“Right,” Wilmer said, and Star nodded and added, “You got it. All very doable. And the obvious place to put your pulse generator is on Cusp Station, out at the end of the shield.”
“But if your interpretation of the Sniffer data or your supernova model is wrong — if all the particles actually arrive independently of each other—”
“Then we’re up shit creek,” Star said cheerfully. “Because the one thing that’s for certain is the particle storm is going to hit sooner than you thought six months ago. That means the shield you got now is no damn good no matter what.”
“Suppose you’re right,” Torrance Harbish said. He had the final word on shield balancing and stability. “All my work for the past eight years will go down the tubes, but that’s not what’s worrying me. You’re saying we have to find and deflect every particle bundle. I don’t understand how we’ll know where each one is. Remember, they’re flying at us at something like ten percent of light speed.”
“We’ve looked into that.” Wilmer did not sound worried. “We generate a wide-angle, low-intensity radiation beam from Cusp Station that extends out toward Alpha C. Easy, and probably best done at microwave frequencies. It won’t be anywhere near strong enough to divert a bundle, but each bundle will interact with the field enough to produce its own weak radiation. We can detect that signal when the bundle gets near enough. It will give us enough information to determine the speed and exact trajectory of each bundle. And that’s what we hit with a pulse strong enough to divert it safely away from Earth.”
“Do we have time to do all that?” Will Davis, like Torrance Harbish, could see his efforts of many years crumbling to nothing. “It sounds like an awful lot of work. I mean, we have to detect a signal, calculate a trajectory, and generate and fire a pulse. How much time do we have between bundle detection and bundle arrival?”
Wilmer nodded. “We’ve studied that, too. Star?”
“No worries. Yer can’t get a useful return beyond about fifteen thousand kilometers. From there the signal takes a twentieth of a second to reach Cusp Station, and the pulse needs that long ter go back. Knock that off the bundle travel time before it gets ter the shield — say half a second — and you’re left with point four seconds to generate a pulse and spit it back out ter the bundle. Bags of time. ’Course, it’s a monster computing problem to know just where ter fire. But I understand you’ve got computers up here coming out your wazoo.”
She saw their faces. “Uh-oh. Did I screw up?”
John spoke first. “I think so. Let me make sure I have this right. We receive a return signal at Cusp Station. From that we compute where the bundle is. On Cusp Station we generate a powerful EM pulse and aim it at the bundle.”
“That’s right. Look, we assume you don’t have equipment on Cusp Station to generate the signal field or the pulses. That’s all right, they can be shipped there easy.”
“Not the problem.” Amanda Corrigan was the computer specialist. Shy and gawky, she ducked her head and made her first contribution to the meeting. “You said we had a ’monster’ computing problem. How monster?”
“Yer might need to do simultaneous path computations for a few million bundles a second. I was told you could do that here, dead easy.”
“We can,” Amanda said. “Here on Sky City. But we don’t have anything near that much power at Cusp Station.”
“So yer beam the information from there—” Star paused.
“You’ve got it,” John said quietly. “We have all sorts of computing power on Sky City. But there’s not much on Cusp Station. The minimum distance between Sky City and Cusp Station is more than a hundred thousand kilometers. That’s more than a third of a second for a one-way signal, two-thirds of a second round trip. Far too long.”
There was a long silence, broken by Wilmer. “We’ve got some time, a few weeks. Ship computers out to Cusp Station, enough to do the job.”
“Amanda?” John Hyslop raised his eyebrows.
She shook her head. “Sorry. The computing system here is integrated and distributed through the whole of Sky City. We have plenty of spare capacity, but it’s impossible to pull part of it out without screwing up everything. Air, water, waste disposal — the systems all call on the same computing resources.”
Star flopped down on the floor and sat with her legs sprawled inelegantly wide. She leaned forward like a gymnast, touched the carpet three times with her forehead, sat up, and said, “Then we are buggered. Any chance we can get enough computer power shipped up from Earth?”
“Possibly.” Bruno Colombo had sat silent through the whole long meeting. Most of the time his eyes were closed. John had wondered if the director was even awake.
“Possibly,” Colombo repeated. “But it’s not an answer that I — or anyone — would be happy with. Either we’d have to ship people up from Earth who know their own systems well but are not used to working in space, or else our staff would be faced with the task of learning unfamiliar equipment and programming intricate life-or-death calculations in a very short time. Not just life-or-death for us. For everyone.”
“Even so,” Wilmer said, “it’s our best shot. I can promise you, even if the old shield were finished and working perfectly, the particle bundles we’re talking about will go through it like it’s not there. We need computer power on Cusp Station, lots of it. If the only place we can find it is on Earth, that’s where we take it from. I know Celine Tanaka, I’m sure she’ll cooperate.”
“Maybe she would.” Bruno Colombo stood up. Suddenly he had gone from being a bystander to the person in control of the meeting. “But I don’t think that’s the best answer. Hyslop? You know Sky City as well as I do, maybe better. Can it be done?”
“I have to check. It will involve accelerations and stresses beyond any that were ever dreamed of. But my gut guess is that yes, we can do it.”
“Do what?” Star was still on the floor, but now she was sitting bolt upright and scowling. “What are you two going on about?”
“If the mountain will not come to Mahomet . . .” Bruno Colombo turned to John. “Hyslop, you and the others here work out the engineering details. I’ll start on resource allocation. Even if it is possible, it’s not going to be easy.”
He hurried out of the room. John felt an odd mixture of irritation and admiration. Just when you were convinced that Bruno Colombo was nothing but a big bag of wind dressed in an expensive suit, he did something to prove that deep inside the pomaded head sat a highly creative brain. Sure, part of it was Colombo protecting his territory — but he also happened to be proposing the only possible solution. And then he left you to “work out the details.”
John found himself once more running the meeting. “It’s going to be an interesting few weeks,” he said. “We need loads of computers out near Cusp Station. We have all kinds of computational power here, but we can’t ship it anywhere else.”
“So Mahomet . . .” Will Davis said.
“That’s right.” In spite of the enormous size of the problem, John felt the thrill of a new technical challenge. “We’re heading for the front line — all of us. We’ll take this place and fly it all the way out to Cusp Station. And then, assuming that Sky City doesn’t disintegrate on the way, and certain people stay out of our hair” — he stared at Star Vjansander, who was grinning at him in delight — “well, then we’ll find out if certain harebrained ideas are anywhere close to reality.”