At least she had some idle moments now. Since the decision to try the scarfed-nozzle approach, they had executed two burns, about twenty-four hours apart, each with a slightly different configuration of the ice nozzle: a canted lip, constructed by the Nat swarm, projecting almost imperceptibly above the aft surface of the shard and bending the torrent of steam slightly. The first of those burns had gotten them spinning the way they wanted to go, though “spinning” might be too strong a word for a rotation that took the better part of a day. During that day the Nats had decamped to the other side of the nozzle’s rim and built a lip there. The second burn, then, had stopped the rotation that the first one had started, and brought them close enough to their desired attitude that the surviving thrusters could handle the details.
Another perigee was coming up soon. This time the nozzle would be aimed the way they wanted it—forward, once again turning the nuclear engine into a powerful retro-rocket. The robots on the inside of the shard had been at work scooping it out, sculpting the walnut-shell architecture that, according to the structural engineering simulations, would enable the whole thing to hold together during the last round of maneuvers. The hoppers were full of ice, with more on the way, and they’d finally learned how to make the system work consistently. Part of that lesson was not to try to accomplish too much with any one burn. It was better to take it easy, set a reasonable delta vee target, get it done and lock it down, then take stock of the situation and plan the next burn at leisure. Consequently their rendezvous with Izzy looked to be happening much later than they’d first expected, and almost every day brought a further postponement. But at the same time it came to seem more and more of a sure thing, less of a wild chance, and this began to affect Dinah’s thinking. Her robots were doing their work almost entirely on autopilot, leaving her somewhat bored. Vyacheslav, sealed up on the other side of a wall of plastic, could be talked to, but preferred keeping to himself. Jiro, on the other hand, had been working almost around the clock and had been showing signs of strain. Dinah would find excuses to float behind him and look over his shoulder at his screen. Was he playing solitaire? Running orbital mechanics simulations? Writing his memoirs? He seemed mostly to be looking at video feeds of machinery. By process of elimination, this had to be near the core of the reactor.
In the floor of the “bottom”-most level, three stories “below” them, was a manhole giving way to a shaft sunk into the ice. At the far end of that shaft was another hatch providing access to what, on an oceangoing ship of Old Earth, would have been called the boiler room. A small pressurized compartment housed control panels and access ports connected to the reactor, which was only a few meters away, on the other side of a heavy wall. The wall was a radiation shield, at least in theory. But sending up a huge piece of lead hadn’t been an option for the hastily assembled Ymir expedition, and so the “boiler room” got washed with neutrons and gamma rays whenever the reactor was used. The radiation detectors that Sean and company had left behind, the last time they’d closed that hatch, didn’t leave much to the imagination. The place was a hellhole now. Fortunately, all the systems connected there had been designed to be operated remotely, from the safety of the command module, so there was no need to go down that ice tunnel and open that hatch.
Their instruments told them they were nearing perigee again. Jiro, assisted by Dinah, executed what they hoped would be the second-to-last burn of the big engine. This went on longer than Jiro had predicted, but it seemed to work. Ymir shed most of her excess velocity. Her orbit, at apogee, was now only a few hundred kilometers higher than Izzy’s. In spite of attrition suffered by the robots as they wore out, broke, or succumbed to radiation damage, Dinah still had enough of them to restock the hoppers for the final major burn, which they calculated would be happening at a perigee a few hours later.
“If you are satisfied with the disposition of your robots,” Jiro said, “I would like to show you how to operate the main propulsion.”
She had grown up in mining camps where older men liked to amuse her, and themselves, by teaching her how to operate heavy machinery, blow things up with dynamite, pilot airplanes, and the like. So Jiro’s offer didn’t seem unusual to her, at first. Teaching people how to do stuff was, among other things, a way to alleviate boredom. But over the course of the next hour it slowly became clear to her that Jiro really was expecting her to operate the engine during the upcoming burn. It might have been the language barrier; but his English was pretty good, and he was being quite persistent in saying things like “you will keep an eye on this thermocouple” and “you might see some flutter in this valve.”
“If you don’t hear from me beyond the thirty-second mark,” he said at one point, “then you are on your own and you will have to initiate shutdown based on observed delta vee.”
“Why would I not hear from you?” Dinah asked. “Where are you going to be?”
“In the boiler room,” Jiro said.
“Why would you go there?”
“Some of the control blade actuators have stopped responding,” he said. “I think that the electronics have been damaged by radiation. It’s okay. We have replacements. But they will have to be installed manually.”
“So you’re going to go down there?”
“Yes,” Jiro said. “And that is where I am going to stay.”