This article originally appeared in Pyramid #10

An Alternate-Present Campaign for GURPS Vehicles
By Chris W. McCubbin and Craig Sheeley
Based on an original idea by Derek Pearcy

(Editor's Note: This article was written for GURPS Vehicles, First Edition, and has not been updated to reflect the second edition of GURPS Vehicles.)

The first confirmed sprocketfall occurred on Oct. 20, 1983, at 9:15 p.m., on Howard Nernst's farm three miles northwest of Columbus, NE. Nernst was driving his combine home after finishing his annual harvest when he observed a meteor-like object fall out of the sky. He thought it had landed in one of his newly-harvested fields but, exhausted from a 16-hour workday, he postponed further investigation until the next day.

On the morning of the 21st, Nernst returned to the field where he believed the object to have struck. The impact site was easy to find in the barren, newly-harvested field. It was a shallow crater 4' deep and 7' wide. At the bottom of the crater was an irregular metallic solid about six inches across. Nernst at first believed that the object was the metallic core of a meteor, but when he picked it up he found its weight and texture more like light plastic.

The object was cool and light (about 20 ounces) and Nernst picked it up and dusted it off. Its surface had a low metallic sheen, except for one small protrusion with a darker discoloration. Nernst wet his thumb and rubbed it briskly across the protrusion, trying to determine if the discoloration was a stain, or an intrinsic irregularity. This firm pressure from Nernst's thumb caused the object to move and expand in his hands. Prudently, he dropped the object and sprinted several yards away.

When Nernst turned around, the small metallic object was gone, and in its place was a strange looking tracked vehicle, the approximate size of a 2-1/2-ton truck. Nernst approached the vehicle and examined it. The two tracks were flexible, but not articulated in any way Nernst -- a certified mechanic -- could identify. The back half of the vehicle consisted of an open-topped cargo bay 7' long, 6' wide and 5' deep. At various points on the outside of the vehicle were a number of tubes, springs and gear mechanisms whose function he could not identify at all. At the rear of the vehicle was a gate leading to the cargo bay. The gate appeared to slide down into the interior of the vehicle. At the front of the vehicle was a single sliding door leading to the cockpit. Although the exterior of the cockpit appeared opaque, from the inside the entire front was transparent as glass, providing nearly a full 180-degree arc of vision. The cockpit could seat three comfortably. Just inside the cockpit door was a protrusion identical to the one which had triggered the change. Suspecting (correctly, as it turned out) that touching this again would reverse the transformation, Nernst left it alone for the moment.

The "control panel" was located in the center of the cockpit, and consisted of a series of pressure-plate-like surfaces. Touching one of the surfaces in a way that seemed merely logical at the time, the vehicle moved ahead through the field, moving smoothly on its treads over the newly-harvested rows. With what he later realized was preternatural quickness, Nernst learned how to accelerate, decelerate, steer and reverse the vehicle (when he placed the vehicle in reverse, a section of the "windshield" darkened, then cleared to show what Nernst realized was a reduced image of the view from the vehicle's rear). Experimentation revealed that the vehicle had a maximum speed of 81.7 mph on straight highway, and that it could negotiate an incline of almost 45 degrees. Its treads could carry it effortlessly over a vertical obstacle up to 18" tall, or a crevasse up to five feet wide. It appeared to need no fuel or coolant whatsoever. The vehicle could pull a load in excess of 10 tons, though it weighed less than one ton. It took the sprocket approximately 12 seconds to shift to vehicular form, a few seconds less to shift back. Perhaps most remarkably, any harm due to minor scrapes, bumps or collisions appeared to repair itself if the vehicle was left inactive, in either form, for a few hours.

Today, nearly a decade after finding his sprocket, Howard Nernst is still using it for hauling on his farm.


In the 12 months following Howard Nernst's initial discovery, about 300 sprockets were found worldwide (and the term "sprocket" was coined when the press became aware of the phenomenon). In the 12 months following that, almost 1,000 more sprockets were found. The pace of the sprocketfall steadily accelerated for the next several years, but for the last five years it appears to have stabilized at 12,000 to 15,000 units a year, worldwide. According to official U.S. Government estimates, approximately 125,000 sprockets have been found in the last decade. This may seem like a lot, but it should be remembered that this represents less than one sprocket for every 40,000 humans. If the earth's population and the rate of sprocketfall remained stable, it would still take half a million years before everybody on earth had a sprocket of their own.

All sprocketfalls seem to follow the pattern set by Farmer Nernst's experience. Originating from some point outside the earth's atmosphere, sprockets fall to earth like meteors. A visible protrusion, discoloration or both will mark the trigger of the newly-fallen sprocket. The first person to key a sprocket's transformation (not necessarily the first person to handle the sprocket) will find himself almost intuitively able to pilot the resulting vehicle. Those who try to learn to operate the sprocket later will find it a much more difficult process.

The global scientific community's study of sprockets has been extensive, and largely frustrating. Although there are a multitude of theories, nobody really knows how or why sprockets change, or why the first person to key the sprocket finds it so much easier to operate it. A few basic facts are known. The sprocket vehicle obtains its mass from a sub-molecular alteration of atmospheric gases, mostly hydrogen. The molecular structure of sprocket-stuff is resistant to analysis, but many scientists believe that each individual sprocket is, in some sense, a single molecule. Although the wheels, tracks or legs of a land-sprocket will move freely while the vehicle is in operation, when the power is off the wheels, tracks or joints appear to fuse together with the hull -- the sprocket becomes effectively one piece. When a sprocket is parked, it is parked.

Sprocket stuff is quite tough, and seems to have the capacity to regenerate damage. However, a sprocket can be damaged to the point where it will not transform or function, and beyond that to the point where it cannot regenerate. Once that second point is reached, a sprocket begins to dissolve, losing about one pound of mass per day, back to the component gasses.

No two sprockets have ever been found exactly alike. There are wheeled sprockets, tracked sprockets, two-and four-legged walking sprockets, hover sprockets, sprocket ships and submarines. There are two broad classes of sprocket fliers, called "floaters" and "flitters." Floaters can hover. Flitters must stay in constant motion, with a stall speed of 30 to 80 mph, but typically have a much higher top speed than a floater. Flitters also need some sort of runway to take off and land. There are also several unique examples of strange and exotic sprockets that correspond to no known human vehicle design. There are rumors of boring sprockets, capable of traveling through the earth's crust. If such vehicles exist, they are highly classified. No sprocket found so far will work outside the earth's atmosphere, since all sprockets so far require atmospheric gases for power.

Sprockets also, for the most part, look funny. A few are extremely sleek and futuristic, and some look like vehicles that could have been built here on Earth. But the vast majority are very odd in appearance, with bizarre protrusions, cogs, springs, flywheels, and other components out of a Rube Goldberg nightmare. All these strange components seem to be important to the sprocket's operation, but scientists have had no luck in determining how or why.

Tracked and submarine sprockets have an average top speed of 60 to 90 mph. Wheeled, hover and seagoing sprockets have an average top speed of 130 to 200 mph (the record top speed for a wheeled sprocket is 416 mph). Floater top speeds can range from 30 to 200 mph, and flitter top speed can range anywhere from 150 mph on up (the record airspeed for a sprocket is over Mach 5). Submarine sprockets usually have a maximum depth of 500 to 1,000 feet, though atypical specimens can reach the floor of the Challenger Deep (and have).

The smallest recorded sprocket vehicle is a one-man hover cycle weighing only 7.3 lbs. expanded, but capable of carrying a payload of up to 500 lbs. The largest is the floater dubbed Cloud City. With more than half a million cubic feet, the Cloud City is more than three times the size of its nearest competitor (the seagoing Princess Diana). Based out of Las Vegas, the Cloud City has been outfitted to serve as a combination casino and aerial cruise ship. In general, there seems to be little correlation between the size of the contracted sprocket and the size of the expanded vehicle, although the Cloud City was also the largest unexpanded sprocket ever found -- about the size of a large suitcase.

The single greatest enigma about the sprockets is, of course, where do they come from? All available evidence suggest that they do not originate from any sort of fixed point on or above the earth, but seem to "just happen" somewhere between the Earth's outer atmosphere and the edge of its gravity well. From there, they begin their long fall inward.

Scientists rapidly concluded that no modern terrestrial technology could produce the sprockets. The most common belief now is that the earth is being "seeded" with the sprockets for some unknown reason. Scientists now soberly debate whether the creators of the sprockets are more likely to turn out to be alien beings or time-traveling humans from earth's future. A significant minority holds that the sprockets are a form of psychoactive extraterrestrial pseudo-life. Attracted to earth by its rich atmosphere, the sprocket takes its vehicular form from the subconscious mind of its triggerer.

One highly controversial theory regarding sprockets is the so-called "Nernst Effect," which postulates that a sprocket somehow selects a master who is most likely to make use of its abilities, or perhaps configures itself to meet its master's needs -- just as Nernst, a farmer, found a highly useful farm vehicle. Statistical evidence for the Nernst Effect is inconclusive -- results depend entirely on how broadly one defines a sprocket's usefulness. Certainly the Nernst Effect is not a universal -- well-known counter-examples include the deep-sea submersible found by a Death Valley hermit, and the heavy earth mover found by a U.S. Navy ship at sea.

Sprocket Stuff

A newly-expanded sprocket has one function and one function only -- it is a vehicle. Sprockets are almost never found with armament, galley or sanitary facilities, communications devices or even door locks -- no extras not directly related to getting from point A to point B. Most sprockets will, however, have surfaces or enclosures where such extras can be conveniently installed or mounted.

At first, installation of extras in sprockets was a bit of a problem. It was almost impossible to penetrate the sprocket-stuff with mounting bolts, and when a bolt was successfully driven, the sprocket's regenerative powers would just push it back out in a day or two. Eventually, however, it was discovered that by using nonferrous bolts in a low-intensity electromagnetic field, the sprocket stuff could be made more malleable, taking the bolt easily and retaining it once it was installed. This process has become known as "coaxing." (Several national governments are believed to be researching possible application of the coaxing process to anti-sprocket weapons.)

If too many accessories are installed, however, the Sprocket loses its ability to contract. If the sprocket's cargo exceeds about 5% of its expanded weight, the sprocket can no longer change. Therefore, most installed extras are designed for easy removal. A long-range radio, for instance, weighing 50 lbs. or more, could be removed in about 10 minutes, leaving behind only its mounting plate and the plate's bolts, both made of a lightweight plastic or alloy, weighing less than a pound. Within this weight limit, however, most installed extras appear to be completely unaffected by the transformation process (major exception: magnetic media like tapes and computer disks appear to lose their data if subjected to a sprocket change).

So far, nobody's been able to come up with a way to run an accessory off the sprocket's power source. Powered extras require a battery or some other energy source.

A sprocket will also refuse to change if it contains more than about an ounce of organic matter, be it animal or vegetable. Sprocket pilots soon condition themselves to remove all food and textiles from the sprocket before triggering the change.

Researchers have identified eight distinct elements which define an expanded sprocket. Three are universal, five are optional.


The hull of the sprocket generally defines its use. Does it have wheels, tracks or wings? Is is streamlined, and if so, how much?

A typical sprocket hull has 25 DR and 30 HP (but see "Armor and Hardpoints," below). Any sprocket with an enclosed bottom is watertight. Any completely enclosed sprocket is airtight (this assumes, of course, that all exterior doors and vents are sealed).

Flitters usually have some sort of wing, for lift and maneuverability, ground vehicles have tracks, wheels or legs, seagoing sprockets often have an anchor of some type.

Power Nodes

The power node is the most important but least understood part of the sprocket, the very heart of the mystery.

On every sprocket there is a small solid area of exceptional toughness (at least 50 hit points and 100 DR, sometimes more). This area cannot be coaxed, and ranges in size from the approximate volume of a baseball to that of a 50-gallon drum. Researchers call this the "power node," and believe that it is the source of the sprocket's energy. In general, larger sprockets seem to require larger power nodes.

As near as anybody can figure out, power nodes convert atmospheric gases (or sometimes water, in aquatic sprockets) directly to kinetic energy. Sprockets don't have jets, propellers or drive shafts -- they just seem to push themselves along over the ground or through the water or air.

Control Station

Every sprocket has a control station, consisting of the pilot's seat and the control panel proper. On the smallest one-man "scooters" the control station can be as simple as an open saddle and a steering handle, but normally it consists of a comfortable, adjustable contour chair and a dashboard-sized control panel consisting mostly of pressure plates. The control panel is always lighted when the ambient light drops below a certain point.

Every function of sprocket operation can usually be performed from the control panel, with the notable exception of contraction -- the contraction control is always found within reach of the entrance.

All sprockets so far require only one pilot, but a few of the very largest sprockets have been found with an extra, redundant control station, apparently as a safety feature.

Imaging and Navigation

The sensor and imaging capacity of sprockets varies greatly. An open, one-man scooter might have no more than a single "headlight" and a reflective surface to serve as a rearview mirror. Farmer Nernst's "truck" had its rear-view wind screen, 360-degree illumination and a front spotlight.

On the other hand, a very fast flitter, or a very large ship, would typically have more complex capabilities, possibly including telescopic imaging, night vision and radar-or sonar-like functions.

Sprockets do not, however, have intrinsic communications or long-range navigational aids -- these must be added as accessories. They also lack automatic pilots, and nobody has been able to develop a practical autopilot for any sort of sprocket.

Cargo and Passenger Areas

Most sprockets will have some sort of cargo area. This could be as small as an open depression the size of a wok, or as large as multiple enclosed cargo bays, each the size of a family home. Cargo areas open to the elements usually have some sort of drainage vents, which can be left open or closed (some seagoing sprockets have extremely efficient pumps). Access to cargo areas is through sliding doors or gates.

Some sprockets are passenger carriers. Passenger seats are quite comfortable, and leave no doubt that regardless of who or what built the sprockets, they built them for human bodies.

Some passenger carriers have a toggle switch on the control panel which allows the passenger compartment to be converted into an open cargo area. If the switch is moved, and then the sprocket is contracted, when the sprocket is expanded again the seats will be gone and the area they occupied open. Other sprockets have a similar toggle switch which affects the roof, making them "convertibles."

Armor and Hardpoints

Some sprocket hulls are much tougher than average -- as much as four or five times more resistant to damage than a normal hull. Sometimes this hardening applies to the whole exterior of the hull -- other times only a certain facing or area will be reinforced. Needless to say, armored or reinforced sprockets are greatly desired for military applications.

Armored sprocket stuff can still be "coaxed," but a proportionally more intense electromagnetic field is required, which in turn requires more powerful and expensive equipment, which makes accessorizing a hardened sprocket generally more difficult and often more expensive.

In game terms, armored sprockets have more DR, but the same hit points. The power node of an armored sprocket will always have DR at least equal to the DR of the toughest external hardpoint.

Climate Control

All enclosed or encloseable sprockets seem to have climate control. Ventilation is good (provided the air vents aren't deliberately sealed) and interior temperature remains within the range of 70 to 80 degrees, whether the sprocket is under the polar ice cap or hovering over the caldera of a volcano.

On some sprockets -- notably submarines and very high altitude flitters -- climate control can be much more sophisticated. Stratospheric flitters have the ability to maintain sea-level air pressure in enclosed areas, keeping the oxygen constantly replenished at ideal levels. Submarines are even more impressive, not only maintaining correct pressure, even during rapid dives or ascents, displaying the ability to filter oxygen out of sea water for the crew to breathe.

Special Features

This is a catch-all category for any unusual capabilities that the individual sprocket might possess. One of the most common categories of special features is external manipulators -- these include arms, pincers, blades and shovels which the driver can use to manipulate or displace objects outside the sprocket.

Although sprockets do not seem to come with weapons as such, certain special features do have an intrinsic offensive capacity. One tracked sprocket is able to extrude a 12' spike with enough force to penetrate 3" of steel plate. Two sprockets have shown the ability to generate a laser beam of lethal intensity. Rumors abound of sprockets able to heat their surroundings to the point of spontaneous combustion, or sprockets able to generate a highly injurious field of sonic vibrations.

A persistent rumor among sprocket aficionados is the "coffin," a recessed, human-sized cavity supposedly found in one sprocket (reports vary wildly as to the form and function of the sprocket). According to the rumor, a human or animal can lie in the "coffin" and the sprocket will compress normally with the passenger still inside. When the sprocket is re-expanded, it is said that the passenger will have no memory or physiological evidence of elapsed time. If the coffin really exists, its sprocket could provide a means of efficient one-way time travel. Most reputable authorities, however, consider the legend of the coffin absurd, or at least unsupported by solid evidence.


Among sprocket buffs, there are few events more exciting than the discovery of an "exotic" -- a sprocket that conforms to no other previously-known configuration, or that violates the normal "rules" of sprocket operation.

"Walkers" -- sprockets that move on legs -- are quite common. Most are bipedal or quadrupedal, with the cockpit/cargo space mounted above the jointed legs, but some have more exotic configurations. There are several "spiders," with 5 to 12 spindly legs that can instantly change direction and climb effortlessly over the roughest terrain. The Corpus Crab is a unique amphibious walker with 8 legs and two front-mounted "pincers" that can be used to hold and manipulate (and, if necessary, severely damage) external objects. Perhaps the strangest exotic sprocket is a tripod which moves by whirling its legs around while the pilot sits above in a gyroscopically-stabilized bubble (at least, researchers think it's gyroscopically stabilized, though if there is a gyroscope it's completely internal and invisible).

Some sprockets are simply inexplicable. The Heaven Hopper, for example, is a small, one-of-a-kind bubble-shaped sprocket with two seats and no cargo capacity. It has only one control -- when the plate is toggled, the hopper flies straight up into the upper stratosphere, then descends rapidly, landing at the exact same spot from which it was launched. It has no other maneuvering capability whatsoever. Nobody has any idea what it might be intended to do. It can't even function as a carnival amusement, since it has no windows.

You and Your Sprocket

Sprocketfall proved to be a major headache for governments worldwide, and national policy on sprockets varies widely from country to country. Under dictatorial regimes, all sprockets are the property of the state. In some countries the initial keying of a sprocket without direct orders from the government is a crime. In others, an individual who masters a sprocket is subject to automatic induction into his country's military as a sprocket pilot.

The U.S. has the most liberal sprocket policy worldwide. In the U.S., a sprocket which falls on private property belongs to the owner of that property, unless the land is being rented or leased, in which case the sprocket belongs to the "primary custodian" of the land -- usually the renter. Sprockets which fall on public lands belong to the finder, as do sprockets recovered at sea. If an on-duty soldier, government official or government employee finds a sprocket on public or government property, that sprocket belongs to the finder's employer. All sprockets recovered on military bases or reservations, or found by military ships, become government property.

There have been no laws passed forbidding anyone from knowingly or unknowingly mastering a sprocket, but if someone knowingly or carelessly masters a sprocket which he does not own, without the owner's prior knowledge and permission, he is subject to civil suit for damages. If an employee (including government employees and soldiers) masters a sprocket belonging to his employer without authorization, he is also subject to administrative penalties at the employer's discretion, up to and including termination of employment.

The only other rule of sprocket triggering is one of common sense: Make sure you have enough room for whatever the sprocket will expand into. There have been cases of stupid sprocket finders triggering the transformation in a closed space like a garage, only to be crushed when the sprocket grew to a much larger size. Deliberately triggering a sprocket in a too-small space so as to harm persons or property is, of course, a crime, depending on the harm done. An expanding sprocket is not the theoretical "unstoppable force," either -- if it encounters an anchored object with 50 hit points or more, it will reverse its transformation, shrinking back to its original size and form. Objects with less than 50 hit points, unless they can be pushed aside, will be broken or crushed by the expanding vehicle.

A new sprocket owner must register his sprocket with the local government within one week of finding it (this time limit can be extended due to mitigating circumstances like disability, illness or extreme geographical isolation). Once a sprocket has been registered, anyone with a counter-claim to ownership must prove their claim in court. Registration includes a detailed description of the sprocket in terms of form (in both expanded and contracted configurations) and function, often including photographs.

While the ownership of the sprocket might be cut and dried, the owner's right to drive it is not so clear cut. Sprockets are subject to all laws and regulations which apply to any other vehicle of similar type. In order to operate a sprocket on public roads, waterways or air lanes the owner must demonstrate a working knowledge of all applicable laws and regulations, and a reasonable proficiency with the sprocket itself. Unlicensed operation of a sprocket is a misdemeanor, except on private property.

Because of the unique nature of sprocket operation, most operator's licenses are granted for a single sprocket only. It is possible to be licensed to operate a whole class of sprockets, but this requires a much longer and more intensive training course -- such training is normally only available through the military, although a truly dedicated hobbyist can sometimes obtain it through sprocket clubs (see below).

The government has the right to restrict the use of sprockets which can interfere with traffic (for instance, a very slow walker) or damage roads (a very heavy tracked vehicle). There is also a federal law which provides for government confiscation of any sprocket which presents "a clear and present threat to national security or public safety," but this law is very seldom used, and is often successfully appealed.

Any time within the first year after a new sprocket is registered, the government has the right to request that it be turned in for scientific analysis. Once the request is made, the owner has up to six months to comply. The government can hold any sprocket for analysis for up to one week -- if held any longer, the owner must be financially reimbursed for any loss or inconvenience due to the absence of the sprocket. The government may not, under any circumstance, hold a sprocket for analysis for more than 30 days without the owner's express consent. The government is forbidden by law to harm any sprocket during analysis, and if it inadvertently does so the owner is entitled to financial reparations.

Currently all sprocket laws and regulations are administered by the states, under federal guidelines. There is talk of creating a federal sprocket administration, but little concrete effort in that direction.

It is normally illegal for a private citizen to mount any offensive or defensive weaponry on his sprocket, but military and police sprockets are often armed.

Sprocket Clubs

As sprockets become more widely distributed throughout society, sprocket owners and fanciers have formed a variety of municipal or regional private sprocket clubs. These offer sprocket owners a chance to meet, compare notes, socialize, hold races and other competitions and sometimes even familiarize themselves with the operation of sprockets other than their own.

The largest private sprocket organization is the American Sprocket Pilots Association (ASPA), which coordinates national conventions, sprocket competition and lobbying efforts on behalf of sprocket owners. ASPA also provides reasonably-priced group liability and theft insurance programs to sprocket pilots and owners.

There are several national magazines designed for sprocket pilots and fanciers. The most popular such magazine is Sprocket Set, with a bimonthly international circulation of almost 100,000.

The Sprocket Market

Sprockets can be bought on the open market, although sprocket sales presents a number of unique problems. Once the sprocket has been keyed, it's much, much harder for anybody except the initial master to operate. On the other hand, before the sprocket is keyed, the prospective purchaser has no idea whether he's getting a luxury yacht or a light cargo hauler. Because of this uncertainty, there are no hard-and-fast rules in the sprocket market. Each deal is absolutely unique.

Most large cities have dedicated sprocket shops which specialize in "coaxing" sprocket modification or custom paint jobs. These establishments are usually the best place to go if you want to purchase a sprocket -- there are no sprocket showrooms.

The most unique profession to come out of sprocketfall is the sprocket prospector. These hardy souls comb remote and isolated wilderness areas searching public land for unclaimed sprockets. This profession has become rather romanticized in recent years, but it's a tedious and very risky career, and most who try it fail.

Gaming Sprockets

Most characters in a Sprockets campaign should be built on 75 to 150 points, with 100-point characters being the norm. If the Sprockets are to be the focus of the campaign, the emphasis should be on their abilities, not their pilots'. Of course, Sprockets can also be added to any other sort of campaign.

If the GM wants the players to design their own sprockets, he can give each PC a budget to do the job, depending on the nature of the campaign, in addition to his normal starting wealth. How much? Simple sprockets can cost as little as $20,000, while most land vehicles are in excess of $100,000 -- and flying or submersible sprockets can easily run into the millions. Whatever budget you set, make sure these "sprocket dollars" are virtual cash which can only be spent to design an unmodified sprocket. Once the sprocket is designed, any remaining money in the design budget is gone for good. Any modifications must be paid for with normal Wealth.

On the other hand, if there are only one or two sprockets in the group, the GM may find it better to forget about budgetary concerns, and just design the sprocket that best fits the needs of his campaign.

The following advantage and two skills are unique to a sprockets campaign.

Sprocket Link 15 points

You were the first one to key your sprocket, and you have an almost instinctive understanding of its operation and capabilities. This advantage automatically gives you the Pilot Imprinted Sprocket skill at IQ level.

Sprocket Link must be bought separately for each sprocket you master (the GM may also rule that no PC can key more than one sprocket).

Normally this advantage is only available to a character who was actually the first human being to key a newly-fallen sprocket, and only one person may be imprinted to a given sprocket. The only exceptions are identical twins or biological children of the person who keyed the sprocket, who may buy a link to the same sprocket if they pay an additional 10-point Unusual Background.

Pilot Sprocket (type) M/VH

Defaults to IQ-12, similar vehicle skill -8, or Pilot Imprinted Sprocket -5*

You have intensively studied sprocket operation, and have learned to operate most sprockets of a given type (sample types: wheeled, tracked, walkers, hovers, floaters, flitters, watercraft, submarines). Note that for default purposes, there is no similar modern vehicle skill which corresponds to Pilot Sprocket (Walker).

* If you have a Sprocket Link, you get an extremely favorable default when piloting sprockets of a similar type to the one you're linked to. However, the maximum skill level in Pilot Sprocket available as a default from Pilot Imprinted Sprocket is 11. If you wish to increase your Pilot Sprocket skill beyond 11, you must do so using Mental/Very Hard point costs.

Pilot Imprinted Sprocket M/E

No default

This skill is only available to characters with the Sprocket Link advantage. The full benefit applies only to the individual sprocket keyed, but this skill defaults very favorably to the Pilot Sprocket (type) skill. See above.

The Sprocket Link advantage includes this skill at IQ level. Pilot Imprinted Sprocket may be taken at greater than IQ level at character creation by spending additional character points.

Sprocket Campaigns

Once sprockets are introduced to the campaign, how can the PCs use them for adventuring?


This is a very low-key campaign, suitable for low-point-value characters. The PCs are private sprocket owners, perhaps the members of a local sprocket club. They use their sprockets in races and competitions, in search operations and rescues, and perhaps to fight local criminals or hoodlums.


This is a less plausible, but more exciting variation of the "hobbyists" campaign. The PCs are private citizens who use their sprockets to fight crime on an ongoing, organized basis. In addition to their sprockets, the PCs probably represent a variety of useful crimefighting skills and backgrounds. The vigilantes might work with the law, outside the law, or depending on the circumstances, both.


The adventurers are on the run, and are using their sprockets to stay ahead of their would-be captors. PCs can be real criminals on the lam, or falsely-accused innocents. They can also be running from an organized crime boss, corrupt corporation or dishonest politician that covets their sprockets.

A variation of this campaign might have the party as revolutionaries using their sprockets to fight an oppressive foreign regime, or even a dictatorial alternate U.S. government.

Law Enforcement

This campaign revolves around a team of cops or federal agents that uses their sprockets to track and capture dangerous criminals. In this campaign, sprockets might be lightly armed.

Fast Response Team

This is a military campaign, centered on a special forces squad of sprocket-mounted soldiers or mercenaries fighting terrorists or hostile governments in international hot-spots like the Persian Gulf, Bosnia or Central America. The team's sprockets are certain to be armed to the teeth. Since sprockets need no fuel, and very little maintenance, they would be greatly favored by covert or guerrilla operations units.


Whoever dropped the sprockets did so because the earth was in imminent danger of invasion from another world. Now the aliens are here, and the sprocket pilots are at the vanguard of global defense.


Suppose sprockets are really evil? What if they eat people? What if they eat souls? What if they're just biding their time posing as non-sentient vehicles until enough of them arrive that they can take over? Why do some people who attempt to master a sprocket just vanish, screaming?

In this campaign the PCs can be cornerstone of an anti-sprocket resistance -- the first (surviving) humans to guess the sprockets' true nature. Or, for an even more paranoid option, everyone might know that the sprockets are evil, but use them anyway, either because the benefits outweigh the negatives (in the short term), or because the sprockets won't let humanity stop using them.

Other Genres

The alternate-present world of sprockets can be easily incorporated into other modern-day genres like Espionage or Special Ops. The sprockets' mysterious origin makes them a natural for Illuminati campaigns, and their powers make them equally suitable for Supers. Supers and sprockets are a natural match, as their powers and connections will make it significantly easier for supers to detect sprocketfalls and beat competitors to fallen sprockets.

Sprockets can also be used in eras or worlds other than our own. It's easy to introduce sprockets into any futuristic campaign, but with a little effort they can even be used in a historical or fantasy campaign. In a low-tech milieu, sprockets would probably be regarded as either bizarre (possibly sinister) magical artifacts or as gifts from the gods. Their pilots would be equally likely to be regarded as either divinely blessed or demon possessed.

Sprockets have several advantages over other vehicle types, most especially the fact that they don't require fuel or more than minimal maintenance. They would be a godsend to time travelers or interplanetary scouts in the field (although, as described above, the known types of sprockets can only be used on worlds with a significant atmosphere).

In a post-holocaust campaign, sprockets could become literally the most important objects in the world. Immediately after the "big one," sprockets would play a key role in rescue and relief operations, and in public security, due to their durability (sprockets are probably immune to EMP and most forms of radiation) and lack of logistical needs. A few generations later, most of humanity might be reduced to hand-carts and water wheels, but the sprockets will still be as shiny and efficient as ever.

Sprocket Damage

A sprocket which is damaged to 0 hit points can no longer operate, but can change. The ability to change form is lost when the sprocket is reduced to a negative value equal to its total hit points.

Sprockets regenerate one hit point per day, as long as they are not operated or changed during that day. The ability to regenerate is only lost if the power node is reduced to negative hit points.

Building Sprockets

You will need the rules in GURPS Vehicles to build sprockets. But the information there doesn't really describe how a sprocket works -- it just gives you a framework for describing the vehicle's capabilities. When it says (in one of the sample vehicle below, for example) that a sprocket has a Fusion Air-Ram with 30,000 lbs. of thrust, that exact piece of equipment is not really on the airplane -- it's just that whatever it is that makes the SkyFlitter go, its performance characteristics come closest to that Air-Ram. Keep that in mind as you go through the vehicle-building process.

Sprockets are, inherently, simple vehicles. Everything about them is geared toward the basic job of transportation; sprockets do not come with CB radios, tape decks, galleys, sleeping quarters, weapons, or anything else that could be considered an "extra." The only things in the "Accessories" section of GURPS Vehicles that will commonly be found in a sprocket are advanced controls and some sort of sensor system. The visibility from inside a sprocket is typically the equivalent of Advanced Low Light TV (p. V76), though most submersible and airborne sprockets also have some sort of sonar and/or radar as well.

When determining the "virtual cost" of your sprocket as you design it and the availability of components, treat a sprocket as TL 13 -- except for the armor and hardpoints, which are TL 15, and the power node.

A sprocket's power node is a complete mystery to modern science -- the closest thing to it in GURPS Vehicles is a TL 14 Total Conversion power plant (p. V35). The power node is not a separate component -- it's weight, cost and volume are all included in the stats for the basic body of the sprocket. How much power does the power node produce? There is no tried and true mathematical formula; the answer seems to be, "enough." When designing a sprocket, just decide what you want it to do (within reason -- farm tractors that can break the land speed record, or ocean liners that can reach escape velocity, or motorcycles that can pull 30-ton loads, should be vetoed by the GM) and assume that the power node has enough juice to get it done.

After the basic sprocket has been built, using the "virtual cash" in the budget set by the referee, you can add accessories. Accessories are limited to the Tech Level of the campaign, and must be paid for (out of "real" money) by the owner. Worthwhile extras might include radios and other communications equipment, supplementary sensor and imaging equipment, crew quarters, sanitary facilities, galley, even simple things like door locks. Remember that a sprocket cannot transform into its unexpanded mode if more than 5% of its total volume is taken up with accessories, though for some sprocket owners, this is not a consideration. Let's face it -- after adding over 500 hotel rooms, 3 restaurants, a theater, a bank vault, offices, and over 3,000 slot machines and gaming tables, the floating Cloud City is never going to be turned back into a suitcase-sized meteor . . .

To make these modifications, though, you need a Coaxing Kit:

Coaxing Kit, $750, weight 30 lbs.

This is a box of the special power tools needed to mount accessories to sprocket hulls. All screws and bolts must be tough but non-ferrous, and the tools themselves have the ability to generate an electromagnetic field. Each kit comes with a couple of hundred assorted non-ferrous bolts, screws, etc. This assortment can be replaced for $50, or they can be purchased individually for $1 each.

The kit above can coax mounts into sprocket-stuff of up to 40 DR. For twice the price a kit can be purchased which will coax sprocket-stuff up to 100 DR, and for three times the price, a kit is available which will coax any known sprocket hull.

Sample Sprockets

Halftrack Farm Vehicle

This is Howard Nernst's utility farm vehicle, the very first sprocket ever found:

Structure: 250 cf light advanced body, unstreamlined, maximum load 6,000 lbs. (body HT 250). Halftrack motive system (Wheels PD 2, DR 2, HT 41; tracks PD 3, DR 5, HT 83).
Propulsion: TL 9+ halftrack drivetrain with 27 kw motive power.
Power: Power Node (HT 50).
Accommodation: Roomy internal seats for pilot and passenger.
Vision: Many windows, virtual panorama.
Accessories: ALLTV.
Armor: 150 points standard armor. 5/25 each side.
Cargo: 100 cf.
Statistics: $61,240, design mass 268.25 lbs., max. payload 5,731.75 lbs., max. cargo load 2,400 lbs., loaded mass 2,668.25 lbs. (1.33 tons), Size Modifier/IR/Radar Signature +4, Acoustic Signature +3.
Ground Performance: Ground speed factor 20, top speed 135 mph, acceleration 13.5 mph/s, deceleration 20 mph/s, MR 0.5, SR 6.
Water Performance: None.
Air Performance: None.


This is one of the strangest sprockets ever found. It is a pentapod housing its pilot in a gyrostabilized cockpit above the leg "hip" rotor. It moves by rotating the "hip" section to bring one leg to contact the ground while the others are in the air. Despite its eccentric and seemingly unstable movement, it is very stable, each leg responding immediately to its controls so that it can walk over virtually any ground that the legs can clear. And standing atop 4-meter legs, that's a lot of ground.

The GyroWalker is also heavily armored, and quite dangerous -- it can step on or kick a target, with a ST 52 punch!

Structure: 150 cf medium unstreamlined advanced body, maximum load 6,000 lbs. (body HT 262). TL 9+ legs with Improved Suspension (4+; leg PD 4, DR 20, HT 52).
Propulsion: 4+ TL 9+ legs drivetrain with 515 kw motive power.
Power: Power Node (HT 50).
Accommodation: Roomy internal seat for pilot.
Vision: Few windows, Virtual Panorama.
Accessories: ALLTV, advanced controls.
Armor: 300 points of ablative, regenerative armor. 6/50 each location.
Cargo: 70 cf.
Statistics: $113,300, design mass 915 lbs., max. payload 5,085 lbs., max. cargo load 2,800 lbs., loaded mass 3,715 lbs. (1.8575 tons), Size Modifier/IR/Radar Signature +5*, Acoustic Signature +2**.
Ground Performance: Ground speed factor 18, top speed 117 mph, acceleration 27 mph/s, deceleration 25 mph/sec, MR 2.75, SR 5.
Water Performance: None.
Air Performance: None.

*The extra signature is due to the GyroWalker's prodigious height.
**Come on . . . its power supply may be silent, but those legs stomp.


The SkyFlitter is a pocket superjet -- just barely big enough for two, capable of awesome, Mach 4+ speeds, with enough cargo space for an extended stay in some far-away pleasure spot. It lands in a parking lot, turns on a dime, and (like all sprockets) zips into a briefcase-sized parcel when you're not using it.

Warning: The SkyFlitter isn't pressurized, and won't provide enough oxygen to go above a couple of miles of altitude! It produces plenty of heat through its ramjet, so cockpit heating is no problem, but bring your own oxygen if you want to soar higher. And pilots are warned that the SkyFlitter's VTOL engine is extremely destructive; operate from hard ground or hardened concrete only, unless you like boring holes in the ground with the jets...

Structure: 300 cf of light, advanced body, maximum load 7,500 lbs. (body HT 300). Radical aerodynamic streamlining with responsive hull, wings (combat-stressed, high-agility, canards, variable-sweep, waverider; PD 4, DR 20, HT 150/wing), Vertol system, sealed body.
Propulsion: Fusion air-ram with 30,000 lbs. of thrust (HT 50)
Power: Power Node (HT 50)
Accommodation: Roomy internal seats for pilot and passenger.
Vision: Few windows; virtual panorama.
Accessories: ALLTV, advanced controls.
Armor: 160 points standard armor; PD 4, DR 20 each location.
Cargo: 70 cf.
Statistics: $17,959,700; design mass 2,300 lbs., max. payload 5,200 lbs., max. cargo load 1,750 lbs., loaded mass 4,050 lbs. (2.025 tons), Size Modifier +4, Radar Signature +4, IR Signature +9, Acoustic Signature +4.
Ground Performance: None.
Water Performance: None.
Air Performance: Stall speed 0, air speed factor 216, top speed 4,210 mph, acceleration 39 mph/s, deceleration 10 mph/s, MR 20.5 (22.25 with variable wings deployed), SR 1, ceiling is limits of atmosphere (the sprocket needs sub-stratospheric atmosphere to operate).

Article publication date: December 1, 1994

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