Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!iuvax!rutgers!aramis.rutgers.edu!athos.rutgers.edu!nanotech From: Daniel.Mocsny@uc.edu (daniel mocsny) Newsgroups: sci.nanotech Subject: Re: Utility Fog Message-ID: Date: 21 Aug 89 21:52:33 GMT Organization: Univ. of Cincinnati, College of Engg. Lines: 69 Approved: nanotech@aramis.rutgers.edu In article , josh@aramis.rutgers.edu writes: > Suppose you have your car filled with molecular-sized robots, floating > around in the air. *Lots* of them. Now when an accident occurs, they > need only reach out and grab the assembler/robot next to them, forming > a 3-dimensional interlocking structure. And incidentally transforming > the air in the car from a gas to a solid. Assuming the network extended > down into your lungs and other airspaces in your body, you could drive > into a brick wall at 100 mph without serious injury. Wrong. You would still die from brain injury. Your brain floats in cerebral-spinal fluid, but it is slightly denser than the surrounding fluid, so in a severe skull impact it "sinks" towards the impact point. The inside of the skull is rough where the interlocking skull bones join, so rough that the brain can be damaged by bumping it even though the dura (tough surrounding membrane) lies between the brain and skull. A typical injury is a subdural haematoma, where the stress on the brain tissue ruptures blood vessels. The subsequent bleeding causes gradual loss of brain function over a period of minutes to hours, possibly leading to death unless a brain surgeon is handy. The ability of the brain to withstand accelerations is well-known. I believe 600 g's is usually fatal; 300 g's leaves you a pretty good mess; 100 g's gives you a severe headache and perhaps a concussion. Helmets for motorcyclists and bicyclists contain crushable material to reduce the accelerations in typical impacts to a survivable level, I think the number was 50 g's. For the utility fog to work, it would have to have some give, like an air bag does. Ideally, it would continuously tailor its properties to keep accelerations on vulnerable bodyparts to survivable levels. In challenging impacts (e.g., airplane crashes) where some injury is unavoidable, it could dynamically optimize its properties to minimize the injury. BTW, standard automobile air bags can already protect in seemingly hopeless impacts. I read about a man driving a light car who hit a tractor-trailer head on. Both vehicles were going over 60 mph, so with change of direction the air-bag equipped car had an impact equivalent to hitting a stationary, unyielding object at 120 mph. The driver had a few broken bones, but he walked away (after the wrecking crew cut him out of the car). I don't have a reference. While we are on the subject of surrounding ourselves with material that changes, I for one would have immediate use for smart clothes that could tailor their thermal properties. I ride a bicycle in winter, and I find that no available clothing works well. When I am climbing a hill, I can be generating body heat at over 10 times my resting rate. My airspeed, and thus my cooling rate, is relatively low at the time. The thermal delay created by winter clothing insures that I get quite sweaty. When I roll down the other side at 40--50 mph my work rate drops to little more than my resting rate while the wind chill gets ridiculous. A few cycles of that spells a curious form of misery where I seem to be freezing and sweating concurrently. Eventually the accumulated sweat wins, and I have to get back indoors. What I need is smart nanotech clothing that gets itself largely out of the way when I am accumulating heat, then comes back when I need it. Dan Mocsny dmocsny@uceng.uc.edu [Decelerating from 100 mph at 100 G you will travel 3.3 feet. A deceleration path of at least that length should be left in any Utility Fog seatbelt designs, should anyone reading this be designing one... --JoSH]