The Prospect continued on its course, slowly, silently, and steadily, through the blackness, under more than two hundred meters of water. After a couple of hours of creeping, Percy flipped the white lights back on, which everyone understood to mean that the situation had returned to something like normal, even though it remained nothing like safe to continue running beyond the edge of their normal operating depth.
“Hemi, join me at the navigation station. It’s time for us to figure out where we’re going,” said Percy.
They climbed down the ladder and turned the lights on over the navigation table. Hemi unsealed and unrolled a new chart and laid it down under the glass. He wiped the old grease pencil marks off with a rag.
“I got us a more up-to-date chart at the depot,” Hemi said. “Look, the depot is here. And…” He looked over some notes on their current course and speed from a clipboard he had been updating over the last couple of hours, then put a small x on the glass, not far from the deserted island that held the depot. “I estimate we are about here, now.”
Percy pointed to a hashed arc printed on the chart that ran past one side of the depot island. “Is that the actual current Authority demarcation line?”
“Yes,” said Hemi. “Western Federated Socialists on the east side of it, Consolidated States of the Archipelago Islands on the west side of it.” He looked at the date printed in the corner of the chart. “At least as of the printing of this chart, eight months ago.”
“We need to head toward Stilt City. But I think we should take a slightly less than direct course.” Percy drew an arcing route on the chart with the tip of her finger. She indicated a point on the arc. “I asked Shakes to rendezvous with us here. I hired him to help us out on this run.”
“Good. And yes, further into the Consolidated States waters will be better. They are far less likely to bother us, and we can travel for a few days while remaining in their waters. But…” He took another chart from the stack of rolled charts and unrolled it in front of Percy. “To get to Stilt City, we eventually have to head through these waters in the south. A highly contested area. At least three — up to five — Authorities all claiming parts of it.”
“Well, we’ll just have to be fucking careful when we move through there. We’ll be disciplined about running on the surface only at night, and max out our underwater time during the day.”
“…In addition to the regular trouble we might encounter with Authorities, there is also that sub with the ram. My guess is they are the ones who fired on the depot patrol sub. It is possible they followed us there.”
“This isn’t a rush job, Hemi. We have the time to take it slow and do the stealth thing right. Let’s just be careful, be silent, and not be found. We’ll deliver the cargo, collect our money, and by that time we’ll be a few territories away — an entirely different part of the world — from wherever that sub with the ram came from. I’ll bet we never see that ugly fuckin’ boat again.”
“I hope you are right.” Hemi paused, running through his mental checklist of all the things that kept the boat going. “Another thing I wanted to bring up with you is that while we were adjusting the trim, it looked like the boat is a little by the bow.”
“Hardly surprising; we never seem to be able to load cargo in a way that doesn’t throw off the fucking balance.”
“True. I would like to bring some of the crew down to the cargo hold and shift cargo back towards the middle of the boat. See if we can get it stowed so it trims more evenly.”
“Sure, but let’s run a little longer first. At our current rate we’ve only made maybe a dozen nautical miles from the depot so far.”
“Think we can risk a little more speed yet?”
Percy considered. “I think so. Take us up to six knots. Only top sonar people deliberately looking for us could hear us at six knots at this range and depth. In a few hours more, we’ll come up a bit shallower and you can start rearranging the hold.”
“Sounds good,” said Hemi as he started climbing back up to the control room to have Owen increase the throttle.
Six knots was still slow, but twice the speed at which they had crawled away from the depot. With three more hours of cruising, they were out of range of all but the very best sonar gear and ears in the world. Percy had them come up to one hundred meters to take some of the strain off the hull.
When the boat reached this shallower depth, Hemi worked the tank trim control panel and made adjustments, pushing water back and forth across the boat. “Sylvia,” he said as she stood behind him, smoking, “I think we can certainly do better with the trim if we move some of the cargo around down in the hold.”
“OK. Take Owen and Bastian down there with you. I’ll watch the trim with Gregory in case she starts to lean or something. Keep in mind that it might be bad if you drop any of those fucking crates.”
Hemi tapped Owen on the shoulder, and they climbed down to the sonar compartment, where Bastian joined them on the trip down to the cargo hold.
When they stuck their noses into the cargo hold and Hemi brought the lights up, it still smelled damp. Hemi was certain the quilted patchwork of steel and frozen slag that covered the split seam of the hull was continuing to seep. They might never have a completely dry cargo hold again. That was OK; that was what bilge pumps were for. But the accumulating bilge water was another good reason to shift the cargo and get some play in the boat trim.
Gregory had stacked the wooden crates into the hold inexpertly. There was a bit of an art to it, and Gregory had only the beginnings of the necessary skill. The crates had been initially laid down all the way up and down the length of the hull along the sides. This was a good start, forming the base for putting the rest of the crates on the top. But then Gregory had gotten lazy and stacked the additional layers of crates mostly toward the bow. That was easier to do and kept the crates out of the way for crew moving in and out of the cargo hold, but put more weight in the bow than Hemi wanted. They needed to move some of the upper layers of the crates in the front toward the rear of the cargo hold while still leaving enough room for the crew to get through.
Hemi had Owen rig a hoist and chain to sliding fixtures on the roof of the cargo hold. Then Owen could climb up on the stack and throw straps around each crate they wanted to move. Hemi and Bastian would pull the chain while Owen guided it off the stack. The individual crates were only modestly sized but surprisingly heavy, requiring Hemi and Bastian’s full combined power to lift them, even with the mechanical advantage of the hoist. The three of them would then drag the airborne crate up the length of the cargo hold with the hoist sliding along the rails, and Owen and Bastian would push it with poles while Hemi lowered it to its new place.
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Every so often they would come across one of the food crates that had not been stowed in the galley earlier, and they would have to interrupt their re-arranging work to unpack the food and move it up to the galley.
It ended up taking a few hours to complete a first pass at rearranging the hold. When Hemi felt like the weight distribution might be good, he left Owen and Bastian smoking in the cargo hold while he ran up to the control room. There, Hemi and Percy made slight adjustments to the trim of the boat, before Hemi returned to the cargo hold to move a few more crates around. It took another hour and three more trips up to the control room before Hemi was happy with the way the cargo sat and the boat was trimmed.
“Fuckin’ A, Hemi,” said Gregory when Hemi was finally settled back into the control room, “seemed like the boat was trim enough when we left the fuckin’ depot. Didn’t slow us down none.”
“A submarine is like the hairs on the back of your neck, Gregory. It always needs a trim.”
Hemi knew Percy would keep the same course, depth, and speed until well after dark, and that was still a few hours off yet, so there was little for him to do for the moment. He took the opportunity to start training Cassandra on sonar.
In the sonar compartment, he sent Bastian off for coffee and a smoke and sat down next to Cassandra. “You have been listening for the last few hours while Bastian worked the sonar, correct?” Hemi asked her.
Cassandra nodded.
“Any of it make any sense?”
“Do you want me to lie?”
“There is nothing to be concerned about. It is not as complex as it might seem. Except for the parts that are, but we will get to those as we come to them. Put your headset over both ears… You need both ears to get a full sense of what any sound you hear on sonar is doing.”
Cassandra adjusted the headset so it sat evenly, with the headphones covering both her ears.
“OK,” said Hemi as he began adjusting and tuning the sonar unit, “this is the ‘passive’ sonar rig. You can think of it as being nothing more than microphones for listening underwater. There’s ‘active’ sonar too — that’s a lot more complicated: active sonar sends a ping out and we listen for its echo. We do not use that often so do not worry about it for now. Passive is simpler, you are just listening, passively. Understand?”
Cassandra nodded.
“The main thing you need to know for operating the sonar is that you can aim the underwater microphones in a specific direction using this thing that looks like a steering wheel.” Hemi turned the stainless steel wheel a half turn. “See that dial there? That shows you which way the microphones are pointed. It goes around 360 degrees. At some point someone will ask you to listen in a specific direction. They will give you the degrees and you just turn the wheel until the needle on that dial shows you are aiming the mics in the direction they are asking about. Make sense?”
“That seems simple enough,” said Cassandra.
“That part is. It will get a lot more complex when we start using the filters and transducers to tune in on a contact later. The thing is, the ocean is never absolutely silent. Let’s start by just listening to what we hear on the sonar where there are no specific contacts we are trying to focus in on.” Hemi and Cassandra both remained quiet for a minute with the background sound of the ocean washing through their headphones. “OK, Cassandra. What do you hear?”
“I don’t know…” She waved one small hand absently. “A hissing sound — white noise?”
“Almost anything could be white noise. Describe it with more detail than that.”
“There’s…a low rumble, a bit of a swishing sound…”
“Good. We are running on the electric motors, underwater, at a modest speed. That is what it sounds like when the boat is moving while submerged. Later, when we are near the surface with the diesel engines running, it will be a lot louder and you will not be able to hear much in the water beyond the engines. But while we are on the electric motors, we can hear more on sonar.
“Sonar requires imagination,” Hemi continued. “You have to put your mind out there in the water. When you hear a sound, you have to match it to an image in your head that shows how the sound could be made. The more detail you can imagine to fit it to the sound, the more accurate your assessment of the contact will be. That is what makes a top sonar person.”
Hemi pointed to the largest of a set of gauges further up the sonar unit in front of them.
“Now, the gauge above the directional indicator is the main signal strength indicator. All those smaller gauges above it show signal strength at different frequencies, but you only need to worry about this main signal strength indicator for now. Watch that needle. If you see it jump, there is a significant sound out there in the water, and you will want to focus on it, listen to it, and try to figure out what it is.
“Let us see…” Hemi turned the direction dial slowly. About a quarter of the way around, the strength indicator dial moved up a little and wavered there. “So, see by the needle that there is something to hear in this direction? What do you hear in your headset now?”
Cassandra listened, her eyes watching the signal strength indicator needle wavering like a hummingbird feeding. It was moving in response to another kind of white noise, higher pitched than the sub’s engines, which she could still hear rumbling in the lower frequencies. This sound was familiar, a washing, churning sound with an occasional rumble mixed in… She smiled. “It’s breaking surf, isn’t it?”
“Correct! There is a small atoll a few miles in that direction and waves are breaking on its shore. Let’s see what else is out there.” Around the directional needle went, and Hemi slowed it, and stopped with the strength indicator needle throbbing slightly, like it had a pulse.
Cassandra closed her eyes. In her headphones she could hear a distant clicking, slow and regular. The clicks had a strange kind of richness to them. They bounced around the underwater landscape, and she could hear not just the clicks but also the echoes of the clicks. The dark world out there lit up in her mind, and she remembered storybooks about sea life from not so long ago when she was a child. “Is that the sound dolphins make?”
“Very good! Dolphins use active sonar, bouncing sounds off underwater objects to locate them. They are much better at it than we are. Did you notice that you could hear the dolphins in one ear slightly before the other?”
Cassandra nodded again.
“That is because the sonar uses a couple of sets of microphones, one on the front of the boat, and one at the rear. Sound coming in hits one microphone before the other, and the sonar rig puts the difference into the earphones for you. With practice, you can use the difference in how long it takes to estimate how far away a contact is. For instance, I can tell you these dolphins are about a third of a nautical mile away. That only works if the contact is close enough that we can hear the difference, though. If you think about it: a contact that is farther away will send out a sound that will be murky enough by the time it gets to us to hit both the microphones on the bow of the Prospect and the stern at basically the same time. It’s not unlike the way the stars in the sky look like they are on a flat plane even though there’s vast differences in the distance they might be from us.”
“OK, ya, that makes sense,” said Cassandra, picturing the sound waves bouncing off the boat in her head.
Hemi smiled. “Miss Cassandra, you may have a career ahead of you. Keep practicing until we surface and we start the diesels later tonight. You will not be able to hear anything after that.”
“OK, Hemi. Thanks.”
Hemi left her there listening to the dolphins and climbed up next to Percy in the control room.
“How’d she do?” asked Percy.
“We may have a pair of ears yet.”
“That would be a nice fucking change. Most of these meatheads are OK at rudimentary steering, but they’re fuckin’ useless on sonar.”