Alderson drive
Encyclopedia
The Alderson drive, named after Jet Propulsion Laboratory
scientist Dan Alderson
, is a fictional device that enables instantaneous interstellar transportation. It is featured in the CoDominium
series of science fiction
novel
s by Jerry Pournelle
, including the Mote series by Larry Niven
and Jerry Pournelle
. Dan Alderson helped Pournelle work out the notional science behind the drive, and how it should work to be a useful plot device
.
drive: it can more nearly be likened to a device able to use a form of wormhole
, whose entry and exit 'Alderson points' are at either end of an 'Alderson tramline'. Alderson points are difficult to find. Alderson tramlines form between points of equipotential
thermonuclear flux
located near star
s. Not all star pairs form Alderson tramlines, and not all those tramlines which do form are large enough to take a spaceship
. This means that in order to travel between star systems, it is frequently necessary to carry out a series of Alderson jumps interspersed with periods of travel between Alderson points in normal space. Alderson tramlines, when they form, form instantaneously, and travel along them appears to take no elapsed time. However, sentient beings who travel using an Alderson drive experience "jump shock", a temporary period of extreme disorientation immediately following an Alderson jump. Computer
s are affected for an even longer period of time, making it difficult to automate spacecraft after a jump. Spacecraft
are thus vulnerable to attack until their occupants recover from jump shock.
At the beginning of The Mote in God's Eye
, only one tramline leads to Mote system. Its inner end is well above the plane of the local ecliptic
and its outer end appears inside the photosphere
of a red giant
star. The Mote civilizations had long been able to construct an Alderson-type drive but, because they had no Langston Field
technology, their many attempts to use the drive always failed: their unshielded ships making a jump were burnt up by the red giant's photosphere. Then the battlecruiser INSS MacArthur arrived in their system, leading to the events in the novel and its sequel.
, four forces are known: gravity, electromagnetism
, nuclear weak, and nuclear strong. The fictional science behind the Alderson drive assumes a fifth force, generated by thermonuclear reactions. The force has little effect in our universe and is barely detectable.
as advanced as the CoDominium and its successors. The location of an Alderson point is dictated by the balance of the fundamental forces, which for a Sol-like star leads to points that can be several astronomical unit
s apart by direct line – even farther when orbital paths are taken into account. Even at constant high acceleration, crossing a system can take weeks. As a result, it may be faster to make several jumps through other systems with points in close proximity than to cross a single system whose points are far apart. Military
ships usually travel under constant acceleration, which saves time, but consumes vast amounts of fuel. Commercial ships generally make use of efficient transfer orbits
which can take several times as long.
As Alderson points can be difficult to find, even when their position is known in principle, human astrogators
bring their ships to as near a complete stop as they can, enabling them to precisely determine their position before jumping. A ship approaching a point thus must decelerate, increasing travel time between points. A possible alternative, discussed in The Gripping Hand
, is to reach the point at speed and activate the drive at precisely the right time. Human astrogators apparently lack the requisite instinct
s and precision, but Motie warriors are capable of this. However, in most alignments of Alderson points, the ship will have to significantly change direction upon arrival in the destination system, possibly requiring significantly more acceleration than after a jump at rest and in most cases wasting time.
Jet Propulsion Laboratory
Jet Propulsion Laboratory is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. The facility is headquartered in the city of Pasadena on the border of La Cañada Flintridge and Pasadena...
scientist Dan Alderson
Dan Alderson
Daniel John "Dan" Alderson was a scientist at the Jet Propulsion Laboratory in California, and a prominent participant in science fiction fandom. He came from a middle class family and had diabetes...
, is a fictional device that enables instantaneous interstellar transportation. It is featured in the CoDominium
CoDominium
-The CoDominium series:*A Spaceship for the King *He Fell into a Dark Hole *The Mote in God's Eye...
series of science fiction
Science fiction
Science fiction is a genre of fiction dealing with imaginary but more or less plausible content such as future settings, futuristic science and technology, space travel, aliens, and paranormal abilities...
novel
Novel
A novel is a book of long narrative in literary prose. The genre has historical roots both in the fields of the medieval and early modern romance and in the tradition of the novella. The latter supplied the present generic term in the late 18th century....
s by Jerry Pournelle
Jerry Pournelle
Jerry Eugene Pournelle is an American science fiction writer, essayist and journalist who contributed for many years to the computer magazine Byte and has since 1998 been maintaining his own website/blog....
, including the Mote series by Larry Niven
Larry Niven
Laurence van Cott Niven / ˈlæri ˈnɪvən/ is an American science fiction author. His best-known work is Ringworld , which received Hugo, Locus, Ditmar, and Nebula awards. His work is primarily hard science fiction, using big science concepts and theoretical physics...
and Jerry Pournelle
Jerry Pournelle
Jerry Eugene Pournelle is an American science fiction writer, essayist and journalist who contributed for many years to the computer magazine Byte and has since 1998 been maintaining his own website/blog....
. Dan Alderson helped Pournelle work out the notional science behind the drive, and how it should work to be a useful plot device
Plot device
A plot device is an object or character in a story whose sole purpose is to advance the plot of the story, or alternatively to overcome some difficulty in the plot....
.
Overview
The Alderson drive is not, strictly, a faster-than-lightFaster-than-light
Faster-than-light communications and travel refer to the propagation of information or matter faster than the speed of light....
drive: it can more nearly be likened to a device able to use a form of wormhole
Wormhole
In physics, a wormhole is a hypothetical topological feature of spacetime that would be, fundamentally, a "shortcut" through spacetime. For a simple visual explanation of a wormhole, consider spacetime visualized as a two-dimensional surface. If this surface is folded along a third dimension, it...
, whose entry and exit 'Alderson points' are at either end of an 'Alderson tramline'. Alderson points are difficult to find. Alderson tramlines form between points of equipotential
Equipotential
Equipotential or isopotential in mathematics and physics refers to a region in space where every point in it is at the same potential. This usually refers to a scalar potential , although it can also be applied to vector potentials...
thermonuclear flux
Flux
In the various subfields of physics, there exist two common usages of the term flux, both with rigorous mathematical frameworks.* In the study of transport phenomena , flux is defined as flow per unit area, where flow is the movement of some quantity per time...
located near star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
s. Not all star pairs form Alderson tramlines, and not all those tramlines which do form are large enough to take a spaceship
Spacecraft
A spacecraft or spaceship is a craft or machine designed for spaceflight. Spacecraft are used for a variety of purposes, including communications, earth observation, meteorology, navigation, planetary exploration and transportation of humans and cargo....
. This means that in order to travel between star systems, it is frequently necessary to carry out a series of Alderson jumps interspersed with periods of travel between Alderson points in normal space. Alderson tramlines, when they form, form instantaneously, and travel along them appears to take no elapsed time. However, sentient beings who travel using an Alderson drive experience "jump shock", a temporary period of extreme disorientation immediately following an Alderson jump. Computer
Computer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...
s are affected for an even longer period of time, making it difficult to automate spacecraft after a jump. Spacecraft
Spacecraft
A spacecraft or spaceship is a craft or machine designed for spaceflight. Spacecraft are used for a variety of purposes, including communications, earth observation, meteorology, navigation, planetary exploration and transportation of humans and cargo....
are thus vulnerable to attack until their occupants recover from jump shock.
At the beginning of The Mote in God's Eye
The Mote in God's Eye
The Mote in God's Eye is a science fiction novel by American writers Larry Niven and Jerry Pournelle, first published in 1974. The story is set in the distant future of Pournelle's CoDominium universe, and charts the first contact between humanity and an alien species. The title of the novel is a...
, only one tramline leads to Mote system. Its inner end is well above the plane of the local ecliptic
Ecliptic
The ecliptic is the plane of the earth's orbit around the sun. In more accurate terms, it is the intersection of the celestial sphere with the ecliptic plane, which is the geometric plane containing the mean orbit of the Earth around the Sun...
and its outer end appears inside the photosphere
Photosphere
The photosphere of an astronomical object is the region from which externally received light originates. The term itself is derived from Ancient Greek roots, φῶς, φωτός/phos, photos meaning "light" and σφαῖρα/sphaira meaning "sphere", in reference to the fact that it is a spheric surface perceived...
of a red giant
Red giant
A red giant is a luminous giant star of low or intermediate mass in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius immense and the surface temperature low, somewhere from 5,000 K and lower...
star. The Mote civilizations had long been able to construct an Alderson-type drive but, because they had no Langston Field
Langston Field
The Langston Field is a fictional device featured in the CoDominium series of science-fiction novels, initiated by SF writer Jerry Pournelle....
technology, their many attempts to use the drive always failed: their unshielded ships making a jump were burnt up by the red giant's photosphere. Then the battlecruiser INSS MacArthur arrived in their system, leading to the events in the novel and its sequel.
The science
In modern physicsPhysics
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...
, four forces are known: gravity, electromagnetism
Electromagnetism
Electromagnetism is one of the four fundamental interactions in nature. The other three are the strong interaction, the weak interaction and gravitation...
, nuclear weak, and nuclear strong. The fictional science behind the Alderson drive assumes a fifth force, generated by thermonuclear reactions. The force has little effect in our universe and is barely detectable.
Astrogation with the Alderson Drive
Interplanetary travel is still no small feat, even for a cultureCulture
Culture is a term that has many different inter-related meanings. For example, in 1952, Alfred Kroeber and Clyde Kluckhohn compiled a list of 164 definitions of "culture" in Culture: A Critical Review of Concepts and Definitions...
as advanced as the CoDominium and its successors. The location of an Alderson point is dictated by the balance of the fundamental forces, which for a Sol-like star leads to points that can be several astronomical unit
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
s apart by direct line – even farther when orbital paths are taken into account. Even at constant high acceleration, crossing a system can take weeks. As a result, it may be faster to make several jumps through other systems with points in close proximity than to cross a single system whose points are far apart. Military
Military
A military is an organization authorized by its greater society to use lethal force, usually including use of weapons, in defending its country by combating actual or perceived threats. The military may have additional functions of use to its greater society, such as advancing a political agenda e.g...
ships usually travel under constant acceleration, which saves time, but consumes vast amounts of fuel. Commercial ships generally make use of efficient transfer orbits
Hohmann transfer orbit
In orbital mechanics, the Hohmann transfer orbit is an elliptical orbit used to transfer between two circular orbits, typically both in the same plane....
which can take several times as long.
As Alderson points can be difficult to find, even when their position is known in principle, human astrogators
Astrogation
Astrogation is the planning of a route through space and the actual navigation of spacecraft, either in interplanetary travel or in interstellar travel...
bring their ships to as near a complete stop as they can, enabling them to precisely determine their position before jumping. A ship approaching a point thus must decelerate, increasing travel time between points. A possible alternative, discussed in The Gripping Hand
The Gripping Hand
The Gripping Hand is a 1993 novel by Larry Niven and Jerry Pournelle. It is a sequel to their multi-award-nominated 1974 work The Mote in God's Eye. The Gripping Hand is, chronologically, the last novel of the CoDominium universe it is set in...
, is to reach the point at speed and activate the drive at precisely the right time. Human astrogators apparently lack the requisite instinct
Instinct
Instinct or innate behavior is the inherent inclination of a living organism toward a particular behavior.The simplest example of an instinctive behavior is a fixed action pattern, in which a very short to medium length sequence of actions, without variation, are carried out in response to a...
s and precision, but Motie warriors are capable of this. However, in most alignments of Alderson points, the ship will have to significantly change direction upon arrival in the destination system, possibly requiring significantly more acceleration than after a jump at rest and in most cases wasting time.