Boundary 2: Threshold (13 page)

"All
right
, all right, I'm awake," Nicholas Glendale grumbled at the insistently buzzing door as he dragged himself to consciousness. Usually he could wake up immediately, but whoever this midnight caller was, they'd caught him on one of the deep-sleep cycles.

He glanced at the clock as he rose from the bed. No, it was past midnight. It was 2:00 A.M., Phobos time.
This had better be worth it,
he thought and palmed the door open.

"I'm terribly sorry, Dr. Glendale," Madeline said, barely before the door finished opening, "But Joe insisted he talk to you right away."

It was a slight shock to see that Joe Buckley was, in fact, right there with her, along with Reynolds Jones, the tall, prissy-looking materials expert. "Well, I admit I prefer a bit of warning. If it's that important or exciting, though, I would hate to put a crimp in our relations over a few hours of desperately needed rest."

"Sorry, Nick," Joe said. The apology sounded genuine but rushed. "Take your time waking up."

That did deserve at least a slight smile, which Nicholas managed. "Why don't you take our late-night visitors to my office, and I will join you in fifteen minutes. Madeline, you don't have to stay."

"Actually, I think she should," Joe said firmly.

"I'll get them to the office and have Joe make us all some coffee," Maddie said.

As the door closed, Nicholas could hear the conversation continuing, "Only if you have the right beans . . ."

He took a quick shower, which was one of the luxuries really only possible with artificial gravity. He had experienced extended weightlessness, and while there were a number of attractive features of that condition, the methods needed to maintain proper hygiene were not one of them.

The shower cleared his head, setting off the usual cycle of waking-up routines. By the time he set out a few minutes later, dressed in comfortable clothing and with hair damp but presentable, he felt almost human.

The scent of brewed coffee greeted him at the office door. "I see you found my beans satisfactory, Joe?"

The gourmet engineer grinned. "I found your stash."

Glendale couldn't quite restrain a slight wince. "Were it anyone else, Joe, I would be a bit annoyed. But I think you can truly appreciate Jamaica Blue."

"I know
I
do, Nicholas," Maddie said appreciatively. He noted that Reynolds Jones was apparently drinking tea rather than coffee.

He took his own cup—pure black, no sugar—and sipped at it. "My God, even better than I make it."

"Well, I
did
design the machine myself," Joe said, bowing modestly, "to deal with the problem of good brewing in differing pressures and so on, so I probably just have a better touch with it. And with these beans to work with, well, you just can't go wrong." He sat down, having finished cleaning off the critical components of the coffee machine, and took his own first sip.

"Now that we're settled and we're using up—at a conservative estimate—about two hundred dollars' worth of coffee, taking into account the rather extravagant shipping expenses, would you like to tell me what this is all about?"

"Thought you'd never ask, Nick," Joe said. "It's about the ship on Ceres. I know what it is. And between me, A.J., and Reynolds, I think we can make it work again."

Nicholas found that he had stopped with his cup halfway to his lips, staring at Joe. "You're joking. That vessel is sixty-five million years old."

Reynolds shook his head. "Yes, yes, of course it is, Nick, but we can do this. It's really an
amazing
combination of serendipitous events, absolutely amazing."

Nicholas blinked. "All right, let's start from the beginning. What
is
that ship? From what A.J. said, it had what appeared to be some kind of fuel tanks, but ridiculously small for any reasonable range, and the places it connected to didn't look anything like rocket exhausts or ion emitters. But the layout of the interior—inhabitable areas, storage spaces, power—all pointed to something that had a pretty long range. A.J. said that he would have thought it was maybe some kind of trailer, a cargo/passenger pod or something of that nature, except that something kept nagging at him, especially one area where a lot of the controls went to which seemed to have a lot of that superconductor material."

"And A.J. was damn right to have that nagging at him," said Joe. "That's a dusty-plasma-sail ship."

"A . . . 
what
?" Nicholas glanced at Maddie and saw that she was as much in the dark as he was. "I've heard of solar sails, and I think of something like a magnetosail, but—"

"A dusty plasma sail combines the ideas of solar sails with magnetosails and gets most of the advantages of both," Joe answered. "A researcher at
NASA
—Dr. Robert Sheldon—first came up with the idea. Basically, a properly ionized plasma can be used to guide and expand, or inflate, a core magnetic field outward, and the plasma can be pretty darn thin—basically the equivalent of hard vacuum on Earth—and still achieve the results. The field confines the plasma and acts as a sail, catching the solar wind, without needing any physical structures like some of the magnetic-sail designs—the force is exerted on the ship through the magnetic field. Then Sheldon noted that if you were to add dust with the right characteristics, the dust, too, could be confined by the ionized plasma and magnetic fields."

"That increases the mass of the whole system," Nicholas pointed out. "I understand how the first part works—and it seems a quite elegant solution to the problem of needing multi-kilometer lengths of superconducting cable—but what's the point of the dust?"

Joe grinned. "Dust reflects sunlight. The solar wind pressure is puny, while sunlight pressure is a hell of a lot more powerful. If you can get just a few percent reflection or absorption, you increase the effective thrust many times. An even more important point is that this system is effectively constant thrust—you'll be accelerating just as fast at the orbit of Jupiter as you were here at the orbit of Earth."

"Now, wait, that doesn't make sense," Maddie said. "The sun's light, and I'd bet the solar wind, is a lot weaker out there. It
can't
be getting the same amount of thrust."

"You would be completely correct if you assumed the sail is a fixed size," Joe agreed. "But that's not the case. The sail will expand and contract in size depending on the magnetic conditions surrounding it, like a balloon rising higher and higher into the air and expanding as the pressure around it drops. The solar magnetic field decreases as you get farther away, until you hit the magnetopause somewhere out past Pluto. So as you get farther away, your sail just keeps getting bigger, catching a proportionately larger amount of sunlight and solar wind, essentially maintaining a constant thrust. Yeah, at some point you have to dump more gas and dust into the mix, but overall it turns out to be reasonably constant thrust."

Madeline looked impressed. Nicholas certainly was. "What sort of thrust are we talking about?"

"Nothing immense in terms of acceleration. You wouldn't feel it, not unless you're awfully sensitive and looking for it, so to speak. But
any
constant-thrust vehicle will kick the crap out of any limited-delta-V system over the long haul, and I'd bet that this ship can at least equal
Odin
's mass-beam approach—and it doesn't need some linear accelerator at the other end being constantly fed. The sun's doing all the work."

"Nice." Madeline's expression showed she was thinking about the implications of the design. "Another nice thing about it, I imagine, is that the drive system itself would serve as a magnetic shield. Remember how much engineering had to go into
Nike
in order to make it safe, and how we had to design special shields for the Mars rovers and shelters?"

Nicholas nodded. That was another area where the Bemmius superconductor was making things much easier. Before, they'd had to maintain liquid nitrogen around sets of isolated magnets, which then generated a magnetic field surrounding the habitable areas—especially a pain in the original
Nike
habitat-ring design. Now they could just put the superconductor in appropriate configurations and charge up the field, removing a huge, huge parasitic mass cost from the system. "I certainly do. So this dusty-plasma drive protects the ship from cosmic radiation?"

"And from some other sorts, too," Joe confirmed.

Nicholas frowned, musing. "With all these benefits, why haven't we ever built one?"

Joe laughed. "Kind of my reaction, really. But, first off, the theory never got a lot of play. Why, I don't know, but even though Dr. Sheldon did several papers on the basic concept and even did some simple but effective demonstrations in the lab, no one was ever really willing to put the money into a test. That might partly be because in order to really test it you needed something to go out past the Earth's magnetosphere, which was a major operation to contemplate back in the beginning of the century. It was pretty easy, relatively speaking, to get something up in low Earth orbit, but tens of thousands of miles up was a whole different ballgame. And controlling the sail was another sort of sticky point. There are ways you might do it, but they were never clearly laid out in the initial research. Also, it really
does
require superconducting magnets to work, and those have always been a pain. What happens if your liquid nitrogen pops a leak and you're out by Jupiter? And there is the eternal question of 'How do I stop this crazy thing?' " He looked at Nicholas with a raised eyebrow.

"And how
do
I stop the crazy thing?" Nicholas asked, obliging him.

"Very carefully," Joe said with a smile. "Seriously, it's a bit of an issue. There are a couple of ways. With just the ship itself, basically you have to be willing to stop accelerating before you reach too high a speed—basically solar escape velocity—and then tack such that you're using the pressure to oppose part of your own vector. In a way it's like regular sailing, but you don't have a water surface to play with. You can also swing around a planet large enough to permit a good-sized Oberth maneuver, but you'll want some rockets for that, because the major slingshot effect comes from dumping mass at an advantageous moment. Then you take a course which opposes your current orbit to enough of an extent that you effectively slow down. It can get pretty tricky, actually, because you'd have to choose your course such that you'd end up at an appropriate planet when you wanted to slow down,
and
—here's the really tricky part—you have to be ready to deal with your sail doing weird things to you when you get close to the other planet."

"Why?"

"Because a lot of planets, like Earth and especially Jupiter, have their own magnetic fields, and when you go through their magnetopause it'll be like suddenly diving underwater. Your fifty-kilometer sail will suddenly squeeze down to five kilometers, or something like that. All of a sudden you've got a lot less thrust—and you might start picking up small but noticeable thrusts from other directions if there's a lot of charged particles being guided by the planetary field. And of course as a magnetic sail, cutting through another magnetic field is going to have an effect on you as well. Even very small thrusts will have a major effect on whether you actually arrive at your destination or wind up a few tens of thousands of kilometers off.

"That's if you're a singleton ship. If you're already spacegoing, you can set up a bunch of stations that are sort of like the
Odin
's mass-drivers except they might fire high-energy particles or light at your sail, slowing you down. You might also use these ships sort of like one-way shipping containers, and when they got to the end destination you might send them back in using a mass-beam or just a long-time ion drive that will get them home eventually."

Nicholas nodded. "Interesting. Combining the problems of a sailing ship and a riverboat on a current. But eliminating the problem of carrying a gigantic sail or many tons of fuel." That struck another chord. "You do need to supply the gas and dust for your sail, and a thirty-kilometer sphere is an awfully large volume. How much gas and dust are you going to need?"

"A few hundred kilograms. A hell of a lot less than you'd need for an even vaguely plausible solar sail, let me tell you."

"I see." He turned to Reynolds, who had just finished his tea. "What's your role here?"

"Mine? Well, material sciences, of course. Reconstructing the ship will require just tons of work making sure we get the materials correct. We think that some of the components are designed to help guide and perhaps even shape the magnetic fields—you know, tacking back and forth, that sort of thing." Reynolds gave an expansive gesture that somehow conveyed the impression of billowing sails. "So much easier to sail when you have rigging, if you know what I mean.

"Now, Bemmie did all that marvelous work with materials that has frustrated A.J. so much when trying to scan through it both by finding
just
the right combination of elements
and
by tremendously careful work on the microstructural end, to the point that it's really quite a job to figure out which characteristics of the material are coming from its composition and which ones are from the unique microstructure. This is still an expanding field, you know, and it's just not something that you can hand to a computer. Even with someone as good as A.J. doing the data-collection work, you need a real expert to make the judgment calls. And, of course, material design and synthesis are my major specialities, Dr. Glendale. So naturally I'm going."

"Going?" He looked up. "You want to
go
there?"

Joe nodded. "I can't supervise this at a distance, really. I have to see it. And A.J. can't do it all himself."

"What's A.J. got to do with reconstructing a ship?" Nicholas found the question coming out more sharply than he'd intended. If Joe left, Madeline would almost certainly want to go, and he really didn't want her just leaving; nor, however, did he want to keep her there against her will. "I'm sorry. Obviously he's the one providing you with data, but—"