This is sort of the opposite of this question: Which SciFi universe has the fastest space ships (hyperspace technology)?

Since the obvious answer is just wherever there is no technology much more advanced than our own, we need to modify the question.

In order to force a unique answer, the metric we will use is: In which universe, despite having slow drive technology, have people traveled the farthest and spread over the most worlds using non-FTL drive ? The non-FTL drive has to be used because it is the fastest drive available, not for some quirky exceptional case. I.e. no one has FTL.

Obviously teleport-type technologies etc. are not allowed. There is no cheating.

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    Our universe. :(
    – user1027
    Jan 6, 2012 at 17:39
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    @Keen be positive. Just because the humans in our universe have very slow (inter)stellar drives doesn't meant that there isn't some other race out there with something faster.
    – Xantec
    Jan 6, 2012 at 18:10
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    This question could potentially spawn any number of lists of works, each one trying to out do the rest. It may be helpful to place additional restrictions on it, as the linked question did by asking specifically about TV shows.
    – Xantec
    Jan 6, 2012 at 18:12
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    This question still needs further fixing before it becomes answerable. As it is, it still has potentially conflicting criteria (furthest traveled/spread over the most worlds), and has conditions not detailed in the actual question (i.e. can't be accidental, must be in widespread use, etc.).
    – Beofett
    Jan 6, 2012 at 21:24

14 Answers 14


In Larry Niven's Known Space stories, much of early Human Space was colonized with a combination of two different STL technologies. These were:

  • Ramrobots (automated crewless Bussard Ramjets)
  • Slowboats (large slow fusion powered ships that carry the colonists).

The Ramrobots perform the initial scouting of potential colonies, and can be used to refuel the Slowboats. The colonists are usually held in suspended animation (when stasis fields are discovered in 'World of Ptavvs'). Colonization takes decades of effort.

Using this method the following Known Space colonies are founded:

  • Jinx (Sirius A)
  • Wunderland (Alpha Centuri)
  • We Made It (Procyon A)
  • Plateau (Tau Ceti)
  • Home (Epsilon Indi)

Many of Niven's novels and short stories are set in a time before Hyperdrive with primarily fusion powered reaction drive STL ships. Humankind develop some extremely efficient fusion engines and you get everything from 1-crew Singleships to giant interstellar Slowboats.

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    Look elsewhere--while they don't colonize, look at the Outsiders. No FTL yet they apparently cover the galaxy. Jan 7, 2012 at 3:48
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    @LorenPechtel - but in ships which accelerate to just below lightspeed using an inertialess drive - so not the slowest drive. Jan 7, 2012 at 5:14
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    Outsiders have hyperdrives. Mentioned in Ringworld Engineers.
    – aramis
    Jan 7, 2012 at 18:01
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    @aramis - Outsiders sold the hyperdrive to humans, but they do not use hyperdrive themselves. The wikipedia article on them says 'rarely use them' - but what I have read (in particular the story Flatlander) implies that they never use them to the point of almost being afraid. I recall reading that even asking them the questions 'why they do not use hyperspace?' and 'why do they follow starseeds?' are priced so high as to be unafordable even to the likes of Gregory Pelton. Jan 7, 2012 at 23:27
  • Even after obtaining the hyperdrive, at 3 1/2 days per light year, it takes some time to get anywhere that matters. Earth to the Ringworld or Eath to the galactic core would have been longer than a human lifetime (without boosterspice). Quantum II hyperdrive solved that, but wasn't cost-effective for normal travel.
    – Zeiss Ikon
    Apr 17, 2019 at 17:47

Two examples from Alastair Reynolds:

  • In the Revelation Space universe, there is no FTL, and in the far-future of the setting the Greenfly are implied to have spread over most of the galaxy and eventually the observable universe.

  • In House of Suns humanity has settled the entire galaxy over the course of 6 million years of slower-than-light travel.


To address the "slowest interstellar travel speed", I propose the novel Footfall.

In the novel, the aliens travel from the Alpha Centauri system, a little over 4 light years away from earth. It takes them 61 years to reach our solar system in a ship powered by a Bussard ramjet.

To address the "furthest distance traveled without FTL being a possibility", The Red Dwarf traveled for 3 million years (ship's time) at near-light speed.

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    I want to say Red Dwarf is a winner. But: (1) it was accidental that Lister was asleep for 3 million years (2) it wasn't routine (3) on a technicality: I'm no Red Dwarf expert, but among all the quirky things that happened on Red Dwarf there must've been teleportation and/or FTL Jan 6, 2012 at 19:51
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    @ThePopMachine I believe (from the Wikipedia article) that teleportation and/or FTL were introduced in the series sometime during or after the 7th season. The 3 million years of travel occurred prior to the first season, though, when FTL and teleportation were not options (so, per your question, the non-FTL drive was used because it was the fastest drive available).
    – Beofett
    Jan 6, 2012 at 20:03
  • It wasn't "used" for three million years because it was the fastest drive. One character just failed was in suspended animation, so he drifted for three million years. This is not a drive. Jan 6, 2012 at 20:30
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    Actually, the ship's computer kept him in suspended animation for 3 million years until the radiation danger was gone. I don't recall anything saying they were drifting. In fact, the episode description for season 1 episode 2 specifically states "Red Dwarf has been steadily accelerating for three million years".
    – Beofett
    Jan 6, 2012 at 20:36
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    I didn't realize from your question that those were requirements....
    – Beofett
    Jan 6, 2012 at 21:19

Well, how about Poul Anderson's "Tau Zero" for maximum distance traveled.

In this tale we have a basic sublight interstellar ramjet with a malfunction which prevents slowdown until repared. Meanwhile, they keep accelerating, pushing time dilation way way down, hence the book's title.

Eventually they fix their problem, but have been flying around long enough to witness the heat-death and eventual collapse of the universe, and they enter the next cycle of the universe's expansion. A great many trillions of years of time elapsed, all of it moving at just a hair under speed of light.


In the universe of Ender's Game, space travel is done using ships which travel at almost the speed of light. Time dilation means that while it takes decades of "real" time for a ship to move between planets, for the travelers only a few weeks have passed.

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    "Almost the speed of light" is still pretty fast. There must be a far-reaching universe where only realistic conventional drives exist, and people have spread out over tens of millions of years. Jan 6, 2012 at 17:42
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    Also, see en.wikipedia.org/wiki/Concepts_in_the_Ender%27s_Game_series: Instantaneous Travel - A simple spacecraft is constructed (later deemed unnecessary due to Jane's precision in transportation), and through holding the image of the traveler in her consciousness, Jane can pick up the image and place it anywhere in the universe instantly. This advancement is threatened by Congress' attempt to deactivate her "program." Found in Children of the Mind. This concept was introduced in the later chapters of Xenocide and necessary for its ending. Jan 6, 2012 at 17:48
  • Le Guin's Ekumen also had nearly-as-fast-as-light travel, but ftl communications by means of the ansible...Looks like Card pretty much adopted this combination straight out of her work.
    – The Photon
    May 4, 2013 at 16:39
  • @ThePhoton Indeed, in Ender's Game, when the ansible is first described its name is said to be taken out of "some old science fiction book", or similar phrase. A clear homage.
    – Ryan Reich
    Aug 24, 2014 at 20:42
  • @ThePopMachine simple acceleration to almost the speed of light would seem make more sense in those circumstances (over thousands or millions of years) than "realistic" propulsion drives.
    – Ber
    Mar 24, 2017 at 5:27

In Return from the Stars from Stanisław Lem, the protagonist and crew return from a mission to Arcturus (36.7 light-years) which took 127 years (10 years for them due to time-dilation).

In the original, Polish version they travel to another star instead, which is only 25 light-years away (the travel also takes 127 years).

It is strongly hinted that there is no other sentient life in the Galaxy, and that humanity will abandon space travel forever (or at least for a long, long time).

  • I haven't read it, but those numbers seem inconsistent. 127 years to Arcturus and back implies an average speed of about 0.58c (0.39c for the original Polish version), which isn't nearly fast enough for that kind of time dilation. Can you recheck the numbers? Or is there some other kind of time dilation going on? Mar 4, 2017 at 21:04
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    @KeithThompson : I don't remember it being discussed in detail in the book, but I guess if they accelerated to almost light-speed in a year or two, then decelerated using a similar time-frame, and were flying at constant higher-than-0.58c in the meantime, it could be plausible to attain such a time dilation. Or, it might be an author oversight, as the travel itself and its destination is not important for the story. The story is set after they arrived back to Earth, and the only plot-relevant thing is that they didn't find anything interesting in space, and that a lot of time went by on Earth.
    – vsz
    Mar 4, 2017 at 21:19

Depends what you mean by "people". In "The Fourth Profession" by Larry Niven, the (alien) Monks have an extensive interstellar trade that uses ships driven only by light sails. Normally, they demand a launching laser from their customers. If they don't get one, they trigger the star to go nova. Either way implies a pretty low max achievable speed.


Schild's Ladder by Greg Egan involves near-lightspeed travel for hundreds of years in an attempt to escape a bubble in space that isn't very friendly to life and expands in every direction at half the speed of light.


There are a few universes where there is interstellar sublight travel. Sometimes it is even mixed with FTL travel, or else it is a necessary precursor to the universe's development of FTL drive tech.

  • In the Star Trek universe, the first fictional Enterprise was a sublight interstellar ship, ECV-330, from the 2100s. Humans have since gained FTL technologies in several variations.
  • In the Star Wars universe, hyperdrives are the primary means of interstellar travel, but it is apparently still feasible to travel at sublight speeds to get places. The Millenium Falcon, for example, travels from the Anoad system to the Bespin system with a broken hyperdrive.
  • In the Riddick universe (Pitch Black, Chronicles of Riddick), humans travel from system to system on sleeper ships. It takes months to get places, but various space lanes are well-established and well-traveled.
  • In the Avatar universe, humans have a fledgling space ferry system between Earth and Pandora (and probably other closer places) using sleeper ships. A trip between Earth and Pandora takes a little more than 5 years.
  • In the computer game Sid Meier's Alpha Centauri, a colony ship is sent from Earth and takes 7 years to arrive at its destination, Planet, in orbit around the Alpha Centauri binary system, travelling under relatively conventional propulsion. This is by no means an everyday occurrence; the launching of the ship is a last-ditch effort to save humanity from an unsalvageable Earth.
  • Similarly, the game Freelancer has its backstory in the endgame of Starlancer, where the Alliance (made up of 5 member Earth nations: America, Britain, Germany, Spain and Japan) sends a fleet of sleeper ships to the Sirius Sector to escape its war with the Coalition (made up of other former Earth nations). The ships travel quite fast as evidenced by the intro movie, but according to in-game story material, the ships are only near-light-speed, hence the need for cryosleep. The game itself uses FTL travel in the form of Jump Gates, but no ship can travel FTL without them.
  • Ender's universe as previously stated uses ships travelling near-light-speed, dealing with the relativity concerns and other concerns as Einstein predicted we'd have to, but using entanglement to provide FTL communication (which science has since disproven; the interactions of quantum entanglement do not exceed light speed).

Most other universes in which FTL travel doesn't exist generally confine travel to members of our own solar system, primarily Earth, Venus, Mars and various moons of the gas giants. Arthur C. Clarke posited several ideas at various stages of human technological evolution; in 2001 and 2010, humans used fission-powered ion drives with cryo-sleep to reduce food usage. In Imperial Earth, we'd colonized a lot of the solar system using ships powered by controlled singularities. These allow travel between Saturn and Earth over a period of about 3 weeks, during which the ship is constantly under power either accelerating or decelerating along its course. By 3001, humans have discovered anti-gravity propulsion, and mining asteroids beyond the orbit of Pluto is relatively commonplace, but we're still not travelling between stars on a regular basis. I remember a Russian sci-fi novel translated into English, in which humans possess a technology that allows for relatively speedy travel within the solar system but does not work for interstellar trips. I read it in high school and have since forgotten the name.

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    Has anyone considered Firefly? Jan 6, 2012 at 20:31
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    Building Harlequin's Moon and Old Twentieth also feature cultures (humans) using STL ships, although these books focus more on the journey rather than the destination.
    – Xantec
    Jan 6, 2012 at 21:47
  • Also, Orson Scott Card's Homecoming series has a human civilization that colonizes a number of planets using sub-light sleeper ships (the number 12 sits in my head, but I am not 100% certain on this).
    – Xantec
    Jan 7, 2012 at 0:11
  • @Adele I believe the entire Firefly "universe" takes place in a single (extremely large) solar system known as the "Verse", so it really doesn't qualify as interstellar travel.
    – Beofett
    Jan 7, 2012 at 1:16
  • @Beofett Fair enough. Jan 7, 2012 at 4:53

The universe in the Passages series: http://localroger.com/. The entire epos is pretty much devoid of far out sci fi tech, except for a form of strong AI.


If your star travelers don't have to be human then I think the all time slowest interstellar voyagers are the aliens in Hal Clement's novel The Nitrogen Fix. They use hollowed out comets as their ships. I don't recall Clement specifying their means of propulsion but it was probably something slow like a gravitational slingshot. Their ships drift from one star system to the next and scan it for planets habitable for their species. If there are none they settle into that system's Oort cloud and wait for such a planet to evolve!

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    If you're going for non-human colonisation, you can do much better than that. Niven's Stage Trees gain orbit from the ground, then drift through space for (potentially) tens of millions of years before landing, breeding and starting a new cycle. They've colonised millions of worlds, all at 0.0000000000000001% of lightspeed
    – Valorum
    Mar 4, 2017 at 21:01
  • Stage Trees are non-sentient and thus are more a form of panspermia than interstellar colonists. If humanity ever perfects suspended animation like Hal Clement's aliens we could colonize the entire galaxy with ships no faster than the Voyager probes. Equip comets with nuclear-thermal rocket engines using cometary mass for propellant, slingshot past several planets to reach solar system escape velocity and just coast. Mar 9, 2017 at 19:56

In the Saga of Seven Suns books by Kevin J. Anderson, the first inter-stellar ships launched from Earth were 11 'generation' ships, where a number of generations of people lived aboard the ships, that moved sub-light-speed, until they were either found by the Ildiran race, or they stopped at the place that eventually becomes known as Rendezvous. The generation ships were in space for a couple of hundred years (I forget the exact length of time). Technically, when the Ildirans find them, they take them to new colony planets using the Ildiran's FTL ships, so not sure this fulfuls your question's limitations or not...

EDIT: Just checked: The Ildirans intercept the first generation ship 144 years after it departs Earth. The Roamers, however, stop themselves, in the Meyer rubble belt which becomes known as Rendezvous, after 96 years.


How about Chronicles of Solace series by Roger Allen McBride? Humans confined by lightspeed, but to get around crazy time involved, they have temporal wormholes (Time shafts) that drop you back X years in time. Thus the net time loss to a person involved is small, and the distance is covered.

The poor ship however is like Marvin the paranoid Android at the Restaurant at the End of the Universe.

Then there are temporal guards who make sure no one abuses the time shafts for real time travel.


Zones of Thought from Vernor Vinge. Portions of the Galaxy have physical rules that do not permit "fantastic" technology. Away from the edge of the Milky Way Galaxy, toward the core, is the "Slow Zone" (where earth would be located). A Deepness in the Sky takes place in this area and the book discusses some of the problems of trying to maintain an interstellar trading culture without access to superluminal travel or to superluminal communication. The physical dimensions of the starfaring culture is not explicitly stated and neither the speeds as far as I can recall, but they do require either suspended animation or longevity technology to make the journeys.

  • The novel makes it clear that the web of intergalactic civilization extends practically to the rim of the galaxy, with the realm beyond being where outrageously advanced things live. From that, I think we can estimate the physical dimensions to be around ~2/3 the radius of the Milky Way.
    – Tom
    Jun 29, 2022 at 23:21

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