Jump drive
Jump drive is the most widespread method of effectively faster-than-light travel in Icathiria, allowing the traversal of long distances in space in much less time than would be possible with conventional rocketry and other mechanical means. While in some parts of the universe star drive is more common, jump drive is the most used method overall. Starships all over Icathiria rely on jump drive (or occasionally star drive) to get between distant places in the universe, although even with jump drive the locales connected by warpholes remain apparently too distant to feasibly cross between without passing through the hole.
Working
A jump drive is capable of converting itself and its immediate surroundings into tau energy, a phenomenon which, despite its name, is not actually energy but a field propagated by a type of tachyon (the tauum, not to be confused with the tauon). After a certain distance, the tau energy tends to decohere and dissipate, reconstituting the (bradyonic) materials that it had been converted from in the first place. The ultimate effect of this is to transport the matter in question at an effective speed of up to eighteen million times the speed of light.
While some control can be exerted over the distance traveled by the tau energy before reverting to normal matter, pinpoint precision is impossible. What precision can be attained depends on the mass of the object and the distance traveled; the greater the object's mass, and the greater the distance, the greater the uncertainty in its final location. The minimum distance traveled also depends on the mass of the object, however, so that it's not possible for a massive object to get to a precise location with arbitrarily small hops. With something the size of a large spacecraft, at best, it is possible to ensure that a jump ends within a couple of light hours of an intended destination. Moreover, there is a maximum distance that a jump can traverse, only about a thousand light years. In practice, this is seldom a problem, because most jump drives don't require any recharge time before they can be used again, so longer distances are simply covered by multiple jumps. Unlike the minimum jump distance, the maximum jump distance seems to not depend strongly on the object's mass—and, if anything, seems to be slightly larger for less massive objects.
Some travelers claim to retain their consciousness as tau energy, recalling their sensations during their trip. Most such travelers report the trip having seemed to take more time subjectively than actually elapsed according to onboard clocks and other methods of time measurement (including the aging of the travelers themselves), the apparent time being greater by a factor of several hundred, such that a jump that actually only lasted a fraction of a second seemed to them to last minutes. Most report a sensation of their body melting or vaporizing, followed by a period of prolonged stimulation something like an electrical shock, accompanied by a disorienting feeling of rapid motion of different parts of their bodies in slightly different directions. Some also report feelings of transitory union with other objects, including living fellow travelers as well as inanimate materials. Most scientists believe that consciousness is suspended during a jump and that these impressions of the traveler's experiences during the jump are false memories reconstructed after the fact, but there's no obvious way of proving this one way or the other.
Hazards
One limitation of jump drive is that the beams of tau energy tend to be subject to diffraction and reflection by any matter they pass through. Beams that have been thus distorted will reconstitute into damaged versions of the original objects at best; at worst, if the damage is bad enough, they may form unrecognizable jumbled messes, or fine dusts of widely dispersed particles. The interstellar medium is thin enough that in deep space this isn't a problem; as long as the jumps are confined to interstellar space far from any celestial bodies or significant amounts of gas or dust, the danger is minimal. Trying to jump through a nebula or through a planet's atmosphere, however, is a recipe for disaster. Interestingly, a thin sheet of dense matter is safer to jump through than a longer distance through a more diffuse material. Due to the typical wavelength of the tau energies involved, any thickness of up to about 2.4 meters tends to be safe to jump through, but greater than that leads to danger of incoherence.
It also sometimes happens, though very rarely, that for whatever reason, the tau energy doesn't reconstitute the original matter on interfering with itself, but instead changes to a different phenomenon called sampi energy. The reasons for this occasional failure of jump drive are a serious matter of study, but remain little understood. Although little is yet known about sampi energy, it seems to travel at least as fast as tau energy, and unlike tau energy is not affected by passing through matter, which leads many engineers to hope that if a reliable means can be discovered to produce it—and, as importantly, to return it to regular matter—then it can lead to an improved version of jump drive. Such means remain for the moment only an elusive dream, but scientists hope someday to correct that. In any case, the probability of the conversion of tau energy to sampi energy rather than bradyonic matter is low enough that it causes little discouragement to the use of jump drive, any more than most people on turn-of-the-millennium Earth are dissuaded from traveling by air due to the remote chance of an airplane's engine failure.
Installation
Jump drives are, of course, most commonly installed on spaceships, allowing them to traverse long interstellar distances with relative ease. Because of the limitations on the accuracy of jump drive, jump drive ships tend to be as small as possible, to be able to better control their jumps. Much more massive jump ships do exist, but they remain far out in interstellar space, and rely on smaller shuttle ships to carry their crew and cargo to and from their destinations.
Much less frequently, small jump drives can be implanted in an ellogous being, wired to their nervous system so they can trigger it at will. These jump implants allow the possessor to transport himself and his immediate surroundings—which may include a (very small) vessel that doesn't have a jump drive of its own. An individual with a jump implant can even transport himself through space without the aid of a vessel, if they're quick about it; as long as they don't spend more than about thirty to sixty seconds total between jumps (which isn't difficult to arrange, since they only need spend a fraction of a second between each pair of successive jumps), they can travel large distances without much danger. Of course, jumping through an atmosphere is still a bad idea, but a person with jump drive can easily jump between spaceships (his mass being small enough that the imprecision of the jump may not be important)—or between planets if he has some means of flight to escape the planet's atmosphere.
Yet another use to which very small jump drives have been put is the implant gun, a weapon that "jumps" its ammunition into the target. Since damage to the ammunition is unimportant, the scrambling due to firing through an atmosphere doesn't matter.