In FTL:2448, Phase Drives are just Hyper drives/Jump drives/pick your adjective drive. You turn them on and you go to another universe with different properties, one of which allows you to travel faster than light in our universe due to the fact that this other universe maps one to one to our universe, but is much smaller or there is no speed of light limit.
That's all fine, except that our current understanding of physics indicates that the only way to connect to that universe would be through a wormhole. Well Hell, if you can form a wormhole stable enough to another universe, why not to another location in our universe?
In fact the method used by Herbert and Lashaw would be akin to picking berries. You pick a microscopic wormhole out of the virtual particle foam, test to see if it is going where you want to go, if not, you pick another, and another, until you find the one to where you want to go.
The process is entirely random, so the energy cost will be the same for a wormhole to the Phase universe as for one to Fomalhaut, or even the Andromeda Galaxy.
This is all well and good, but if we start using wormholes, then the nature of the game changes, and changes radically. So let's keep the Phase Drive, but let me lay out a new way for it to work and be consistent with what we know or might know...
Dr. John Lashaw was the premier String Theory theorist of his day. His treatise on String Resonance and Folded Space time spurred the young Janice Herbert into testing one of his predictions: That any one of the 12 dimensions of the fabric of space time could be "rolled up" into a non-dimensional space.
Part of String Theory is the postulation that our universe has 12 dimensions and that 8 of them have been rolled up into a non- dimensional space, leaving the remaining four, height, width, breadth, and time, behind.
What Lashaw had proposed that using electromagnetic forces, one could warp space time and "roll up" the remain four dimensions into this space.
What Herbert proposed was a means to determine how to actually do this. Her paper in 2049 got the attention of Lashaw and the two of them worked on the equations to derive a magnetic coil design that when powered, would fold space time and roll it up into this non- dimensional space. Similar tests using lasers to form regions of twisted space time had been successful up to a point, that point being where a channel to the future would be formed. Then most of the laser systems would undergo a failure of some sort and space time would unfold.
One result of their work together was the realization that once something was rolled up into this non-dimensional space, it could be unrolled at a different location, as long as the Phase Space for each of the rolled up dimensions was altered to match the Phase Space of the location.
Funding was procured, and a primitive Phase Coil was wound on Luna. The coil was massive, a sphere nearly 7 meters across. The autonomous testbed with the coil and large fusion power plant, was towed out to the orbit of Jupiter and the drive tested. It was slow, the charge took a while to build up in the coil. But as the charge built, the region within the magnetic field of the coil began to go out of phase with normal space. Light bent as it passed through the interface, and particles were deflected. Larger objects, the size of pebbles, were tossed and they bounced off the interface for the most part. One vigorously thrown pebble partially penetrated and vaporized. It didn't explode, but the portion that crossed the boundary was polished smoother than any technology could ever do.
At 45 degrees of Phase, about 20 hours after the start of the test, the testbed was harder to see as more light was bent and refracted by the boundary. At 90 degrees of Phase, 9 hours later, it was nearly invisible, the data stream from the test equipment was still strong, but was now 90 degrees our of phase. Additionally the volume of space time around the testbed had shrunk by 25%.
Once 90 degrees of Phase was reached, the process accelerated exponentially. In a matter of minutes the region of space had shrunk to about 5% and then seconds later, it was gone.
Then ten minutes later, it came back, just like it was programmed to. Only... there was no data, and the unrolling process was going faster than planned. What took 30 hours to do previously, took less than thirty minutes. The drive was fused and twisted, the recording equipment was a solid mass, only by luck were they able to extract the data from those ten minutes in that non-dimensional space.
The data was odd. It indicated that coils overheated from some form of induction and that this was only evident when the drive was at 175 degrees of Phase. Herbert and Lashaw worked the data and found that the induction was caused by the curvature of space time. Jupiter's orbit was too far into the Sun's influence. Based on this data, they determined that for the drive to work properly, it needed to be used out near Neptune's orbit, preferably on the opposite side of the Sun from Neptune.
It was after this revelation that Herbert and Lashaw vahished.
Today we know that the concept of a "non-dimensional space" was wrong, and that String Theory was just a stepping stone to other theories. But it's one prediction, that several dimensions, now believed to number around a hundred, occupy a different portion of space time than the one we do. The Phase Drive allows use to move a portion of local space time into this other space time and then through various adjustments of universal space time, the Phase Drive will translate the ship to a new location. This process, as always, takes time, but newer drives can do this faster than the earlier ones. For some reason, one that vexes modern theorists, distance does matter, so father away an object is, the more power and time it takes to translate to the new coordinates.
Most races in known space use a form of Phase Drive to travel between the stars.
Objects that pass outside of the Phase Field do not reenter the normal universe as energy, but instead reenter as fundamental particles. Across the entire universe.
If a ship unfolds too fast, it can create a temporary "crease" in space time. This crease can damage equipment and harm living creatures. Mild forms of these creases can cause "phase sickness" in living creatures and cause equipment to glitch.
If a ship unfolds in under a minute, it will reappear in normal space... folded. This is the euphemism for what happens to ship that's been through 4th dimensional origami. It is 100% fatal. We pray to God it is...
One side effect of the "warm up" phase of a Phase Drive is that once the ship is just a little out of phase with normal space, it can move freely through normal space through an intricate means of continual spatial translation. Speeds up to 14% of the speed of light have been achieved, but are not recommended. At speeds above 1% light, if you encounter something massive enough, it will pass through the phase boundary as a spray of fine matter... moving at the speed you encountered the object at. Even at 1% the speed of light, dust can vaporize the hull of a ship.
The Nordholm Quantum-Jump and the Kitch-Grice Quantum-Jump drives are not Phase Drives, but are quantum tunneling drives. They are based in large part on dissected Whurrian ships and their Blink Drive. Because the organic components of a Whurrian ship decay fairly rapidly, and the Blink Drive itself partially jumps when the ship dies, both of these drives are still highly experimental and rumors that a stable version of the Nordholm has been installed on ISCO warships is just rumor.
Whurrian ships use the technique of quantum tunneling to cross the vastness of space. If they wanted to, a Whurr ship could tunnel the entire distance to another star. However, if one were to try, more than likely it would miss it's target by several light years. Instead, they travel in short hops, where they get their bearings and hop again. Along well known routes, they can reduce the number of hops to mere handful.
The Vesh are known to have two different FTL drives: The Vesh Flux drive and their "GetTheHellOutOfHere" drive (A direct translation). The Flux drive allows ships to travel along the line of Phase Flux that occur naturally between close stars. Phase Flux is best described as creases in universal space time that form when two large stellar masses are in close proximity to each other. Close is defined as within 25 light years, though lines of Phase Flux are complex when multiple stars are near each other. There is a region in the two star systems that represents the opening of the Flux crease, typically about an AU in volume. Within this volume, the Flux drive can engage and send the ship along the crease at apparent FTL speeds.
For example, the Flux lines connecting Sol, Alpha Centauri, Beta Centauri, Proxima Centauri, and two brow dwarfs between the larger stars, form shapes and points in deep space that a ship could exit from. From the Flux region in the Sol system, a Vesh ship could travel to any of the other nearby systems, as long as the ship was skillful enough to surf the connections.
The "GetTheHellOutOfHere" drive is a true wormhole drive. It can create a wormhole around a Vesh ship. The unfortunate problem with this drive is that you're not guaranteed to arrive in the same universe as the one you left. Typically if a Vesh ship has the time to work out all the connections, returning to the same universe is almost a certainty. Almost.
However when in combat, the ship will panic and invoke the drive without doing anything at all other than dump energy into the drive. Where and when the ship will reappear, is unknown. Odds are that these ships appear in universes with significantly different physical laws that they cannot exist and die. The two ships that appeared in ISCO space are considered the lucky ones. Both were heavily damaged and were only a portion of the full ship according to research and interviews with the surviving Vesh.
The first Vesh ship could not be examined as it suffered a Flux drive mishap when it tried to engage its Flux drive in a region where were was no Flux crease opening. If a Vesh Flux drive is engaged in a region that does not have a crease or a crease opening, the energy pumped into the drive is expelled... as energy. The ship exploded into fragments.
The second ship was so heavily damaged that it was only partially aware and soon died later. However the Vesh prevented any inspection of the ship or its internal organs, so nothing much is none about the "GetTheHellOutOfHere" drive.
The future of travel in 2448 is changing. The development of the Phase Zero pod, is making travel faster and safer, and promises to do away with the need for fusion drives for system ships. The Phase Zero pod only takes the pod and anything within its field of effect only a degree or two out of Phase. Matter can still pass through the boundary region and the pod does not suffer any destabilization due to extreme space time curvature. It is only the fact that each Phase Zero coil must be handwound, that the cost of the Phase Zero technology is only in reach of the rich and of the ISCO government.