20th century humans learned the value of redundant engines on aircraft. If one fails, you can keep flying.

But in the Star Trek universe, Federation ships like the Enterprise have only one warp core. (AFAIK — I can't say I've examined every Federation ship before asking this question.)

Why is this so? If the warp core is so important, why wouldn't ships be built with two, so they have a backup? That way, if one fails, you wouldn't need to, oh I don't know, send key crew members into an irradiated area to fix it.

I understand that a second warp core would, in practice, deprive Star Trek of many storylines. What I'm asking is whether this restriction has ever been explained in-universe.

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    Busy at work, but my first guess from looking at old schematics is an issue of space. The warp core is large, bulky and radioactive (needs shielding) so I imagine they are so large fitting more than one normal sized core is probably difficult when you look at the size of most Federation ships. Perhaps in the Abrams-verse, with the Enterprise being SO MUCH LARGER two cores would be possible and reasonable... Commented Jul 23, 2013 at 17:41
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    the Enterprise E ejects it core, and yet was still able to fight. en.memory-alpha.org/wiki/Star_Trek:_Insurrection
    – Zoredache
    Commented Jul 23, 2013 at 20:57
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    Why would you want two incredibly fragile anti-matter explosive chambers on board? ;)
    – HorusKol
    Commented Jul 24, 2013 at 2:09
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    @HorusKol because i would rather have a less than 100% chance of being blown up by an engine, than a 100% chance of being blown up by the enemies when you cant move?
    – user14898
    Commented Jul 24, 2013 at 12:49
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    Star Trek is built on the premise of bad engineering. We're talking about a universe where people are electrocuted because no one has ever heard of putting a fuse between a control panel and the systems that it's connected to.
    – John O
    Commented Dec 20, 2013 at 17:54

16 Answers 16


Brandon and gnovice have made some good points, and I just want to add that:

  • If a single-engine plane loses that engine for just a minute or two, it's going down. This isn't the same situation with vessels like submarines and cars, which generally only have a single power supply. The Los Angeles class attack subs only have a single nuclear reactor, though it powers multiple steam turbines which in turn create electricity and drive the propeller. The same is true of the Ohio class ballistic sub. If the reactor were to lose power or need shutting down, they'd probably just surface using battery power (or their emergency diesel backup). Losing the reactor in itself isn't a catastrophic disaster.

    Similarly, starships don't actually "fly" most of the time. They're in deep space or at least high orbit. If the ship suddenly went dead, it would just be adrift, not fall out of the sky.

  • Indeed, if a starship's warp drive were to go offline, it would likely be fine for several days, which should be enough time to make repairs, evacuate, or ask for assistance. In fact, the saucer section seems to be able to travel for quite some time using its own impulse engines and warp sustainers completely separated from the warp drive. So there must be enough leftover drive plasma circulating through the saucer section or enough leftover electric energy stored in batteries for the Saucer section to continue operating under normal power for at least a few days.

  • On the other hand, if a ship like Voyager were flying within a planetary atmosphere, and it suddenly lost impulse power, it would likely crash even faster than a plane. But most starships seem to have multiple impulse engines.

Also, warp drives are much more reliable than jet turbines or internal combustion engines. They do occasionally need to be shut down for maintenance or get taken out of commission by spacial anomalies or enemy attacks, but these are incredibly rare events that are similar to nuclear reactor meltdowns.

Ideally, yes, you would have redundancy for all critical systems (an extra main computer, extra main deflector, extra dilithium matrix, an extra captain, etc.), but you have to weigh the costs of operation and maintenance (and the additional dangers of operating a second warp drive) against the actual benefits you'd gain from it. And it's not clear the benefits of a second warp drive are worth doubling the size of the engineering section and engineering crews on each ship.

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    This is the best answer because it a) doesn't argue with the premise of the question, b) uses more in-universe facts and c) applies better reasoning by analogy. Thanks. Commented Jul 25, 2013 at 17:24
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    I disagree with the warp cores being reliable - they tend to be finicky things that destabilize at the worst possible times (usually just before a commercial!). The engineers are highly skilled at controlling them and keeping them from blowing up, but that doesn't make them stable or reliable.
    – Jeff
    Commented Aug 11, 2013 at 16:01
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    @Jeff: Not being indestructible is not the same as being unreliable. Warp cores only rarely malfunction during intense battles or when encountering the odd spatial anomaly. They don't shut off or break just because there's heavy rain/hail, volcanic ash, a bird strike, etc. They also don't appear to require a complete overhaul every 4 months. Considering that Voyager made a 7-year deep space journey without an extra warp core or Federation service stations and was only shown to set down once (6 years into the journey) for warp drive maintenance, I'd say that's pretty damn reliable. Commented Aug 11, 2013 at 16:50
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    If I recall correctly the warp core is not the only power source for a ship; that fusion reactors provide day to day power (including for the impluse engines). So as long as you didn't want to go to warp you could go without a warp core indefinately; en.memory-alpha.org/wiki/Fusion_reactor
    – user20310
    Commented Dec 20, 2013 at 15:16
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    You could argue a reactors efficiency point - that given engineering effort and expense X, you're far better off building a single reactor of size 2X than building two reactors of size X. That is, the bigger the reactor, the more efficient it is...this is actually true for many power production systems, up to a certain point, of course. Commented Apr 20, 2014 at 19:53

I've never heard it explained in-universe, but there is one thing wrong with the reasoning in your first sentence: extra engines generally aren't added to aircraft solely for redundancy, they're added due to increased power demands. If you need to haul more people/freight/weaponry, add another engine(s). Single-engine aircraft are still very common if you think about it... crop dusters, helicopters, even jets.

A warp core is a specialized, finely-tuned, advanced piece of critical technology (read "super-expensive"[1]). It would generally come down to a cost-benefit analysis of adding a redundant system which may never get used, but costs a lot and takes up much more room. It's probably better to just build another ship around the second core and have two ships instead of one (i.e. move the redundancy up one to the level of whole ships instead of ship subsystems).

In addition, the stories told in the shows/movies are going to focus on where the action is. For every Enterprise that is battling with some hostile new race, there may be hundreds or thousands of other ships that live safe and boring lives shuttling passengers and freight to and fro or patrolling uneventful regions of space. And for every battle where the Enterprise's warp core ends up as a casualty, there are plenty of mundane trips that she makes looking at stars and doing scientific research where nothing much happens. The rate of warp core failures, when considered for all ships and all missions (both on-screen and off-), likely ends up being too low to warrant the redundancy in the design.

[1]: Although there is no "cost" in the Federation (it is "post-money", so to speak), specialized materials can still be scarce or difficult to manufacture in large quantities, thus limiting use of that technology in the same manner as a monetary cost would.

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    "Extra engines generally aren't added to aircraft for redundancy": that's simply not true. "[M]ulti-engine airplanes are designed to fly with one engine inoperative." (en.wikipedia.org/wiki/Turbine_engine_failure) Single-engine aircraft remain common only in situations where economics (crop duster) or flight requirements (helicopters & fighter jets) demand it. Since these conditions are not at issue for Federation starships in the ST universe, the question stands. Commented Jul 23, 2013 at 19:59
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    @Monty129: You can interpret the word "cost" more generally as "availability". If certain materials are very scarce or slow/difficult to manufacture, it's going to limit how much of them you will use just as if they were monetarily hard to come by.
    – gnovice
    Commented Jul 23, 2013 at 20:24
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    @xrayspec: Your quote states that the aircraft design is such that it can still work properly with an engine failure, but that doesn't mean the sole reason for adding that extra engine was for the purpose of such redundancy. Also, see my response to Monty regarding a more general interpretation of "cost".
    – gnovice
    Commented Jul 23, 2013 at 20:27
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    Cost will always be an issue, otherwise we could fly manned missions to Mars the moment we have no monetary system. Brain power is limited, energy is limited and there is competition on resources.
    – flq
    Commented Jul 23, 2013 at 20:46
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    The one issue I have with this is how safety-focused the Federation tends to be. It reminds me of that one scene in DS9 when O'Brien is trying to set up a triple redundancy and the Cardassian he's supposed to be working with scoffs at how overcautious that is.
    – Izkata
    Commented Jul 23, 2013 at 22:58

Klingon Birds of Prey are equipped with two warp cores. The reason for this is their high value on redundancy. Klingon physiology has a lot of redundant systems. The cores are both running all of the time so you don't have the space issue of an unused core. The cores are 50 % the size they would need to completely power the ship to its maximum warp. So if one core is out of action they could reach about half of their top speed. They both feed charged plasma through a regulator that balances the energy and feeds it too the warp coils. Issues that arise from this situation is the power from each core has to be at near the same. if the system is out of balance you would have efficiency issues. The same issue arises with multi engined aircraft as you want the engines outputting the same amount of power. The reason ships can still function without the warp core is that 90% of the energy generated goes into warp flight. The rest of the ships power loads can come from the 10%. If the warp core goes offline they get power from the Impulse drive which is fusion based. Fusion is very inefficient for trying to generate enough energy for warp so they use antimatter warp cores instead. Due to Klingons obsession with redundancy they can run the impulse reactors at 140% and shunt that power to the warp coils to get it to warp 1 if they really need too. The Enterprise did this once in the original series also.

In the real world most large ships have multiple reactors Aircraft carriers have 2. Most US subs are single reactor but a lot of Russian subs have 2 for redundancy. So for Starfleet its probably a engineering culture thing.

Source here http://www.amazon.com/Star-Trek-Klingon-Bird---Prey/dp/145169590X/ref=sr_1_6?ie=UTF8&qid=1376158042&sr=8-6&keywords=klingon

  • I was just about to ask a question on using multiple smaller cores too. Nice find
    – user16696
    Commented Jan 21, 2015 at 20:22
  • "So if one core is out of action they could reach about half of their top speed." This raises an interesting question: Do we know anything about the ratio of speed (on the warp scale) vs. power?
    – Mirko
    Commented Jul 2, 2021 at 22:17

According to Insurrection, the Enterprise-E is equipped with at least a few spare warp cores. After they eject the core, Geordi says "...and we're fresh out of warp cores", after looking towards a storage unit for the spare cores (at least I assume that's what it is, and he's not just being sarcastic).

Quote taken from http://www.scifiscripts.com/scripts/Trek/Star_Trek_IX.htm, line 198.

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    While bigger starship like Sovereign or Galaxy might have enough spare parts to build another warp core from scratch. In this instance Geordi was being sarcastic because it was the only thing that saved the ship from subspace weapon and nothing were to save Enterprise should the son'a fired another.
    – Zeela
    Commented Jul 24, 2013 at 7:47
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    I had always assumed that he was making a very back joke Commented Jul 24, 2013 at 11:10
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    Pretty sure they just had one, and since sub-space weaponry is considered illegal (because of its over-efficiency... we never use overkill, I guess). Jordi is just being sarcastic in battle.
    – Jersey
    Commented Jul 24, 2013 at 20:52
  • I am certain that this was just a joke. Commented Dec 4, 2014 at 14:43

Perhaps future ships will have multiple cores after it is evidenced that a single core is a bad idea.

The Soviet K19 submarine only had one cooling system for its nuclear reactor, and when that failed and the crew had to enter an irradiated area to fix it they decided to build backup cooling into future nuclear submarines.

Humans seem to prefer to wait for catastrophe and adjust rather then avoid it. Also since a warp core breach can cause the ship to self destruct perhaps ignoring such an issue and resorting to a backup engine would ultimately result in a complete loss of the ship.

  • 1
    The phenomenon of "tombstone technology" is generally caused by ignorance/apathy/greed. Getting rid of the money motive gets rid of only one of those factors; cultural advancement may combat the other two to a large degree, but even the best and most well-intentioned engineers can't foresee all possible dangers. But right now the evidence is still out whether the "standard second warp drive" (as Brandon stated, at least some ships carry spare cores) is a case of future tombstone tech. As you alluded to, a backup can pose its own dangers. Commented Jul 24, 2013 at 7:50
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    the failure in K19 was the lack of redundancy in reactor cooling systems, not reactors. If it had had 2 reactors, each with one cooling system, the same thing would have happened (though they might have been able to keep her on the surface longer, allowing more of the crew to survive).
    – jwenting
    Commented Jul 25, 2013 at 6:09

this schematic shows the spare core.

imo, voyager launched too early so the spare core never had the chance to be installed. image borrowed from http://www.cygnus-x1.net/links/lcars/lcars24.php


voyager had a spare core, the master system display clearly shows it in the engineering section, though it is not labelled.
I would assume like warp field coils and other critical bulky components it involves long casting processes taking years and requires lots of storage space, and so they couldn't just be replicated or replaced on most ships. In federation space there would be warp tugs to tow an unpowered ship. Any ship with a damaged core would power down or eject it, and simply wait for a tow. The ship usually isn't in danger because the core is breaching, the core is breaching because the ship has been critically damaged. Something powerful enough to penetrate the hull and damage the core, has probably damaged the rest of the ship beyond repair. A second core would be inefficient, problematic, a potential danger and unnecessary.

Also from a production design perspective, it is easier to centre a set or a shot around 1 object than it is to try and frame 2 or more.

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    This answer would be way better if it contained a screenshot of Voyager's spare warp core on the system display.
    – Ellesedil
    Commented Dec 4, 2014 at 21:13
  • Word of god is that the spare core was never fully functional. It was mainly intended as a supply of spare parts and was cannibalised (beyond useful repair) at some point in the first season. "Voyager carries an auxiliary warp core. This is not a direct replacement for the main core, but a series of components that can be used to construct a new core in an emergency." - Star Trek Magazine
    – Valorum
    Commented Dec 6, 2014 at 22:03

Voyager has two cores. My sources is the blueprint from the official star trek fact files. But in the enterity of voyager it's never mentioned and it was never seen. It would make more sence for a starship to have a spare flat pack warp core the could assemble out side of the ship and then load into the engineering bay. And possibly a machine workshop to replace torpedos and other stuff. I feel voyager never made use of these ideas witch would add realism to the series.

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    Welcome to SFF:SE. Your answer would be improved with more detail about your source, possibly a link.
    – Politank-Z
    Commented Apr 1, 2016 at 17:40

It is a simple cost / profit calculation.

  • Gain:
    • Additional Energy
    • Redundancy, i.e. they gain some time if the Warp Core were to be damaged. They'd gain a few days in case of a problem with the Warpcore and they'd have do maintenance.
  • Cost
    • Increased risk of problem with the Warp Core
    • Increased maintenance (they have to maintain two Warp Cores, not one)
    • Increased crew due to increased maintenance (also, more people at risk)
    • Increased space needed (for reactors and crew)
    • The ship is now a bigger target in case of combat, also, less manouverable
    • Increased cost of purchase (Antimatter can't be replicated, therefore difficult to get and valuable)
    • Increased time to produce the ship (ships cannot simply be replicated)

With that in mind, it probably is way better to create one superb Warpcore with a very low risk of failure than having two good warpcores.

Imagine nuclear reactors for electricity. What would you prefer: one extraordinary reactor that never fails or two that should not fail? The cost for one extraordinary vs two good reactors is probably the same.

And 20th century humans have NOT learned the value of double engines. E.g. the F35 is a single engine jet. So yes, there are double engine airplanes, but not all airplanes are multiengine. For exactly those reasons, it is a simple cost / profit calculation.


Having two warp cores would spoil a number of opportunities for dramatic tension. However, if one wishes to invent a reason why there are none, either they are physically incompatible, or scaling by duplication is less favorable than simply increasing the size of the core.


I don't think the exact nature of the power from the warp core is detailed, but one can envision discontinuous schemes where some sort of rebounding shock wave is used to aid containment, and the precise frequency of the output power would depend precisely on the geometry of a particular core; syncing up two cores might be nigh impossible (or unreliable), and having beating power surging through your system is a good way to exceed maximum currents and blow things up. In this scenario, your second warp core would have to be off (useless) until your first one broke. For the same size/weight, you are liable to be better off with upgraded shields, better physical protection of your one warp core, etc..

Unfavorable scaling

If containment field strength and power output increases faster than linearly with warp cores, a single warp core that's twice as big would both be better protected and more powerful than two warp cores of the original size. For instance, energy stored in a magnetic field can go as the cube of the volume. If you double your materials, you could either double your volume in two warp cores, or build one with double the surface area and 2^(3/2) the stored magnetic field energy (about 2.8x). If that stored energy (not just the local field strength) plays an important role in some aspect of the reaction, it would be foolish to create two cores instead of one bigger one.


On the initial supposition that the core is highly specialized, presumably expensive and is clearly sizeable. Add the fact that what you see in Engineering is only a small part of the overall warp drive system. Note the Warp Nacelles on the outside og most Federation Starships. It is likely you could argue that the warp field of one core would require the second core to be offline in order to operate properly. If the multiple cores were to operate connected to the same Nacelles (i.e. we don't need a separate set of nacelles for the second core) then the complexity arises of preventing a breach of one core's system from bleeding into the second core, efectively destroying the second core.

In this context by breach of the system, I do not mean breach of the core its self, but of the plasma conduits, energy transfer systems, and connections to the nacelles themselves.

On the flip side, if you make the two cores completely independent of each other (no crossover, except perhaps the stored fuel sources; then you would add even more additiona conduits, relays and, yes, even nacelles. If the warp dore and nacelles are a very large portion of the total cost or resource requirements of the vessel, then you could have, for example, possibly three Galaxy Class starships as designed for the equivilent cost/resources of perhaps 1.5-2 Galaxy class starships operating with a reserve Warp Core. And three starships means presence in three places at once.

If a secondary warp core would be installed, I would imagine it would likely be a smaller, more 'emergency use' type which likely would have neither the range nor speed of the main warp core. (Like an emergency generator for when the power goes out, or a 'small' spare tire. etc.)


Losing the core prevents it from FTL travel in most cases, prior to the alternate timeline, on the newest movie they maintained warp after ejecting the core.

From my experience as a Trekkie that is very technologically sound and savvy. Just because you eject a core the ship is not powerless, the intricate systems of gel-packs, power-inducers, back-up generators, isolinear technology, and fuel cells provide many ways to store power so a ship can effectively operate, but as a general rule can not initiate warp without the cold and the cold fusion reaction needed to generate a warp bubble.

However, FTL speeds are capable without a warp core but at the expense of other things, safely you can use impulse through a Wormhole, but if you like the risk you can use a deflector dish to create a transwarp conduit. usually if this is done it will likely blowout the dish and you are looking at a one way travel, If you lost your warp core for good reason, this is about the last resort to get home and spend months explaining why you need a new warp core and deflector just to save a ship..

Personally, I would also like to see the Federation build a dual or quad core that can effective operate collectively, co-dependently and independently....

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    This is not helpful as it does not answer the question of whether this restriction has ever been explained in-universe. Please see the following for the guidelines of the site, and while you're there you can earn your first badge: scifi.stackexchange.com/tour Commented Dec 20, 2013 at 11:54
  • Is this true? A starship can remain at warp without a core?
    – Vogon Poet
    Commented Oct 12, 2019 at 15:39

If you look at Roddenberry's Andromeda series, you find that the ship has multiple reactors to sustain combat operations. When not in combat, the Andromeda runs only one reactor and has the other three idle. There is no reason that a Federation starship could not have a second or third warp core, save for the high cost of dilithium to run them. Personnel, space, and other considerations are moot given that cornucopia technology exists in that world. As such, only the scarcity of material would prohibit it's use. One has to assume that Dilithium cannot be replicated and must therefore be mined in order to be employed. Given that it is extremely rare, that would make the warp core far more expensive than any other system on the ship.

Romulans on the other hand use singularity cores and that would require far less dilithium than a matter/anti-matter reactor. So a better question would be why don't Romulan ships have multiple cores? In the context of the game, Star Trek Online, it is likely because Cryptic wants to avoid giving Romulan ships a heavy edge on Fed and Klink ships. Other than that, there is no real reason to not use multiple cores for additional power to weapons and shields.

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    Romulan cores seem to be sufficiently expensive that they harvest and recycle them into new ships. It seems likely that having two would be overkill, not to mention the extra cost of having to maintain a (largely unnecessary) secondary core. The same is arguably true on Federation ships.
    – Valorum
    Commented Feb 17, 2015 at 23:44

Leaving aside dramatic reasons or technical reasons I can see one primary and very simple reason.

That is that having warp-core redundancy is so similar to having whole-ship redundancy that they just build a ship around every warp core. This maximises the effectiveness of building more warp cores.

So, in a sense they do have redundant warp cores, just implemented in a maximally efficient way.

  • Hi and welcome! Please read the bounty description, I’m looking for someone to put all the great answers into one post. Right now several people have parts of it. You can edit this by just adding those posts together.
    – Vogon Poet
    Commented Oct 17, 2019 at 8:36
  • Ahh. Thank you for the clarification. I am happy for someone else to get the bounty by adding my post to theirs then. :)
    – deMangler
    Commented Oct 17, 2019 at 8:38
  • Yeah it’s work. That’s why 100r
    – Vogon Poet
    Commented Oct 17, 2019 at 8:39

The star ship is more like a submarine than a plane. It has two nacelles. The core is the engine providing power not the thrusters. Most devices have one engine and power supply. The nacelles are the thrust the core provides power nacelles provide the movement. Much like a submarine they have one engine room but to or more thruster ports.

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    Welcome! Tip: not a great way to start an answer with, "you are thinking wrong". Commented Dec 4, 2014 at 13:11

i was always under the impression that warp technology bends space or compresses space so that the distance traveled is actually closer which achieves the speed travelled as opposed to creating thrust to propel the ship which i always believed was the job of impulse drives, also i always thought that the ships have two engines connected to one warp core. warp cores are commodities especially in voyager where without the core they're marooned so its very valuable. in voyager the borg have trans warp coils, which i was thinking about today, there seems to be some sort of benchmark of travelling beyond warp factor 10. anyway i agree with other comments about the dramatic effect of only having one warp core as it aids story arc especially in voyager. i like future Janeway's updated voyager in the last episode where she steals borg trans warp coils and the high tech super armour/sheilding from the future and goes back in time and adds it to make the voyager awesome different shows have different versions of these types of fictional technology such as FTL drives in Battlestar Galactia, hyper drive in starwars whatever the TARDIS does within the time vortex my favorite is of course the infinite improbability drive of which im sure you only need one of!

okay i have looked over the other comments and i'm thinking that i've went off course a bit anyway in an episode of Enterprise, nx01 enterprise and nx02 columbia join toghether and there combined warp cores increse the warp field so in essence a star ship is not so much like plane that flys via propulsion from its engines overcoming friction via thrust a star ship moves through space inside a warp field which i still believes distorts space to achieve movement. i like the other post which state that having two warp cores would be better placed in two ships which could then work in unison to create a larger warp field. i'm not sure if this is just my imagination here or not but i thought that star ships have anti-gravity drives to aid flight within atmospheres on planets where they also use impulse drive. i'm not really sure about the analogy between the planes and submarines because there engines propell them at non super spectacular speeds against friction - water/ atmosphere i don't think that they are really comparable to star ships and the relative speeds they acomplish with warp cores. so i think that having more than one warp core would be useful in a ship that could separate into separate ships and recombine i think i seen this in voyager the ship cetainly split into three however i really don't know about the warp core scematic on that ship and i can't remember the episode. i like this discussion though but i'm new to this site.

  • 2
    Welcome to SFF.SE. FYI, this isn't really a discussion site -- it's a Q/A site. Commentary such as "I like..." is welcome in comments or Science Fiction & Fantasy Chat but should be avoided in answers. Also, please try to use proper capitalization, grammar, etc.
    – Null
    Commented Feb 17, 2015 at 19:35

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