View Full Version : Mote In God's Eye, The - Larry Niven & Jerry Pournelle

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06-07-2007, 08:09 PM
Chapter 6 - The Light Sail

One gravity only-with queasy sensations as MacArthur lined up on her proper interception course. Elastic webbing held him in the acceleration chair during these few moments of changing but normal gravity-minutes, Rod suspected, that he'd soon look back on with wistful longing.
Kevin Renner had been mate of an interstellar trading vessel before -joining MacArthur as her sailing master. He was a lean man with a narrow face, and he was ten years older than Blaine. As Rod steered his acceleration chair up behind him, Renner was matching curves in a view screen; and his self-satisfied grin was not the expression of a Navy man.
"Got our course, Lieutenant Renner?"
"Yes, sir," Kevin Renner said with relish. "Right into the sun at four gees!"
Blaine gave in to the desire to call his bluff. "Move her."
The warning alarms sounded and MacArthur accelerated. Crew and passengers felt their weight settle gradually deeper into beds and chairs and couches, and they nerved themselves for several days of weighing far too much.
"You were joking, weren't you?" Blaine asked.
The Sailing Master looked at him quizzically. "You knew we were dealing with a light-sail propulsion system, sir?"
"Then look here." Renner's nimble fingers made a green curve on the view screen, a parabola rising sharply at the right. "Sunlight per square centimeter falling on a light -- sail decreases as the square of the distance from the star. Acceleration varies directly as the sunlight reflected from the sail."
"Of course, Mr. Renner. Make your point."
Renner made another parabola, very like the first, but in blue. "The stellar wind can also propel a light sail. Thrust varies about the same way. The important difference is that the stellar wind is atomic nuclei. They stick where they hit the sail. The momentum is transferred directly-and it's all radial to the sun."
"You can't tack against it," Blaine realized suddenly. "You can tack against the light by tilting the sail, but the stellar wind always thrusts you straight away from the sun." -
"Right. So, Captain, suppose you were coming into a system at 7 percent of the speed of light, God forbid, and you wanted to stop. What would you do?"
"Drop all the weight I could," Blaine mused. "Hmm. I don't see how it'd be a problem. They must have launched the same way."
"I don't think they did. They're moving too fast. But pass that for a minute. What counts is they're moving too fast to stop unless they get very close to the sun, very close indeed. The intruder is in fact -- diving right into the sun. Probably it will tack hard after the sunlight has decelerated it enough -...provided the vessel hasn't melted and the shrouds haven't parted or the sail ripped. But it is such a close thing that they simply have to skydive; they have no choice."
"Ah," said Blaine.
"One need hardly mention," Renner added, "that when we match course with them, we too will be moving straight toward the sun...
"At 7 percent of the speed of light?"
"At 6. The intruder will have slowed somewhat by then. It will take us one hundred twenty-five hours, doing four gees most of the way, slowing somewhat near the end."
"That's going to be hard on everybody," Blaine said. And suddenly he wondered, belatedly, if Sally Fowler had in fact gotten off. "Especially the passengers. Couldn't you give me an easier course?"
"Yes, sir," Renner said instantly. "I can pull alongside in one hundred and seventy-hours without ever going over two and a half gees-and save some fuel too, because the probe will have more time to slow down. The course we're on now gets us to New Ireland with dry tanks, assuming we take the intruder under tow."
"Dry tanks. But you liked this course better." Rod was learning to dislike the Sailing Master and his grin that constantly implied that the Captain had forgotten something crucial and obvious. "Tell me why," he suggested.
"It occurred to me the intruder might be hostile."
"Yes. So?"
"If we were to match courses with him and he disabled the engines...
"We'd be falling into the sun at 6 percent of light speed. Right. So you match us up as far from Cal as possible, to leave time to do something about it."
"Yessir. Exactly."
"Right. You're enjoying this, aren't you, Mr. Renner?"
"I wouldn't have missed it for anything, sir. What about you?"
"Carry on, Mr. Renner." Blaine guided his acceleration chair to another screen and began checking the Sailing Master's course. Presently he pointed out that the Sailing Master could give them nearly an hour at one gee just before intercept, thereby giving everyone a chance to recuperate. Renner agreed with idiot enthusiasm and went to work on the change.
"I can use friends aboard my ship," Captain Cziller used to tell his midshipmen, "but I'd sell them all for a competent sailing master." Renner was competent. Renner was also a smartass; but that was a good bargain. Rod would settle for a competent smartass.

At four gravities nobody walked; nobody lifted anything. The black box replacements in the hold stayed there while MacArthur ran on Sinclair's makeshifts. Most of the crew worked from their cots, or from mobile chairs, or didn't work at all.
In crew sections they played elaborate word games, or speculated on the coming encounter, or told stories. Half the screens on the ship showed the same thing: a disc like the sun, with Murcheson's Eye behind it and the Coal Sack as background.
The telltales in Sally's cabin showed oxygen consumption. Rod said words of potent and evil magic under his breath. He almost called her then, but postponed it. He called Bury instead.
Bury was in the gee bath: a film of highly elastic mylar over liquid. Only his face and hands showed above the curved surface. His face looked old-it almost showed his true age.
"Captain, you chose not to put me off on Brigit. Instead, you are taking a civilian into possible combat. Might I ask why?"
"Of course, Mr. Bury. I supposed it would be most inconvenient for you to be stranded on a ball of ice with no assured transportation. Perhaps I was mistaken."
Bury smiled-or tried to. Every man aboard looked twice his age, with four times gravity pulling down on the skin of his face. Bury's smile was like weight lifting. "No, Captain, you were not mistaken. I saw your orders in the wardroom. So. We are on our way to meet a nonhuman spacecraft."
"It certainly looks that way."
"Perhaps they will have things to trade. Especially if they come from a nonterrestrial world. We can hope. Captain, would you keep me posted on what is happening?'
"I will probably not have the time," Blaine said, choosing the most civil of several answers that occurred to him.
"Yes, of course, I didn't mean personally. I only want access to information on our progress. At my age I dare not move from this rubber bathtub for the duration of our voyage. How long will we be under four gees?"
"One hundred and twenty-five hours. One twenty-four, now."
"Thank you, Captain." Bury vanished from the Screen.
Rod rubbed thoughtfully at the knot on his nose. Did Bury know his status aboard MacArthur? It couldn't be important. He called Sally's cabin.
She looked as if she hadn't slept in a week or smiled in years. Blaine said, "Hello, Sally. Sorry you came?"
"I told you I can take anything you can take," Sally said calmly. She gripped the arms of her chair and stood up. She let go and spread her arms to show how capable she was.
"Be careful," Blaine said, trying to keep his voice steady. "No sudden moves. Keep your knees straight. You can break your back just sitting down. Now stay erect, but reach behind you. Get both the chair arms in your hands before you try to bend at the waist -- "
She didn't believe it was dangerous, not until she started to sit down. Then the muscles in her arms knotted, panic flared in her eyes, and she sat much too abruptly, as if MacArthur's gravity had sucked her down.
"Are you hurt?"
"No," she said. "Only my pride."
"Then you stay in that chair, damn your eyes! Do you see me standing up? You do not. And you won't!"
"All right." She turned her head from side to side. She was obviously dizzy from the jolt.
"Did you get your servants off?"
"Yes. I had to trick them-they wouldn't have gone without my baggage." She laughed an old woman's laugh. "I'm wearing everything I own until we get to New Caledonia."
"Tricked them, did you? The way you tricked me. I should have had Kelley put you off." Rod's voice was bitter. He knew he looked twice his age, a cripple in a wheel chair. "All right, you're aboard. I can't put you off now."
"But I may be able to help. I am an anthropologist." She winced at the thought of trying to get up again. "Can I get you on the intercom?"
"You'll get the middie of the watch. Tell him if you really need to talk to me. But, Sally-this is a warship. Those aliens may not be friendly. For God's sake remember that; my watch officers haven't time for scientific discussion in the middie of a baffle!"
"I know that. You might give me credit for a little sense." She tried to laugh. "Even if I don't know better than to stand up at four gees."
"Yeah. Now do me another favor. Get into your gee bath."
"Do I have to take my clothes off to use it?"
Blaine couldn't blush; there wasn't enough blood flowing to his head. "It's a good idea, especially if you've got buckles. Turn off the vision pickup on the phone."
"And be careful. I could send one of the married ratings to help -- "
"No, thank you."
"Then wait. We'll have a few minutes of lower gee at intervals. Don't get out of that chair alone in high gee!"
She didn't even look tempted. One experience was enough.

"Lermontov's calling again," Whitbread announced.
"Forget it. Don't acknowledge."
"Aye aye, sir. Do not acknowledge."
Rod could guess what the cruiser wanted. Lermontov wanted first crack at the intruder-but MacArthur's sister ship wouldn't even get close to the aliens before the approach to the sun was just too close. Better to intercept out where there was some room.
At least that's what Rod told himself. He could trust Whitbread and the communications people; Lermontov's signals wouldn't be in the log.
Three and a half days. Two minutes of 1.5 gee every four hours to change the watch, grab forgotten articles, shift positions; then the warning horns sounded, the jolt meters swung over, and too much weight returned.
At first MacArthur's bow had pointed sixty degrees askew of Cal. They had to line up with the intruder's course. With that accomplished, MacArthur turned again. Her bow pointed at the brightest star in the heavens.
Cal began to grow. He also changed color, but minutely. No one would notice that blue shift with the naked eye. What the men did see in the screens was that the brightest star had become a disc and was growing hourly.
It didn't grow brighter because the screens kept it constant; but the tiny sun disc grew ominously larger, and it lay directly ahead. Behind them was another disc of the same color, the white of an F8 star. It, too, grew hourly larger. MacArthur was sandwiched between two colliding suns.
On the second day Staley brought a new midshipman up to the bridge, both moving in traveling acceleration chairs. Except for a brief interview on Brigit, Rod hadn't met him: Gavin Potter, a sixteen-year-old boy from New Scotland. Potter was tall for his age; he seemed to hunch in upon himself, as if afraid to be noticed.
Blaine thought Potter was merely being shown about the ship; a good idea, since if the intruder turned out hostile, the boy might have to move about MacArthur with total familiarity-possibly in darkness and variable gravity.
Staley obviously had more in mind. Blaine realized they were trying to get his attention. "Yes, Mr. Staley?"
"This is Midshipman Gavin Potter, sir," Staley said. "He's told me something I think you ought to hear."
"All right, go ahead." Any diversion from high gravity was welcome.
"There was a church in our street, sir. In a farm town on New Scotland." Potter's voice was soft and low, and he spoke carefully so that he blotted out all but a ghostly remnant of the brogue that made Sinclair's speech so distinctive.
"A church," Blaine said encouragingly. "Not an orthodox church, I take it -- "
"No, sir. A Church of Him. There aren't many members. A friend and I snuck inside once, for a joke."
"Did you get caught?"
"I know I'm telling this badly, sir. The thing is- There was a big blowup of an old holo of Murcheson's Eye against the Coal Sack. The Face of God, just like on postcards. Only, only it was different in this picture. The Eye was very much brighter than now, and it was blue green, not red. With a red dot at one edge."
"It could have been a portrait," Blaine suggested. He took out his pocket computer and scrawled "Church of Him" across its face, then punched for information. The box Linked with the ship's library, and information began to roll across its face. "It says the Church of Him believes that the Coal Sack, with that one red eye showing, really is the Face of God. Couldn't they have retouched it to make the eye more impressive?" Rod continued to sound interested; time enough to say something about wasting his time when the middies were through. If they were wasting time...
"But -- " said Potter.
"Sir -- " said Staley, leaning too far forward in his chair.
"One at a time. Mr. Staley?"
"I didn't just ask Potter, sir. I checked with Commander Sinclair. He says his grandfather told him the Mote was once brighter than Murcheson's Eye, and bright green. And the way Gavin's describing that holo-well, sir, stars don't radiate all one color. So -- "
"All the more reason to think the holo was retouched. But it is funny, with that intruder coming straight out of the Mote...
"Light," Potter said firmly.
"Light sail!" Rod shouted in sudden realization. "Good thinking." The whole bridge crew turned to look at the Captain. "Renner! Did you say the intruder is moving faster than it ought to be?"
"Yes, sir," Renner answered from his station across the bridge. "If it was launched from a habitable world circling the Mote."
"Could it have used a battery of laser cannon?"
"Sure, why not?" Renner wheeled over. "In fact, you could launch with a small battery, then add more cannon as the vehicle got farther and farther away. You get a terrific advantage that way. If one of the cannon breaks down you've got it right there in your system to repair it."
"Like leaving your motor home," Potter cried, "and you still able to use it."
"Well, there are efficiency problems. Depending on how tight the beam can be held," Renner answered. "Pity you couldn't use it for-braking, too. Have you any reason to believe -- "
Rod left them telling the Sailing Master about the variations in the Mote. For himself, he didn't particularly care. His problem was, what would the intruder do now?
It was twenty hours to rendezvous when Renner came to Blaine's post and asked to use the Captain's screens. The man apparently could not talk without a view screen connected to a computer. He would be mute with only his voice.
"Captain, look," he said, and threw a plot of the local stellar region on the screen. "The intruder came from here. Whoever launched it fired a laser cannon, or a set of laser cannon-probably a whole mess of them on asteroids, with mirrors to focus them-for about forty-five years, so the intruder would have a beam to travel on. The beam and the intruder both came straight in from the Mote."
"But there'd be records," Blaine said. "Somebody would have seen that the Mote was putting out coherent light."
Renner shrugged. "How good are New Scotland's records?"
"Let's just see." It took only moments to learn that astronomical data from New Scotland were suspect, and no such records were carried in MacArthur's library because of that. "Oh, well. Let's assume you're right."
"But that's the point: it's not right, Captain," Renner protested. "You see, it is possible to turn in interstellar space. What they should have done -- "
The new path left the Mote at a slight angle to the first. "Again they coast most of the way. At this point" -- where the intruder would have been well past New Cal -- "we charge the ship up to ten million volts. The background magnetic field of the Galaxy gives the ship a half turn, and it's coming toward the New Caledonia system from behind. Meanwhile, whoever is operating the beam has turned it off for a hundred and fifty years. Now he turns it on again. The probe uses the beam for braking.
"You sure that magnetic effect would work?"
"It's high school physics! And the interstellar magnetic fields, have been well mapped, Captain."
"Well, then, why didn't they use it?"
"I don't know," Renner cried in frustration. "Maybe they just didn't think of it. Maybe they were afraid the lasers wouldn't last. Maybe they didn't trust whoever they left behind to run them. Captain, we just don't know enough about them."
"I know that, Renner. Why get in such a sweat about it? If our luck holds, we'll just damn well ask them."
A slow, reluctant smile broke across Renner's face. "But that's cheating."
"Oh, go get some sleep."

Blaine smiled-one gravity-and felt the smile tighten. One hour to match velocities with the intruder. He activated his watch screens, to see a blaze of light fore and aft. MacArthur was sandwiched between two suns. Now Cal was as large as Sol seen from Venus, but brighter.
Cal was a hotter star. The intruder was a smaller disc, but brighter still. The sail was concave.
It was effort merely to use the intercom. "Sinclair."
"Engineering, aye aye, Captain."
Rod was pleased to see that Sinclair was in a hydraulic bed. "How's the Field holding, Sandy?"
"Verra well, Captain. Temperature steady."
"Thank you." Rod was pleased. The Langston Field absorbed energy; that was its basic function. It absorbed even the kinetic energy of exploding gas or radiation particles, with an efficiency proportional to the cube of the incoming velocities. In battle, the hellish fury of hydrogen torpedoes, and the concentrated photon energies of lasers, would strike the Field and be dispersed, absorbed, contained. As the energy levels increased, the Field would begin to glow, its absolute black becoming red, orange, yellow, climbing up the spectrum toward the violet.
That was the basic problem of the Langston Field. The energy had to be radiated away; if the Field overloaded, it would release all the stored energy in a blinding white flash, radiating inward, as well as outward. It took ship's power to prevent that-and that power was added to the Field's stored energies as well. When the Field grew too hot, ships died. Quickly.
Normally a warship could get hellishly near a sun without being in mortal danger, her Field never growing hotter than the temperature of the star plus the amounts added to maintain control of the Field. Now, with a sun before and another behind, the Field could radiate only to the sides-and that had to be controlled or MacArthur would experience lateral accelerations. The sides were getting narrower and the suns bigger and the Field hotter. A tinge of red showed on Rod's screens. It wasn't an impending disaster, but it had to be watched.
Normal gravity returned. Rod moved quickly to the bridge and nodded to the watch midshipman. "General quarters. Battle stations."
Alarms hooted through the ship.

For 124 hours the intruder had shown no awareness of MacArthur's approach. It showed none now; and it drew steadily closer.
The light sail was a vast expanse of uniform white across the aft screens, until Renner found a small black dot. He played with it until he had a large black dot, sharp edged, whose radar shadow showed it four thousand kilometers closer to MacArthur than the sail behind it.
"That's our target, sir," Renner announced. "They probably put everything in one pod, everything that wasn't part of the tail. One weight at the end of the shrouds to hold the sail steady."
"Right. Get us alongside it, Mr. Renner. Mr. Whitbread! My compliments to the Yeoman of Signals, and I want to send messages in clear. As many bands as he can cover, low power."
"Yes, sir. Recording."
"Hello, light-sail vessel. This is Imperial Ship MacArthur. Give our recognition signals. Welcome to New Caledonia and the Empire of Man. We wish to come alongside. Please acknowledge. Send that in Anglic, Russian, French, Chinese, and anything else you can think of. If they're human there's no telling where they're from." Fifteen minutes to match. Ship's gravity changed, changed again as Renner began to match velocities and positions with the intruder's cargo pod instead of the sail.
Rod took a moment to answer Sally's call. "Make it fast, Sally. If you please. We're under battle conditions."
"Yes, Rod, I know. May I come to the bridge?"
"Afraid not. All seats occupied."
"I'm not surprised. Rod, I just wanted to remind you of something, don't expect them to be simple."
"I beg your pardon?"
"Just because they don't use Alderson Drive, you'll expect them to be primitive. Don't. And even if they were primitive, primitive doesn't mean simple. Their techniques and ways of thought may be very complex."
"I'll keep it in mind. Anything else? OK, hang on, Sally. Whitbread, when you've got no other duties, let Miss Fowler know what's going on," He closed the intercom from his mind and looked at the stern screen even as Staley shouted.
The intruder's light sail was rippling. Reflected light ran across it in great, ponderous, wavy lines. Rod blinked but it didn't help; it is very difficult to see the shape of a distorted mirror. "That could be our signal," Rod said. "They're using the mirror to flash -- "
The glare became blinding, and all the screens on that side went dead.

The forward scanners were operative and recording. They showed a wide white disc, the star New Caledonia, very close, and approaching very fast, 6 percent of the velocity of light; and they showed it with most of the light filtered away.
For a moment they also showed several odd black silhouettes against that white background. Nobody noticed, in that terrible moment when MacArthur was burned blind; and in the next moment the images were gone.
Kevin Renner spoke into the stunned silence: "They didn't have to shout," he complained.
"Thank you, Mr. Renner," Rod said icily. "Have you other, perhaps more concrete suggestions?"
MacArthur was moving in erratic jolts, but the light sail followed her perfectly. "Yes, sir," Renner said. "We'd do well to leave focus of that mirror."
"Damage control, Captain," Cargill reported from his station aft. "We're getting a lot of energy into the Field. Too much and damned fast, with none of it going anywhere. If it were concentrated it would burn holes in us, but the way it washes across, we can hold maybe ten minutes."
"Captain, I'll steer around behind the sail," Renner said. "At least we've got sun-side scanners, and I can remember where the pod was -- "
"Never mind that. Take us through the sail," Rod ordered.
"But we don't know -- "
"That was an order, Mr. Renner. And you're in a Navy ship."
"Aye aye, sir." -- -
The Field was brick red and growing brighter; but red wasn't dangerous. Not for a while.
As Renner worked the ship, Rod said casually, "You may be assuming the aliens are using unreasonably strong materials. Are you?"
"It's a possibility, sir." MacArthur jolted; she was committed now. Renner seemed to be bracing himself for a shock.
"But the stronger the materials are, Mr. Renner, the thinner they will spread them, so as to pick up the maximum amount of sunlight for the weight. If they have very strong thread they will weave it thin to get more square kilometers per kilo, right? Even if meteors later get a few square km of sail, well, they still made a profit, didn't they? So they'll make it just strong enough."
"Yes, sir," Renner sang. He was driving at four gees, keeping Cal directly astern; he was grinning like a thief, and he was no longer bracing himself for the crash.
Well, I convinced him, Rod thought; and braced himself for the crash.
The Langston Field was yellow with heat.
Then, suddenly, the sunward scanners showed black except for the green-hot edge of MacArthur's own Field, and a ragged blazing silhouette of white where MacArthur had ripped through the intruder's sail.
"Hell, we never felt it!" Rod laughed. "Mr. Renner. How long before we impact the sun?"
"Forty-five minutes, sir. Unless we do something about it."
"First things first, Mr. Renner. You keep us matched up with the sail, and right here." Rod activated another circuit to reach the Gunnery Officer. "Crawford! Put some light on that sail and see if you can find the shroud connections. I want you to cut the pod off that parachute before they fire on us again!"
"Aye aye, sir." Crawford seemed happy at the prospect. There were thirty-two shrouds in all: twenty-four around the edge of the circular fabric mirror and a ring of eight nearer the center. Conical distortions in the fabric told where they were. The back of the sail was black; it flashed to vapor under the pinpoint attack of the forward laser batteries.
Then -- the sail was loose, billowing and rippling as it floated toward MacArthur. Again the ship swept through, as if the light sail were so many square kilometers of tissue paper.
And the intruder's pod was falling loose toward an F8 sun.
"Thirty-five minutes to impact," Renner said without being asked.
"Thank you, Mr. Renner. Commander Cargill, take the con. You will take that pod in tow."
And Rod felt a wild internal glee at Renner's astonishment.