When the good ship Serenity is traveling in deep space, the crew experiences what looks like an Earth-normal (or Earth That Was-normal) level of gravity. Is it ever explained how the ship is able to generate artificial gravity? The ship doesn't spin, so rotation is out. Linear acceleration is a possibility, but I think the gravity in the ship pulls in a direction that is perpendicular to the direction the ship is usually traveling in, not opposite, like this method would require.

So: how does she pull it off?

Extra credit: how does she pull it off in the episode "Out of Gas"? Serenity's engine is totally dead, to the extent where not even life support systems are online. Yet Mal still has to valiantly haul himself around on the floor to replace the compression coil, so whatever creates the artificial gravity on Serenity is clearly still going. How?

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    Extra extra credit: if the ship generates gravity independently of any other system on the ship and without intervention from humans, why isn't there double gravity on board when she lands on planets that have their own gravity?
    – hairboat
    Commented Mar 23, 2012 at 18:44
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    I suspect that, if you asked the show's creators, "How does gravity work on Serenity?" they would say, "It works very well, thank you." Commented Mar 23, 2012 at 21:12
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    It's exactly the same as on Star Trek, Star Wars, Lost in Space, Battlestar Galactica (TOS), Space:AAB, Red Dwarf, and MST3K. Energized Nano-Handwavium
    – SteveED
    Commented Mar 24, 2012 at 2:49
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    @Pselus I do care. I care very deeply. It keeps me awake at night. (Truth: you are right that it's insignificant, but it's hard to write an episode that is about critical systems failing on a ship and not bring up what is probably one of the two most critical systems.)
    – hairboat
    Commented Mar 25, 2012 at 3:00
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    @AbbyT.Miller : I wish I could find the quote, but Joss was asked questions like this when the show was on, and he flat out said (paraphrasing) that he didn't care about the science of the show. He didn't care if there were scientific inaccuracies. He said that if that mattered to you in a show, Firefly wasn't for you. Was mainly making a joke on you though, but also worth noting that you will find situations like that in Firefly because the show creators didn't care to make it scientifically solid. Commented Mar 25, 2012 at 13:33

9 Answers 9


Perhaps the answer is found in the following two references:

In the companion volume "Firefly: Still Flying", there is a short story by series writer Jane Espenson called "What Holds Us Down" that describes the various aspects of the gravity rotor and the Honecutt Capacitors that are a part of the system for generating a relative gravity and inertia damping effects throughout the ship.

In the story, Kaylee and Wash are trapped inside a dead Series 1 Firefly in a junkyard, and she uses the capacitors to charge the grav rotor back up. Obviously the capacitors have some residual gravitational "charge".

Also, a careful examination of the "Serenity Blueprints" from QMX show various gravity amplifiers on the ventral side of Serenity that feed the output of the grav rotor around the ship to provide a "down force" relative to the floor of Serenity.

Since both these references were made/created with the blessing/authorization of Joss Whedon, perhaps they should be considered canonical?

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    I'd absolutely consider those canon, just like Star Wars EU is.
    – hairboat
    Commented Aug 8, 2014 at 1:26
  • @abbyhairboat Mr Lucas has written off the Star Wars EU. It is now all non-canon.
    – Gusdor
    Commented Dec 2, 2014 at 10:30
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    @Gusdor True, but Mr Lucas has also written Jar Jar Binks, so...
    – BMWurm
    Commented Mar 13, 2015 at 7:43

I found an article on SerenityVerse entitled "Serenity Ship Specifications and Plans". It states:

The Firefly class ships [sic] gravity comes from a rotating ring just aft of the ships [sic] midsection. It produces a gravity field using the “Peristere Principal" [sic], that also acts as an momentum dampener to allow passengers more freedom of movement during all aspects of flight.

(I don't think this site is the original source of this information - any tips you guys can find would be appreciated.)

This "principal" seems to be named after Loni Peristere, a visual effects supervisor who worked with Joss Whedon on Firefly/Serenity, as well as on Buffy/Angel and other projects.

To me, that seems like a tongue-in-cheek way of saying "gravity works on Serenity because we say so". That holds with the interview mentioned in Pselus's comment on this question.


The Firefly / Serenity universe clearly includes some sort of control over the laws of acceleration and inertia. After all, the crew members don't fly against the back of the ship every time it flies off into the sunset. The Crazy Ivan in particular would have flung them to bits instead of just lightly pushing them around. Since there's no real difference between acceleration and gravity. (This was the primary insight which led to Einstein's e=mc^2), the same technology could be used to supply artificial gravity. Don't forget that Jubal Early had to use magnetic boots to stay attached to the outside of Serenity. It must be a pretty localized effect.

And I wouldn't be surprised at all to learn that there are all kinds of battery backups and failsafes preventing the loss of gravity control. You can't fix the life support if your nuts and bolts and tools (and mechanic!) are all floating about.

It should also be noted that it's unlikely that all of the planets and moons in the Firefly solar system had roughly the same gravity, and yet there seems to be no complaints about high or low gravity conditions. Part of the terraforming process must be.. well.. here's an interesting theory.

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    Not sure I agree with your second paragraph. Consider: you can't fix the gravity drive if your mechanic has asphyxiated.
    – hairboat
    Commented Mar 24, 2012 at 13:37
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    Well, technically E=mc^2 came first... not that it matters ;-)
    – David Z
    Commented Mar 29, 2012 at 20:45
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    In real spacecraft, the crew can (and do) fix things while floating about in free fall. I would say life support is more fundamental. Commented Jul 23, 2014 at 9:37

The Verse In Numbers (aka TVIN) is an extensive fan work to make the Firefly universe internally consistent. It, and the Serenity RPG, are the excellent technical references to the Firefly universe. Are they canon? Here's what TVIN has to say about that in "Lies, Damn Lies & Canon".

...the next 100 pages (no, really, 100 pages) represent the most painstakingly-researched and thoughtful effort to make sense of a bunch of hooey that I've encountered...

So, what does that make The Map of the Verse? Canon? Extended Canon? Speculation? Here's how I like to think about it - it's as accurate as it's possible to be right now. Meaning to say, it's 100 percent accurate, until Joss says it isn't. It's Joss' Verse, after all. We're just lucky that we were allowed to visit and bring home a few souvenirs.

The OP asks So: how does she pull it off? TVIN describes a civilization with the ability to control gravity at a stellar scale. It mentions that quantum gravity has been solved in 2035 leading to extensive applications.

  1. The quantum nature of gravity is deduced, allowing for rapid and unprecedented advances in gravity manipulation technologies. Creation of artificial gravity and gravity screening soon follow.

TVIN goes a little bit into the history, but you're not going to get much more than something something quantum gravity.

...in 2006, a lab funded by the European Space Agency, created an artificial gravity pulse that measured 1/10,000th of a G. Unlike the previous claim, the experiments were successfully repeated, and gravity pulses were again created, but it wasn’t until the late 2020’s that artificial gravity fields were being produced of sufficient strength and duration to have commercial applications, and cheaply enough to be afforded by more than just governments.

By the time they arrive in The Verse they have such control over gravity they can compress brown dwarf stars to ignite them into small stars and use it to terraform worlds to have Earth-like gravity. This makes producing episodes cheaper.

Serenity manipulates gravity in two ways and TVIN has a whole section on the Gravity Drive. External gravity screening partially isolates the ship from the pull of gravity making her lighter. That's what the big rotor is on Serenity. Thus she needs less thrust to fly in atmosphere, reach escape velocity, and support her own weight.

In some ship designs, such as the Firefly design (all models) the primary gravity rotor assembly is visible as a rotating ring around the waist of the ship. The dampeners and rotor assembly work in concert to negate the force of gravity acting on the ship, and help dampen the effects of acceleration on the structure of the ship.

TVIN mentions an example where this is fundamental to the success of the Firefly class.

The hinge that allows the engines to fold down to parked and maintenance positions, is not strong enough to support the weight of the ship. Without gravity screening to reduce the weight of the ship, the engines would snap off of their mounts when lifting the ship.

Then there is the internal gravity field, that's what keeps the crew's feet on the floor. It also negates the effects of acceleration, though not perfectly. This allows the crew to be whipped around in extreme maneuvers for some dramatic tension.

Gravity field realignment easily compensates for typical maneuvering. However, sudden changes in direction and speed can temporarily exceed the rotors’ speed at realigning the internal gravity. In some cases, the onboard computer’s attempts at matching gravity alignment with existing natural gravity, during hard maneuvering, can actually magnify the adverse effect of sudden changes in acceleration3. This is why almost all lockers and cabinets on a ship have latches, and most shelves have some sort of guardrail or lip to keep items from sliding off.

Finally, the OP sensibly asks why gravity continues to work in "Out Of Gas" despite even life support being out. @Plutor speculates they would have extensive backups which is plausible if the ship will be crushed under its own weight or torn apart by maneuvers without it. Again, TVIN has something to say...

Without gravity screening, the engines would be directly connected to the axle, and it would be much thicker. With gravity screening, a firefly is quite nimble for a cargo transport. Without, it would be an ungainly hulk unable even able to lift itself while empty of any cargo. Additionally, the landing legs of a firefly cannot support the weight of the ship without gravity screening.

TVIN's explanation is that a gravity field only dissipates slowly after the generator is turned off...

However, an artificial gravity field is a series of pulses that occur very rapidly. The effect is continuous since the pulses are so close together that there is no discernable decrease between pulses. The longer the field is active, the longer the decay of a given pulse. After the field has been active for a few dozen hours, the decay between pulses virtually ceases to exist. Shutting down a gravity generator that has been in operation for months results in a decay of that last pulse that can last for weeks at near full strength.

Since according to TVIN "the only time the gravity screening is entirely powered down is while the ship is supported by a maintenance gantry", and we can be fairly sure Serenity hasn't seen one of those in a long time, we can assume Serenity in "Out Of Gas" has weeks of full gravity.


Maybe "dense-matter" material using black holes or neutronium? Alternatively, it may use some kind of superconductor gravity generating system that is more efficient at sustaining a residual charge than more active life-support systems like air purifiers. All just speculation though.

For extra, extra credit the gravity generating system seems most likely. It should be easy adjust the level of gravity being generated to keep a constant 1g (where local is less than that), or to match the local gravity (i.e. turn the system off when on a planet).

  • I wonder if it would work in the opposite direction and keep the ship's gravity a constant 1g on planets with more than 1g of their own. There is probably no way to know.
    – hairboat
    Commented Mar 25, 2012 at 12:25
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    @AbbyT.Miller I suppose with similar gravity systems in the ceiling, maybe it could produce a "middle ground" effect. But a lot things were left unexplained in the series, not the least of which was artificial gravity. Although it may not be too far a stretch to assume that if you've mastered artifical gravity then perhaps you've also mastered anti-gravity.
    – Xantec
    Commented Mar 25, 2012 at 12:37
  • +1 for residual charge. I remember reading about a lab in England that successfully levitated a frog. They had to use as much power as a small city uses to pull it off. It stands to reason that artificially-generating gravity would require some means of holding a persistent charge since generating that energy on-demand would probably be unfeasible (we're talking many megawatts for a 2oz. frog). I'd imagine that gravity plating or modules could be purchased, pre-charged, and have their charge maintained or prolonged via the ship's power systems.
    – Chad Levy
    Commented Aug 16, 2012 at 17:49

[Edit] It seems the script says otherwise, but plenty of people other than myself heard it as "Gravity supplies" rather than "Grab any supplies".

During the first episode of the series when the crew land on Persephone, Mal instructs his crew to buy more gravity. Gravity is never mentioned again in the series.

In the final episode of the series, we clearly see that when outside the ship gravity works as expected, in that being pushed away gently sends you into space rather than landing back on the ship. This implies the ship only produces gravity internally, through some mechanism which requires purchasing more from time to time.

I imagine when on a planet you don't get double gravity as you turn off the gravity generator to save gravity supplies (or maybe its set to boost gravity to 1g only)

  • Someone stated previously that Mal says to "buy gravity" - just to clarify, he says to grab any supplies they are low on. Also even if the spinning disk supplies Serenity's gravity, where does Early's ship get its gravity?
    – user8319
    Commented Aug 15, 2012 at 23:36
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    @chris-WWMRD I remember it being "gravity supplies" rather than "grab any supplies". I'll have to watch it again and check!
    – Nick
    Commented Aug 16, 2012 at 7:24
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    The line is "grab any supplies". Here's a transcript.
    – Schwern
    Commented Aug 11, 2015 at 7:14
  • @Schwern Oh, that's disappointing. I liked hearing gravity supplies better!
    – Nick
    Commented Aug 11, 2015 at 21:36

I found these articles here, both of which seem to come from the serenity RPG.



If I understand them correctly, the artificial gravity on Serenity works by using electromagnetic radiation to alter the weak nuclear force to compress localized space-time, which is used to both increase the relative internal gravity of the serenity and to negate the gravitational pull of outside bodies. Now my understanding of Relativistic and quantum physics is conceptual at best, so I'm not sure how realistic this is, but that seems to be the lore explanation

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    This is a good answer, however it's normally better to provide the information from the linked website in your answer as links often go dead. You can block quote parts and source them appropriately.
    – Edlothiad
    Commented Dec 7, 2017 at 21:27

The other answers draw from legit sources, but even so, I'm not convinced. They all seem to reference some sort of active component in the ship (a ring, a "rotor", radiation, etc.), which doesn't quite explain how it keeps working in the episode Out of Gas.

In that episode, Kaylee and Mal have this conversation:

KAYLEE: Main life support's down on account of the engine being dead.

MAL: Right. But we got auxiliary life support.

KAYLEE: No, we don't. Ain't even on. Explosion must've knocked it out.

If they don't have enough power for life support, where is the power coming from for the "gravity generators" (or whatever they are)?

I think it's more likely that they use a technology similar to Star Trek's "Gravity Plating", which is a passive technology built into the floors of the ship. It requires no power, and is never fully explained, but theoretically there's some really dense material that creates a gravitational field, and can be "directed" so it only pulls from the floor above, and not through the ceiling.

  • How do you know that the gravity system isn't extremely energy-efficient and just runs on a 9V battery somewhere in the engineering bay? The lights are still on, as are some of the other instruments so there's clearly some power.
    – Valorum
    Commented Dec 21, 2017 at 1:15
  • Haha good point. Plus as I rewatch that scene, I notice that the lights are on. So... better question: why not disconnect the lights and gravity generator from whatever source they're using, and connect life support to it instead?
    – LevenTrek
    Commented Dec 21, 2017 at 1:18
  • Because trying to run life support off of a 9V battery isn't going to work.
    – Valorum
    Commented Dec 21, 2017 at 1:19
  • Hey man, if you can make gravity from a 9V, why not oxygen? It's all speculation :-)
    – LevenTrek
    Commented Dec 21, 2017 at 1:20

Well, the ring, for one, acts as a "gravity" generator, in the sense that it runs off the principle of force vectors. In the ring itself (say, the crew compartments were in the ring along the outer edge), the outward momentum that the rotation of the ring gives you, would imitate gravity.

As far as the rest of the ship is concerned, I could only guess that energy is bled off that reactor to compartmentalized "gravity wells" that can produce residual gravity for a set amount of time after primary power is lost, something that can convert the power plant energy into ultra-high density matter of some sort, which would be a safety feature since most of all the equipment is designed to be fully maintained in shipyards that themselves have gravity.

If you keep floating away from that crucial circuit that has to be bypassed in 20 seconds, there's a problem there.

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