I wasn't so sure. Perhaps Darryl was right and it was all just money to her, but maybe she had fixated on the truth nano as though, in all its ramifications, it might hold the key to her own tumult. The death of her father explained a lot about why she'd picked me, of all PIs, and why she'd been so generous with her money.
But now wasn't the time to debate it. “Darryl, remember the nano."
“But it's true. I—"
“Shut up. You're feeling guilty and confused, and the nano might not know the difference."
“Well, one thing I'm sure of is that I'm not making the antidote. Letting that get out is a risk I won't take."
I had no idea how big a risk it actually was, but he didn't clutch his chest and drop dead, so it didn't matter: it was too much for him, and that was that.
* * * *
There were, of course, myriad practical matters. First, Darryl had to learn that being a basically honest person wasn't enough. Even on the most mundane subjects, he had to make sure he thought very carefully before speaking. I suggested he write everything out in advance. That way, he could play with the wording to his heart's content without doing anything the nano might see as lying.
Then we had to decide what to do with Megan's body. There really was only one choice, so we buried her among the trees. If we called in the authorities, Darryl would either die under questioning or be forced to reveal the nano, and then everything would have been in vain. Afterward, he stood by the river: quiet, pensive. Then with a sidearm gesture, he threw something in that skipped like a stone, followed by another, and another.
The next day, I headed for home. The trip out was as tough as the one in, but lonelier. It sounds odd to miss a woman who might have killed me, but I'll always wonder whether she realized we were kindred spirits, or knew in her final moments that in losing herself, she saved me.
Back home, I used her money to pay off Trevor's nanos. Then, as soon as the lease was up, I moved a cot into my office. Not exactly high-class, but at least I'm solvent, and it's another reason I'll always think kindly of Megan.
Someday, when my divorce is final and I get my savings unfrozen, I'll pay off the rest of my nanos. Then maybe I'll actually make some of that bad art. Or maybe it will be good art and I'll become famous. More likely, by that time the world will again be coming down around everyone's ears. Because one thing I'm sure of is that ideas can't be suppressed forever—and if it's possible to develop a nano that reads moods, it's probably possible to invent one that creates them. Such as LOVE ME or LET ME MANAGE YOUR INVESTMENTS or VOTE FOR X.
If I see it coming, I know where I'm going. Darryl could use a mining partner. And if he tells me he knows of rich diggings, I know I can trust him to a degree unique in the history of mining.
Every few months, he puts a carefully worded classified ad in Goldbug magazine so that when the time comes, I'm sure I can find him.
Copyright © 2006 Richard A. Lovett
* * *
SCIENCE FACT: THE RIGHT STUFF: MATERIALS FOR AEROSPACE AND BEYOND
by Kyle Kirkland
In the 2000 movie Battlefield Earth, aliens have invaded the Earth in order to mine its metals, particularly the “most valuable” metal, gold. The overwhelmed and technologically inferior humans are reduced to living in primitive societies, continually hiding from the aliens, who use Earth captives as slave labor.
A lot of people hate this movie. To me it's entertaining, despite its flaws—the aliens remind me too much of 1930s gangsters, but I can overlook that. One thing in the movie really bothers me, though: the aliens’ motivation for invading the Earth. Metal? You mean a civilization that can build an interstellar transporter still relies on a metal-based industry and economy?
I doubt it. Even we of early twenty-first-century Earth—who still putter around in pollution-belching, accident-prone cars—are being weaned from our dependence on metal. The Bronze Age and Iron Age are long past. Swords and cannons are quaint antiques, and although steel continues to make the frames that hold up skyscrapers and the rails and trains that move cargo, the importance of metal is diminishing. SpaceShipOne, the ship built by Scaled Composites which won the X PRIZE in October 2004 by achieving an altitude of 100 kilometers (62 miles) twice within two weeks, was made out of graphite (a form of carbon) and epoxy.
New materials are needed, and not just because of a scarcity of old ones. Materials for any engineering design must have specific properties, and without the right material, the design stays on the drawing board. Engineers often dream up ingenious devices that can only be built with “unobtainium” or “no-such-thingium.” For instance, the development of the jet engine lagged behind the piston engine by decades, but not because jets were unknown—engineers knew about them all along. Jet airplanes first appeared in the 1940s because that's when people could make parts, particularly the turbine blades, that didn't melt under the conditions in which a jet engine operates.
Some of the biggest dreamers have always been people who think about flight and space travel. NASA's space shuttle contains advanced materials because it's the only way to get a machine to and from orbit without roasting. The thermal tiles (made from silica), now famous for the gap filler incident in Discovery's 2005 mission, must endure a temperature of thousands of degrees during the shuttle's reentry. And since NASA wants to replace the aging shuttle fleet, now more than ever it needs The Right Stuff—the best materials for the job.
* * * *
Plastic Planes and Spaceships
Suppose you walk into your local car dealership with a request. “I want a car,” you say politely to the salesman, “that never rusts even if I park it at the beach in the summer or drive all winter on salted roads. The car must be able to withstand a crash at 70 miles per hour, and weigh less than a thousand pounds so I can get great gas mileage. And it can't cost much because I'm poor."
If you get anything but a strange look, you're doing better than I did.
Perhaps one day the car I was asking for will be built with metal, but more likely it'll need other materials. Metal has its uses—jet engines still require “superalloys” such as nickel-based alloys, for example—but metal's got problems, too. It's strong but dense—and in the space and aviation business, mass is a killer expense. Carrying around extra weight means you burn a lot of extra fuel. Even worse, increasing the amount of fuel on a space launch adds more mass to the ship, which therefore requires yet more fuel to achieve escape or orbit velocity.
Metal's problems don't end there. Metal can be difficult to shape, it often corrodes, and it suffers fatigue (which is a weakening of the material due to periodic stress).
Composite materials use combinations of materials, and with the right mix you can get just about any property you want. They're not a new idea: thousands of years ago, Egyptians were making bricks from mud and straw because the combination was a better structural material than mud alone.
Today, composites are made of a stiff fibrous material glued with another material, called the matrix, which forms a structural web holding everything together. Common matrix materials are ceramics, polymers (long chains of molecules) such as epoxy, or sometimes metal; fibers are commonly made from glass, boron, or carbon.
Some people use the word “plastic"—technically, a material made from polymers—to describe just about any material that isn't metal or ceramic, and the word is sometimes used with little affection. Recently the American Film Institute composed a list of memorable movie quotes, and number 42 was in 1967's TheGraduate, where Dustin Hoffman receives a one-word piece of advice on the best career opportunity: “Plastics.” I'm not sure why that line is so memorable; does the word conjure up a sense of irony? Useful yet insubstantial?
For some people, perhaps it does. As materials scientist J.E. Gordon recalled in his book, TheScienceofStructuresandMaterials, in the years after World War II some of the engineers who wanted to design nonmetal components for airplanes had a great deal of trouble. No airplane could fly at the
Royal Aircraft Establishment at Farnborough, England, without approval of the Structures Department, but because of their bias for metal, any plastic structure had to be 50% stronger than a comparable metal component. Not equally strong, but 1.5 times stronger.
Plenty of other examples exist. I recall a friend who owned one of those old mid-twentieth-century cars, a two-ton metal monster. One time a driver smashed into the rear bumper of my friend's car and damaged her car's front end pretty good. My friend's car was barely scratched—he spat on the bumper, wiped it clean with a rag, and it was good as new. He looked at the other car and said, “They don't make them like they used to."
It's true. The fiberglass of modern car bodies is lightweight but can be brittle. But another reason modern cars damage easily is because they are designed to have crumple zones to absorb the energy of impact, unlike the indestructible, solid steel cars of the good old days. If my friend had ever been going fast and hit something in that old car, the steel shell would have rung like a bell—and he would have been the clapper. Even wearing a seatbelt, he'd have suffered serious injury. (No air bags in that good-old-days car.)
The right material for the job is sometimes metal, but sometimes—and increasingly often—it isn't. A carbon composite enabled the super-light Voyager airplane (which was made entirely of composite materials) to circle the world non-stop in 1986. Try that with lead or steel.
Unfortunately the aerospace industry frequently seems to have a fixation with metal. Not lead or steel, of course, but rather aluminum and its alloys. Fine materials, to be sure: aluminum is nearly three times less dense than steel, but is strong and doesn't corrode as easily. Another important feature in flight materials is stiffness: most of the time you want to avoid bending or twisting, and aluminum handles torsion fairly well.
Aluminum's combination of stiffness and light weight makes it a good choice for many aerospace applications. What's more, metals are usually isotropic—they have the same properties in any direction—so it's easy for engineers to design the structure. Composites are typically expensive (though aluminum isn't cheap either), and they're generally not as simple as an isotropic chunk of metal.
But it's this variety and range that make composites the only choice in a growing number of applications. Composites can deliver good performance at an ultralight weight, and although fabrication can be complicated, putting together the parts doesn't require as many rivets or fasteners. Believe it or not, that alone is important.
One of the first aircraft to use composites extensively in the structure and wing was the AV-8B Harrier jet in the 1980s, in which about a quarter of the weight was from composites. One of the latest fighter jets, the F-22 Raptor, is about a third composite in its structural weight.
In contrast, much of the commercial aviation fleet is still aluminum. The big Boeings and Airbuses of today make use of composites, but the structures are mostly metal. Half of the weight of the Boeing 777, for example, is from aluminum.
Why is the military using “plastic” a lot more than the big passenger jets, even though the military isn't known for making weak, wimpy planes? The reason is the same as before—the right material for the right job—but the right material is often based on economics and logistics as much as engineering.
Composites tend to be lighter than aluminum alloys, but are more costly and require more maintenance. (That's not true in all cases, but it generally holds.) Despite the fact that airlines haven't been making any money lately, their reason for existence is to make a profit. In the past, their economic plan has been to pay a little more for fuel, due to heavier planes, but save on initial cost and maintenance.
The military has other goals. A fighter pilot's life may depend on getting an extra burst of speed from his plane at a crucial moment, and the last thing he wants is to tote around unnecessary weight. Newton's second law: acceleration equals force divided by mass.
How about NASA's space shuttle? You might think that the orbiter is mostly made of some kind of fabulously advanced composite material. If so, you'd be wrong.
The structure of the orbiter has nine major sections: the forward fuselage, wings, mid-fuselage, payload bay doors, aft fuselage, forward reaction control system, vertical tail, body flap, and control system pods. The majority of these structures are plain old aluminum alloy.
The forward fuselage, for example, is made of over 2,000 aluminum alloy panels, frames, and bulkheads. The wings are aluminum alloy, with a corrugated spar web and truss-type ribs. Most of the other sections are also aluminum. Rivets and bolts hold everything together. The space shuttle has advanced materials—the heat-resistant tiles, for instance—but by and large, it's metal. In an age of high-tech composites, the space shuttle is still mired for the most part in the metal age; that's like a nineteenth-century messenger who ignored the pony express and instead relied on a wallowing old ox.
Okay, so I know that isn't quite fair. Metal alloys containing aluminum, titanium, beryllium, nickel, or other elements can be just as high-tech as composites. But when you're fighting the ancient wisdom of the metal age, it's hard to play nice.
Even the commercial aviation industry is waking up. Boeing suddenly decided to welcome the twenty-first-century with the design of their newest ship: the 787 (formerly 7E7) Dreamliner. For the first time, the majority of the weight of a big passenger jet will be from “plastic."
It's a bold move—almost a bet-the-ranch type of move. Boeing has been in trouble lately because of gains made by their major competitor, Airbus. Boeing, known for its stable of passenger jets like the old reliable 737 and 747, along with the newer 767 and 777, is going composite with the 787. The structural weight of the 787 will be about 50% composite, 20% aluminum, 15% titanium, 10% steel, and 5% other materials. Compare that to the 777, which is 50% aluminum and 12% composite.
Boeing apparently thinks the time is right for composites. According to the pre-delivery sales figures, they seem to be correct. Boeing has already received hundreds of orders for the 787, making it one of their fastest-selling models of all time. Buyers seem to like the price: the 787 retails for 120 million dollars, less than what people had expected to pay.
It seems like a good buy. Boeing engineers say that the 787 will be 20% more fuel-efficient than other, same-capacity passenger jets. Part of this greater efficiency is due to engine and aerodynamics advances, but part of the reason for the better gas mileage is due to the lighter weight—the 787 will be about 30,000-40,000 pounds lighter than Airbus's A330-200.
Composites have other advantages. Since the material doesn't corrode as much as metal, the 787's cabin can be pressurized and humidified to a more comfortable degree. (To me, having suffered from sinus attacks during flights, this is a huge plus.) The superior strength of the material will let Boeing install bigger windows—another big plus for an inveterate window-gazer like me. And with composites, Boeing can manufacture the plane with bigger, fewer parts, saving time and effort. One section of a metal fuselage typically needs 1,500 aluminum sheets fastened with about 50,000 rivets, while the composite material needs only about a fifth as many fasteners.
Boeing engineers have decided the main composite material will be made of graphite with a matrix of toughened epoxy—rather like SpaceShipOne. The wings will also have titanium-graphite composites. The company has scheduled the 787's maiden flight for 2007.
The design stunned Airbus, Boeing's competitor. After initially decrying the design as a space-age fantasy, Airbus is now awash in murmurs about making a similar aircraft (and may have already made an announcement, one way or another, by the time you read this). That would be the highest series of compliments a competitor can pay: first deny, then imitate.
NASA has a similar decision coming up as they design and build a replacement for the space shuttle. Perhaps they should follow Boeing's lead, rather than making another golden calf.
Don't get me wrong. Like many technogeeks, I have a fondness for the space shuttle. Yet in my opinion, the space shu
ttle never really fulfilled its goal of making space launches relatively affordable.
Would composites do a better job than aluminum? NASA may be gun-shy. Lockheed's X-33—which in the 1990s was deemed a prototype of the shuttle's successor—had a big problem in 1999 with cracks in some giant fuel tanks, which were made out of composite materials. Engineers decided to replace the composites with—you guessed it—aluminum. Didn't matter, since the program was axed a few years later.
There's no doubt that composites can be temperamental. And with every new and risky design, the first time something goes wrong there's always someone to say, “Told you so."
So you have to be careful. And it seems to me that many people today are more interested in propulsion methods than new materials. It makes for impressive results: the X-43A, for instance, broke jet speed records in November 2004 when it reached Mach 10 (about 12,000 kilometers/hr—7,000 mph) using a scramjet engine. A scramjet is simpler than a conventional jet engine because it doesn't use a compressor; normally the air to support fuel combustion needs to be compressed in order to provide enough oxygen in the chamber, but a scramjet allows air to enter at high velocity and ram itself into compression. (Obviously this only works when the craft is traveling at a high rate of speed.) A scramjet doesn't do anything for you in the vacuum of space, but it could be used as a first-stage propulsion unit for space launches.
Friction at Mach 10 caused temperatures to rise to well over 3,000°F, and the leading edges of the test craft had to be surfaced with carbon composites. But it's the speed of the ship that made the 11 o'clock news.
And yet, if the material you need to make a fully operational craft is unobtainium, it's not going to fly no matter how ingenious the blueprint or the prototype.
NASA has been pretty much all over the place when it comes to replacing the shuttle. These days they talk about something called the Crew Exploration Vehicle (CEV), the specifications of which seem to be influenced by President George W. Bush's goal of manned missions to the Moon and, later, to Mars. NASA wants to retire the shuttles by 2010 and have an operational CEV shortly thereafter.
Analog SFF, September 2006 Page 7
