Pushing Ice (22 page)

“It’s a long way behind us now.”

“But closer than anything else. Did anyone remember to check the beacon?”

“I’ll refer it to the technical team,” Schrope said.

“You still want my free-flier?” asked Saul Regis, his voice characteristically slow and somnambulant.

“As soon as you can prepare it,” Bella said. “I want it rigged to match the output frequency and strength of the Earth uplink. Make sure you adjust for Doppler shift, of course.”

“Of course,” Saul Regis said laconically.

“Trivial?”

“Very. I can have the free-flier outside in an hour.”

“Do it,” Bella said, “and then maybe we’ll get somewhere. I don’t like being cut off for this long. It makes me nervous.” Then she turned back to Svetlana. “I’m sorry. I’d like to have worked something out. But you had your chance.”

“So did you,” Svetlana said.

* * *

Bella watched as the three robotics technicians completed their preparations. Jens Fletterick and Eva Hinks stood next to each other in the cargo airlock, comparing read-outs on their flexies, linked by data spools to ports in the robot’s chrome-yellow tubular chassis.

Saul Regis stood behind his two team members, saying nothing but watching everything with narrow-eyed intensity, ready to intervene if he saw one of them make a mistake. They all had the slightly unnatural postures of people standing up under weightless conditions, glued to the floor by their shoes.

Calling the cupboard-sized thing a robot was something of a stretch, Bella thought. The free-flier was mostly fuel tank, feeding a tiny nuclear-assisted gimballed rocket motor. At a quarter of a gee, the free-flier could shadow
Rockhopper
for six hours before it needed refuelling. That wouldn’t be an issue now: having reached the initial study point, the ship was in free fall, apart from the small amount of thrust required to hold itself at a constant distance from Janus. But the technical team assured Bella that the free-flier would need to reach a significant distance behind
Rockhopper
before its own radio emissions could be considered a realistic approximation to the uplink signal. Bella didn’t want to wait for the robot to crawl out to that distance on a fuel-conserving cruise.

Regis turned back to her. “We’re go. It took a bit longer than I was expecting: we had to load new software to allow for the expected timelag at the end of the burn.”

Bella looked at her watch: by her estimate, Regis was within a minute of his promised delivery time. “You understand you won’t be getting this machine back? I mean, if there’s anything valuable aboard it —”

“We’ve stripped it of everything it doesn’t need for this one mission,” Regis said, directing her attention to a tiny cluster of processor boards floating at eye-level next to Hinks. “You still want to go ahead with this, right?”

“We haven’t had any luck picking up the omni-directional transmitters,” Bella said.

“Doesn’t that mean there has to be a problem at our end after all?”

“Not necessarily. The detection probabilities were already marginal, and we might not be looking in exactly the right direction, or the beacons might have failed, or someone else might have claim-jumped our property. I admit it’s a
little
puzzling, but that’s why we need to run this experiment as well.”

In five minutes they had cleared and depressurised the airlock so that the wide outer door could be opened to space. Fletterick had strapped himself into a teleoperations couch in the puppet booth and was already lifting the free-flier from its pallet using micro-bursts from its chemical steering thrusters. Flexies on the wall showed cam images of the free-flier from different angles as it turned its long axis through an arc of ninety degrees. Above the drone of pumps Bella heard Fletterick say, “Hold.”

He flipped up the visor of the immersion headset. “She checks out okay. Star-trackers are off-line, but we should be able to rely on the inertial gyro.”

“Star-trackers are down?” Bella asked.

“Hinks the Jinx must have removed the wrong board.”

“Hey, don’t blame me,” she said. “I removed exactly what we agreed to remove.”

“We can live without the star-trackers,” Bella said. “Just get her on a solid gyro heading and fire up the main rocket.”

Fletterick lowered the visor again and returned to the telepresence realm of the robot. “Resume,” he said, and began delivering another series of clearly enunciated verbal commands.

The cams showed the robot drifting to a safe distance from
Rockhopper
before engaging its main rocket. It fell rapidly away at one gee, as if it had been dropped from a tall building on Earth. The nuclear rocket would burn for ninety minutes before exhausting its fuel, and by then the free-flier would have put half a light-second between itself and
Rockhopper
: more than a second of timelag for its telepresence operator. It would have achieved a terminal speed of more than fifty kilometres per second relative to its current motion.

That sounded fast, and by any sane measure it was, but
Rockhopper
— and the alien machine it shadowed — were both moving eighteen times faster than that. When it finished its burn, the free-flier would still be moving with them into interstellar space, just a bit slower.

It would still be headed for Spica.

Bella returned to her quarters in the centrifuge section and waited for news. She pottered with her fish. After ten minutes, she learned that the uplink antenna aboard
Rockhopper
was successfully receiving the test signal from the free-flier. Nothing about the detection revealed any anomalies.

Earth was still silent.

After thirty minutes she called Belinda Pagis. The woman looked exhausted. “It’s only telling us what we already knew,” she said. “The antenna’s working fine. Every single test has confirmed that.”

“But you can’t test the sensitivity at the low end,” Bella said, fingering a hardcopy of the earlier technical note. “Not without something like the free-flier.”

“Agreed — but we’ve no reason to assume a problem with the sensitivity. And the uplink signal should be well above our noise limit.”

“Then there must be extra noise leaking in from somewhere.” Bella glared at the technical note: it swam in and out of focus like a fish under water. “Have you looked at the cooling system on the pre-amplifier box?”

“Yes,” Pagis said with a heavy sigh. “In fact, that was about the first thing we looked at.”

“Sorry — just trying to make helpful suggestions.”

“It
was
helpful,” Pagis said, with something like contrition, “it’s just that we’ve already gone through all the obvious stuff.”

“Keep trying,” Bella said. “At least in half an hour we’ll know if the sensitivity is the issue. That’ll help, won’t it?”

“I guess,” Pagis said, unenthusiastically.

Bella let her get on with her work. The next thirty minutes oozed past, the passage of time made slower by the regular notifications that probe and ship were still in contact, but with the signal becoming slowly fainter. The falling away of the signal strength was exactly as predicted, with no loss in detection efficiency due to some antenna fault.

Bella reminded herself that she still had a ship to run, and that Janus was still sitting there waiting to be examined. Her inbox contained a dozen messages from Nick Thale, each of which — as she skimmed them quickly — contained updating summaries of the latest remote-sensing operations. By contrast to the uplink, the equipment under Nick’s guidance was all working normally. Thale’s most recent message requested Bella’s formal permission to launch a free-flier on a pseudo-orbit that would take it around the far side of Janus, observing the as yet unseen “bow” face.

Bella authorised it without hesitation. The technical aspects of the mission had already been covered, and the flier would not be approaching any closer to Janus than
Rockhopper
had already come. There would be no additional risk.

With five minutes left until Fletterick’s free-flier had reached its terminal velocity, Bella decided she could no longer stand the wait. She called Pagis again and asked her to meet her at the puppet booth. Jens Fletterick was still in the couch, barely moving. Every now and then he whispered some arcane command to his machine. Timelag was now appreciable.

“Here’s something odd,” said Hinks, holding a Ziploc plastic bag in which she had gathered the free-flier’s spare processor boards. “That star-tracker glitch Jens tried to pin on me?”

Bella blinked back to an hour earlier. “Yes,” she said, with an ominous sense of premonition.

“We’ve got a similar problem with the flier you just authorised Nick Thale to launch. I never went anywhere near the star-tracker boards on that machine.”

“Doesn’t make any sense.”

Hinks nodded. “Add it to the pile.”

“Wait,” Bella said. “We have to clear this up. One star-tracker failure I can understand, but two, in completely isolated machines?”

Hinks looked at Bella with a dawning comprehension. “You think the two things might be connected?”

“I don’t know what I —” But Bella halted, looking at Jens Fletterick. He’d flipped up his visor.

“The free-flier has reached terminal velocity,” Fletterick said. “All systems are functioning normally, including the uplink antenna.”

Bella looked to Pagis for confirmation. Pagis had a stiffened flexy across her forearm, hectic with sketchy, hand-annotated diagrams in primary colours. “Still reading you,” she said. “Signal’s on the nose, too: it’s exactly where it should be. Doppler’s flattened out now that the machine isn’t accelerating.”

“And this represents the strength of the uplink signal from Earth,
if
they were sending?” Bella asked.

“Within a few per cent of the modulated average.”

“Then our system
must
be good,” Bella said.

Pagis nodded meekly. “We’ll continue to collect data as the free-flier falls away from us at terminal velocity, but I don’t think it’s going to tell us much we don’t already know.”

“Keep listening anyway.”

“Is it me,” Hinks said, “or is this beginning to make no sense at all?”

“It’s not you,” Bella said.

TEN

Jens Fletterick’s hands moved in exaggerated arcs, like a shadow-boxer. Bella, Hinks and Pagis stared at him, mesmerised. He kept that up for another minute, his gestures gradually becoming slow and resigned, until he stopped moving completely. He lay still for another minute, breathing shallowly. At the end of that minute he flipped up the opaque mask of the immersion headset and unbuckled himself from the couch.

“It’s gone,” he said.

“Gone?” Bella asked.

“The link is dead. I can’t talk to the machine any more.”

“But you were nowhere near the limit of radio communications,” Hinks said. “Was there a falling off of signal strength?”

“Nothing,” he said. “It just disappeared. One moment I was there, looking back at
Rockhopper
. I could still see Janus. And then I just wasn’t there any more.”

“As if someone cut the puppet strings,” Bella said.

“No,” he said, correcting her with gentle firmness. “That’s not quite how it felt. There was a moment… a transition.” For once, this usually precise man struggled for words. “It was as if the strings became stretched, pulled, until they snapped. But not cut. Not cut at all.”

Hinks knelt down next to the couch. “This looks funny,” she said, scratching a finger across one of her flexy read-outs. “Look at the Doppler on your telemetry.”

Fletterick removed the heavy immersion gear. Still gloved, he took the flexy from her. “It should have been flat,” he said.

“It was, after you stopped burning fuel. That is, right until the end. Then something funny happened.”

“Show me,” Bella said.

The free-flier had accelerated away from
Rockhopper
, firing its nuclear rocket until it had run out of fuel. The radio signals sent back by the free-flier had become red-shifted as its recessional velocity increased. That was entirely expected, as was the flattening of the red-shift curve from the moment that the fuel ran out and the free-flier coasted away at constant velocity. And it should have stayed like that all the way until loss of radio contact.

But it hadn’t.

In the last six seconds before Fletterick lost contact with the free-flier, the Doppler curve had begun to rise again. The rise was sharp, as well, the slope of the curve steeper than it had been during the hour-long boost phase.

With a mere six seconds of data to go on, Bella could only estimate the surge in acceleration that the free-flier had experienced, but she judged that the slope was around five times steeper — which meant that the free-flier had experienced a boost in acceleration of five gees before radio contact was interrupted.

“That isn’t possible,” she said, shaking her head in flat denial. “There has to be a mistake, a misreading.”

“It’s all right there,” Hinks said.

“Then give me an explanation for it. Could there have been a re-ignition of the motor at five gees?”

Fletterick chose to answer. “No. It was programmed to burn until the fuel was completely exhausted. And even if there’d been a small amount of fuel left in the system — which there wasn’t — there’s no reason why the motor would ramp up to five gees unless we specified that in the burn sequence. Which we didn’t.”

“An explosion, then,” Bella said. “Something uncontained. A detonation of fuel vapour violent enough to provide some impetus to the free-flier.”

“If there had been an explosion,” Fletterick said, “I think we’d have seen some of the telemetry channels drop out. Unless it was a very selective explosion that managed not to damage any mission-critical systems, yet still hurl the free-flier away from us at five gees along exactly the same vector it was already following.”

Bella smiled at him. She loved sarcasm, especially from engineers.

“Oh, wait,” Hinks said, scowling at one of the flexy readouts. “This is really odd. This
really
makes no sense.”