Gravitics is the as-yet fictional science of artificially generating and manipulating gravity. This article mostly concerns small vehicles for use in and around planets or similar human-inhabited environments. An article on using gravitics for space drives is linked to at the end of this article.
Because we still do not fully understand the basic quantum nature of gravity, it is unknown if gravitic technology as discussed here could ever be developed in the real world. As such, its placement on the Tech Level scale is somewhat arbitrary and given to interpretation. Here, we place the theoretical breakthroughs for it at Tech Level 16, and practical applications of the technology follow in the levels shortly after that. This way, gravitic technology and vehicles can coincide with their use in space opera civilizations, where they're most often seen in science fiction stories. Because gravitics is still almost completely speculation, most of the discussion presented here comes from grav technology as depicted in science fiction.
Artificial gravity technology saturates popular scifi, appearing in Star Trek, Star Wars, Stargate SG-1, Babylon 5, Asimov's Foundation and Robot stories, Brin's Uplift novels, Niven's Known Space stories, and a large host of others. For on-screen sources, this is mostly a financial consideration; its much cheaper and easier to show actors walking around in Earth-normal gravity on spaceships and such than to spend large percentages of the budget showing them floating about in simulated zero gee. Hence, gravitics in those fictional sources are a mature and ubiquitous technology to rationalize away this limitation.
Artificial gravity technology also showed up in many other aspects of a franchise's universe as well, especially its vehicles. Sleek cars and other craft floating effortlessly through futuristic cityscapes is one of the most iconic visions of the future from any source. In most fictional universes where its shown, gravitic vehicles have in large part completely replaced other types of small vehicle propulsion, consigning wheels, propellers, jets, hovercraft, and so on to the realm of museums and hobbyists.
On the science side, gravity is the most well known and easily observed of the four fundamental forces of the universe, yet it is also by far the least understood. While gravity control has always been a popular feature of science fiction, it is also one of those speculative technologies whose exact workings in stories is always left conveniently obscure.
So far, the only way we know how to create a gravity field is the same way nature does--by piling a lot of matter in one place. In order to produce a gravity field equivalent to the planet Earth's, one needs a mass equivalent to Earth. However, as that could be very detrimental to many practical vehicle applications, other means of controlling this force would have to be found.
It would also be possible to create an 'artificial' gravity field by taking a mass of superdense matter and accelerating it to near-light speed, where it would accumulate more mass as it approached c. The gravity field would grow proportionately with its velocity, and if set in a ring or coil, like that of a particle accelerator, it would generate a gravity field that could be moderated by controlling the mass's velocity. Since it would be zipping through the coil so fast, the effects of its gravity would be felt all along the length of the coil without an appreciable drop off in performance. However, this scheme would require truly vast amounts of energy to achieve and sustain, usually at levels that would not be practical for most civilizations to apply.
A method that still relies on a great deal of still-fuzzy theory is to use quantum manipulation to create gravitons--the theoretical carrier particles of gravity. If a dense enough population of gravitons can be created for a given input of energy, practical artificial gravity generation may become possible.
Lacking the ability to do this, devices may instead concentrate on manipulating or enhancing existing gravity fields instead of generating their own from scratch. Again, this would probably rely on some advanced form of quantum particle manipulation we can only guess at with our humble twenty-first century understanding. Manipulating existing gravity fields could allow engineers to strengthen or weaken fields within a given range, or even shuffle fields about, allowing the force to be felt at angles differing from where the field actually originated from.
Another aspect that could arise from the artificial manipulation of gravity is the emergence of technology that utilizes a true anti-gravity, or repulsive, force. There is emerging evidence that anti-gravity of a sort may be at work in the cosmos in the form of so-called "dark energy", but its effects are very weak and can only be observed over very large--as in intergalactic--distances. An intricate understanding of gravity could also lead to the knowledge needed to understand and manipulate this new force of nature--if it is ever proven definitively to actually exist.
Antigravity would act like gravity, but would repel as opposed to attract. It could counteract gravity fields of like strength.
Most gravitic (often abbreviated as 'grav') vehicles are usually very similar to modern vehicles, but with gravitic mechanisms and generators in place of more conventional propulsion means. Their exact size and configuration would depend on their intended purpose. A small vehicle intended to operate near the ground and function as a means of personal transportation would appear very similarly to movdern day cars, but with gravitic suspension instead of wheel. One intended for high-altitude, high-speed flight would still look very sleek and still sport wings and other control surfaces to regulate airflow over its surface.
Gravitic vehicles as depicted in science fiction are amazingly versatile. They can glide close to the ground like a hovercraft, fly like a conventional aircraft, and hover in mid-air like a helicopter. They are very quiet, have long ranges, have relatively low power requirements, and often offer very smooth, hassle-free rides.
Whether they actually would be so idealized in reality would be another matter. Given the specific type of gravitic propulsion used, they could present a number of hazards beyond the usual vehicle headaches of mechanical problems and fuel costs. Gravity neutralizers would negate gravity not only on the vehicle in general but also on those inside, forcing them to deal with zero-gravity effects inside the vehicle. A gravitic repulsor might make for a very bumpy ride as it glides over variations in the local gravity field. Riding a combined gravity drive with its many fluctuating modes of gravity manipulation might be akin to riding a roller coaster. People on the ground under or near a grav vehicle could also experience discomfort or disorientation from the craft's varying gravitic influence.
Power requirements would be another consideration. Gravitic propulsion in science fiction is usually portrayed as some quantum trick or technique, and often does not require more power than, say, modern-day aircraft of comparable size. Whether this will bear out if gravitics becomes a reality remains to be seen. Even so, given the Tech Level gravitics is assumed to become a practical applied technology (17), potent compact power sources may be readily available for them no matter their actual requirements.
Whether gravitic vehicles would displace other types of transportation would depend on how easy they are to engineer and how energy-efficient gravitic engines would be. If they were at least as economical as other vehicles of equivalent size and capability, they would likely rise to dominance because of their versatility and utility. If they were very expensive and difficult to produce, they would probably be reserved only for certain special functions, and/or as status symbols.
How a society handled the proliferation of antigravity vehicles would vary, but its safe to assume that they would be much more heavily regulated than automobiles are today. The possibility of catastrophic and deadly crashes increases exponentially when you add a third dimension. Aircraft deaths and injuries today are much less than those of cars in part because of much stricter operating requirements and regulations.
But its also because there are much fewer aircraft in the sky than there are automobiles on the ground--an equation that could change dramatically with the advent of cheap gravitic vehicles. The biggest economic stumbling block to the wide spread use of this technology at first may not be the cost of development, purchase, or maintenance, but that of insurance costs. Gravitic vehicles may eventually be forced to use regulated 'sky ways' to keep crashes in heavily-populated areas concentrated to places where emergency facilities are close by, and sophisticated autopilots specializing in safety may become mandatory except in special circumstances. Certain sensitive areas, like government facilities, historical monuments, and so on, would likely be no-fly zones.
The upper speed of a grav vehicle would depend on its sophistication, but in science fiction they are depicted as averaging below Mach 1, and usually not much faster than an average civilian prop plane. Very high tech models, or those with specialized purposes such as combat vehicles, may be able to fly much faster, even at hypersonic speeds.
But despite these potential drawbacks, grav vehicles would offer unprecedented freedom of movement for those who owned one. Imagine being able to drive literally anywhere within its range, no roads required, and with less overall travel time than modern cars. For societies that put a great deal of emphasis on personal mobility, like the USA, a vehicle like a grav car would be the ultimate expression of that ideal.
Below are a listing of gravitic vehicle types commonly found in science fiction. Some of these may warrant their own dedicated articles on Orbital Vector in the future.
Also called a hover pack, grav pack, or a grav belt. This is not technically a vehicle, but a minimal means of flying transportation. A gravitic harness is basically a compact gravitic engine and power source configured into a backpack for personal use. The user would strap it on, activate the harness, and fly away. In many ways it would be similar in use to a jet pack or an astronaut's manned maneuvering unit, except it would use gravitic propulsion.
Controls are most often envisioned as one or two joysticks attached by articulated metal arms to the grav harness. Other means of control are possible, such as glove or belt controls, or through a cybernetic link.
Depending on the power source and efficiency of the engine, a user may remain aloft anywhere from less than a minute to many hours. Their top speed are generally limited to considerably less than 120 miles per hour, beyond which an unprotected human would find it increasingly hard to catch his breath. Users properly equipped with protective clothing and an air supply, such as the grav belt-equipped Powered Armor Troopers in the Traveller universe, may be able to go much faster.
Also sometimes called a grav sled, hover sled, hoverboard, grav pod, or grav disk. Probably the most well-known example is the hoverboard from the Back to the Future movie series. It usually has a wide, flat surface, sometimes with raised edges and sometimes not. It also sometimes has a raised steering column or can be run by remote or through foot-pad controls.
This is by far the simplest type of gravitic vehicle, basically a gravitic engine and a power source with a flat surface built directly on top of both. Small versions can be used for personal transport (think of a Segway that floats), while large versions can be used for hauling cargo.
This is small, one or two person open vehicle configured horizontally similarly to a motorcycle. It is often depicted as being similarly operated, with the rider manipulating handlebar-like controls. And like with real motorcycles, these would probably have only a limited utility niche, but may still be widely used in sports and as a style choice.
The professed dream of almost every futurist, this is small multi-person flying vehicle of similar size and configuration to modern-day automobiles. Examples include the Jetson's bubble car, aerodynes from Blade Runner, and air-rafts from the Traveller tabletop RPG. They are also depicted as coming in as many models and types as real cars and trucks, sometimes being nothing more than current road models with a gravitic suspension instead of wheels. There would be gravitic convertibles, gravitic vans, gravitic pick-up trucks, and so on.
Most popularly seen in the Star Wars movies, these are gravitic vehicles designed to stay low to the ground but travel at high land speeds, much like a very advanced form of hovercraft. However, they would be far quieter, and not require a skirt in contact with the ground for stability. They could travel equally well over water as well as land, and depending on the model can lift themselves higher for a short time to clear almost any major obstacle.
Some speeders may be armed, and would be used very similarly to modern military hovercraft or hovertanks.
These are armored fighting vehicles with gravitic engines. Their use would be very similar to that of modern-day attack helicopters, but because they can carry much heavier loads, can be much more heavily armored and carry more potent firepower. How exactly they are configured would depend on the kind of targets they are designed to engage. Ground-strafing grav tanks would have its main armament underslung on its main chassis; a grav tank designed to fire against airborne targets such as other grav tanks may have a configuration similar to modern tanks; one designed for a variety of roles may have turrets along two or more axes, or may have a main gun turret that can track in all three dimensions. They may even be made spherical to allow 360-degree target tracking.
Capabilities would depend on the supporting technology level, but even so low-recoil main weapons would usually be the best choice for them, such as lasers or particle beams. More sophisticated models may have adequate enough compensation systems to carry high-recoil weapons like conventional tank guns or plasma cannons.
Grav tanks are a popular feature in the Traveller and Warhammer 40K tabletop RPG universes, and they can occasionally be seen in the Star Wars movies and extended universe.
These are essentially grav tanks with a spinal mount configuration--the vehicle is built around a single immense weapon rather than just having the weapon attached in a turret. This allows a much more powerful weapon to be carried than normal by sacrificing some maneuverability and targeting flexibility. The entire vehicle has to turn to track and target an enemy with direct fire. It makes up for this by the increased range and damage potential of its much larger spinal-mount gun.
The darling of military scifi anime for decades now, these are pretty much what the name implies--large gravitic-enabled battle wagons bristling with guns and armor, each the size of modern naval warships or bigger. They are often configured similarly to naval ships as well, because their bulk and weight often dictates them being moored in the water when not in the air.
Flying battleships often overlap in capability with space battleships, but some, such as in the anime series The Last Exile, are designed to operate within an atmosphere only.
Made famous by many science fiction sources, particularly the Cloud City of Bespin in the movie The Empire Strikes Back, these are basically grav platforms sporting structures the size of modern buildings or larger. As the name implies, these are designed to act as residences for what could be many thousands of people. They are also usually designed to float or be moored in one particular place, but they can be made mobile if necessary. As vehicles, however, they would usually be very slow and ponderous.
|<GRAVITY NEUTRALIZER VEHICLES
Tech Level: 17
|The flying "spinner" cars from the movie Blade Runner appeared to use gravity neutralizers combined with ducted-air propulsion.|
These vehicles would use a device that exerts a field to prevents gravitons from outside the field from interacting with mass inside of it. In other words, it cuts off the vehicle wholly or in part from any surrounding gravity field. A gravity neutralizer is also sometimes called a gravitic shield, as it "shields" the mass within from outside gravitational influence.
One method suggested for doing this is to surround the mass with a material that has anti-gravity properties, such as negative matter. However, generating or cultivating enough negative matter, still a theoretical substance, could prove very difficult. One would need as much negative matter for the shell as normal matter in the vehicle in order to completely shield it from surrounding gravity fields.
Another method may use advanced quantum manipulation to generate dense amounts of anti-gravitons along the outer shell of the mass to be lifted. The anti-gravitons cancel out the incoming gravitons from the surrounding masses. The more energy fed into the system, the more anti-gravitons are generated, and the more normal gravitons are intercepted and neutralized.
Gravity neutralizers need not totally cancel out the surrounding gravity field; it can do so partially in order to lighten the load of the vehicle and make it easier to move through other means.
Note that neutralizing local gravitational influence should not be confused with neutralizing the vehicle's mass. A 50-ton gravity-neutralized vehicle will still resist changes to its state of motion as any normal 50-ton vehicle, aside from any direct effects of the gravity shielding. By their nature, gravity neutralizers usually have to be coupled with another means of locomotion in order to get the vehicle to go where the pilot wants.
If used to completely neutralize the local gravity field, air pressure and wind will slowly push the vehicle upward. In many ways, a gravity-neutralized object will act like a hot air balloon, but with no upper ceiling to how far it can rise. If left completely on its own, a gravity neutralizer would eventually drift the vehicle up into orbit or beyond after a number of hours.
Masses can enter or leave the gravity-neutralizing field freely. More or less mass within the field may require more or less energy by the device to maintain its effect.
There seems to be a bit of a debate as to what happens to any object that's directly above a gravity-neutralizing field. The gravity field directly below it is cut off, so does that mean it will float off into space as well?
The answer is no. While the gravity directly below it is cut off, its assumed that close to the surface of a planet the planet's mass is still acting on it from other angles. Imagine yourself fifty feet above a gravity-shielded object anchored to the ground. The gravity neutralizing field is 10 feet in diameter. Directly below you there is no gravity, but gravity is still reaching you at an angle from the surrounding landscape. The amount of gee forces you experience may be less than normal, and you may certainly feel lighter, but there is little chance of you floating up unchecked.
The higher the gravity-neutralizing field is, however, the more of the planet's gravitational influence is blocked on an object above it by the field. So if you maintain your fifty-foot distance above the gravity-shielded object, you will feel gravity falling off more and more sharply as you and the vehicle ascend.
Usually a secondary means of locomotion will be employed with a gravity neutralizer in order to make the vehicle much more useful. The neutralizer will negate its weight, allowing its secondary means of propulsion to work much more efficiently without expending the energy it would normally need to fight gravity as well. A good metaphor for this type of vehicle would be a blimp--the gas envelop provides the lift, while a secondary source of propulsion--propellers--make the ship go where the pilot wants. Unlike a blimp, however, the neutralizer would work on any type of vehicle that can mount it, whether it be a car or an airplane or a spaceship.
Gravity neutralizers are ineffective as a means of locomotion away from large source of gravity, like a planet. They will prove useless in deep space, for instance.
The opposite of a gravitic neutralizer, an enhancer multiplies and intensifies the effects of gravity on a mass, by creating many more gravitons around it than it could generate normally. This increase in graviton flux enhances the attraction between the gravitic-enhanced object and any other nearby mass or gravitic field.
Gravitic enhancers' role in propulsion is mostly to work in conjunction with more advanced artificial gravity propulsion schemes, allowing them to generate and use gravity fields of immense strength, but would sometimes be used singularly in specialized circumstances, such as in orbital bombardment by kinetic energy weapons.
|<GRAVITIC REPULSOR VEHICLES
Tech Level: 18
|Luke Skywalker's iconic landspeeder from the movie Star Wars is an example of a gravitic repulsor vehicle. Image copyright Lucasfilm.|
As our understanding of gravity grows sophisticated enough to allow its outright manipulation, it may lead to the discovery and understanding of a true anti-gravity force. Even though the existence of an anti-gravity force is currently postulated by many theorists, it has yet to be proven to actually exist. However, if it does, gravitic technology would seem to inevitably lead to its manipulation and artificial generation.
As previously stated, both "negative matter" and "dark energy" are theorized to have anti-gravity-like properties. A gravitic repulsor may need to have some quantity of one or the other, either with the exotic substance acting on its own or its effects intensified in some way. Alternately, quantum manipulation may produce carrier particles of the force in sufficient quantity to produce noticeable counter-gravity effects.
True anti-gravity will act like gravity, but in reverse. It will push away matter instead of pulling it closer. The intensity at which it pushes will also be dependent on the inverse square law, unless artificially intensified or redirected in some way. Also, it needs a mass to push against--like a gravity neutralizer, the effectiveness of a gravitic repulsor as a means of propulsion will fall away quickly the farther from a planet it gets, and will be useless in deep space.
In many ways, a gravitic repulsor will act like a gravity neutralizer, basically counteracting the effects of gravity under the vehicle to allow lift. Gravity is not completely neutralized, however; even though gravity directly beneath the repulsor is countered, gravity from the planet's surface will still be acting on it from other angles. Unlike a neutralizer, however, a repulsor can be used for lateral propulsion in its own right. By canting one or more repulsor units on a vehicle at an angle to the ground, the vehicle will gain a lateral acceleration as the repulsor "pushes" against the gravity field of the planet.
A good way to think of them is as a bit analogous to hovercraft. The turbofans on a hovercraft provide lift, and turned at an angle toward the ground, will provide part of their thrust for sideways motion as well. Of course this metaphor can only go so far. A repulsor-fitted vehicle could lift itself into orbit just like a neutralizer, whereas a hovercraft can only lift itself up a few meters. Also, repulsors need a mass to actually push against; angling one completely sideways so that its not pushing against the planet at all would negate its effect.
An odd device found in some science fiction sources, a gravitic displacer takes an existing gravity field and redirects it effects, or "displaces" it, outside of its originating mass. In other words, if a gravitic displacer was directed at you, the gravity field the mass of your body generates would no longer be centered on you, but rather at a chosen spot near you, say six feet to your right. Your body, which still retains its original mass and inertia, would therefore be gravity-neutralized and would begin floating up.
As a means of locomotion, a gravitic displacer is usually used on a small section of planet a vehicle is resting on. It displaces the field acting under the grav vehicle, projecting it overhead instead of from below, allowing the ship to rise, as if it were 'falling' up. (In fact, this is exactly what it is doing--the gravity field that would normally make it fall down is simply being projected in a different location.) The displacer can then project the field ahead of the vehicle, propelling it forward as its pulled by the redirected gravity field. Used in conjunction with a gravitic enhancer, this can prove to be a very effective means of propulsion around a planet.
|<COMBINED GRAVITY DRIVE
Tech Level: 20
|The Jetson's zippy and versatile flying bubble car may be an example of a combined gravity drive. Image copyright Hanna-Barbera.|
The Combined Gravity Drive is representative of a number of advanced and incredibly versatile gravitic engines found in science fiction.
Basically, this is an all-in-one artificial gravity propulsion system. It can act as, and combine the effects of, a gravity neutralizer, a gravitic repulsor, a gravitic enhancer, and a gravitic displacer. Employing multiple such units allows the ships to perform some truly astounding feats of flight nearly impossible with other drive schemes. Computer control-systems read what the pilot wants of the vessel, and employs the various effect of its gravity drive to deliver. Need to hover mysteriously in place? The drive neutralizes 90%+ of the ship's gravity, just enough to counter the effects of air pressure pushing it up, so it can float effortlessly. Need to rapidly climb at 20 Gs? The drive creates a powerful repulsor field to push the vehicle rapidly against the planet surface below. Need to then stop on a dime? The drive creates a displaced gravity-point source behind the vehicle, enhanced to a high enough level--perhaps on the order of hundreds of G's--to suddenly stop it dead in mid-air. And so on and so forth. Of course protecting a biological pilot and crew from the effects of such rapid and potentially devastating accelerations and decelerations would be the responsibility of other systems.
Two on-screen sources show what appear to be advanced gravitic drives of this sort. The first is Close Encounters of the Third Kind, where the aliens' glowing subcraft zip about the landscape, pulling wild maneuvers effortlessly within meters of the ground. The second is Flight of the Navigator, as an alien ship uses its advanced propulsion system to fly rings around its human-created counterparts.
IN THE MEDIA
Star Wars, et al
Isaac Asimov's Robot and Foundation series
Larry Niven's Known Space series
Traveller, et al
Warhammer 40K, et al
ADVANCED GRAVITY THEORYhttp://relativity.livingreviews.org/Articles/lrr-1998-1/ http://web.archive.org/web/20060428001322/http://www.qgravity.org/