But, while they have not yet built a machine to replace us, they’ve surely thought up some honeys to help us. The suit, in particular.

No need to describe what it looks like, since it has been pictured so often. Suited up, you look like a big steel gorilla, armed with gorilla-sized weapons. (This may be why a sergeant generally opens his remarks with «You apes — » However, it seems more likely that Caesar’s sergeants used the same honorific.)

But the suits are considerably stronger than a gorilla. If an M.I. in a suit swapped hugs with a gorilla, the gorilla would be dead, crushed; the M.I. and the suit wouldn’t be mussed.

The «muscles,» the pseudo-musculature, get all the publicity but it’s the control of all that power which merits it. The real genius in the design is that you don’t have to control the suit; you just wear it, like your clothes, like skin. Any sort of ship you have to learn to pilot; it takes a long time, a new full set of reflexes, a different and artificial way of thinking. Even riding a bicycle demands an acquired skill, very different from walking, whereas a spaceship— oh, brother! I won’t live that long. Spaceships are for acrobats who are also mathematicians.

But a suit you just wear.

Two thousand pounds of it, maybe, in full kit — yet the very first time you are fitted into one you can immediately walk, run, jump, lie down, pick up an egg without breaking it (that takes a trifle of practice, but anything improves with practice), dance a jig (if you can dance a jig, that is, without a suit) — and jump right over the house next door and come down to a feather landing.

The secret lies in negative feedback and amplification.

Don’t ask me to sketch the circuitry of a suit; I can’t. But I understand that some very good concert violinists can’t build a violin, either. I can do field maintenance and field repairs and check off the three hundred and forty-seven items from «cold» to ready to wear, and that’s all a dumb M.I. is expected to do. But if my suit gets really sick, I call the doctor — a doctor of science (electromechanical engineering) who is a staff Naval officer, usually a lieutenant (read «captain» for our ranks), and is part of the ship’s company of the troop transport — or who is reluctantly assigned to a regimental headquarters at Camp Currie, a fate-worse-than-death to a Navy man.

But if you really are interested in the prints and stereos and schematics of a suit’s physiology, you can find most of it, the unclassified part, in any fairly large public library. For the small amount that is classified you must look up a reliable enemy agent — «reliable» I say, because spies are a tricky lot; he’s likely to sell you the parts you could get free from the public library.

But here is how it works, minus the diagrams. The inside of the suit is a mass of pressure receptors, hundreds of them. You push with the heel of your hand; the suit feels it, amplifies it, pushes with you to take the pressure off the receptors that gave the order to push. That’s confusing, but negative feedback is always a confusing idea the first time, even though your body has been doing it ever since you quit kicking helplessly as a baby. Young children are still learning it; that’s why they are clumsy. Adolescents and adults do it without knowing they ever learned it — and a man with Parkinson’s disease has damaged his circuits for it.

The suit has feedback which causes it to match any motion you make, exactly — but with great force.

Controlled force… force controlled without your having to think about it. You jump, that heavy suit jumps, but higher than you can jump in your skin. Jump really hard and the suit’s jets cut in, amplifying what the suit’s leg «muscles» did, giving you a three-jet shove, the axis of pressure of which passes through your center of mass. So you jump over that house next door. Which makes you come down as fast as you went up… which the suit notes through your proximity & closing gear (a sort of simple-minded radar resembling a proximity fuse) and therefore cuts in the jets again just the right amount to cushion your landing without your having to think about it.

And that is the beauty of a powered suit: you don’t have to think about it. You don’t have to drive it, fly it, conn it, operate it; you just wear it and it takes its orders directly from your muscles and does for you what your muscles are trying to do. This leaves you with your whole mind free to handle your weapons and notice what is going on around you . . . which is supremely important to an infantryman who wants to die in bed. If you load a mud foot down with a lot of gadgets that he has to watch, somebody a lot more simply equipped — say with a stone ax — will sneak up and bash his head in while he is trying to read a vernier.

Your «eyes» and your «ears» are rigged to help you without cluttering up your attention, too. Say you have three audio circuits, common in a marauder suit. The frequency control to maintain tactical security is very complex, at least two frequencies for each circuit both of which are necessary for any signal at all and each of which wobbles under the control of a cesium clock timed to a micromicrosecond with the other end — but all this is no problem of yours. You want circuit A to your squad leader, you bite down once — for circuit B, bite down twice — and so on. The mike is taped to your throat, the plugs are in your ears and can’t be jarred out; just talk. Besides that, outside mikes on each side of your helmet give you binaural hearing for your immediate surroundings just as if your head were bare — or you can suppress any noisy neighbors and not miss what your platoon leader is saying simply by turning your head.

Since your head is the one part of your body not involved in the pressure receptors controlling the suit’s muscles, you use your head — your jaw muscles, your chin, your neck — to switch things for you and thereby leave your hands free to fight. A chin plate handles all visual displays the way the jaw switch handles the audios. All displays are thrown on a mirror in front of your forehead from where the work is actually going on above and back of your head. All this helmet gear makes you look like a hydrocephalic gorilla but, with luck, the enemy won’t live long enough to be offended by your appearance, and it is a very convenient arrangement; you can flip through your several types of radar displays quicker than you can change channels to avoid a commercial — catch a range & bearing, locate your boss, check your flank men, whatever.

If you toss your head like a horse bothered by a fly, your infrared snoopers go up on your forehead — toss it again, they come down. If you let go of your rocket launcher, the suit snaps it back until you need it again. No point in discussing water nipples, air supply, gyros, etc. — the point to all the arrangements is the same: to leave you free to follow your trade, slaughter.

Of course these things do require practice and you do practice until picking the right circuit is as automatic as brushing your teeth, and so on. But simply wearing the suit, moving in it, requires almost no practice. You practice jumping because, while you do it with a completely natural motion, you jump higher, faster, farther, and stay up longer. The last alone calls for a new orientation; those seconds in the air can be used — seconds are jewels beyond price in combat. While off the ground in a jump, you can get a range & bearing, pick a target, talk & receive, fire a weapon, reload, decide to jump again without landing and override your automatics to cut in the jets again. You can do all of these things in one bounce, with practice.

But, in general, powered armor doesn’t require practice; it simply does it for you, just the way you were doing it, only better. All but one thing — you can’t scratch where it itches. If I ever find a suit that will let me scratch between my shoulder blades, I’ll marry it.

There are three main types of M.I. armor: marauder, command, and scout. Scout suits are very fast and very long-range, but lightly armed. Command suits are heavy on go juice and jump juice, are fast and can jump high; they have three times as much comm & radar gear as other suits, and a dead-reckoning tracker, inertial. Marauders are for those guys in ranks with the sleepy look — the executioners.

As I may have said, I fell in love with powered armor, even though my first crack at it gave me a strained shoulder. Any day thereafter that my section was allowed to practice in suits was a big day for me. The day I goofed I had simulated sergeant’s chevrons as a simulated section leader and was armed with simulated A-bomb rockets to use in simulated darkness against a simulated enemy. That was the trouble; everything was simulated — but you are required to behave as if it is all real.