what zero gravity is like -- 5/30/18
Today's selection -- from Packing for Mars by Mary Roach. What zero gravity is like:
"Last night on NASA TV an astronaut, in response to a schoolchild's question, said that being in zero gravity was like floating in water. Not exactly. In water, you sense the liquid's help -- buoying you and supporting your weight. When you move, you feel it push back on you. You are floating, but a heaviness remains. [In zero gravity], you are floating in air without effort, without help, without resistance. Gravity has given you a hall pass. ...
"Mission Specialist [Lee] Morin told me it takes about a week to feel comfortable floating. 'Then it seems like the natural thing. To float like an angel. I don't know whether it's like you're, you know, back in the womb or something, but it's like the natural way. And it seems very odd to think about walking with shoes.' ...
"Weightlessness is like heroin, or how I imagine heroin must be. You try it once, and when it's over, all you can think about is how much you want to do it again. But apparently the thrill wears off. 'At first,' wrote astronaut Michael Collins in a book for young adults, 'just floating around is great fun, but then after a while it becomes annoying, and you want to stay in one place .... My hands kept floating up in front of me, and I wished I had pockets or somewhere to put them.' Astronaut Andy Thomas told me how irritating it was to never be able to set something down. 'Everything has to have a bit of Velcro on it. You're forever losing things. I brought one nail file with me on [first modular space station] Mir, so I was very careful with it. About a month before the end of the mission, it popped out of my hand. I turned to grab it, and it was just gone. It went down with Mir. Once we lost a whole Sharps container. Big thing. Gone. We never saw it again.' ...
|Science writer Mary Roach experiences weightlessness in a parabolic flight.|
"Nothing works as it's supposed to in zero gravity, or zero G, as it's also known. 'Even something as simple as a fuse,' astronaut Chris Hadfield told me, mistaking me for someone who knows how a fuse works. Now I know: Fuses have a metal strip that melts in response to a surplus of current. The molten bit drips away, leaving a gap that interrupts the power flow. Without gravity, the droplet doesn't drip, so the power continues to flow until the metal boils, by which time the equipment has fried. Zero gravity is part of the reason NASA price tags seem so extravagant. For every new piece of equipment that goes up on a mission -- every pump, fan, throttle, widget -- a prototype must be flown on the C-9 to be sure it works in weightlessness.
"Overheating equipment is a common theme in zero G. Anything that generates heat tends to overheat, because there are no convection currents in the air. Normally, hot air rises -- because it's thinner and lighter; the livelier molecules are all bouncing off each other and spreading out more than they do in cooler air. When hot air rises, cooler air flows in to take its place. Without gravity, nothing is any lighter than anything else. It's all weightless. The heated air just sits where it is, getting hotter and hotter and eventually causing damage to the equipment.
"Human machinery tends to overheat for the same reason. Without fans, all the heat that exercising astronauts generate would hang around their bodies in a tropical miasma. As would exhaled breath. Crew members who hang their sleeping sacks in poorly ventilated spots get carbon dioxide headaches."
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