I decided I just had to make it work right.

First I swabbed it out with Clorox to kill the locker-room odor. Then I got to work on the air system.

It's a good thing they included that manual; most of what I thought I knew about space suits was wrong.

A man uses around three pounds of oxygen a day-pounds mass, not pounds per square inch. You'd think a man could carry oxygen for a month, especially out in space where mass has no weight, or on the Moon where three pounds weigh only half a pound. Well, that's okay for space stations or ships or frogmen; they run air through soda lime to take out carbon dioxide, and breathe it again. But not space suits.

Even today people talk about "the bitter cold of outer space"-but space is vacuum and if vacuum were cold, how could a Thermos jug keep hot coffee hot? Vacuum is nothing-it has no temperature, it just insulates.

Three-fourths of your food turns into heat-a lot of heat, enough each day to melt fifty pounds of ice and more. Sounds preposterous, doesn't it? But when you have a roaring fire in the furnace, you are cooling your body; even in the winter you keep a room about thirty degrees cooler than your body. When you turn up a furnace's thermostat, you are picking a more comfortable rate for cooling. Your body makes so much heat you have to get rid of it, exactly as you have to cool a car's engine.

Of course, if you do it too fast, say in a sub-zero wind, you can freeze- but the usual problem in a space suit is to keep from being boiled like a lobster. You've got vacuum all around you and it's hard to get rid of heat.

Some radiates away but not enough, and if you are in sunlight, you pick up still more-this is why space ships are polished like mirrors.

So what can you do?

Well, you can't carry fifty-pound blocks of ice. You get rid of heat the way you do on Earth, by convection and evaporation-you keep air moving over you to evaporate sweat and cool you off. Oh, they'll learn to build space suits that recycle like a space ship but today the practical way is to let used air escape from the suit, flushing away sweat and carbon dioxide and excess heat-while wasting most of the oxygen.

There are other problems. The fifteen pounds per square inch around you includes three pounds of oxygen pressure. Your lungs can get along on less than half that, but only an Indian from the high Andes is likely to he comfortable on less than two pounds oxygen pressure. Nine-tenths of a pound is the limit. Any less than nine-tenths of a pound won't force oxygen into blood-this is about the pressure at the top of Mount Everest.

Most people suffer from hypoxia (oxygen shortage) long before this, so better use two p.s.i. of oxygen. Mix an inert gas with it, because pure oxygen can cause a sore throat or make you drunk or even cause terrible cramps. Don't use nitrogen (which you've breathed all your life) because it will bubble in your blood if pressure drops and cripple you with "bends." Use helium which doesn't. It gives you a squeaky voice, but who cares?

You can die from oxygen shortage, be poisoned by too much oxygen, be crippled by nitrogen, drown in or be acid-poisoned by carbon dioxide, or dehydrate and run a killing fever. When I finished reading that manual I didn't see how anybody could stay alive anywhere, much less in a space suit.

But a space suit was in front of me that had protected a man for hundreds of hours in empty space.

Here is how you beat those dangers. Carry steel bottles on your back; they hold "air" (oxygen and helium) at a hundred and fifty atmospheres, over 2000 pounds per square inch; you draw from them through a reduction valve down to 150 p.s.i. and through still another reduction valve, a "demand" type which keeps pressure in your helmet at three to five pounds per square inch-two pounds of it oxygen. Put a silicone-rubber collar around your neck and put tiny holes in it, so that the pressure in the body of your suit is less, the air movement still faster; then evaporation and cooling will be increased while the effort of bending is decreased. Add exhaust valves, one at each wrist and ankle-these have to pass water as well as gas because you may be ankle deep in sweat.

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.