to a happy conclusion with the vacuum-chamber test. I think the exercise was as much psychological as it was technological, since they can test the suit perfectly well without a cosmonaut inside. But it was fun nonetheless.
We started off with a medical exam, mainly ear-nose-throat because of the pressure changes that I would undergo. Then we trundled off to Tomilino, where Zvezda has its headquarters, at the south-eastern edge of Moscow.
I was more than a little nervous, because this was the first time I would be sitting inside a chamber with the air sucked out. We've worked a lot with suits under simulated depress conditions, but that involved pumping air *into* the suit, which as far as I'm concerned is a whole lot healthier than sucking air out of anything. In a worst-case situation in the sim, the suit loses pressure and I blow an eardrum or two, but then we're back to normal atmospheric pressure. In this vacuum chamber, if the suit loses pressure, I'm sitting in a vacuum. And that just sounds unhealthy. There is a definite edge to the exercise.
When we arrived there was the now-familiar crowd of experts, doctors and supporters, all ready to go. They assured me that they'd tested the suit alone in the vacuum chamber already, and it passed with flying colours, so without any further ado I was suited up and led through a maze of twisty little passages, all looking the same, to the “barochamber”.
Assume the position
This is basically a large metal box in the middle of a room full of other large metal things, except this one has thick walls and a very impressive porthole. Outside is an array of terminals and dials and medical stations where the crowd of experts gathered to prepare for the test.
It was damn awkward walking around in the suit, so I was quite grateful to climb straight into the waiting chamber, and lie down in the Soyuz position, on my back with knees tightly bent. It took about twenty minutes for all the medical sensors, pressure sensors, emergency oxygen supplies and ventilation hoses to be attached, and for all the
specialists to huddle around their monitors and declare themselves ready to proceed. Meanwhile, a delightful lady who seemed to have been quietly co-ordinating everything in the background, helped me practise some Russian and shares a few jokes. Clearly she'd done this before.
Apparently, in an emergency, they can throw open a set of valves that will pour air into the chamber, taking it from a vacuum to effectively 7km altitude in just three seconds. Three very long seconds indeed, I'd imagine. Also, that must make one hell of a noise, not that one would be hearing much after that sort of pressure change. I wonder if any poor monkeys or worse, humans, were ever tested under those circumstances back in the crazy early days of the space programme here or in the US. Apparently, one way to win early release from Siberia was to volunteer for medical testing. Tough choice.
Eventually it was all systems go. We did a leak test of the suit, which meant pressurising it. I felt strangely relaxed. We'd done this any times before. I remembered the first time I tried on the suit and how excited I was at testing its seal... now it feels like the sort of routine thing one does every day. Once we were satisfied that the suit was well sealed, the test began and they started pumping air out of the chamber. They gave me a running commentary of the absolute pressure, in millimetres of mercury (sea level is 790mm), as well as the effective
At 5km, as planned, the ventilation to the suit cut out. From then on my body heat would not be removed by the flow of air through the suit as it normally is in the sim. From then on it was just the flow of oxygen, which is much lower and only goes to the helmet, not the feet or wrists. The limit of the suit is 135 minutes in depress, not because of oxygen constraints, but because of body heat build-up without convection.
Talk about stewing in your own juices. At 7km, I felt the suit start to inflate. It was set to maintain 0,4 atmospheres (about 315mm) of pressure, and at 7km the atmospheric pressure is about that. From then on, the suit would keep the necessary pressure around me even as the air was removed from the chamber.
Pretty soon the suit was tightly inflated, and the pressure in the chamber had dropped to 3mm, or 0.005 atmospheres. 99.5% of the air had been sucked out. Effectively, this was like being at 37km altitude, far higher than any airplane can fly. It was quite amazing to hold my hand out in front of my face, and know there was no air between the helmet and the glove.
Except for the sounds coming through the headset, and the hiss of the oxygen supply, everything was perfectly quiet. Someone could be firing a machine-gun in the room next door and I wouldn't hear a thing – there was no air to conduct the sound to me. Now the waiting set in – I had to survive two hours like this. Fortunately, between their tweaking the suit and my figuring out how to keep moving so that blood circulated a little bit every few minutes, it was surprisingly easy to last. In our first fitting, I was toast after 20 minutes, but this test went smoothly and while it was uncomfortable it was never agony. The heat build-up was much less than I expected... I think the 135 minute figure must be extremely conservative, because it didn't feel too bad after 120 minutes. That's good to know.
It felt like a big milestone in the process, and from a psychological point of view it feels great to know that I've been through a depress and survived. If we should get into a situation like that during the flight, it would be much easier to stay focused on the work process having been through this, which is why I suspect it's as much a psyche-support training exercise as a suit test.