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  "Why?"

  "Well, it's obvious. To keep the engine going, you'd have to haul a great big damn barge full of gas, and how fast could you possibly go if . . . Oh. I see."

  "Yup. Welcome to the rocket equation. On Earth, on the oceans, we can get by just by making the ships big enough. That works, well enough, with speeds that low. But it really doesn't work, if you're trying to cross stellar distances with a rocket drive. That's because the mass ratio problem gets progressively worse, the faster you go. And with distances like that, you have to go very fast, or you'll spend . . . Oh, with chemical fuels, it would take thousands of years just to reach Alpha Centauri—and you'd need a fuel tank about the size of the Moon. Nuclear drives are better, but not that much better."

  "What you're saying, in short," Helen came in, "is that a reactionless drive is the equivalent of using sails to cross the ocean. However the Bemmie system worked, they were able to use some sort of energy that they didn't need to carry with them."

  "Right. Or, at least, carry just enough fuel to keep whatever the engines were running. But they wouldn't be blowing most of the fuel out the back end. Their drive would still be slow—meaning sublight speeds, even if it was much faster than rockets. But not so slow or with such handicaps that it couldn't be done at all."

  He waved a hand, stifling A.J. "Yeah, yeah, I know. Bussard ramjets. But that's just an engineer's daydream, so far as anyone knows. Obviously, the Bemmies never took that route. Why bother, when you have a drive that detours the whole fuel problem altogether?"

  Joe had been thinking about it further, even while he talked. With the earlier dream of an FTL drive so rudely shattered by A.J.'s cold logic, a number of other things about the model of the Bemmie spacecraft they'd found in the Vault were starting to make sense.

  "I'm willing to bet it wasn't even that fast a drive," he mused. "I hate to say it, but now that I look on that model in the cold light of day, that almost flying-saucer design makes a lot of sense. They spun it, I'll betcha. Because they needed centrifugal force to substitute for gravity just as much as we do."

  A.J.'s eyed widened. Unfortunately, there had been no scale provided—that humans could read, anyway—to give any sense of how big the ship modeled actually was. "That big?"

  "Why not? Sure, with that modified tuna can design it'd outmass Nike by an order of magnitude. At least. Even assuming it was no bigger—an assumption we have no reason to make. And so what? With a reactionless drive, mass doesn't really mean that much, if you've got the time to make the trip in the first place. And there are a lot of advantages to a big ship, especially for long trips."

  He considered the problem, for a few seconds. "I'm also willing to bet that, leaving the issue of propulsion aside, their drive worked more or less along the same principles as our ion drives, in other respects. A very low acceleration—much too low to provide artificial gravity itself, which is why you have to spin the ship—but one you can sustain for a long time. So you could cross interstellar distances. But it'd take an awfully long time. Maybe even require generation ships, although . . . "

  A.J. shook his head. "Not if you can keep the acceleration constant. Still, you're talking trips measured in years, maybe decades— and that's just to cross between nearby stars."

  "Yep. Alas. Bye-bye that daydream."

  Madeline sat up straight. "Put together a short summary of all that, would you? Or, rather—Joe, you do it. A.J. has to concentrate on solving Rich's little problem. If he can."

  The imaging specialist sat up even straighter. "If I can? Ha! O ye of little faith, watch—" Madeline smiled at Helen. "See how I cheered him up?"

  The next morning, A.J. was scrutinizing Rich Skibow's "little problem."

  It wasn't all that little, actually, speaking physically.

  "You're sure? That'd be one hell of a big book. Using the term loosely."

  "Well, Jane and I aren't sure. But, yes, we're almost positive that has to be the Rosetta Stone. More precisely, the key to getting at any of them." He waved a hand, backward. "The one I thought was a Rosetta Stone when we first entered turns out to be just one of dozens like it. They've all got that multiple-script feature, but Jane and I think this thing is the key to unlocking the puzzle. Insofar as it can be unlocked at all, anyway. Since none of these has a script in a language we know—obviously—they aren't really the same thing as a Rosetta Stone. But it's as close as we'll ever come. Just having a number of languages for comparison will help us a lot—especially because I'm pretty sure this thing is what amounts to a superdictionary."

  After Rich finished, A.J. went back to scrutinizing the object. The item in question rested in a case that, from the looks of it, had at one time also been sealed in inert gases. Here, though, the passage of millions of years had taken its toll. However it had happened, one corner of the case had cracked. The crack wasn't much, but it was enough for whatever gas had filled the case to have leaked out long since.

  Of course, the case itself had still been in the inert atmosphere that had filled the entire Vault. But the simple fact that the Bemmies had taken the trouble to seal it separately indicated how critical they'd apparently considered the item it contained.

  The item itself was a little more than a third of a meter across, composed apparently of mostly manufactured diamond plated over a substrate of their composite with maybe platinum as a coating, since it was shiny like a mirror. A circular mirror with a polychromatic reflective surface; A.J. thought it looked rather like a giant DVD surfaced with faceted crystals.

  After studying the thing carefully for a few minutes, A.J. turned back to Rich. "Okay, I'm pretty sure your guess is right. If so, what we have here is something like a digital data disc. They took advantage of refractive tricks to allow them several layers to write on with different wavelengths. They're probably using a binary encoding— that's at least reasonable—but their coding table I'm going to have to figure out . . . hmmm . . . "

  He looked back at the item he'd tentatively labeled a data disc. "Looks like it's all here, though. The problem is that we haven't got a reader for it. And whatever readers they might have had—which we haven't found yet, and may never—they wouldn't work by now, anyway. Bemmie super construction notwithstanding, nothing that relies in any way on moving parts is still going to be functional after sixty-five million years. At least, nothing on that level of precision; the door mechanism worked, but that's several orders of magnitude cruder and works on what amounts to brute force. So the question becomes, are we smart enough to build a gadget that will substitute?"

  "Are you?"

  A.J. frowned. "Of course I'm smart enough. Well. I think. But here I don't have the stuff I'd need. I need emitters in just the right wavelengths—tunable, mind you—I need control circuitry, I need a way to spin the sucker and get the timing right, yada yada yada. And you can bet I'll have to experiment with it a lot, because we're bound to stumble across some obvious, critical, need-to-know information that we don't know, like: 'well, of course the files are all encoded with three primes.' If I was on Earth I could whip together some kind of test-bed, but here I'd have to cannibalize something, especially for the moving parts."

  "So you can't do it?" Jane said in a disappointed tone. She was following the discussion from the Nike, using relays established by the bread crumbs that A.J. now had scattered throughout the Vault.

  "Stop jumping on me! I know you're excited about this, both of you, but hell, you're asking me . . . Well, it'd be like going back to the 1970s and handing someone a DVD. Even if you told them about it, they might not have the gadgets to read it with, and they'd sure need to think about it. Especially if you left out something about how, oh, MPEG encoding worked. I have to assume these guys gave me all the critical info, but they could have dropped the ball anywhere along the line." A.J. frowned. "I'll think about it for a bit."

  He left the inner area and went back, musing on the problem. He found Helen carefully going over the scaly hide of a velociraptor of some
kind. A Deinonychus, he thought, although he wasn't sure.

  "What's up, sweetheart?"

  She jumped. "Don't startle me like that." She pointed to the raptor mummy. "Look close."

  He did so, studying the hide in the area she indicated with his usual eye to detail. "Oh, those little depressed markings?"

  "Yes. I think those are marks of some kind of parasite—a louse or something. I'm hoping I can find one intact, or at least some pieces left in the scales. The problem with these being preserved is that someone cleaned them up which eliminates all that kind of thing."

  "Listen to you! You're complaining about someone having left you perfectly preserved dinosaurs to work on!"

  Helen laughed and hugged him suddenly. The spacesuits eliminated the sensuousness of the embrace, but A.J. still found the gesture heartwarming.

  "Yeah, pretty ungrateful, aren't I?" She looked back at the dinosaur. "And that's what brought us together, too."

  He grinned. "I remember. I came out there to give you a look at your dinosaurs through the rock, and then you guys almost killed me for faking the scan."

  "Well, you can't blame us. You were showing off. Mr. 'Look, I have a halo!'"

  "Okay, I'm no angel, but—"

  He froze.

  Chapter 52

  After a while, he became aware that Helen was poking him.

  "A.J.? Answer me! You just cut off there and—"

  He made a sharp gesture with his hand and she went quiet; he was glad she could recognize the signs. The idea was there and it was a hell of an idea. It seemed like it could work . . .

  "It would work," he muttered to himself, "if I can pull it off. Not easy . . . cross talk . . . network topology . . . emitters, yeah, but how much will I need? Power supply for the whole thing, higher constant use than design . . . but with Nike to help . . ."

  He suddenly gave a whoop, picked Helen up and spun her around. In Mars' gravity, this caused them to spin out of control— fortunately for continued harmony, not into the raptor mummy— and over in what might have been an embarrassing position if they hadn't both been wearing spacesuits.

  "Yes! Thank you, thank you, you are gorgeous and brilliant and just plain always say the right thing at the right time!"

  She was laughing. "You nut. What is this all about?"

  A.J. rose, giving a hand to Helen at the same time. "You and old fangface there and a few reminiscences. I can do it, Helen!"

  He felt the grin just about splitting his face from ear to ear. "I know how to decode that damn disc! Screw Earth, I don't even need to go back to Nike, I just need her bandwidth and some design work that we can do right here!"

  "Joe! Hey, Joe, you and me have got some detective work to do." As A.J. and the Tayler Corporation had programmed, the smart suit recognized when the wearer spoke a name in such a way as to indicate "connect me with this person" and opened an appropriate channel. Not waiting for Joe's response, A.J. continued marshaling his resources. "Yo, Jackie!"

  "Ms. Secord is sleeping at the moment," came an automated reply. "If this is an emergency—"

  "Not really, no. Is Dr. Gupta there?"

  The unmistakable sonorous voice answered in a moment. "Yes, I am here. A.J.? What is it that you need? No emergency, I hope?"

  "No, just a hell of a job. I'm going to need a lot of the processing capacity of Nike dedicated to running an ad-hoc network with, um. . . a few billion individual nodes."

  To his credit, Dr. Gupta's reaction was only slightly delayed. "That is indeed a formidable task, especially if as I suspect you will be passing data through the network for analysis. You will have the protocols for us and the specifications on what functions you will need? And when exactly this will be needed?"

  "Oh, you can bet on my having the exact code for you. When? Ah . . . let's say the day after tomorrow. I've got some engineering work to do down here with Joe. I just want you guys to make sure that I'll have the system clear for me then."

  "It shall be done, assuming that the captain approves. What is the reason for this interesting task?"

  "Getting that disc Rich found a couple of days ago to spill its guts so Rich and Jane can really go to town."

  "Ah. In that case I cannot see any reason why you would not have access to virtually all of our processing capacity at the time you specify."

  "Didn't think so. A.J. out."

  He started for the exit. "Joe! You coming?"

  "Yeah, yeah, I'm coming. Remember that Mr. Gimpy is slower than you are. Mind telling me exactly what it is we have to tinker together out of duct tape and WD-40?"

  "Sure, won't take a minute."

  Joe had a lot of questions and comments that changed the design somewhat. But by the time they got back to Thoat and the tools they needed, the basic design was already visible in their HUDs.

  "Not too hard. Yeah, A.J., we can do that in a day."

  It actually took ten hours and seventeen minutes.

  A.J. carefully unpacked the device from the container he'd used to carry it all the way from the surface to the innermost sanctum of the Vault. He placed it on the polished, flat surface that was clearly a desk or table and, despite millions of years of waiting, seemed to be just as solid as the day it was made.

  "It's showtime."

  Rich looked at the thing in bemusement. "Just what is it? It looks like something you and Joe dreamed up with a box of metal Tinkertoys and a few electronic lab kits."

  The object was about half a meter across, a square framework of slender metal tubes or thick wires with a carefully arranged clamping device in the center, and round black cases at the corners. Wires trailed from it to connect to a fuel cell.

  "That," A.J. said, as he gingerly extracted the precious disc from its case, "is the support and supply framework for the device that's going to read this old book-on-disc for you."

  "Ah . . . there's no reader or anything on that framework," Rich pointed out, as A.J. clamped the disc carefully into the holder. "And that clamp won't let the disc spin, which seems almost certain to be the way it was read."

  "There will be, and it doesn't have to spin," A.J. replied confidently. "Just watch."

  And with that, he took the entire bag of Fairy Dust he'd brought with him and upended it onto the framework, disc, and all.

  In that large a mass, the dust-sized, motile sensor motes looked more like liquid graphite than dust, but unlike any liquid, the mass stopped flowing long before it could spill off the table. Eerily, the stuff began to move upward, spreading first along all the structural supports of the framework, and then filling in the gaps, and covering the entire surface of the alien disc.

  "You know, I'm not sure anyone's ever used this many smart-dust motes before in one application. Hell, Dust-Storm freaked when I told them before we left how many of my custom motes I was going to need to take with me. They'd never done a single run that large before. But I sure as hell wasn't getting caught short way out here, and now I'm real, real glad I didn't. I'm still offloading a lot of the housekeeping and data analysis tasks off to Nike, except for the ones that just have to be done local."

  Rich had backed up a bit. He clearly found the oily, alien flowing motion unnerving.

  "Relax, Rich. I know it looks funky, but I'm pretty sure it's not going to become an alien intellect and suck out all our brains."

  "Ha, ha." Rich came closer. "So how are you getting around the need to spin the thing?"

  "I'm scanning it in various wavelengths as indicated, and if I can manage to get down to the resolution we need—that's the tricky part, and why I'm using a lot of capacity—we can basically replicate each layer of the disc and emulate spinning it by reading the data directly, if you see what I mean."

  Rich's eyebrows rose inside his helmet. "Yes . . . yes, I think I do see. But do you really need so many to just read it?"