The bottles are big and clumsy, weighing around sixty pounds apiece, and each holds only about five mass pounds of air even at that enormous pressure; instead of a month’s supply you will have only a few hours-my suit was rated at eight hours for the bottles it used to have. But you will be okay for those hours-if everything works right. You can stretch time, for you don’t die from overheating very fast and can stand too much carbon dioxide even longer-but let your oxygen run out and you die in about seven minutes. Which gets us back where we started-it takes oxygen to stay alive.
To make darn sure that you’re getting enough (your nose can’t tell) you clip a little photoelectric cell to your ear and let it see the color of your blood; the redness of the blood measures the oxygen it carries. Hook this to a galvanometer. If its needle gets into the danger zone, start saying your prayers.
I went to Springfield on my day off, taking the suit’s hose fittings, and shopped. I picked up, second hand, two thirty-inch steel bottles from a welding shop-and got myself disliked by insisting on a pressure test. I took them home on the bus, stopped at Pring’s Garage and arranged to buy air at fifty atmospheres. Higher pressures, or oxygen or helium, I could get from the Springfield airport, but I didn’t need them yet.
When I got home I closed the suit, empty, and pumped it with a bicycle pump to two atmospheres absolute, or one relative, which gave me a test load of almost four to one compared with space conditions. Then I tackled the bottles. They needed to be mirror bright, since you can’t afford to let them pick up heat from the Sun. I stripped and scraped and wire-brushed, and buffed and polished, preparatory to nickel-plating.
Next morning, Oscar the Mechanical Man was limp as a pair of long johns.
Getting that old suit not just airtight but helium-tight was the worst headache. Air isn’t bad but the helium molecule is so small and agile that it migrates right through ordinary rubber-and I wanted this job to be right, not just good enough to perform at home but okay for space. The gaskets were shot and there were slow leaks almost impossible to find.
I had to get new silicone-rubber gaskets and patching compound and tissue from Goodyear; small-town hardware stores don’t handle such things. I wrote a letter explaining what I wanted and why-and they didn’t even charge me. They sent me some mimeographed sheets elaborating on the manual.
It still wasn’t easy. But there came a day when I pumped Oscar full of pure helium at two atmospheres absolute.
A week later he was still tight as a six-ply tire.
That day I wore Oscar as a self-contained environment. I had already worn him many hours without the helmet, working around the shop, handling tools while hampered by his gauntlets, getting height and size adjustments right. It was like breaking in new ice skates and after a while I was hardly aware I had it on-once I came to supper in it. Dad said nothing and Mother has the social restraint of an ambassador; I discovered my mistake when I picked up my napkin.
Now I wasted helium to the air, mounted bottles charged with air, and suited them. Then I clamped the helmet and dogged the safety catches.
Air sighed softly into the helmet, its flow through the demand valve regulated by the rise and fall of my chest-I could reset it to speed up or slow down by the chin control. I did so, watching the gauge in the mirror and letting it mount until I had twenty pounds absolute inside. That gave me five pounds more than the pressure around me, which was as near as I could come to space conditions without being in space.
I could feel the suit swell and the joints no longer felt loose and easy. I balanced the cycle at five pounds differential and tried to move- And almost fell over. I had to grab the workbench.
Suited up, with bottles on my back, I weighed more than twice what I do stripped. Besides that, although the joints were constant-volume, the suit didn’t work as freely under pressure. Dress yourself in heavy fishing waders, put on an overcoat and boxing gloves and a bucket over your head, then have somebody strap two sacks of cement across your shoulders and you will know what a space suit feels like under one gravity.