Excerpt from the Encyclopedia Galactica, on the topic of the history of
space travel:

The main forms of interstellar travel in the universe, prior to the
twenty-sixth century, had been essentially divided into two main methods:

1) Non-Relativistic
 The non-relativistic forms of travel are those that use a form of advanced
field projection to create a zone around the ship by which relativistic
rules can be bypassed.  These are:
 a) Warp Field Technology:  By using a Warp Field Generator (essentially a
short-range graviton projector), a "warp bubble" of space is created in
which the vehicle floats.  The name bubble is a poor misnomer, since it is
in fact a "wave" of warped space.  This wave travels through space at faster
than light speeds, and the ship rides or "surfs" on the wave.  In areas of
significant gravity gradient the energy cost to create the bubble goes up
exponentially, so they are ideally instigated at Legrange points (areas of
extremely low gravity gradient, for example between a planet and its primary
moon) or far enough away from the large masses of the system that their
gravitic influence is insignificant.  Improved and more powerful Warp
Engines can achieve a higher speed and can achieve warp with less energy -
at the time of this printing, modern carrier-class ships of the Kingdom of
Earth can enter warp from high Earth orbit, a mere light-minute from the
planet's surface.  Warp Field Technology is extremely well known, and
extremely reliable.  It is the favored form of travel for most races, even
if it is not the fastest.

"Hey, it may not win races, but even I can't mess up warp travel." - Remark
attributed to Orange Shieldsman Ryoga Hibiki.

 b) Fold Technology: This method of propulsion relies on the creation and
manipulation of artificial singularities.  By manipulating the singularity,
space can be "folded" so that two distant points in space are brought close
together.  While Fold Technology is incredibly fast, allowing
near-instantaneous travel, it suffers from some dangerous drawbacks:
-First, inaccuracies in the calculations involved in generating the fold can
cause disasterous results, such that a so-called "mis-fold" can result in a
craft missing its destination in space OR time.  Famous examples of this
include the inadvertant expedition to the Lesser Mellangelic Cloud by a
deep-space survey craft (Farseer 1) which used incorrect mass calculation,
and the expected "reappearance" of the rescue craft (Retriever 1) sent to
retrieve the survey craft - the rescue craft ended up moving relatively
little distance in space, but a great distance in time, such that it will
appear somewhere near Alpha Centauri in the year 4371.
-Second, the energy cost is prohibitive for most applications - it rises
exponentially with mass, but only logarithmically with distance.

 Today, Fold Technology is only used by automated (non-sapient) drones and
intergalactic travel, the former to minimize risks, the latter due to energy
restictions.

"The idea of bending space like origami gives me the creeps." - Remark
attributed to Justy Ueki Tylor, captain of the Earth Destroyer Soyokaze.

2) Extra-Dimensional
 In general, extra-dimensional travel is seldom used by all but a few races.
However, their use has such a major impact on the galactic community that
they are still considered a major form of interstellar travel.  There are
three main "types":
 a) Hyperdrive: Hyperdrive is the practical application of Hyper-spatial
technology as it applies to interstellar travel.  The ship is shifted by the
engines into parallel spatial dimension that is congurent to our own in
which a ships sublight drives can easily propell it to superluminal speeds.
Hyperspace is an empty place, however, masses in normal space leave "tears"
in hyperspace.  These tears are seen as dark regions in the normal neutral
gray of hyperspace, and are far larger than the respective object - for
example, the tear associated with Sol extends to beyond the Oort cloud,
restricting a hyperdrive-capable ship to travel the leftover distance using
regular sublight drives.  While hyperdrive is far more efficient than warp
travel, it has a severe side effect that limit its use.  That effect is
caused by the entry and exit to hyperspace that only occurs consistent use
of ship-sized portals - increasing instability in nearby stars ("nearby"
meaning approximately all stars in a 50 light year radius).  While the exact
mechanism of the destabilization is unclear, the novae it causes are.  All
hyperdrive is banned in the Orion Arm, and its use is punishable by instant
destruction of the offending craft.

"Nice idea, hyperspace.  Pity about the suns exploding and all, but these
things happen." - Remark attributed to an unnamed Druuge research scientist
before the entire business unit was obliterated by a multilateral punitive
force.

 b) Quasidrive: Little is known about quasispace, as the only race that has
consistent access to it is the Arilou, who are extremely secretive about it.
Quasispace is to hyperspace as hyperspace is to normal space, but distances
in quasispace are drasically reduced.  Normally, a ship must enter banned
hyperspace to then enter quasispace, but the Arilou have developed a series
of technologies that allow them to enter quasispace while bypassing
hyperspace.

"Stupid Arilou.  Always *jumping in front* when Orz try to *dance*.  *Below*
is much better than *above*." - Remark attributed to unnamed Orz captain.

 c) Subdrive: Subdrive is similar to hyperdrive, but instead of moving "up"
to hyperspace, the ship travels "down" into subspace.  Subspace is a highly
dangerous dimension, so much so that it is usually only used for faster than
light communications.  Subspace, unlike hyperspace, is inhabited by
creatures that live in it like an ocean, albeit one that appears to be
little more than a breathable atmosphere.  Not much is known of these
creatures, other than that they consider most intelligent life in normal
space to be food.  Almost any lifeform entering subspace is immediately
swarmed by these creatures and devoured - a ship's hull is no obstacle to
them.  However, certain rare individuals act like a repellent to these
creatures, so much so that they refuse to even approach a ship carrying such
a person.  Gifted are rare - an average race has less than one Gifted per
billion.  However, Humanity has an incredibly high instance of Gifted, a
rate of roughly one per thousand.   Due to this, Humanity is the
near-exclusive users of Subdrive.

"Fun place, Subspace.  An atmosphere that smells like hell, looks worse, and
is full of things that wants to eat you.  Reminds me of New Jersey." -
Remark attributed to EXternal Civil Enforcement League (EXCEL) member
Shinichi "Nabeshin" Watanabe