One night at dinner his father had asked him to describe just what it was that the Nobel did in circum-Terra patrol. He had tried to oblige. "After we lift from Moon Base we head for Terra on an elliptical orbit. As we approach the Earth we brake gradually and throw her into a tight circular orbit from pole to pole-"
"Why pole to pole? Why not around the equator?"
"Because, you see, the atom-bomb rockets are in pole-to-pole orbits. That's the only way they can cover the whole globe. If they were circling around the equator-"
"I understand that," his father had interrupted, "but your purpose, as I understand it, is to inspect the bomb rockets. If you-your ship-circled around the equator, you could just wait for the bomb rockets to come past."
Tow may understand it," his mother had said to his father, "but Z don't."
Matt looked from one to the other, wondering which one to answer-and how. "One at a time . . . please," he protested. "Dad, we can't just intercept the bombs; we have to sneak up on them, match orbits until you are right alongside it and making exactly the same course and speed. Then you bring the bomb inside and ship and inspect it."
"And of what does that inspection consist?"
"Just a sec, Dad. Mother, look here for a moment." Matt took an orange from the table's centerpiece. "The rocket bombs go round and round, like this, from pole-to-pole, every two hours. In the meantime the Earth is turning on its axis, once every twenty-four hours." Matt turned the orange slowly in his left hand while moving a finger of his right hand rapidly around it from top to bottom to simulate a pole-to-pole bomb. "That means that if a bomb passes over Des Moines on this trip, it will just about pass over the Pacific Coast on its next trip. In twenty-four hours it covers the globe."
"Goodness! Matthew, I wish you wouldn't talk about an atom bomb being over Des Moines, even in fun."
"In fun?" Matt had been puzzled. "As a matter of fact ... let me think; we're about forty-two north and ninety-four west-" He glanced at his watch finger and studied for a few moments. "Jay-three ought to be along in about seven minutes-yes, it will be almost exactly overhead by the time you finish your coffee." Long weeks in the Nobel, plotting, calculating,, and staring in radarscopes had gotten Matt so that he knew the orbits of circum-Terra prowler rockets a bit better than a fanner's wife knows her own chickens; Jay- three was an individual to him, one with fixed habits.
His mother was looking horrified. She spoke directly to her husband as if she expected him to do something about it. "John. ... I don't like this. I don't like it, do you hear me? What if it should fall?"
"Nonsense, Catherine-it can't fall."
Mart's younger brother chortled. "Mom doesn't even know what holds the Moon up!"
Matt turned to his brother. "Who pushed your button squirt? Do you know what holds the Moon up?"
"Sure-gravity."
"Not exactly. Suppose you give me a quick tell, with diagrams."
The boy tried; his effort was hardly successful. Matt shut him off. "You know somewhat less about astronomy than the ancient Egyptians. Don't make fun of your elders. Now, look, Mother-don't get upset. Jay-three can't fall on us. It's in a free orbit that does not intersect the Earth-like smarty-pants here says, it can't fall down any more than the Moon can fall. Anyhow, if the Patrol was to bomb Des Moines tonight, at this time, it wouldn't use Jay-three for the very reason that it is overhead. To bomb a city you start with a rocket heading for your target and a couple of thousand miles away, because you have to signal its robot to start the jet and seek the target. You have to slow it down and bend it down. So it wouldn't be Jay-three; it would be-" He thought again. "-Eye-two, or maybe Ache-one." He smiled wryly. "I got bawled out over Eye-two."
"Why?" demanded his brother.
"Matt, I don't think you have picked the right tack to quiet your mother's fears," his father said dryly. "I suggest we not talk about bombing cities."
"But I didn't- Sorry, Father."
"Catherine, there really is nothing to get worked up over -you might just as well be afraid of the local policeman. Matt, you were going to tell me about inspection. Why do the rockets have to be inspected?"
"I want to know why Mattie got bawled out!"
Matt cocked an eyebrow at his brother. "I might as well start by telling him, Dad-it has to do with inspection. Okay, Bill-I made a poor dive when we started to pick it up and had to come back on my suit jet and try again."
"What do you mean, Matthew?"
"He means-"
"Pipe down, Billie. Dad, you send a man out in a suit to insert the trigger guard and attach a line to the rocket so you can bring her inboard of the ship and work on her. I was the man. I made a bad push-off and missed the rocket entirely. She was about a hundred yards away and I guess I misjudged the distance. I turned over and found I was floating on past her. I had to jet back and try again."
His mother still seemed confused, but did not like what she heard. "Matthew! That sounds dangerous to me."
"Safe as houses, Mother. You can’t fall, any more than the rocket can, or the ship. But it's embarrassing. Anyhow, I finally got a line on her and rode her back into the ship."
"You mean you were riding an atom bomb?"
"Shucks, Mother, it's safe-the tamper around the fission material stops most of the radioactivity. Anyhow, the exposure is short."
"But suppose it went off?"
"It can't go off. To go off it has to either crash into the ground with a speed great enough to slap the sub-critical masses together as fast as its trigger- gun could do it, or you have to fire the trigger-gun by radio. Besides that, I had inserted the trigger guard-that's nothing more nor less than a little crowbar, but when it's in place not even a miracle could set it off, because you can't bring the sub-critical masses together."
"Maybe we had better drop this subject, Matt. It seems to make your mother nervous."
"But, Dad, she asked me."
"I know. But you still haven't told me what you inspect for."
"Well, in the first place, you inspect the bomb itself, but there's never anything wrong with the bomb. Anyhow, I haven't had the course for bomb- officer yet-he has to be a nucleonics engineer. You inspect the rocket motor, especially the fuel tanks. Sometimes you have to replace a little that has escaped through relief valves. But mostly you give her a ballistic check and check her control circuits."
"Ballistic check?"
"Of course, theoretically you ought to be able to predict where a prowler bomb would be every instant for the next thousand years. But it doesn't work out that way. Little things, the effect of the tidal bulges and the fact that the Earth is not a perfect uniform sphere and such, cause them to gradually wander a little away from the predicted orbits. After you find one and service it-they're never very far from where they ought to be-you correct the orbit by putting the whole ship in just precisely the proper trajectory and then put the rocket outside the ship again. Then you go after the next one."
"Clear enough. And these corrections have to be made often enough that a ship is kept busy just inspecting them?"
"Well, no, Dad, we inspect oftener than we really have to-but it keeps the ship and the crew busy. Keeps it from getting monotonous. Anyhow, frequent inspections keep you on the safe side."
"Sounds like a waste of taxpayers' money to inspect too often."
"But you don't understand-we're not there to inspect; we're there to patrol. The inspection ship is the ship that would deliver an attack in case anybody started acting up. We have to stay on patrol until the next ship relieves us, so we might as well inspect. Granted that you can bomb a city from Moon Base, you can do a better, more accurate job, with less chance of hitting the wrong people, from close by."
His mother was looking very upset. His father raised his eyebrows and said, "We've wandered back to the subject of bombing, Matt."