gutfreund.umass-coins@UDel-Relay@sri-unix (11/25/82)
From: Steven Gutfreund <gutfreund.umass-coins@UDel-Relay> It seems to me, that in order to show that pressureless suits are infeasable due to "hot blood" one would have to show one of two things: a. A documented case of someone whose blood boiled or had massive blood temperature elevation due to being exposed to a vacuum. b. The mechanism or statistics that show how the blood vessels expand when the body is exposed to a vacuum. However, there still may be an out. There must be some sort of drug that can constrict and stiffen the blood vessels. Afterall, alcohol is a good dialator of blood vessels. Could not such a drug be used to decrease the problem of lower blood pressure and consequent temperature rise? - Steven Gutfreund
David.Smith@CMU-CS-A@sri-unix (11/28/82)
From: David.Smith at CMU-CS-A (C410DS30) You want A documented case of someone whose blood boiled or had massive blood temperature elevation due to being exposed to a vacuum. I can't give you anything of the sort. All I can point to is the excerpt from the pilot's manual that someone posted recently. (Sorry, I forgot the name.) But what's this about blood temperature elevation? Nobody ever said that vacuum raised the blood temperature. Boiling is caused by reduced gas pressure. I see two dimensions by which space suits can be classified: by pressurization, and by thermal control. Three types of pressurization are gas pressure (full-pressure), elastic garment pressure (partial pressure), and none. Thermal control can be active or passive. Current space suits are gas-pressurized, with active thermal control. Air force pilots wear partial-pressure suits, which use garment elasticity and inflatable tubing to apply pressure to the body. I think these suits exclude the hands, feet, and head. Their main purposes are to apply external pressure to the rib cage and abdomen, and to serve as G-suits. U-2 and SR-71 pilots wear full-pressure suits. (The astronauts on STS-1 through -4 wore SR-71 suits.) I just can't see a non-pressurized suit succeeding, whether or not blood boils. 3.1 psi inside the lungs, with 0 psi at the outside of the chest, is a tremendous force. I'll bet bagpipers don't generate anywhere near that. At a minimum, you need external pressure on the thorax and abdomen. I believe that pressure (gas or elastic garment) must be applied to the whole body. If pressure is taken off one part (say, a cell), it will see a differential of 0.8 psi between inside and outside, as long as there is still liquid water in it, no matter how far it has already expanded. (I came up with 0.8 psi because that is the pressure at 65000 feet.) If the skin is sufficiently impermeable, then a partial-pressure suit might work. The neck seal must hold gas pressure on the head end, but it would not subject the wearer to a sudden change of skin pressure (unless that is what it takes to get the gas seal). If the skin is (sufficiently) impermeable, then the pressure supplied by the (permeable) garment would keep the body fluids from boiling. The questions to answer are (1) Is the skin sufficiently impermeable, and (2) can a practical neck seal be made? There must be a reason that pilots who fly planes over 65000 feet are given full-pressure (=gas-pressure) suits, as BACKUP systems. Here are my rough & ready thoughts on thermal control. In low earth orbit, you spend around 40 minutes at a stretch in darkness, so you need something to keep you warm. That may just require good insulation, but maybe you need a heater. (Do the present space suits have heaters?) On the other hand, working in space gets quite strenuous, and you can easily overheat. But there's that insulation stopping you from radiating your excess heat. Enter an active cooling system. Note: astronauts (e.g., Cernan on Gemini 9) have overheated while working in space, even with active cooling. David.Smith @ cmu-cs-a