Implicit in all of this was a hell of a lot of robot activity, which was why Sean had taken the extraordinary step of traveling personally to Izzy to clean out Dinah’s supply of them before proceeding to his rendezvous with Ymir. The reactor had to be fed with ice. Because ice was a solid, it couldn’t flow through tubes. Robots had to mine ice from the shard and transfer it to a feed system: a set of augers that would move it into the reactor chamber to be melted and vaporized. A Siwi robot could move a lot of material in a hurry by embedding its “tail” in the ice and then using a whirring mill on its “head” to throw off a fountain of fine shavings that could be collected and carried off by Nats. The long intervals of time between burns could be used to store up a supply of shredded ice in hoppers that would feed the augers.
Downstream of the engine, robots were also needed to maintain the shape of the rocket nozzle. This was a long duct with a wide mouth on the aft face of the shard, tapering to a narrow throat near the reactor. The throat had been constructed on Earth and launched up with the reactor. It was made of a corrosion-resistant alloy called Inconel. Any other material would rapidly wear out from the hot steam blasting through it. Conditions in the long spreading bell of the nozzle, however, were more benign, and so it worked fine for that to be sculpted from ice. Nonetheless, it changed its shape as it was used. Deeper in, where the exhaust was hot, it grew wider as its walls were melted by the torrent of steam. Closer to the exit, where the exhaust had cooled to below freezing, it accumulated on the walls and narrowed the passage. So robots had to scuttle around reshaping the nozzle. This was a fine task for the Nats that Larz had experimented with in Seattle.
Finally there was a third “crew” of robots living on the exterior surface of the shard, trying to keep it from falling apart by embedding fibrous reinforcement in the outer layer of ice and wrapping cables and nets around it, somewhat like a butcher tying up a roast to prevent it from collapsing in the oven. This was a good match for the capabilities of the Grimmed (steel-armored) robots, which were mostly Grabbs.
All of these robots needed power, of course. They could store a little of it in batteries, but those had to be recharged. Some of them collected energy from sunlight; others had to converge from time to time on one of Ymir’s little nuclear generators to sip electricity.
The general picture was that Ymir would not be anything like the traditional idea of a spaceship, in the sense of an orderly, symmetrical piece of architecture. It would be more like a flying robotic anthill, constructed out of a natural found object. The robots crawling around on and in it had general instructions as to what they were supposed to be doing, but could make their own judgments from moment to moment to avoid collision with other robots, or from hour to hour as to when they needed to recharge their batteries.
Or that had been the general scheme, anyway. Since there’d been no guessing what Sean would find, there’d been no way of coming up with any plan worthy of that name. Instead they had sent him up with tools, resources, and ingenuity. Dinah, Markus, Vyacheslav, and Jiro were about to inherit the tools and the resources.
Jiro’s Eenspektor made steadily more noise as they approached, but the growth was slow enough that their minds didn’t quite register it. Jiro did not seem alarmed by the level of radioactivity, but Dinah didn’t know how to interpret that. Earlier in the mission, she had probed him for some general background about what to expect. “If it’s very bad, we all just lose consciousness and the mission fails,” he’d said. “The flux of radiation just shuts down our nerves, our sphincters open, we never even know it’s happening.”
“In that case,” Markus had pointed out, somewhat testily, “there is little point in discussing that scenario.”
“If all four of us throw up,” Jiro had continued, “and, say, one or more of us gets diarrhea, then we have hours to live. In that case we should just transmit a warning to Izzy and encourage them to send a second mission. In the meantime, maybe we can transmit some useful information to them. Eenspektor data, pictures, et cetera.”
“Noted,” Markus had said.
“If, say, one of us throws up, then it means that half of us will probably die, and so we have some chance of accomplishing the mission. If no one is barfing, then none of us is likely to die, at least over a time span of weeks.”
“Thanks for that,” Dinah had said, and tried to put it out of her mind. Now that they were actually approaching Ymir, however, it was coming back to her, and she was trying to convince herself that she wasn’t feeling any nausea.
“I am going to traverse the nozzle mouth in about thirty seconds,” Markus announced.
“Roger,” Jiro said, and then switched off his Eenspektor altogether. He pulled up a window on the screen of his tablet. “Switching to the external gamma spec now.”