From: ShldWulf@a...
Date: Tue, 7 Apr 1998 06:31:05 EDT
Subject: Fwd: sci-fi ftl drives
JUst a bit of info for the list, sent to me by a freind. Thought it might come
in handy with the Campaign topic.
Randy
http://www.clark.net/pub/nyrath/stardrv.txt
--------------------
STAR DRIVES IN SCIENCE FICTION: A Catalog by Geoffrey A. Landis
<geoffrey.landis@lerc.nasa.gov> Originally appeared in the Usenet newsgroup
rec.arts.sf.science.
(Mr. Landis makes reference to the EMF classification created by Erik Max
Francis <max@alcyone.com>,
this appears in the appendix. -WC)
Four fundamental separate categories of starflight: STL: Slower than light
drive travel Lightspeed: Travel *at* the speed of light FTL: Faster than light
travel Otherspace: Travel to other dimensions, universes, parallels, etc.
The meaning of STL is obvious, and it is the basis for all spaceflight in
reality so far.
Lightspeed is not used very much in fiction. If you could travel at exactly
the speed of light, time would stop for you. Occasionally this appears in SF.
Williamson recently has been writing short stories featuring a "quantum drive"
that operates at exactly the speed of light; from the point of view of the
riders, it is instantaneous. Also, many teleport systems are assumed to
transport at the speed of light (cf. Niven)
FTL is, of course, faster than light. This is used so much in SF that there's
little need to define it.
Otherspace is a category I include for completeness. Note that going to a
different universe can get you starflight, if there are stars in the other
universe, without the FTL paradoxes. Several books have
*implied* such a system in throw-away lines, but it hasn't been
discussed very much in any detail. [and most "alternate history" travel sf
assumes that travel takes you from the surface of the Earth to the surface of
the Earth. What a helpful coincidence!]
OK. Here I will try to classify *only* FTL; this is the one that's got the
paradoxes. The classifications are completely on how they appear; not on the
actually physics of operation.
[1.0] Discontinuous Drives ("teleport-like").
[1.1] Flash gates.
[1.1.1] Transmitter to receiver.
[1.1.2] Transmitter to anywhere.
[1.1.2.1] Transmitter to anywhere /variant.
[1.1.3] Anywhere to receiver.
[1.1.4] Distant transmitter.
[1.2] "Door" gates.
[1.2.1] Portal to portal.
[1.2.2] Portal to anywhere.
[1.2.3] Anywhere to portal.
[1.2.4] Distant portal.
[1.3] "Permanent" gates (Wormholes).
[1.4] Teleportation (aka "jump")
[1.4.1] Single jump.
[1.4.1.1] Single jump/variant.
[1.4.2] Multiple-connection.
[1.4.3] Multi-jump (Stutter).
[1.4.4] Hopscotch drive.
[1.4.5] FTL by time travel.
[1.5] "Fold" drive ( Telportation/variant ).
[2.0] Continuous Drives.
[2.1] "Railroad" drives
[2.1.1] Fixed trail
[2.1.2] Consumable trail
[2.2] "Non-railroad" drives.
[2.2.1] Real space drives.
[2.2.1.1] Newtonian space drives.
[2.2.1.2] Post-relativistic space drives.
[2.2.1.3] Tachyonic travel.
[2.2.1.4] Modified local speed of light.
[2.2.1.5] Modified regional speed of light.
[2.2.1.6] Modified universal speed of light.
[2.2.1.7] Tachyonic teleportation.
[2.2.1.8] Other real drives.
[2.2.1.9] "Bubble" drives.
[2.2.2] Alternative space (non-real space drives)
[2.2.2.1] Alternative space with fixed nodes.
[2.2.2.1.1] Hyperspace with transmitter and receiver.
[2.2.2.1.2] Hyperspace with transmitter.
[2.2.2.1.3] Hyperspace with receiver.
[2.2.2.1.4] Hyperspace with distant transmitter.
[2.2.2.2] Alternative space without fixed nodes.
[2.2.2.2.1] "Jump" hyperspace.
[2.2.2.2.2] Direction hyperspace.
[2.2.2.2.3] Navigable hyperspace.
[3.0 Modifying the Universe
[3.1] Modify distance in space.
[3.2] Modify the speed of light.
[3.3] Universal parameter change.
FTL travel breaks down into two main categories:
[1.0] DISCONTINUOUS DRIVES ("Teleport-like")
Discontinuous drives are ones in which the traveler does not traverse the
space between origin and destination.
[2.0] CONTINUOUS DRIVES ("Ship-like")
Continuous drives, on the other hand, are ones in which the traveler does
traverse the space between start and finish. A ship gets from point X to point
Y by traveling rather than by an instant "jump", although the travel is not
necessarily in "real" space.
The word "ship-like is a little fuzzy, since many SF writers use
'ships' to accomplish what is actually teleportation- like travel.
This is, I think, because ships are such a great story device
[3.0] MODIFYING THE UNIVERSE
A final category of FTL, not precisely fitting in elsewhere, requires
modifying the universe. Some items in this category also could be made to fit
other categories.
Subcategories:
[1.0] DISCONTINUOUS DRIVES ("Teleport-like")
[1.1] FLASH GATES
Devices in which the object transported disappears from point X and reappears
at point Y.
[1.1.1] TRANSMITTER TO RECEIVER
Teleport in which a discrete transmitter and a receiver are needed. May
require a ship, or may not.
[1.1.2] TRANSMITTER TO ANYWHERE
Teleport in which a transmitter is needed, but a receiver is not; the
transporter can select the target location ("Beam me down" is
the most well-known example)
[1.1.2.1] TRANSMITTER TO ANYWHERE/ VARIANT
Transmitter can be transported with the teleportation.
See also [1.4.1.1] "Single jump/variant".
[1.1.3] ANYWHERE TO RECEIVER
Teleport in which a receiving unit is needed, but a transmitter is not. ("Beam
me up" is an example of this.)
[1.1.4] DISTANT TRANSMITTER
A teleport system in which a fixed unit is needed, but this unit can teleport
you from a place to another place. (The "point to point" use of the
transporter in Trek is an example.)
[1.2] "DOOR" GATES
Gates in which an opening is made between point X and point Y which exists for
some finite time; the object transported then moves though the gate.
[1.2.1] PORTAL TO PORTAL
A transmitting device to act as the "out" door and a receiving device to act
as the "in" door are both required. (e.g., Poul Anderson,
_The Enemy Stars_.)
[1.2.2] PORTAL TO ANYWHERE
Here the transmitting door opens a receiving door without requirement for any
device at the receiving end. ('Tak Halus'
(pseud. of Steven Robinette) did a series of stories in _Analog_in
early 70s with this premise)
[1.2.3] ANYWHERE TO PORTAL
The same as [1.2.2] "Portal to anywhere", but traveling in the opposite
direction.
[1.2.4] DISTANT PORTAL
Anywhere to anywhere, device located elsewhere. Here "door" opens from X to Y
by use of a device at a third location C. The 'door' equivalent of [1.1.4]
"Distant transmitter".
[1.3] "PERMANENT" GATES (Wormholes).
"Permanent" here means that these stay open without the requirement of a
device, that is, they are a path from X to Y without being energized. There
are a wide variety of subsets of this.
Recently the most talked-about are Lorentzian wormholes, which are
apparently allowed by the general theory of relativity if the presence of
negative matter is permitted. General relativity
variants include Morris-Thorne spherical wormholes, Visser portals,
Kerr ring-wormholes, Einstein-Rosen bridges (nb: which actually
collapse before allowing you to traverse them), Tippler rotating cylinders
(nb: which don't actually serve as bridges, but at least one SF writer, Poul
Anderson, wrote a book which assumed that they
did). A non-relativity version is the "mirrors" used in Wolfe's
_New Sun_series of books.
[1.4] TELEPORTATION (aka "jump")
Here I use "teleportation" to imply something that can transport itself
without a fixed transmitter or receiver. Reference to quantum "tunneling" is
often made. Some books imply that humans can do this
unassisted (_Tyger, Tyger_/_The Stars My Destination_).
Many more use ships which can 'jump" with some device. Here I use 'jump' or
'teleportation' only for the case that physical travel is not required in some
alternate version of space, in distinction to some SF writers who use the term
or a variant for cases where a ship 'jumps' to some 'hyperspace' (jumpspace,
subspace, etc) where it can travel FTL.
[1.4.1] SINGLE JUMP
A ship (or person) who can jump from place to destination in a single step,
and can select the target.
[1.4.1.1] SINGLE JUMP/ VARIANT
In the variant, this only works at selected places, and takes you
only to selected spaces (_The Mote in God's Eye_). This type of
variant in general can be considered a
version of the [1.1] "Flash-gate" discussed above.
[1.4.2] MULTIPLE-CONNECTION
The ship can engage a "jump" drive, which will connect your location
in space-time with another location in space-time that is fixed by
the universe. [may depend on your state of motion in some variants]. The
connection will vary from place to place, so to go to a given destination you
need a "map" of where to go in space to find the place that jumps to the right
spot. The analogy is of the universe to a crumpled sheet of paper. An ant can
cross from one place on the paper to another where the paper touches itself.
(Heinlein). For some locations, a long trip moving from one place to another
to take multiple jumps may be necessary.
[1.4.3] MULTI-JUMP (Stutter)
A ship can jump from place to place, but not far enough to travel in a single
jump. Thus, the ship travels by a series of short jumps. In the limit of very
short jumps, the ship "appears" to be traveling through space at a "pseudo"
velocity without actually having any momentum. (This shades into [1.4.1]
"Single jump" as the length of jump gets longer).
[1.4.4] HOPSCOTCH DRIVE
Use of any version of a gate or portal to accomplish self-motivated
teleportation by having a transmitter transmit a transmitter, so that a ship
"bootstraps" across space by continuously beaming itself incremental
distances. (Such a drive is somewhere in the fuzzy region between a [2.0]
"Continuous" and a [1.0] "Discontinuous drive").
[1.4.5] FTL BY TIME TRAVEL
In FTL by time travel, faster than light travel is achieved by traveling to
the destination at ordinary slower-than-light speed, then teleporting
backward in time to arrive at the same time you started
[1.5] TELEPORTATION/ VARIANT ("Fold" drive)
A "fold" drive appeals to the "folded space" concept of [1.4.2]
"Multiple-connection", but now assumes that the ship can intentionally
"fold" space to produce the direct connection between point X and point Y
required. Since this categorization is by how the drive appears, and not how
it functions, "fold" variants are identical to actual teleport (or "portal")
variants, cf. [1.2] "Door gates")
[2.0] CONTINUOUS DRIVES ("Ship-like")
[2.1] "RAILROAD" DRIVES
[2.1.1] FIXED TRAIL
A "railroad" drive is one in which it is assumed that some physical structure
connects two points, and that FTL travel is possible, but only traveling along
this structure (as railroad travel is only possible along a railroad). One
might appeal to the concept of a cosmic string, or some other astrophysical
object. The railroad is
in some ways a conceptual link between wormhole-like drives and
ship-like drives. If the travel is actually instantaneous, with an
object leaving one end appearing at the same time at the other end, the
railroad drive becomes a variant of [1.3] "Permanent gate".
[2.1.2] CONSUMABLE TRAIL
In a consumable trail, some structure must be put in place between a and b,
and the drive consumes this material as it travels in order to produce FTL.
Some versions of the Alcubierre drive, for example, require that a structure
of negative energy be put in place along the path from x to y, and the ship
can then travel between the two points, but destroys the structure as it
travels.
I don't recall having seen either type of railroad drive proposed in SF. (Note
from Winchell Chung: I seem to recall a railroad style drive in Glen Cook's
THE DRAGON NEVER SLEEPS. There is also something like it in Kim Stanley
Robinson's THE MEMORY OF WHITENESS)
[2.2] NON-RAILROAD DRIVES
This section covers continuous drives (that is, drives where the ship
traverses space to get to the place desired) which do not require a structure
in place in space. EMF categorizes these as realdrive, hyperdrive, warpdrive,
and fakedrive depending on the operating principle used to go faster than
light. I will instead categorize them in to main categories, depending on
whether the ship remains in the "real" universe or leaves it, however, since
my categories are similar to EMF's, I quote him where appropriate
[2.2.1] REAL SPACE DRIVES
Real space drives assume that faster than light travel is possible in physical
space. In terms of appearance, all of these drives apparently operate the same
way (you go faster than light), and so if I were to keep to my strict
classification, these would all be in the same category. The main difference
between the drives is how they talk around relativity.
[2.2.1.1] NEWTONIAN SPACE DRIVES
This version of a FTL drive simply ignores relativity. The ship goes faster
than light merely by speeding up to a velocity which is faster than light.
[2.2.1.2] POST-RELATIVISTIC SPACE DRIVES
This is a minor variant [2.2.1.1] "Newtonian space drive"; the drive assumes
that there is some (yet unknown) "correction" to relativity such that the
speed of light is not, in fact, a barrier. Often this correction will be some
added term which applies only very close to the speed of light.
[2.2.1.1] and [2.2.1.2] are both "fakedrives" in the
classification by EMF.
[2.2.1.3] TACHYONIC TRAVEL
Tachyonic travel notes that faster than light speeds are in fact permitted by
relativity for bodies of imaginary rest mass, and assumes that there is some
way to reach the faster than light state (often invoking "tunneling") from
slower than light states without leaving "real" spacetime. (nb: tachyonic FTL
travel still has causality paradoxes in special relativity).
[2.2.1.4] MODIFIED LOCAL SPEED OF LIGHT
Drive assumes that the speed of light in the vicinity of the ship can be
modified by the drive system in some way, so that although the ship does not
exceed the speed of light, it nevertheless can travel faster than 300,000
kilometers per second.
[2.2.1.5] MODIFIED REGIONAL SPEED OF LIGHT
Assumes that the speed of light is greater than 300,000 kilometers per second
in some places in the universe. Faster speeds can be achieved in other places
in the universe.
[2.2.1.6] MODIFIED UNIVERSAL SPEED OF LIGHT
A scientist discovers a way to change the speed of light in the entire
universe, and does so. Now any ship can go faster than (what used to be) the
speed of light.
[2.2.1.7] TACHYONIC TELEPORTATION
The ship and/or person is converted into a stream of tachyons and
beamed across space, then reconstituted at the receiver. Actually a
variant of [2.2.1.2] "Tachyonic travel" and/or [2.2.2.1.1]
"Hyperspace with transmitter and receiver"; listed separately because it is
significant that the ship does not travel as a cohesive unit. Other variant
names can be used for the particles, which can travel either through real
space or some alternative space.
[2.2.1.8] OTHER REAL DRIVES
This covers other ways of dealing with relativity problems without leaving
real space. (Usually this involves employing doubletalk and bafflegab.)
[2.2.1.9] "BUBBLE" DRIVES (EMF classification: warpdrive)
"A bubble of different space is projected around the ship so that
the ship can travel faster-than-light while still in realspace."
This is listed last, since it is an intermediate step between "real space"
drives and alternative space drives, with some nature of both. (This seems to
be the FTL system used on Star Trek.)
[2.2.2] ALTERNATIVE SPACE DRIVES (non-real space drives)
In SF parlance, often called hyperspace, hyper, jumpspace, FTL space, and
other such words. EMF classification: "Type I; hyperdrive: The ships enters
some different space during the trip, whether or not time passes for the crew
while in this space."
[2.2.2.1] HYPERSPACE WITH FIXED NODES
Like teleport systems, a alternative space drive may require a fixed station.
[2.2.2.1.1] HYPERSPACE WITH TRANSMITTER AND RECEIVER
A fixed station boosts the ship into hyperspace; another station is needed to
retrieve the ship out of hyperspace. In some variants, only specific locations
are nodes which can be used to access hyperspace.
[2.2.2.1.2] HYPERSPACE WITH TRANSMITTER
A fixed station boosts the ship into hyperspace. (Babylon-5)
[2.2.2.1.3] HYPERSPACE WITH RECEIVER
A ship can enter hyperspace on its own, but needs a receiver to get back into
real space. Another one I've never seen in SF.
[2.2.2.1.4] HYPERSPACE WITH DISTANT TRANSMITTER
In this variant, a fixed machine is needed to access hyperspace, but the
machine need not be at either the original location or the destination. I've
never seen this in SF; included for completeness.
[2.2.2.2] ALTERNATIVE SPACE WITHOUT FIXED NODES
These are the variants of the classic SF hyperdrive. There are probably more
examples of this in SF than all other of the drive types combined, and hence
it is possible to make very fine divisions within the type. EMF
classification: "Type I; hyperdrive: The ships enters some different space
during the trip, whether or not time passes for the crew while in this space."
The space is often explained away as being a dimension different from the four
dimensions we currently can perceive (this explanation typically advanced by
people who seem to have only a foggy idea what a "dimension" is). There are
many variants based on the supposed "theory" of how the drive works, including
entering a space where the speed of light is faster, entering a space which
maps onto real space with a mapping such that points far apart in real space
are closer in the alternative space, entering a space where the ship expands
and then contracts to a different place, entering a space where everything
moves at the same FTL speed, etc. Likewise, there are a long list of
"conditions" which hyperspace drives are imagined to require. A common one is
that the FTL space cannot be entered when "in the
gravitational well of a massive body," (Niven, _Ringworld_ series) or
that your ship must have a high velocity in real space before you can
enter FTL space (Niven, _World of Ptavvs_, O'Donnell,
_Fire on the Border_) These two are convenient for sf writers,
because they explain why spaceships are required. Important questions for
hyperspace concepts are whether ships can see
and/or dock with each other in hyperspace, whether all ships travel
the same speed, and whether a ship can navigate while in hyperspace. These
questions can also be asked of [2.2.2.1] "Hyperspace with fixed nodes". I will
take this last to be the question used for subdivisions.
[2.2.2.2.1] "JUMP" HYPERSPACE
The destination is fixed when the ship enters the alternative space, either as
a function of its position and velocity entering, or else by some settings in
the drive. After a ship enters the alternative space, there is no way for it
to change the destination.
[2.2.2.2.2] DIRECTIONAL HYPERSPACE
A ship's direction is fixed when the ship enters hyperspace (often, but not
always, fixed by the direction the ship was traveling when it entered). How
far it travels, however, is a variable that can be changed. Usually the
distance is proportional to time spent in hyperspace, but may be a more
complicated function. The ship may or may not be able to calculate its
position in real space while in hyperspace.
[2.2.2.2.3] NAVIGABLE HYPERSPACE
The ship is able to completely navigate in hyperspace. It may or may not be
able to calculate its position in real space while in hyperspace. Sometimes
the hyperspace may have geography or dangers which must be navigated around.
[3.0] MODIFYING THE UNIVERSE
[3.1] MODIFY DISTANCE IN SPACE
Remove or shrink the space between two points.
[3.2] MODIFY THE SPEED OF LIGHT
Change the value of the speed of light in the region where travel is desired
(see [2.2.1.6] "Modified universal speed of light")
[3.3] UNIVERSAL PARAMETER CHANGE
Gain access to the parameters that describe the universe, possibly by hacking
into the operating system that the universe runs. Find the parameters which
describe your location. Rewrite these parameters to
put you in the place you want to be. (Greg Bear, _Moving Mars_)
____________________________________________
Geoffrey A. Landis, Ohio Aerospace Institute at NASA Lewis Research Center
physicist and part-time science fiction writer