Space travel, or space flight (less often, starfaring or star voyaging ) is a classic science-fiction theme that has captivated the public and is almost archetypal for science fiction. Space travel, interplanetary or interstellar, is usually performed in space ships, and spacecraft propulsion in various works ranges from the scientifically plausible to the totally fictitious.
While some writers focus on realistic, scientific, and educational aspects of space travel, for others the concept may be seen as a metaphor for "free[ing] mankind from the prison of the solar system". Though the science-fiction rocket has been described as a 20th-century icon, according to The Encyclopedia of Science Fiction "The means by which space flight has been achieved in sf – its many and various spaceships – have always been of secondary importance to the mythical impact of the theme". Works related to space travel have popularized such concepts as time dilation, space stations, and space colonization.
While generally associated with science fiction, space travel – involving magic or supernatural entities such as angels – has also occasionally featured in fantasy.
History
A classic, defining trope of the science-fiction genre is that the action takes place in space, either aboard a spaceship or on another planet. Early works of science fiction, called "proto SF" – such as novels by 17th-century writers Francis Godwin and Cyrano de Bergerac, and astronomer Johannes Kepler – include "lunar romances", much of whose action takes place on the Moon. Science-fiction critic George Slusser also pointed to Christopher Marlowe's Doctor Faustus (1604), in which the main character is able to see the entire earth from high above, and noted the connections of space travel to earlier dreams of flying and air travel, seen as far back as the writings of Plato and Socrates. In such a grand view, space travel and inventions such as various forms of "star drive" can be seen as metaphors for freedom, one of whose aspects is to "free mankind from the prison of the solar system".
In the ensuing centuries, while science fiction addressed many aspects of futuristic science in addition to space travel, the latter proved the most influential with the general public and the genre's writers and readers, evoking their sense of wonder. Most works were mainly intended to amuse readers, but a small number, often by authors with a scholarly background, strove to educate readers about various aspects of space-related science, including concepts from astronomy; the latter aspiration was shown by, among others, the influential American editor Hugo Gernsback, who dubbed this approach "sugar-coated science" and "scientification". Science-fiction magazines, including Gernsback's Science Wonder Stories, alongside works of pure fiction, popularized early studies and discussed the feasibility of space travel; many science-fiction writers published nonfiction on space travel, such as Willy Ley's articles and David Lasser's book, The Conquest of Space (1931).
From the late 19th and early 20th centuries onward there was a visible distinction between more "realistic" and scientific fiction (which later would evolve into hard sf), whose writers, often scientists like Konstantin Tsiolkovsky and Max Valier, focused on the more plausible concept of interplanetary travel (to the Moon or Mars), whereas the more grandiose but less grounded in realism were the stories of "escape from Earth into a Universe filled with worlds", which gave rise the genre of space opera, pioneered by E. E. Smith, popularized by the televisions series Star Trek that debuted in 1966. This trend continues to the present day, with some works focusing on "the myth of space flight", others are centered on "realistic examination of space flight"; the difference can be also described as that between the writers' concern on the "imaginative horizons rather than hardware". The success of the 20th century space program, such as the Apollo 11 Moon landing, was often described as "science fiction come true", and it has also served to further "demystify" the concept of space travel within the solar system, as from that point onward, the writers who wanted to focus on the "myth of space travel" were increasingly likely to do so through the concept of interstellar travel. While the theme of space travel is seen as one of the very optimistic in general, some revaluatory stories, often more pessimistic and disillusioned, juxtapose both of those trends, contrasting the romantic myth of space travel with a more down-to-earth reality. George Slusser suggested that "science fiction travel since World War II has mirrored the United States space program: anticipation in the 1950s and early 1960s, euphoria into the 1970s, modulating into skepticism and gradual withdrawal since the 1980s."
On the screen the French movie 1902 A Trip to the Moon, by Georges Méliès, also described as the first science fiction film, linked special effects to the depictions of spaceflight. Together with other early movies such as Woman in the Moon (1929), Thing to Come (1936) they contributed to the early recognition of the concept of the rocket as the iconic and primary means of space travel, decades before the space program begun in earnest. Later milestones in film and television include the Star Trek series and movies, and the 2001: A Space Odyssey film by Stanley Kubrick (1968), which visually advanced the concept of space travel, allowing it to evolve away from the simplistic rocket towards that of a more complex space ship.
Methods of travel
Generic terms for engines enabling spacecraft propulsion in science fiction include those of a space drive and star drive. In 1977 The Visual Encyclopedia of Science Fiction listed the following methods of space travel: anti-gravity, atomic (nuclear), bloater, cannon one-shot, Dean, faster-than-light (FTL), hyperspace, inertialess, ion, photon, plasma, ram-jet, R. force, solar sail, spindizzy and torchship. The 2007 Brave New Words: The Oxford Dictionary of Science Fiction listed the following vocabulary related to the concept of a space drive: gravity drive, hyperdrive, ion drive, jump drive, overdrive, ramscoop (a synonym of a ram-jet), reaction drive, stargate, ultradrive, warp drive and the torchdrive. Several of those terms are entirely fictitious or based on rubber science, while others are based on real scientific theories. Many fictitious ways of travelling through space, in particular, faster than light travel, tend to go against our current understanding of physics, in particular, the theory of relativity. Some works can sport numerous alternative star drives; for example the Star Trek universe, in addition to its iconic warp drive, has introduced concepts such as transwarp, slipstream and the spore drive, among others.
Many writers, particularly of early science fiction, did not address the method of travel in much detail, and many works of the "proto SF" era had to contend with their authors living in the time where knowledge about the "space" was very limited — in fact, many early works did not even consider the concept of vacuum and instead assumed that atmosphere of sorts, composed of air or aether, continues indefinitely. Highly influential in popularizing the "science" part of the science fiction was the 19th-century French writer Jules Verne, whose method of space travel in his 1865 novel, From the Earth to the Moon (and its sequel, Around the Moon), was explained mathematically, and whose vehicle — the gun-launched space capsule — was described as the first such vehicle to be "scientifically conceived" in fiction. Percy Greg's Across the Zodiac (1880) featured a space ship with a small garden, an early prediction of hydroponics. Another writer who attempted to merge concrete scientific ideas with science fiction prose was the turn of the century Russian writer and scientist, Konstantin Tsiolkovsky, known for popularizing the concept of rocketry. George Mann pointed to works such as Robert A. Heinlein's Rocket Ship Galileo (1947) and Arthur C. Clarke's Prelude to Space (1951) as some of the early, influential modern works that focused on the scientific and engineering aspects of space travel. From the 1960s onward, the growing popularity of modern technology with the public also led to increasing depictions of interplanetary spaceships as based on the advanced but plausible extension of real, modern technology.
Interstellar travel
Slower than light
With regard to interstellar travel, in which faster-than-light speeds are mostly considered unrealistic, more realistic depictions of the theme have often focused on the idea of "generation ships" that travel at sub-light speed for many generations before arriving at their destination. Other scientifically plausible concepts of interstellar travel include suspended animation and, less often, ion drive, solar sail, Bussard ramjet, and time dilation.
Faster than light
Some works involve discussion of Einstein's general theory of relativity and challenges it faces from the quantum mechanics, and include concepts of space travel through wormholes or black holes. Many writers, however, gloss over such problems, introducing entirely fictional concepts such as hyperspace (also, subspace, nulspace, overspace, jumpspace or slipstream) travel using inventions such as hyperdrive, jump drive, the warp drive or space folding. Invention of completely made up devices enabling space travel has a long tradition — already in the early 20th century, Verne criticized H. G. Wells' The First Men in the Moon (1901) for abandoning realistic science (his spaceship relied on anti-gravitic material called "cavorite"). Out of the fictitious drives, by mid-70s the concept of travelling through hyperspace has been described as having achieved the most popularity, and would subsequently be further popularized — as hyperdrive — through its use in the Star Wars franchise. While the fictitious drives "solve" many problems related to physics as understood today (namely, the difficulty of faster-than-light travel), some writers introduce new wrinkles — for example, a common trope involves the difficulty of using such drives in close proximity to other objects, in some cases allowing their use only from the outskirts of solar systems.
While usually the method of traveling through space is just a means to an end, for some works, particularly short stories, it is a central plot device. Such works focus on themes such as the mysteries of hyperspace, or the consequences of getting lost after an error or malfunction.
