The Worlds Of Robert A. Heinlein Part 11

"That's a fact, Ed."

"It is. Got a cigarette, Doc?"

"It won't do you any good, Ed."

"It won't do me any harm, either - now, will it?"

"Well, not much" McCracken unregretfully gave him his last and watched him smoke it.

Later, Morgan said, Dad's ready for you, Captain. So long."

"So long. Don't forget. Half a pill at a time. Drink all the water you want, but don't take your blankets off, no matter how hot you get."

"Half a pill it is. Good luck."

"I'll have Ted check on you tomorrow."

Morgan shook his head. "That's too soon. Not for a couple of days at least."

McCracken smiled. "I'll decide that, Ed. You just keep yourself wrapped up.

Good luck." He withdrew to where Carter waited for him. "You go ahead, Dad.

I'll bring up the rear. Signal Art to start."

Carter hesitated. "Tell me straight, Doc. What kind of shape is he in?"

McCracken studied Carter's face, then said in a low voice, "I give him about two hours."

"I'll stay behind with him."

"No, Dad, you'll carry out your orders." Seeing the distress in the old man's eyes, he added, "Don't you Worry about Morgan. A free man can take care of himself. Now get moving."

"Yes, sir."

Blowups Happen

"PUT DOWN that wrench!"

The man addressed turned slowly around and faced the speaker. His expression was hidden by a grotesque helmet, part of a heavy, leaden armor which s.h.i.+elded his entire body, but the tone of voice in which he answered showed nervous exasperation.

"What the h.e.l.l's eating you, Doc?" He made no move to replace the tool in question.

They faced each other like two helmeted, arrayed fencers, watching for an opening. The first speaker's voice came from behind his mask a shade higher in key and more peremptory in tone. "You heard me, Harper. Put down that wrench at once, and come away from that 'trigger.' Erickson!"

A third armored figure came around the s.h.i.+eld which separated the uranium bomb proper from the control room in which the first two stood. "Whatcha want, Doc?"

"Harper is relieved from watch. You take over as engineer-of-the-watch.

Send for the stand-by engineer."

"Very well." His voice and manner were phlegmatic, as he accepted the situation without comment. The atomic engineer, whom he had just relieved, glanced from one to the other, then carefully replaced the wrench in its rack.

"Just as you say, Dr. Silard - but send for your relief too. I shall demand an immediate hearing!" Harper swept indignantly out, his lead-sheathed boots clumping on the floor plates.

Dr. Silard waited unhappily for the ensuing twenty minutes until his own relief arrived. Perhaps he had been hasty. Maybe he was wrong in thinking that Harper had at last broken under the strain of tending the most dangerous machine in the world - an atomic power plant. But if he had made a mistake, it had to be on the safe side - slips must not happen in this business; not when a slip might result in the atomic detonation of two and a half tons of uranium.

He tried to visualize what that would mean, and failed. He had been told that uranium was potentially forty million times as explosive as TNT. The figure was meaningless that way. He thought of it, instead, as a hundred million tons of high explosive, two hundred million aircraft bombs as big as the biggest ever used. It still did not mean anything. He had once seen such a bomb dropped, when he had been serving as a temperament a.n.a.lyst for army aircraft pilots. The bomb had left a hole big enough to hide an apartment house. He could not imagine the explosion of a thousand such bombs, much, much less a hundred million of them.

Perhaps these atomic engineers could. Perhaps, with their greater mathematical ability and closer comprehension of what actually went on inside the nuclear fission chamber - the "bomb" - they had some vivid glimpse of the mind-shattering horror locked up beyond that s.h.i.+eld. If so, ho wonder they tended to blow up -

He sighed. Erickson looked up from the linear resonant accelerator on which he had been making some adjustment. "What's the trouble, Doc?"

"Nothing. I'm sorry I had to relieve Harper."

Silard could feel the shrewd glance of the big Scandinavian. "Not getting the jitters yourself, are you, Doc? Sometimes you squirrel sleuths blow up, too - "

"Me? I don't think so. I'm scared of that thing in there - I'd be crazy if I weren't."

"So am I," Erickson told him soberly, and went back to his work.

The accelerator's snout disappeared in the s.h.i.+eld between them and the bomb, where it fed a steady stream of terrifically speeded up subatomic bullets to the beryllium target located within the bomb itself. The tortured beryllium yielded up neutrons, which shot out in all directions through the uranium ma.s.s. Some of these neutrons struck uranium atoms squarely on their nuclei and split them in two. The fragments were new elements, barium, xenon, rubidium - depending on the proportions in which each atom split. The new elements were usually unstable isotopes and broke down into a dozen more elements by radioactive disintegration in a progressive chain reaction.

But these chain-reactions were comparatively unimportant; it was the original splitting of the uranium nucleus, with the release of the awe-inspiring energy that bound it together - an incredible two hundred million electron-volts - that was important - and perilous.

For, while uranium isotope 235 may be split by bombarding it with neutrons from an outside source, the splitting itself gives up more neutrons which, in turn, may land in other uranium nuclei and split them. If conditions are favorable to a progressively increasing reaction of this sort, it may get out of hand, build up in an unmeasurable fraction of a micro-second into a complete atomic explosion - an explosion which would dwarf the eruption of Krakatoa to popgun size; an explosion so far beyond all human experience as to be as completely incomprehensible as the idea of personal death. It could be feared, but not understood.

But a self-perpetuating sequence of nuclear splitting, just under the level of complete explosion, was necessary to the operation of the power plant.

To split the first uranium nucleus by bombarding it with neutrons from the beryllium target took more power than the death of the atom gave up. In order that the output of power from the system should exceed the power input in useful proportion it was imperative that each atom split by a neutron from the beryllium target should cause the splitting of many more.

It was equally imperative that this chain of reactions should always tend to dampen, to die out. It must not build up, or the entire ma.s.s would explode within a time interval too short to be measured by any means whatsoever.

Nor would there be anyone left to measure it.

The atomic engineer on duty at the bomb could control this reaction by means of the "trigger," a term the engineers used to include the linear resonant accelerator, the beryllium target, and the adjacent controls, instrument board, and power sources. That is to say, he could vary the bombardment on the beryllium target to increase or decrease the power output of the plant, and he could tell from his instruments that the internal reaction was dampened - or, rather, that it had been dampened the split second before. He could not possibly know what was actually happening now within the bomb - subatomic speeds are too great and the time intervals too small. He was like the bird that flew backward; he could see where he had been, but he never knew where he was going.

Nevertheless, it was his responsibility, and his alone, not only to maintain the bomb at a high input-output efficiency, but to see that the reaction never pa.s.sed the critical point and progressed into ma.s.s explosion.

But that was impossible. He could not be sure; he could never be sure.

He could bring to the job all of the skill and learning of the finest technical education, and use it to reduce the hazard to the lowest mathematical probability, but the blind laws of chance which appear to rule in subatomic action might turn up a royal flush against him and defeat his most skillful play.

And each atomic engineer knew it, knew that he gambled not only with his own life, but with the lives of countless others, perhaps with the lives of every human being on the planet. n.o.body knew quite what such an explosion would do. The most conservative estimate a.s.sumed that, in addition to destroying the plant and its personnel completely, it would tear a chunk out of the populous and heavily traveled Los Angeles-Oklahoma Road City a hundred miles to the north.

That was the official, optimistic viewpoint on which the plant had been authorized, and based on mathematics which predicted that a ma.s.s of uranium would itself be disrupted on a molar scale, and thereby rendered comparatively harmless, before progressive and accelerated atomic explosion could infect the entire ma.s.s.

The atomic engineers, by and large, did not place faith in the official theory. They judged theoretical mathematical prediction for what it was worth - precisely nothing, until confirmed by experiment.

But even from the official viewpoint, each atomic engineer while on watch carried not only his own life in his hands, but the lives of many others - how many, it was better not to think about. No pilot, no general, no surgeon ever carried such a daily, inescapable, ever-present weight of responsibility for the lives of other people as these men carried every time they went on watch, every time they touched a vernier screw or read a dial.

They were selected not alone for their intelligence and technical training, but quite as much for their characters and sense of social responsibility.

Sensitive men were needed - men who could fully appreciate the importance of the charge intrusted to them; no other sort would do. But the burden of responsibility was too great to be born indefinitely by a sensitive man.

It was, of necessity, a psychologically unstable condition. Insanity was an occupational disease.

Dr. c.u.mmings appeared, still buckling the straps of the armor worn to guard against stray radiation. "What's up?" he asked Silard.