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Skystalkby Charles SheffieldFinlay's Law: Trouble comes at 3:00 A.M. That's always been my experience, and I've learned to dreadthe hand on my shoulder that shakes me to wakefulness. My dreams had been bad enough, blasting offinto orbit on top of an old chemical rocket, riding the torch, up there on a couple of thousand tons ofvolatile explosives. I'll never understand the nerve of the old-timers, willing to sit up there on one of thosemonsters.I shuddered, forced my eyes open, and looked up at Marston's anxious face. I was already sitting up.?Trouble?? It was a stupid question, but you're allowed a couple of those when you first wake up.His voice was shaky. ?There's a bomb on the Beanstalk.?I was off the bunk, pulling on my undershirt and groping around for my shoes. Larry Marston's wordspulled me bolt upright.?What do you mean,on the Beanstalk???That's what Velasquez told me. He won't say more until you get on the line. They're holding a codedcircuit open to Earth.?I gave up my search for shoes and went barefoot after Marston. If Arnold Velasquez were right-and Ididn't see how he could be-then one of my old horrors was coming true. The Beanstalk had beendesigned to withstand most natural events, but sabotage was one thing that could never be fully ruled out.At any moment, we had nearly four hundred buckets climbing the Stalk and the same number goingdown. With the best screening in the world, with hefty rewards for information even ofrumors ofsabotage, there was always the small chance that something could be sneaked through on an outboundbucket. I had less worries about the buckets that went down to Earth. Sabotage from the space end hadlittle to offer its perpetrators, and the Colonies would provide an unpleasant form of death to anyone whotried it, with no questions asked.Arnold Velasquez was sitting in front of his screen door at Tether Control in Quito. Next to him stood aman I recognized only from news pictures: Otto Panosky, a top aide to the president. Neither manseemed to be looking at the screen. I wondered what they were seeing on their inward eye.?Jack Finlay here,? I said. ?What's the story, Arnold??There was a perceptible lag before his head came up to stare at the screen, the quarter of a second that ittook the video signal to go down to Earth, then back up to synchronous orbit.?It's best if I read it to you, Jack,? he said. At least his voice was under control, even though I could seehis hands shaking as they held the paper. ?The president's office got this in over the telecopier abouttwenty minutes ago.?He rubbed at the side of his face, in the nervous gesture that I had seen during most major stages of theBeanstalk's construction. ?It's addressed to us, here in Sky Stalk Control. It's quite short. ?To the head ofSpace Transportation Systems. A fusion bomb has been placed in one of the outgoing buckets. It is offour megaton capacity, and was armed prior to placement. The secondary activation command can begiven at any time by a coded radio signal. Unless terms are met by the president and World Congress onor before 02:00 U.T., seventy-two hours from now, we will give the command to explode the device.Our terms are set out in the following four paragraphs. One-"??Never mind those, Arnold.? I waved my hand, impatient at the signal delay. ?Just tell me one thing. WillCongress meet their demands??He shook his head. ?They can't. What's being asked for is preposterous in the time available. You knowhow much red tape there is in the intergovernmental relationships.??You told them that???Of course. We sent out a general broadcast.? He shrugged. ?It was no good. We're dealing withfanatics, with madmen. I need to know what you can do at your end.??How much time do we have now??He looked at his watch. ?Seventy-one and a half hours, if they mean what they say. You understand thatwe have no idea which bucket might be carrying the bomb. It could have been planted there days ago,and still be on the way up.?He was right. The buckets-there were three hundred and eighty-four of them each way-moved at asteady five kilometers a minute, up or down. That's a respectable speed, but it still took almost five daysfor each one of them to climb the cable of the Beanstalk out to our position in synchronous orbit.Then I thought a bit more, and decided he wasn't quite right.?It's not that vague, Arnold. You can bet the bomb wasn't placed on a bucket that started out more thantwo days ago. Otherwise, we could wait for it to get here and disarm it, and still be inside their deadline.It must still be fairly close to Earth, I'd guess.??Well, even if you're right, that deduction doesn't help us.? He was chewing a pen to bits betweensentences. ?We don't have anything here that could be ready in time to fly out and take a look, even if it'sonly a couple of thousand kilometers. Even if we did, and even if we could spot the bomb, we couldn'trendezvous with a bucket on the Stalk. That's why I need to know what you can do from your end. Canyou handle it from there??I took a deep breath and swung my chair to face Larry Marston.?Larry, four megatons would vaporize a few kilometers of the main cable. How hard would it be for us torelease ballast at the top end of the cable, above us here, enough to leave this station in position???Well...? He hesitated. ?We could do that, Jack. But then we'd lose the power satellite. It's right out atthe end there, by the ballast. Without it, we'd lose all the power at the station here, and all the bucketstoo-there isn't enough reserve power to keep the magnetic fields going. We'd need all our spare powerto keep the recycling going here.?That was the moment when I finally came fully awake. I realized the implications of what he was saying,and was nodding before he'd finished speaking. Without adequate power, we'd be looking at a verymessy situation.?And it wouldn't only be us,? I said to Velasquez and Panosky, sitting there tense in front of their screen.?Everybody on the Colonies will run low on air and water if the supply through the Stalk breaks down.Damnit, we've been warning Congress how vulnerable we are for years. All the time, there've been fewerand fewer rocket launches, and nothing but foot-dragging on getting the second Stalk started with aKenya tether. Now you want miracles from us at short notice.?If I sounded bitter, that's because Iwas bitter. Panosky was nodding his head in a conciliatory way.?We know, Jack. And if you can pull us through this one, I think you'll see changes in the future. But rightnow, we can't debate that. We have to know what you can do for usnow, this minute.?I couldn't argue with that. I swung my chair again to face Larry Marston.?Get Hasse and Kano over here to the Control Room as soon as you can.? I turned back to Velasquez.?Give us a few minutes here, while we get organized. I'm bringing in the rest of my top engineering staff.?While Larry was rounding up the others, I sat back and let the full dimensions of the problem sink in.Sure, if we had to we could release the ballast at the outward end of the Stalk. If the Beanstalk below uswere severed we'd have to do that, or be whipped out past the Moon like a stone from a slingshot, asthe tension in the cable suddenly dropped.But if we did that, what would happen to the piece of the Beanstalk that was still tethered to Earth,anchored down there in Quito? There might be as much as thirty thousand kilometers of it, and as soonas the break occurred it would begin to fall. Not in a straight line. That wasn't the way that the dynamicswent. It would begin to curl around the Earth, accelerating as it went, cracking into the atmosphere alongthe equator like a billion-ton whip stretching halfway around the planet. Forget the carrier buckets, andthe superconducting cables that carried electricity down to the drive train from the solar power satelliteseventy thousand kilometers above us. The piece that would do the real damage would be the central,load-bearing cable itself. It was only a couple of meters across at the bottom end, but it widened steadilyas it went up. Made of bonded and doped silicon whiskers, with a tensile strength of two hundred millionNewtons per square centimeter, it could handle an incredible load-almost two-thirds of a billion tons atits thinnest point. When that stored energy hit that atmosphere, there was going to be a fair amount ofexcitement down there on the surface. Not that we'd be watching it-the loss of the power satellite wouldmake us look at our own survival problems; and as for the Colonies, a century of development would beended.By the time that Larry Marston came back with Jen Hasse and Alicia Kano, I doubt if I looked any morecheerful than Arnold Velasquez down there at Tether Control. I sketched out the problem to the twonewcomers; we had what looked like a hopeless situation on our hands.?We have seventy-one hours,? I concluded. ?The only question we need to answer is, what will we bedoing at this end during that time? Tether Control can coordinate disaster planning for the position onEarth. Arnold has already ruled out the possibility of any actualhelp from Earth-there are no rocketsthere that could be ready in time.??What about the repair robots that you have on the cable?? asked Panosky, jumping into theconversation. ?I thought they were all the way along its length.??They are,? said Jen Hasse. ?But they're special pu... 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