Hyperspace Gate • Digital Gate • Ion Drive • Gravity Drive • Tunnel Drive • Hyperspace Navigation
Well, technically, they're "Gravity Well Gates"... but most spacers simply refer to them as "hyper gates" or "jump gates."
Although faster-than-light travel is still beyond the reach of human technology, scientists have done an end-run around physics by travelling through hyperspace to reach other star systems in days instead of decades. Hyperspace is pocketed with gravity wells (formed by massive bodies like stars and gas giants in real space) that pulls space downward, thus making two points closer together. For example, traveling 100 miles over a gravity well in hyperspace might result in travelling 1,000,000,000 miles in real space. (NOTE: The simplified notion of "over" and "downward" are not technically accurate when discussing gravity wells, but for the purpose of this discussion they're good enough.)
To cross between hyperspace and real space, however, a jumpgate is needed. These huge devices generate a narrow gravity well powerful enough to rip a hole through the fabric of spacetime into hyperspace. Once the portal is opened, ships can pass through into hyperspace. Upon reaching their destination in hyperspace, ships will need another jumpgate to cross back into real space. This is how most military and all civilian ships travel between star systems, and every populated system in the Federation has at least one jump gate (and often several).
Hyperspace Jumpgates come in two varieties: commercial and military. Commercial Jumpgates and hyperspace lanes can be used freely by cargo freighters and passenger liners. Military Jumpgates are limited to Earth Fleet warships and require military-encrypted activation codes to operate. This is mainly to keep civilians away from dangerous systems like the Bug-infested planets of the Arachnid Quarantine Zone, or the Soul Eaters on Fieras 5.
Interesting Trivia: Many spiritual creatures and even the Technocracy knew of hyperspace by various definitions, the most common name being the Deep Umbra, although no one ever realized that its laws of physics and geometries did not correspond to regular space until rather recently.
A radical concept developed by the TI shortly before the second contact with the bugs, the Digital gate took a new look at interstellar travel. Using some truly advanced mathematical calculations, scientists reasoned that as an ion-driven ship came closer to the speed of light, with Einstein telling us that more of its mass would be converted to energy, it could be possible to force-convert the remaining mass and absorb the energy into a powerful matrix of receptors. The digital image of a ship passing through a digital gate crosses into hyperspace at an entry point no larger than an atom, beamed through hyperspace at .99998 the speed of light, then reassembled through a digital gate on the opposite end and forced out.
Digital gate technology is currently the fastest means of long range travel available to humanity. Due to their massive power consumption (requiring almost 400 nuclear reactors!), digital gates are prohibitively expensive to build and operate. Consequently, they are generally only used to link densely populated core systems with a high volumes of commercial traffic. Currently, there are only two digital gate lanes - between Earth and Avalon, and Avalon and New Paris.
Ion drives are the primary propulsion system of all commercial and military spacecraft, and can accelerate a ship up to .97 the speed of light. At such speeds, however, time dilation becomes a factor, and so special shielding technology was developed by Time mages and Void Engineers to negate the effects. Ion drives are generally powered by multiple nuclear or antimatter reactors.
Despite their impressive speed, it would still take years for an ion drive ship to cross between star systems. Therefore, ion drives are used mostly by commerical spacecraft to move between a hyperspace jumpgate and the planets of a solar system, or by warships to patrol, pursue, and maneuver during space battles.
Not only are gravity drives essentially portable jumpgates, allowing ships equipped with them to cross between real space and hyperspace whenever and wherever they want, but then can also generate powerful gravity shields and allow ships to travel at incredibly high speeds. Gravity drives are massive devices, so any warship smaller than a heavy cruiser is simply too small to carry one. In the Earth Federation, gravity drives are limited to military vessels. It's illegal (and carries severe penalties) for civilian ships to be equipped with one.
Gravity drives have been around for decades, and the technology has evolved and advanced over time. There are currently four types of gravity drives still in service on Earth Fleet vessels:
JUMP POINT GENERATION
Gravity drives can generate a tight gravity well at a pinpoint location in space strong enough to rip open a "jump point," or hyperspace portal. The jump point can be projected up to 100 kilometers away from the ship (this may sound like a great distance, but in space combat this is actually very close range) to allow other, smaller vessels to cross through the portal first. Generating a jump point takes between thirty seconds to a minute to form. While forming a jump point, a ship cannot use its gravity drive for propulsion or shielding. In a modified form, a jump point projector is the basis of the capital weapon, the Gravitic Ram.
Gravity drives can generate a field of gravimetric energy around their ship. This gravity shield can also be expanded to protect other, smaller vessels clustered around the ship, although this comes at the price of proportionately expanded power consumption and reduction in the shield's duration.
Any projective (torpedoes, missiles, shells, plasma, etc.) attempting to penetrate the shield will be stopped in its tracks and crushed by the intense gravity. Beam weapons (chemlasers, grav lasers, and particle cannons) can penetrate a gravity shield, but their effects are highly degraded. Gravitic weapons (graviton cannons, gravitic rams, and grav lances) can disrupt gravity shields and ultimately overload them, forcing the defending ship to either drop their gravity shield or be destroyed when their gravity drive explodes.
The main disadvantage of gravity shields is that although your enemy can't fire through your shield, neither can you. To return fire, you'd have to drop your gravity shield. Furthermore, a defending ship must maintain at least 90% hull integrity to avoid being literally ripped apart by the powerful gravitic forces of its own shield. Therefore, any damage from weapons that do manage to penetrate the shield can quickly become catastrophic.
A gravity drive can generate a focused gravity well in any direction, and the ship to and literally "falls" toward the well at speeds relative to the gravity well's power level. Gravity propulsion works in both real space and hyperspace, and can reach acceleration rates of up to a hundred Earth-standard gravities (or 981 m/s2), much faster than those of an ion drive. Like gravity shields, gravity propulsion well can be expanded (with a corresponding power drain) to pull other, smaller vessels along with the main ship. While using gravity propulsion, a gravity drive can't simultaneously be used to generate gravity shielding or a jump point.
It is important to point out that gravity drives can be used for propulsion OR shields OR creating a jump point, but not all three (or even two) functions at the same time. In other words, a ship cannot maneuver AND maintain a gravity shield at the same time. It CAN, however, coast on a ballistic trajectory while maintaining a gravity shield (although it would have to drop the shield in order to accelerate, decelerate, or change course) or creating a jump point. Likewise, a warship trying to withdraw from combat would have to drop its gravity shield before it could form a jump point to escape to hyperspace.
The Horadrim, an ancient race with highly advanced technology, have an interstellar drive that is much more advanced than anything humanity has come up with. It allows near-instantaneous travel to any point in the universe. Very few humans have seen a tunnel drive in action. The experience has been described as a flash, travelling a short distance inside a massive technological tunnel, another flash, and then arriving at your destination, parsecs from where you were. Tunnel drives do not asppear to travel through hyperspace, but rather through another spatial dimension or perhaps a different layer of the Deep Umbra. Other than that, not much is known about Horadrim tunnel drives. Research is ongoing.
Hyperspace does not have an exact point-to-point correlation with real space. This is a benefit and a handicap. The benefit is that there are fewer points in hyperspace, thus the points in hyperspace corresponding to (for example) Earth and Avalon are a lot closer in hyperspace than they are in normal space. The downside is that such points may bear little or no relationship to each other's directional relationship in normal space, making navigation rather difficult. Jump gates broadcast a network of beacons that can be used for navigation. However, even hyperspace is darn big, and the somewhat random gravitational and magnetic fields in hyperspace mean that such beams have to be unidirectional to have enough power to reach the next gate. You can travel from one gate to another along the navigational beam, and thus find your way through hyperspace even in a small shuttle. Also, jump gates broadcast a gravitic wave that can carry ships along like a conveyor belt, further speeding up hyperspace travel.
If you go "off the beam," there are a tiny number of landmarks you can use for navigation. Large gravity wells in real space (such as those around stars or gas giant planets) create a gravitic "buckle," sort of a small mirror-image version of themselves in hyperspace. A ship with gravitic sensors (basically, all warships and most larger commercial vessels, but few shuttles or small freighters) can sense these buckles and know they are near a star or planet. Smaller terrestrial planets (like Earth) and moons create tiny, nearly undetectable buckles, but powerful enough gravitic sensors can still pick them up. Large areas of hyperspace have been charted, so anywhere near an inhabited system you can bet you can navigate in. You just can't always be sure that you will come out exactly where you think you will if you're not near a landmark like a grav buckle. If you try to jump into normal space a light-year out in deep space, you could jump into normal space up to several million miles away from where you think you are. Since a light-year is about six TRILLION miles, on that scale, this is acceptable, since there isn't anything for you to bump into by accident. Near grav buckles, you can jump into normal space with much more precision. A large gravity well in normal space creates a "hyper limit", within which you can't jump, extending up to a couple million miles from a large gravity well like that of the sun, or barely beyond the surface of smaller worlds like Mars, Earth, or the Moon.