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VEHICLES FOR FUTURE WARS

Long before the first ram-tipped bireme scuttled across the Aegean, special military vehicles were deciding the outcomes of warfare. If we can judge from the mosaics at Ur, the Mesopotamians drove four-horsepower chariots thundering into battle in 2500 B.C.; and bas-reliefs tell us that some Assyrian genius later refined the design so his rigs could be quickly disassembled for river crossings. In more recent times, some passing strange vehicles have been pressed into military service—Hannibal's alp-roving elephants and six hundred troop-toting Paris taxicabs being two prime examples. Still, people had seen elephants and taxis before; application, not design, was the surprise element. Today, military vehicle design itself is undergoing rapid change in almost all venues: land, sea, air, space. Tomorrow's war chariots are going to be mind-bogglers!

Well, how will military vehicles of the next century differ from today's? Many of the details are imponderable at the moment, but we can make some generalizations that should hold true for the future. And we can hazard specific guesses at the rest.

It's possible to list a few primary considerations for the design of a military vehicle without naming its specific functions. It should have higher performance than previous vehicles; it should be more dependable; and it should be more cost-effective. Those three criteria cover a hundred others including vulnerability, speed, firepower, maintenance, manufacturing, and even the use of critical materials. Any new design that doesn't trade off one of those criteria to meet others is likely to be very, very popular.

It may be fortunate irony for peace lovers that the most militarily advanced countries are those with the biggest problems in cost-effectiveness. Any nation that pours billions into a fleet of undersea missile ships must think twice before junking the whole system—tenders, training programs and all—for something radically different. That's one reason why the U.S. Navy, for example, hasn't already stuffed its latter-generation Polaris missiles (after Poseidon and Trident, what's next?) into the smaller, faster, more widely dispersed craft. A certain continuity is essential as these costly systems evolve; otherwise, costs escalate like mad.

Still, new systems do get developed, starting from tiny study contracts through feasibility demonstrations to parallel development programs. There is probably a hundred-knot Navy ACV (Air Cushion Vehicle) skating around somewhere with an old Polaris hidden in her guts, working out the details of a post-Trident weapon delivery system. Even if we don't already have one, chances are the Soviets do—and if we can prove that, we'll have one, all righty.

The mere concept of Polaris-packing ACVs says little about the system design, though. We can do better but, before taking rough cuts at specific new designs, it might be better to look at the power plants and materials that should be popular in the near future.


POWER PLANTS

 

Internal combustion engines may be with us for another generation, thanks to compact designs and new fuel mixtures. Still, the only reason why absurdly powerful Indianapolis cars don't use turbines now is that the turbine is outlawed by Indy officials: too good, too quiet, too dependable. In other words, the turbine doesn't promise as much drama, sound and fury—perfect reasons for a military vehicle designer to choose the turbine, since he doesn't want drama; he wants a clean mission.

Turbines can be smaller for a given output if they can operate at higher temperatures and higher RPM. Superalloy turbine buckets may be replaced by hyperalloys or cermets. Oiled bearings may be replaced by magnetic types. Automated manufacturing could bring the cost of a turbine power unit down so low that the unit could be replaced at every refueling. In short, it should be possible to design the power plant and fuel tanks as a unit to be mated to the vehicle in moments.

The weapons designer won't be slow to see that high-temperature turbines can lend themselves to MHD (magnetohydrodynamics) application. If a weapon laser needs vast quantities of electrical energy, and if that energy can be taken from a hot stream of ionized gas, then the turbine may become the power source for both the vehicle and its electrical weapons. Early MHD power plants were outrageously heavy, and required rocket propellants to obtain the necessary working temperatures. Yet there are ways to bootstrap a gas stream into conductive plasma, including previously stored electrical energy and seeding the gas stream with chemicals. If the vehicle needs a lot of electrical energy and operates in a chemically active medium—air will do handily—then a turbine or motor-driven impeller of some kind may be with us for a long time to come.

Chemically fueled rockets are made to order for MHD. If the vehicle is to operate in space, an MHD unit could be coupled to a rocket exhaust to power all necessary electrical systems. The problem with chemical rockets, as everybody knows, is their ferocious thirst. If a vehicle is to be very energetic for very long using chemical rockets, it will consist chiefly of propellant tanks. And it will require careful refueling, unless the idea is to junk the craft when its tanks are empty. Refueling with cryogenic propellant—liquid hydrogen and liquid fluorine are good bets from the stored-energy standpoint—tends to be complicated and slow. By the end of this century, rocket-turbine hybrids could be used for vehicles that flit from atmosphere to vacuum and back again. The turbine could use atmospheric oxidizer while the vehicle stores its own in liquid form for use in space. The hybrid makes sense because, when oxidizer is available in the atmosphere, the turbine can use it with reduced propellant expenditure. Besides, the turbine is very dependable and its support equipment relatively cheap.

Some cheap one-shot vehicles, designed to use minimum support facilities, can operate with power plants of simple manufacture. When their backs neared the wall in World War II, the Japanese turned to very simple techniques in producing their piloted "Baka" bomb. It was really a stubby twin-tailed glider, carried aloft by a bomber and released for a solid rocket-powered final dash onto our shipping. The Nazis didn't deliberately opt for suicide aircraft, but they managed something damned close to it with the Bachem "Natter." Bachem hazarded a design that could be produced in under 1,000 man-hours per copy, a manned, disposable flying shotgun featuring rocket ascent and parachute recovery. "Hazard" was the operative word—or maybe they started with factory seconds. On its first manned ascent, the Natter began to shed parts and eventually blended its pilot with the rest of the wreckage. Yet there was nothing wrong with the basic idea and a nation with low industrial capacity can be expected to gobble up similar cheapies in the future using simple, shortlife power plants.

There's reason to suspect that simple air-breathing jet engines such as the Schmidt pulsejet can also operate as ramjets by clever modifications to pulse vanes and duct inlet geometry. In this way, sophisticated design may permit a small have-not nation to produce air-breathing power plants to challenge those of her richer neighbors, in overall utility if not in fuel consumption. A pulsejet develops thrust at rest, and could boost a vehicle to high subsonic velocity where ramjets become efficient. Supersonic ramjets need careful attention to the region just ahead of the duct inlet, where a spike-like cowl produces exactly the right disturbance in the incoming air to make the ramjet efficient at a given speed. A variable-geometry spike greatly improves the efficiency of a ramjet over a wide range of airspeeds, from sonic to Mach five or so. We might even see pulse-ram-rocket tribrids using relatively few moving parts, propelling vehicles from rest at sea level into space and back.

For a nation where cost-effectiveness or material shortages overshadow all else, then, the simplicity of the pulse-ram-rocket could make it popular. A turbine-rocket hybrid would yield better fuel economy, though. The choice might well depend on manufacturing capability; and before you can complain that rockets absolutely demand exacting tolerances in manufacturing, think about strap-on solid rockets.

MHD is another possible power source as we develop more lightweight MHD hardware and learn to use megawatt quantities of electrical energy directly in power plants. An initial jolt from fuel cells or even a short-duration chemical rocket may be needed to start the MHD generator. Once in operation, the MHD unit could use a combination of electron beams and jet fuel to heat incoming air in a duct, and at that point the system could reduce its expenditure of tanked oxidizer. We might suspect that the MHD system would need a trickle of chemical, such as a potassium salt, to boost plasma conductivity especially when the MHD is idling. By the year 2050, MHD design may be so well developed that no chemical seeding of the hot gas would be necessary at all. This development could arise from magnetic pinch effects, or from new materials capable of withstanding very high temperatures for long periods while retaining dielectric properties.

It almost seems that an MHD power plant would be a perpetual motion machine, emplaced in an atmosphere-breathing vehicle that could cruise endlessly. But MHD is an energy-conversion system, converting heat to electricity as the conductive plasma (i.e., the hot gas stream) passes stationary magnets. The vehicle would need its own compact heat generator, perhaps even a closed-loop gaseous uranium fission reactor for large craft. A long-range cruise vehicle could be managed this way, but eventually the reactor would need refueling. Still, it'd be risky to insist that we'll never find new sources of energy which would provide MHD power plants capable of almost perpetual operation.

Whether or not MHD justifies the hopes of power plant people, other power sources may prove more compact, lighter, and—at least in operation—simpler. Take, for example, a kilogram of Californium 254, assuming an orbital manufacturing plant to produce it. This isotope decays fast enough that its heat output is halved after roughly two months; but initially the steady ravening heat output from one kilo of the stuff would be translatable to something like 10,000 horsepower! No matter that a kilo of Californium 254 is, at present, a stupefyingly immense quantity; ways can probably be found to produce it in quantity. Such a compact heat source would power ramjets without fuel tanks, or it could vaporize a working fluid such as water. In essence, the isotope would function as a simple reactor, but without damping rods or other methods of controlling its decay. Like it or not, the stuff would be cooking all the time. Perhaps its best use would be for small, extended-range, upper-atmosphere patrol craft. There's certainly no percentage in letting it sit in storage.

For propulsion in space, several other power plants seem attractive. Early nuclear weapon tests revealed that graphite-covered steel spheres survived a twenty kiloton blast at a distance of ten meters. The Orion project grew from this datum, and involved nothing less in concept than a series of nukes detonated behind the baseplate of a large vehicle. As originally designed by Ted Taylor and Freeman Dyson, such a craft could be launched from the ground, but environmentalists quake at the very idea. The notion is not at all far-fetched from an engineering standpoint and might yet be used to power city-sized space dreadnoughts of the next century if we utterly fail to perfect more efficient methods of converting matter into energy. Incidentally, the intermittent explosion rocket drive was tested by Orion people, using conventional explosives in scale models. Wernher von Braun was evidently unimpressed with the project until he saw films of a model in flight.

This kind of experiment goes back at least as far as Goddard, who tested solid-propellant repeater rockets before turning to his beloved, persnickety, high-impulse liquid fuels. No engineer doubts there'll be lots of glitches between a small model using conventional explosives, and a megaton-sized version cruising through space by means of nuke blasts. But it probably will work, and God knows it doesn't have a whole slew of moving parts. Structurally, in fact, it may be a more robust solution for space dreadnoughts than are some other solutions. It seems more elegant to draw electrical power from the sun to move your space dreadnought, for instance—until we realize that the solar cell arrays would be many square kilometers in area. Any hefty acceleration with those gossamer elements in place would require quintupling the craft's mass to keep the arrays from buckling during maneuvers. The added mass would be concentrated in the solar array structure and its interface with the rest of the craft.

On the other hand, there's something to be said for any system that draws its power from an inexhaustible source—and the Orion system falls short in that department since it must carry its nukes with it. The mass driver is something else again. It can use a nearby star for power, though it must be supplied with some mass to drive. Lucky for dwellers of this particular star system: we can always filch a few megatons of mass from the asteroid belt.

The mass driver unit is fairly simple in principle. It uses magnetic coils to hurl small masses away at high speed, producing thrust against the coils. Gerard O'Neill has demonstrated working models of the mass driver. In space, a mass driver could be powered by a solar array or a closed-cycle reactor, and its power consumption would not be prohibitively high. The thrust of the device is modest—too low for planetary liftoff as currently described. Its use in an atmosphere would be limited, power source aside, by aerodynamic shock waves generated by the mass accelerated to hypersonic velocity within the acceleration coils.

For fuel mass, O'Neill suggests munching bits from a handy asteroid—though almost any available mass would do. The mass need not be magnetic since it can be accelerated in metal containers, then allowed to continue while the metal "buckets" are decelerated for re-use.

In case you're not already ahead of me, notice that the mass driver offers a solution to the problem of "space junk" that already litters orbital pathways. The mass-driver craft can schlep around until it locates some hardware nobody values anymore, dice and compact it into slugs, feed it into the mass driver buckets, and hurl the compacted slugs away during its next maneuver. Of course, the craft's computer will have to keep tabs on whatever is in line with the ejected masses, since the slugs will be potentially as destructive as meteorites as they flee the scene. Imagine being whacked by a ten-kilogram hunk of compacted aluminum garbage moving at escape velocity!

Solar plasma, the stream of ionized particles radiated by stars, has been suggested as a "solar wind" to be tapped by vast gossamer sails attached to a space vehicle—with the pressure of light radiation adding to the gentle "wind." Carl Wiley, writing as "Russell Saunders," outlined the space windjammer proposal in 1951. His sail was envisioned as a parachute-like arrangement of approximately hemispherical shape, made of lithium, many square kilometers in area. Wiley argued that, while such a craft could hardly survive any environment but space, it could be made to revolve with its sail as it circles a planetary mass. By presenting a profile view of the sail as it swings toward the sun, and the full circular view as it swings away again, the craft could gradually build up enough velocity to escape the planet entirely. Even granting this scheme, a sail quickly deflated or rearranged into windsock proportions, it seems unlikely that a starsailer could move very effectively into a solar wind in the same way that a boat tacks upwind. The interstellar yachtsman has an advantage, though: he can predict the sources of his winds. He cannot be sure they won't vary in intensity, though; which leads to scenarios of craft becalmed between several stars until one star burns out, or becomes a nova.

It takes a very broad brush to paint a military operation of such scale that solar sails and mass drivers would be popular as power plants. These prime movers are very cost-effective, but they need a lot of time to traverse a lot of space. By the time we have military missions beyond Pluto, we may also have devices which convert matter completely into photons, yielding a photon light drive. In the meantime, nuclear reactors can provide enough heat to vaporize fuel mass for high-thrust power plants in space. So far as we know, the ultimate space drive would use impinging streams of matter and antimatter in a thrust chamber. This is perhaps the most distant of far-out power plants, and presumes that we can learn to make antimatter do as we say. Until recently, there was grave doubt that any particle of antimatter could be stable within our continuum. That doubt seems to be fading quickly, according to reports from Geneva. Antiprotons have been maintained in circular paths for over eighty hours. The demonstration required a nearly perfect vacuum, since any contact between antimatter and normal matter means instant apocalypse for both particles. And as the particles are mutually annihilated, they are converted totally into energy. We aren't talking about your workaday one or two percent conversion typical of nuclear weapons, understand: total means total. A vehicle using an antimatter drive would be able to squander energy in classic military fashion!

The power plants we've discussed so far all lend themselves to aircraft and spacecraft. Different performance standards apply to land- and water-based vehicles, which must operate quietly, without lethal effluents, and slowly at least during docking stages. Turbines can be quiet, but they produce strong infrared signatures and they use a lot of fuel, limiting their range somewhat. When you cannot be quick, you are wise to be inconspicuous. This suggests that electric motors might power wheeled transports in the near future, drawing power from lightweight storage batteries or fuel cells. The fuel cell oxidizes fuel to obtain current, but the process generates far less waste heat than a turbine does. The fuel cell also permits fast refueling—with a hydride, or perhaps hydrogen—which gives the fuel cell a strong advantage over conventional batteries. However, remember that the fuel cell "burns" fuel. No fair powering a moonrover or a submarine by fuel cells without an oxidizer supply on board.

When weight is not a crucial consideration, the designer can opt for heavier power plants that have special advantages. The flywheel is one method of storing energy without generating much heat as that energy is tapped. A flywheel can be linked to a turbine or other drive unit to provide a hybrid engine. For brief periods when a minimal infrared signature is crucial, the vehicle could operate entirely off the flywheel. Fuel cells and electric motors could replace the turbine in this hybrid system. Very large cargo vehicles might employ reactors; but the waste heat of a turbine, reactor, or other heat engine is always a disadvantage when heatseeking missiles are lurking near. It's likely that military cargo vehicles will evolve toward sophisticated hybrid power plants that employ heat engines in low-vulnerability areas, switching to flywheel, beamed power, or other stored-energy systems producing little heat when danger is near. As weapons become more sophisticated, there may be literally almost no place far from danger—which implies development of hybrid power plants using low-emission fuel cells and flywheels for wheeled vehicles.

 

 

MATERIALS

 

Perhaps the most direct way to improve a vehicle's overall performance is to increase its payload fraction, i.e., the proportion of the system's gross weight that's devoted to payload. If a given craft can be built with lighter materials, or using more energetic material for fuel, that craft can carry more cargo and/or can carry it farther, faster.

Many solids, including metals, are crystalline masses. Entire journals are devoted to the study of crystal growth because, among other things, the alignment and size of crystals in a material profoundly affect that material's strength. Superalloys in turbine blades have complex crystalline structures, being composed of such combinations as cobalt, chromium, tungsten, tantalum, carbon, and refractory metal carbides. These materials may lead to hyperalloys capable of sustaining the thermal shock of a nuke at close range.

As we've already noted, graphite-coated steel objects have shown some capacity to survive a nuke at close quarters. There may be no alloy quite as good as the old standby, graphite, especially when we note that graphite is both far cheaper and lighter in weight. Superalloys aren't the easiest things to machine, either. Anybody who's paid to have superalloy parts machined risked cardiac arrest when he saw the bill. Graphite is a cinch to machine; hell, it even lubricates itself.

More conventional alloys of steel, aluminum, and titanium may be around for a long time, with tempering and alloying processes doubling the present tensile strengths. When we begin processing materials in space, it may be possible to grow endless crystals which can be spun into filament bundles. A metal or quartz cable of such stuff may have tensile strength in excess of a million pounds per square inch. For that matter, we might grow doped crystals in special shapes to exacting tolerances, which could lead to turbine blades and lenses vastly superior to anything we have today. Until fairly recently, quartz cable had a built-in limitation at the point where the cable was attached to other structural members. Steel cable terminals can simply be swaged—squeezed—over a steel cable, but quartz can't take the shear forces; you can cut through quartz cable with a pocketknife. This problem is being solved by adhesive potting of the quartz cable end into specially formed metal terminals. Your correspondent was crushed to find himself a few months behind the guy who applied for the first patents in this area. The breakthrough takes on more importance when we consider the advantages of cheap dielectric cable with high flexibility and extremely high tensile strength at a fraction of the weight of comparable steel cable. Very large structures of the future are likely to employ quartz cable tension members with abrasion-resistant coatings.

Vehicles are bound to make more use of composite materials as processing gets more sophisticated. Fiberglass is a composite of glass fibers in a resin matrix; but sandwich materials are composites too. A wide variety of materials can be formed into honeycomb structures to gain great stiffness-to-weight characteristics. An air-breathing hypersonic craft might employ molybdenum honeycomb facing a hyperalloy inner skin forming an exhaust duct. The honeycomb could be cooled by ducting relatively cool gas through it. On the other side of the honeycomb might be the craft's outer skin; say, a composite of graphite and high-temperature polymer. Advanced sandwich composites are already in use, and show dramatic savings in vehicle weight. The possible combinations in advanced sandwich composites are almost infinite, with various layers tailored to a given chemical, structural, or electrical characteristic. Seventeen years ago, an experimental car bumper used a composite of stainless steel meshes between layers of glass and polymer to combine lightness with high impact resistance. A racing car under test that year had a dry weight of just 540 lb., thanks to a chassis built up from sandwich composite with a paper honeycomb core. The writer can vouch for the superior impact and abrasion resistance of this superlight stuff, which was all that separated his rump from macadam when the little car's rear suspension went gaga during a test drive. The vehicle skated out of a corner and spun for a hundred meters on its chassis pan before coming to rest. The polymer surface of the pan was scratched up a bit, yet there was no structural damage whatever. But we considered installing a porta-potty for the next driver . . .

Today, some aircraft use aluminum mesh in skins of epoxy and graphite fiber. The next composite might be titanium mesh between layers of boron fiber in a silicone polymer matrix. The chief limitation of composites seems to be the adhesives that bond the various materials together. It may be a long time before we develop a glue that won't char, peel, or embrittle when subjected to temperature variations of hypersonic aircraft. The problem partly explains the metallurgists' interest in welding dissimilar metals. If we can find suitable combinations of inert atmosphere, alloying, and electrical welding techniques, we can simply (translation: not so simply) lay a metal honeycomb against dissimilar metal surfaces and zap them all into a single piece.

Several fibers are competing for primacy in the search for better composites; among them boron, graphite, acetal homopolymer, and aramid polymers. Boron may get the nod for structures that need to be superlight without a very high temperature requirement, but graphite looks like the best bet in elevated temperature regimes. Sandia Laboratories has ginned up a system to test graphite specimens for short-term high temperature phenomena including fatigue, creep, and stress-rupture. The specimens are tested at very high heating rates. It's easy to use the report of this test rig as a springboard for guessing games. Will it test only graphite? Very high heating rates might mean they're testing leading edges intended to survive vertical re-entry at orbital speeds. Then again, there's a problem with the heat generated when an antitank projectile piles into a piece of Soviet armor. Do we have materials that can punch through before melting into vapor? And let's not forget armor intended to stand up for a reasonable time against a power laser. For several reasons, and outstanding heat conductivity is only one of them, graphite looks good to this guesser. If the Sandia system isn't looking into antilaser armor, something like it almost certainly will be—and soon.

Before leaving the topic of materials, let's pause to note research into jet fuels. A gallon of JP-4 stores roughly 110,000 Btu. Some new fuels pack an additional 65,000 Btu into a gallon. Even if the new fuels are slightly heavier, the fuel tank can be smaller. The result is extended range. It seems reasonable to guess that JP-50, when it comes along, will double the energy storage of JP-4.

 

 

VEHICLE CONFIGURATIONS

 

Now that we're in an age of microminiaturization, we have a new problem in defining a vehicle. We might all agree that a vehicle carries something, but start wrangling over just how small the "something" might be. An incendiary bullet carries a tiny blazing chemical payload; but does that make the bullet a vehicle? In the strictest sense, probably yes. But a bullet is obviously not a limiting case—leaving that potential pun unspent—when very potent things of almost no mass can be carried by vehicles of insect size.

Payloads of very small vehicles could be stored information, or might be a few micrograms of botulism or plutonium, perhaps even earmarked for a specific human target. Ruling out live bats and insects as carriers, since they are normally pretty slapdash in choosing the right target among possibly hundreds of opportunities, we could develop extremely small rotary-winged craft and smarten them with really stupendous amounts of programming without exceeding a few milligrams of total mass. A swarm of these inconspicuous mites would be expensive to produce, but just may be the ultimate use for "clean room" technology in which the U.S. has a temporary lead.

The mites would be limited in range and top speed, so that a hypersonic carrier vehicle might be needed to bring them within range of the target like a greyhound with plague fleas. The carrier would then slow to disgorge its electromechanical parasites. One immediately sees visions of filters to stop them; and special antifilter mites to punch holes in the filters; and sensors to detect antifilter mite action; and so on.

It's hard to say just how small the mites could be after a hundred years of development. One likely generalization is that the smaller the payload, the longer the delay before the payload's effect will be felt. Take the examples of plutonium or botulism: a human victim of either payload can continue performing his duties for a longer time—call it mean time before failure—if he is victimized by a tinier chunk of poison. Some canny theorists will be chortling, about now, at the vision of a billion mites slowly building a grapefruit-sized mass of plutonium in some enemy bunker. That's one option, for sure. But the blast, once critical mass is reached, would be ludicrously small when compared with other nuke mechanisms.

The best use of mites might be as spies, storing data while hunkered down in an inconspicuous corner of the enemy's war room, scaring the bejeezus out of the local spiders. Or would the enemy's spiders, too, be creatures of the clean room? Pick your own scenario. . . .

There is no very compelling reason why mites couldn't actually resemble tiny flies, with gimbaled ornithopter wings to permit hovering or fairly rapid motion in any direction. There may be a severe limitation to their absolute top speed in air, depending on the power plant. Partly because of square/cube law problems, a mite could be seriously impeded by high winds or rain. A device weighing a few milligrams or less would have the devil's own time beating into a strong headwind. Perhaps a piezoelectrically driven vibrator could power the tiny craft; that might be simpler than a turbine and tougher to detect. Whatever powers the mite, it would probably not result in cruise speeds over a hundred miles an hour unless an antimatter drive is somehow shoehorned into the chassis. Even with this velocity limitation, though, the mites could probably maneuver much more quickly than their organic counterparts—which brings up a second dichotomy in vehicles.

Information storage is constantly making inroads into the need for human pilots, as the Soviets proved in their unmanned lunar missions. A military vehicle that must carry life-support equipment for anything as delicate as live meat, is at a distinct disadvantage versus a similar craft that can turn and stop at hundreds of g's. Given a human cargo, vehicle life-support systems may develop to a point where bloodstreams are temporarily thickened, passengers are quick-frozen and (presumably) harmlessly thawed, or some kind of null-inertia package is maintained to keep the passenger comfortable under five-hundred-gravity angular acceleration. During the trip, it's a good bet that the vehicle would be under computer guidance, unless the mission is amenable to very limited acceleration. It also seems likely that women can survive slightly higher acceleration than men—an old SF idea with experimental verification from the people at Brooks AFB. Women's primacy in this area may be marginal, but it's evidently true that Wonder Woman can ride a hotter ship than Superman. It's also true that your pocket calculator can take a jouncier ride than either of them. In short, there will be increasing pressure to depersonalize military missions, because a person is a tactical millstone in the system.

Possibly the most personalized form of vehicle, and one of the more complex per cubic centimeter, would be one that the soldier wears. Individualized battle armor, grown massive enough to require servomechanical muscles, could be classed as a vehicle for the wearer. The future for massive man-amplifying battle dress doesn't look very bright, though. If the whole system stands ten meters tall it will present an easier target; and if it is merely very dense, it will pose new problems of traction and maneuverability. Just to focus on one engineering facet of the scaled-up bogus android, if the user hurls a grenade with his accustomed arm-swing using an arm extension fifteen feet long, the end of that extension will be moving at roughly Mach I. Feedback sensors would require tricky adjustment for movement past the trans-sonic region, and every arm-wave could become a thunderclap! The user will have to do some fiendishly intricate rethinking when he is part of this system—but then, so does a racing driver. Man-amplified battle armor may pass through a certain vogue, just as moats and tanks have done. The power source for this kind of vehicle might be a turbine, until heat-seeking missiles force a change to fuel cells or, for lagniappe, a set of flywheels mounted in different parts of the chassis. The rationale for several prime movers is much the same as for the multi-engined aircraft: you can limp home on a leg and a prayer. Aside from the redundancy feature, mechanical power transmission can be more efficient when the prime mover is near the part it moves. Standing ready for use, a multiflywheel battle dress might even sound formidable, with the slightly varying tones of several million-plus RPM flywheels keening in the wind.

For certain applications including street fighting, there may be a place for the lowly skateboard. It's a fact that the Soviets have bought pallet loads of the sidewalk surfers, ostensibly to see if they're a useful alternative to mass transit. It's also true that enthusiasts in the U.S. are playing with motorized versions which, taking the craze only a step further, could take a regimental combat team through a city in triple time. But if two of those guys ever collide at top speed while carrying explosives, the result may be one monumental street pizza.

No matter how cheap, dependable, and powerful, a military vehicle must be designed with an eye cocked toward enemy weapons. Nuclear warheads already fit into missiles the size of a stovepipe, and orbital laser-firing satellites are only a few years away. A vehicle that lacks both speed and maneuverability will become an easier target with each passing year. By the end of this century, conventional tanks and very large surface ships would be metaphors of the Maginot Line, expensive fiascos for the users.

The conventional tank, despite its popularity with the Soviets, seems destined for the junk pile. Its great weight limits its speed and maneuverability, and several countries already have antitank missile systems that can be carried by one or two men. Some of these little bolides penetrate all known tank armor and have ranges of several kilometers. Faced with sophisticated multistage tank killer missiles, the tank designers have come up with layered armor skirts to disperse the fury of a high-velocity projectile before it reaches the tank's vitals. Not to be outdone, projectile designers have toyed with ultrahigh-velocity projectiles that are boosted almost at the point of impact. It may also be possible to develop alloy projectile tips that won't melt or vaporize until they've punched through the tank's skirt layers. Soon, the tanks may employ antimissile missiles of their own, aimed for very short-range kills against incoming antitank projectiles. This counterpunch system would just about have to be automated; no human crew could react fast enough. The actual mechanism by which the counterpunch would deflect or destroy the incoming projectile could be a shaped concussion wave, or a shotgun-like screen of pellets, or both. And it's barely possible that a tank's counterpunch could be a laser that picks off the projectile, though there might not be time to readjust the laser beam for continued impingement on the projectile as it streaks or jitters toward the tank.

Given the huge costs of manufacturing and maintaining a tank, and the piddling costs of supplying infantry with tank-killing hardware, the future of the earthbound battle tank looks bleak. It's wishful thinking to design tanks light enough to be ACV's. Race cars like the Chaparral and the formidable Brabham F1, using suction for more traction, are highly maneuverable on smooth terrain. Still, they'd be no match for homing projectiles; and with no heavy armor or cargo capacity for a counterpunch system, they'd almost surely be gallant losers.

All this is not to suggest that the tank's missions will be discarded in the future, but those missions will probably be performed by very different craft. We'll take up those vehicles under the guise of scout craft.

More vulnerable than the tank, an aircraft carrier drawing 50,000 tons on the ocean surface is just too easy to find, too sluggish to escape, and too tempting for a nuclear strike. It's more sensible to build many smaller vessels, each capable of handling a few aircraft—a point U.S. strategists are already arguing. Ideally the aircraft would take off and land vertically, as the Hawker Harrier does. Following this strategy, carriers could be spread over many square kilometers of ocean reducing vulnerability of a squadron of aircraft.

A pocket aircraft carrier might draw a few hundred tons while cruising on the surface. Under battle conditions the carrier could become an ACV, its reactor propelling it several hundred kilometers per hour with hovering capability and high maneuverability. Its shape would have to be clean aerodynamically, perhaps with variable-geometry catamaran hulls.

Undersea craft are harder to locate. Radar won't reveal a submerged craft, and sonar—a relatively short-range detection system unless the sea floor is dotted with sensor networks—must deal with the vagaries of ocean currents, and temperature and pressure gradients as well as pelagic animals. There may be a military niche for large submersibles for many years to come, perhaps as mother ships and, as savant Frank Herbert predicted a long time ago, cargo vessels.

A submerged mother ship would be an ideal base for a fleet of small hunter-killer or standoff missile subs. These small craft could run at periscope depth for a thousand miles on fuel cells, possibly doubling their range with jettisonable external hydride tanks. A small sub built largely of composites would not be too heavy to double as an ACV in calm weather, switching from ducted propellers to ducted fans for this high-speed cruise mode. From this, it is only a step to a canard swing-wing craft, with schnorkel and communication gear mounted on the vertical fin. The sub packs a pair of long-range missiles on her flanks just inside the ACV skirt. The filament-wound crew pod could detach for emergency flotation. High-speed ACV cruise mode might limit its range to a few hundred kilometers. The swing wings are strictly for a supersonic dash at low altitude, using ducted fan and perhaps small auxiliary jets buried in the aft hull, drawing air from the fan plenum.

Heavy seas might rule out the ACV mode, but if necessary the little sub can broach vertically like a Poseidon before leveling off into its dash mode. With a gross weight of some thirty tons it would require some additional thrust for the first few seconds of flight—perhaps a rocket using hydride fuel and liquid oxygen. The oxygen tank might be replenished during undersea loitering periods. Since the sub would pull a lot of g's when re-entering the water in heavy seas, the nose of the craft would be built up with boron fibers and polymer as a composite honeycomb wound with filaments. The idea of a flying submersible may stick in a few craws, until we reflect that the SUBROC is an unmanned flying submersible in development for over a decade.

On land, military cargo vehicles will feature bigger, wider, low-profile tires in an effort to gain all-terrain capability. Tires could be permanently inflated by supple closed-cell foams under little or no pressure. If the cargo mass is distributed over enough square meters of tire "footprint," the vehicle could challenge tracked craft in snow, or churn through swamps with equal aplomb. The vehicle itself will probably have a wide squat profile (tires may he as high as the cargo section) and for more maneuverability, the vehicle can be hinged in the middle. All-wheel drive, of course, is de rigeur. 

It's a popular notion that drive motors should be in the wheels, but this adds to the unsprung portion of the vehicle's weight. For optimal handling over rough terrain, the vehicle must have a minimal unsprung weight faction—which means the motors should be part of the sprung mass, and not in the wheels which, being between the springing subsystem and the ground, are unsprung weight.

Relatively little serious development has been done on heavy torque transmission via flexible bellows. When designers realize how easily a pressurized bellows can be inspected, they may begin using this means to transmit torque to the wheels of cargo vehicles.

The suspension of many future wheeled vehicles may depart radically from current high-performance practice. Most high-performance vehicle suspensions now involve wishbone-shaped upper and lower arms, connecting the wheel's bearing block to the chassis. A rugged alternative would be sets of rollers mounted fore and aft of the bearing block, sliding vertically in chassis-mounted tracks. The tracks could be curved, and even adjustable and slaved to sensors so that, regardless of surface roughness or vehicle attitude above that surface, the wheels would be oriented to gain maximum adhesion. Turbines, flywheels, fuel cells and reactors are all good power plant candidates for wheeled vehicles.

The bodies of these vehicles will probably be segments of smooth-faced composite, and don't be surprised if two or three segment shapes are enough to form the whole shell. This is cost-effectiveness with a vengeance; one mold produces all doors and hatches, another all wheel and hardware skirts, and so on. On the other hand, let's not forget chitin.

Chitin is a family of chemical substances that make up much of the exoskeletons of arthropods, including insects, spiders and crabs. The stuff can be flexible or inflexible and chemically it is pretty inert. If biochemists and vehicle designers get together, we may one day see vehicles that can literally grow their skins and repair their own prangs. As arthropods grow larger, they often have to discard their exoskeletons and grow new ones; but who's betting the biochemists won't find ways to teach beetles some new tricks about body armor?

Some cargo—including standoff missiles, supplies, and airborne laser weapons—will be carried by airborne transports. In this sense a bomber is a transport vehicle. Here again, advanced composite structures will find wide use, since a lighter vehicle means a higher payload fraction. Vertical takeoff and landing (VTOL), or at least very short takeoff and landing (VSTOL), will greatly expand the tactical use of these transports which will have variable-geometry surfaces including leading and trailing edges, not only on wings but on the lifting body. Consider a VSTOL transport. With its triple-delta wings fully extended for maximum lift at takeoff, long aerodynamic "fences" along the wings front-to-rear guide the airflow and the lower fences form part of the landing gear fairings. Wing extensions telescope rather than swing as the craft approaches multimach speed, and for suborbital flight the hydrogen-fluorine rocket will supplant turbines at around thirty kilometer altitude. In its stubby double-delta configuration the craft can skip-glide in the upper atmosphere for extended range, its thick graphite composite leading surfaces aglow as they slowly wear away during re-entry. During periodic maintenance, some of this surface can be replaced in the field as a polymer-rich putty.

As reactors become more compact and MHD more sophisticated, the rocket propellant tanks can give way to cargo space although, from the outside, the VSTOL skip-glide transport might seem little changed. Conversion from VSTOL to VTOL could be helped by a special application of the mass driver principle. In this case the aircraft, with ferrous metal filaments in its composite skin, is the mass repelled by a grid that would rise like scaffolding around the landing pad. This magnetic balancing act would be reversed for vertical landing—but it would take a lot of site preparation which might, in turn, lead to inflatable grid elements rising around the landing site.

Once an antimatter drive is developed, cargo transports might become little more than streamlined boxes with gimbaled nozzles near their corners. Such a craft could dispense with lifting surfaces, but would still need heat-resistant skin for hypersonic flight in the atmosphere. But do we have to look far ahead for cargo vehicles that travel a long way? Maybe we should also look back a ways.

For long-range transport in the lower atmosphere, the dirigible may have a future that far outstrips its past. Though certainly too vulnerable for deployment near enemy gunners, modern helium-filled cargo dirigibles can be very cost-effective in safe zones. Cargo can be lifted quietly and quickly to unimproved dump areas, and with a wide variety of power plants. The classic cigar shape will probably be lost in the shuffle to gain more aerodynamic efficiency, if a recent man-carrying model is any guide. Writer John McPhee called the shape a deltoid pumpkin seed, though its designers prefer the generic term, aerobody. So: expect somebody to use buxom, spade-nosed aerobodies to route cargo, but don't expect the things to fly very far when perforated like a collander from small-arms fire. The aerobody seems to be a good bet for poorer nations engaged in border clashes where the fighting is localized and well-defined. But wait a minute: what if the gasbags were made of thin, self-healing chitin? Maybe the aerobody is tougher than we think.

Among the most fascinating military craft are those designed for scouting forays: surveillance, pinpoint bombing sorties, troop support, and courier duty being only a few of their duties. The Germans briefly rescued Mussolini with a slow but superb scout craft, the Fieseler Storch. Our SR-71 does its scouting at Mach 3, while the close-support A-10 can loiter at a tiny fraction of that speed. Now in development in the U.S., Britain, and Germany is a family of remotely piloted scout craft that may be the next generation of scout ships, combining the best features of the Storch and the SR-71.

The general shape of the scout ship is that of a football flattened on the bottom, permitting high-speed atmospheric travel and crabwise evasive action while providing a broad base for the exhaust gases of its internal ACV fans. The ship is MHD powered, drawing inlet air from around the underlip of the shell just outboard of the ACV skirt. The skirt petals determine the direction of deflected exhaust for omnidirectional maneuvers, though auxiliary jets may do the job better than skirt petals.

The scout uses thick graphite composite skin and sports small optical viewing ports for complete peripheral video rather than having a single viewing bubble up front. The multiple videos offer redundancy in ease of damage; they permit a stiffer structure; and they allow the occupant, if any, maximum protection by remoting him from the ports.

The question of piloting is moot at the moment. Grumman, Shorts, and Dornier are all developing pilotless observation craft for long-range operations, but a scout craft of the future would probably have a life-support option for at least one occupant. The design has an ovoid hatch near its trailing edge. For manned missions, an occupant pod slides into the well-protected middle of the ship, and could pop out again for emergency ejection. For unmanned missions the occupant pod might be replaced by extra fuel, supplies, or weapons. Some version of this design might inherit the missions of the battle tank, but with much-improved speed and maneuverability.

Well, we've specified high maneuverability and a graphite composite skin. Given supersonic speed and automatic evasion programs, it might be the one hope of outrunning an orbital laser weapon!

Of course the scout doesn't exceed the speed of light. What it might do, though, is survive a brief zap long enough to begin a set of evasive actions. Let's say the enemy has an orbital laser platform (OLP) fairly near in space, not directly overhead but in line-of-sight, four hundred miles from the scout which is cruising innocently along at low altitude at a speed of Mach 1. The laser is adjusted perfectly and fires.

What does it hit? A thick polished carapace of graphite composite, its skin filaments aligned to conduct the laser's heat away from the pencil-wide target point. Sensors in the scout's skin instantly set the craft to dodging in a complex pattern, at lateral accelerations of about 10 g's. At this point the occupant is going to wish he had stayed home, but he should be able to survive these maneuvers.

Meanwhile the OLP optics or radar sense the change of the scout's course—but this takes a little time, roughly two millisec, because the OLP is four hundred miles away. Reaiming the laser might take only ten millisec, though it might take considerably longer. Then the OLP fires again, the new laser burst taking another two millisec to reach the target.

But that's fourteen thousandths of a second! And the scout is moving roughly one foot per millisec, and is now angling to one side. Its change of direction is made at well over three hundred feet per sec, over four feet of angular shift before the second ("corrected") laser shot arrives. The scout's generally elliptical shell is about twenty feet in length by about ten in width. Chances are good that the next laser shot would miss entirely, and in any case it would probably not hit the same spot, by now a glowing scar an inch or so deep on the scout's shell.

Discounting luck on either side, the survival of the jittering scout ship might depend on whether it could dodge under a cloud or into a steep valley. It might, however, foil the laser even in open country by redirecting a portion of its exhaust in a column directly toward the enemy OLP. The destructive effect of a laser beam depends on high concentration of energy against a small area. If the laser beam spreads, that concentration is lost; and beam spread is just what you must expect if the laser beam must travel very far through fog, cloud, or plasma. If the scout ship could hide under a tall, chemically seeded column of its own exhaust for a few moments, it would have a second line of defense. And we must not forget that the laser's own heat energy, impinging on the target, creates more local plasma which helps to further spread and attenuate the laser beam.

One method of assuring the OLP more hits on a scout ship would be to gang several lasers, covering all the possible moves that the scout might make. The next question would be whether all that fire-power was worth the trouble. The combination of high-temperature composites, MHD power, small size, and maneuverability might make a scout ship the same problem to an OLP that a rabbit is to a hawk. All the same, the hawk has the initial advantage. The rabbit is right to tremble.

An unmanned scout ship, capable of much higher rates of angular acceleration, would be still more vexing to an OLP. If the OLP were known to have a limited supply of stored energy, a squadron of unmanned scouts could turn a tide of battle by exhausting the OLP in futile potshots. It remains to be seen whether the jittering scout craft will be able to dodge, intercept, or just plain outrun a locally-fired weapon held by some hidden infantryman. But given a compact reactor or an antimatter drive, the scout ship could become a submersible. In that event the scout craft could escape enemy fire by plunging into any ocean, lake, or river that's handy. The broad utility of such a craft might make obsolete most other designs.

But what of vehicles intended to fight in space? As colonies and mining outposts spread throughout our solar system, there may be military value in capturing or destroying far-flung settlements—which means there'll be military value in intercepting such missions. The popular notion of space war today seems to follow the Dykstra images of movies and TV, where great whopping trillion-ton battleships direct fleets of parasite fighters. The mother ship with its own little fleet makes a lot of sense, but in sheer mass the parasites may account for much of the system, and battle craft in space may have meter-thick carapaces to withstand laser fire and nuke near-misses.

Let's consider a battle craft of reasonable size and a human crew, intended to absorb laser and projectile weapons as well as some hard radiation. We'll give it reactor-powered rockets, fed with pellets of some solid fuel which is exhausted as vapor.

To begin with, the best shape for the battle craft might be an elongated torus; a tall, stretched-out doughnut. In the long hole down the middle we install the crew of two—if that many—weapons, communication gear, life support equipment, and all the other stuff that's most vulnerable to enemy weapons. This central cavity is then domed over at both ends, with airlocks at one end and weapon pods at the other. The crew stays in the very center where protection is maximized. The fuel pellets, composing most of the craft's mass, occupy the main cavity of the torus, surrounding the vulnerable crew like so many tons of gravel. Why solid pellets? Because they'd be easier than fluids to recover in space after battle damage to the fuel tanks. The rocket engines are gimbaled on short arms around the waist of the torus, where they can impart spin, forward or angular momentum, or thrust reversal. The whole craft would look like a squat cylinder twenty meters long by fifteen wide, with circular indentations at each end where the inner cavity closures meet the torus curvatures.

The battle craft doesn't seem very large but it could easily gross over 5,000 tons, fully fueled. If combat accelerations are to reach 5 g's with full tanks, the engines must produce far more thrust than anything available today. Do we go ahead and design engines producing 25,000 tons of thrust, or do we accept far less acceleration in hopes the enemy can't do any better? Or do we redesign the cylindrical crew section so that it can eject itself from the fuel torus for combat maneuvers? This trick—separating the crew and weapons pod as a fighting unit while the fuel supply loiters off at a distance—greatly improves the battle craft's performance. But it also means the crew pod must link up again very soon with the torus to replenish its on-board fuel supply. And if the enemy zaps the fuel torus hard enough while the crew is absent, it may mean a long trajectory home in cryogenic sleep.

Presuming that a fleet of the toroidal battle craft sets out on an interplanetary mission, the fleet might start out as a group of parasite ships attached to a mother ship. It's anybody's guess how the mother ship will be laid out, so let's make a guess for critics to lambaste.

Our mother ship would be a pair of fat discs, each duplicating the other's repair functions in case one is damaged. The discs would be separated by three compression girders and kept in tension by a long central cable. To get a mental picture of the layout, take two biscuits and run a yard-long thread through the center of each. Then make three columns from soda straws, each a yard long, and poke the straw ends into the biscuits near their edges. Now the biscuits are facing each other, a yard apart, pulled toward each other by the central thread and held apart by the straw columns. If you think of the biscuits as being a hundred meters in diameter with rocket engines poking away from the ends, you have a rough idea of the mother ship.

Clearly, the mother ship is two modules, upwards of a mile apart but linked by structural tension and compression members. The small battle craft might be attached to the compression girders for their long ride to battle, but if the mother ship must maneuver, their masses might pose unacceptable loads on the girders. Better by far if the parasites nestle in between the girders to grapple onto the tension cable. In this way, a fleet could embark from planetary orbit as a single system, separating into sortie elements near the end of the trip.

Since the total mass of all the battle craft is about equal to that of the unencumbered mother ship, the big ship can maneuver itself much more easily when the kids get off mama's back. The tactical advantages are that the system is redundant with fuel and repair elements; a nuke strike in space might destroy one end of the system without affecting the rest; and all elements become more flexible in their operational modes just when they need to be. Even if mother ships someday become as massive as moons, my guess is that they'll be made up of redundant elements and separated by lots of open space. Any hopelessly damaged elements can be discarded, or maybe kept and munched up for fuel mass.

Having discussed vehicles that operate on land, sea, air, and in space, we find one avenue left: within the earth. Certainly a burrowing vehicle lacks the maneuverability and speed of some others—until the burrow is complete. But under all that dirt, one is relatively safe from damn-all. Mining vehicles already exist that cut and convey ten tons of coal a minute, using extended-life storage batteries for power. One such machine, only 23 inches high, features a supine driver and low-profile, high traction tires. Perhaps a future military "mole" will use seismic sensors to find the easiest path through rocky depths, chewing a long burrow to be traversed later at high speed by offensive or defensive vehicles, troop transports, and supply conduits. Disposal of the displaced dirt could be managed by detonating a nuke to create a cavern big enough to accept the tailings of the mole. The present plans to route ICBMs by rail so that enemies won't know where to aim their first strike, may shift to underground routing as the subterranean conduit network expands.

 

 

AN ALTERNATIVE TO VEHICLES?

 

A vehicle of any kind is, as we've asserted, essentially a means to carry something somewhere. So it's possible that the vehicle, as a category, might be obsolete one day. The matter transmitter is a concept that, translated into hardware, could obsolete almost any vehicle. True, most conceptual schemes for matter transmitters posit a receiving station—which implies that some vehicle must first haul the receiving station from Point A to Point B. But what if the transmitter needed no receiving station? A device that could transmit people and supplies at light speed to a predetermined point without reception hardware would instantly replace vehicles for anything but pleasure jaunts. The system would also raise mirthful hell with secrecy, and with any armor that could be penetrated by the transmitter beam. If the beam operated in the electromagnetic spectrum, vehicles might still be useful deep down under water, beneath the earth's surface, or inside some vast Faraday cage.

But until the omnipotent matter transmitter comes along, vehicle design will be one of the most pervasive factors in military strategy and tactics.

 

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