Artificial gravity - a brainbug?

[Gullible Jones]

The SF novel I'm currently reading (Odyssey by Jack McDevitte) doesn't take place in a particularly advanced future, but McDevitte has artificial gravity in his starships. In an otherwise (IMHO) not terribly unbelievable vision of the future, it sticks out like a priapism.

And for some reason, this isn't uncommon in SF literature. Think about this for a moment. On TV and in movies, artificial gravity saves on production costs, but what good is it in text?

As far as I can see, the chief benefit of artificial gravity is in maintaining the health of a spaceship's crew. Is there any reason why we couldn't have medical treatments for the effects of microgravity within a few hundred years? Heck, how about fifty years? Researchers are already making some inroads.

Whereas articial gravity via acceleration isn't always practical, and simulating gravity without accelerating the ship... That might not even be possible. Oh sure, if the Higgs boson exists you could (theoretically) mess around with inertia, but how does that enable them to create a convenient gravitational attraction to the "floor" on their spacecraft, on stacked decks no less? And even if you had some kind of magic reactionless drive that could produce genuine, Trek-quality artificial gravity, wouldn't it be a bit excessive to put the things under the floors or whatever? Just because you have the technology to do something, doesn't mean it's sane or practical to do it.

Is there any really good reason that authors continue to artificial gravity all the time? Is it just laziness, or convenience? Because I just don't see it having a place in SF with any level of "hardness".

[General Zod]

Physical character limits. Authors can only cram so much into a book at their publisher's whim. So if gravity isn't even a remotely important plot point or element, then there's no need to waste extra pages going into detail about how the characters float around from point to point in a ship or how they aren't thrown against the wall when the the ship accelerates.

[Uraniun235]

Also, I'm not familiar with the text, so another important question is: Is it meant to be science-fiction, or space opera? There's a difference.

Speaking of which...

Is it just laziness, or convenience?

What's the difference?

[Academia Nut]

Well, we kind of hashed this discussion out a bit in the summer, but the guy arguing against artificial gravity was an idiot and a troll, so we didn't really get anywhere.

If you want a look over it, here's the link to the relavent thread in the Hall of Shame

Anyway, part of thing is that its a lot easier to handwave an artificial gravity system than get the various complexities of microgravity or rotationally simulated gravity correct, especially for certain stories such things don't matter. For artificial gravity, we're already looking at the possibility of systems that may be able to apply the equivalent of a gravitational field using electromagnetics on neutrally charged objects. Considering how much more powerful EM is than gravity, getting the energy and force balances correct would be a breeze under such conditions.

[Paolo]

Whereas articial gravity via acceleration isn't always practical, and simulating gravity without accelerating the ship... That might not even be possible.

Don't forget rotation.

[Paolo]

Are there any authors notorious for their infodumps about artificial gravity and acceleration dampeners? I know there's the Star Trek manual.

[Zixinus]

Personally, I think this is a typical example where sci-fi writers take ideas from other sci-fi rather then from actual science like the name suggests. Yes, I KNOW its fiction.

[RedImperator]

Olivia Yates Cortez monkey-barred through Upper Quito's main concourse, through and around a panicky throng of refugees towards the Canadian Pacific terminal, heedless of how her two suitcases tugged and battered her thanks to all the play she'd left in the straps. Most of the mob were pure groundlings who had no idea how to maneuver in microgee, and were stuck gingerly moving from one strap to the next, or riding the people mover, whereas she knew the space travel drill. On the other hand, at any time, a groundling--or worse, a wailing groundling spawn--could come detached and start to float helplessly across the concourse, right into Livvy's path, and she'd have to grab a bar and waste momentum swinging around it once to give the flailing idiot time to float by. She'd deliberately cut it close getting here, and had expected some crowding and confusion, but the density and cattle-stampede mentality of this crowd was seriously cutting into her margin for error.

In a 130,000 word novel, this is the longest single block of text describing microgravity. It's absurd to argue it takes "pages" to describe life in freefall. There are a lot of other points where the fact the characters are in freefall is relevant, and there are times when I substitute "floated" or "flew" for "walked" and "pushed off" for "got up", but nothing that measurably lengthens the novel.

There are good story reasons to include artificial gravity--the very high accelerations common in sci-fi require some piece of whizbang to cancel inertia for the crew, and once you have one of them, artificial gravity is a cinch--but saving space isn't one of them. I agree with Gullible Jones and Destructionator--it has no business in anything aspiring to "hardness".

[FSTargetDrone]

It doesn't need to take pages. Just change a few words to show them kicking off instead of walking or whatever. Generic words like 'he went to the control room' without describing how is also fine.

Or better yet, "He floated/glided to the control room."

[Junghalli]

It saves the writer from the headaches of considering what the effects of working in freefall would be. But mostly I think it's just a brainbug: most writers do it because everybody else does it, and don't really stop to think about how implausible it actually is. Like Zixinus said, it's a matter of writers taking their ideas from other writers instead of straight from the source (actual science).

Unlike FTL, it's a bit of rubber science that's usually more-or-less unnecessary. A starfaring civilization can function just fine without it. Though, of course, if you did have it, it would alleviate quite a few headaches. Not least of which would be that it would also give you a reactionless drive: turn it on its side and you've got 1 G acceleration with no expenditure of propellant.

And even if you had some kind of magic reactionless drive that could produce genuine, Trek-quality artificial gravity, wouldn't it be a bit excessive to put the things under the floors or whatever? Just because you have the technology to do something, doesn't mean it's sane or practical to do it.

Assuming that you can do that, why not? It's a lot less bulky than centrifugal gravity. The big question is whether you can. Even if you have a gravity drive, there's no guarentee you can manipulate it finely enough to have comfortable gravity throughout the ship.

[Axiomatic]

Plus, if you put it under your floors, it makes it kind of cruelly easy to repel boarders - just isolate them in a given area, then crank up the artificial gravity to "compact gravy".

[Lord of the Abyss]

Are there any authors notorious for their infodumps about artificial gravity and acceleration dampeners? I know there's the Star Trek manual.

David Weber in his Honor Harrington series, I suppose, but only because he's notorious for infodumps in general. Mind you, I like them, but that's just me. And the details of how it works do matter, since it affects tactics.

[Coalition]

Closest I ever got in a fanfiction was writing a full paragraph about how people walked into a control cabin, then rewriting it a half dozen times. I then realized that they did not have artificial gravity, so down was towards the engine, and instead of having to walk through a door, they would have to climb a ladder.

It was a B5 tale, so it would have been out of place.

[Patrick Degan]

I've toyed with the idea of EM-based artificial gravity worked as a repulsor effect, pushing the ship's inhabitants downward, and a ship in the form of a cyllinder. There would be greater internal area available, a simple structure which can be easily sectioned, and a core space in which the ship's machinery and circuitry would be housed.

[B5B7]

The SF novel I'm currently reading (Odyssey by Jack McDevitte) doesn't take place in a particularly advanced future, but McDevitte has artificial gravity in his starships. In an otherwise (IMHO) not terribly unbelievable vision of the future, it sticks out like a priapism.

Jack McDevitt future realistic - sorry no! - his books are fun light reading, but their realism - in terms of technology, society and character behaviour - well realism is a word that does not apply.

As to artificial gravity - it's a reasonable trope to use - like FTL - but it becomes unreasonable when have situations that notoriously occur in say Star Trek where have no power and/or almost every other system is malfunctioning, yet AG keeps going on and on in a normal manner - no fluctuations - it is most reliable system on ship. Could make the case that need it to be ultra-reliable otherwise the crew could turn into jam.

As many of their problems occur because of ship's computer being co-opted, perhaps it is not under the main computer's control but a separate system with an also independent power supply. Possibly AG system does not require power once turned on.

[Gullible Jones]

There are good story reasons to include artificial gravity--the very high accelerations common in sci-fi require some piece of whizbang to cancel inertia for the crew, and once you have one of them, artificial gravity is a cinch--but saving space isn't one of them. I agree with Gullible Jones and Destructionator--it has no business in anything aspiring to "hardness".

That's actually one of the things I was talking about in the OP. You might be able to reduce a ship's inertia, but how does that let you produce a unidirectional gravitational attraction to the ship's "floors"?

[Lord of the Abyss]

There are good story reasons to include artificial gravity--the very high accelerations common in sci-fi require some piece of whizbang to cancel inertia for the crew, and once you have one of them, artificial gravity is a cinch--but saving space isn't one of them. I agree with Gullible Jones and Destructionator--it has no business in anything aspiring to "hardness".

That's actually one of the things I was talking about in the OP. You might be able to reduce a ship's inertia, but how does that let you produce a unidirectional gravitational attraction to the ship's "floors"?

Any likely method for "reducing inertia" is probably going to mask it, not really get rid of it. Like producing a gravitational, electromagnetic, or outright technobabble field to counter the effects of inertia; it's still there, just being countered by the field. If you can produce a field that counters the effects of inertia by pushing against it, you can probably use the field when there's no inertia to produce gravity, or an imitation thereof.

[Junghalli]

I don't see how this would work. You and the magic gravity generator would be pulled toward each other, as if there was an invisible rope between you. Changing the momentum of the system as a whole (ship + gravity generator) would be just as impossible as moving yourself in space by tugging a rope attached to your feet.

Mount a gravity generator on a boom in front of your ship. Your ship falls toward the generator, pushing the generator ahead as it does so.

[Paolo]

Mount a gravity generator on a boom in front of your ship. Your ship falls toward the generator, pushing the generator ahead as it does so.

Doesn't quite work that way. Unless the gravity generator is also imparting motion, you'll note that the work done by system of two gravitating masses physically separated by material is zero (and likewise, the sum of forces in the system sum to nil).

[Typhonis 1]

Artificial gravity is as easy as constant thrust. Just orient your ship properly.

[Gullible Jones]

Mount a gravity generator on a boom in front of your ship. Your ship falls toward the generator, pushing the generator ahead as it does so.

At the same time, the ship exerts a force on the generator toward it:

Code: Select all

 Gravitational Force     Reaction force
Ship -------> ooooo <------- generator
        Connecting boom

The net effect here is merely a compressive force on the boom. The ship wouldn't accelerate.


I guess you could have some magic device that doesn't take the reaction force in this way, but this creates far, far more problems than it solves. Better to give your crew magic bone and muscle maintenance pills than to throw out a fundamental physical law like conservation of momentum.

Even if you do throw out CoM, and have, say, a gravitational field separated from its source, the ship and its occupants will have the same acceleration, so there won't be any artificial gravity.

Artificial gravity is as easy as constant thrust. Just orient your ship properly.

That works. For once, though, it poses problems for users of reactionless drives.

[SirNitram]

I have it pretty consistantly because I really don't aspire to 'hard' sci-fi. I don't aspire, really, to 'soft' sci-fi. I don't view it in those terms. If a story called for microgravity or null-G, or if I thought I could have some fun with it narratively, I'll dispense with it. Otherwise, it's convenience, a detail I don't need to worry about forgetting.

[Sam Or I]

Has anyone considered what producing actual gravity do to a solar system? Traveling through a solar system producing 1 G is like an Earth Sized object going through the system. It could disrupt the orbit of smaller planets astroids and comets.

[Junghalli]

Has anyone considered what producing actual gravity do to a solar system? Traveling through a solar system producing 1 G is like an Earth Sized object going through the system. It could disrupt the orbit of smaller planets astroids and comets.

There's no reason an AG system would have to simulate the whole mass of the Earth. You'll feel three times Earth's normal gravity on the space shuttle during its ascending burn and it isn't in any danger of pulling Earth out of orbit.

[Lord Relvenous]

Has anyone considered what producing actual gravity do to a solar system? Traveling through a solar system producing 1 G is like an Earth Sized object going through the system. It could disrupt the orbit of smaller planets astroids and comets.

I think the term you're looking for is 1 g. g is acceleration due to gravity (on Earth), but also acceleration equal to acceleration due to gravity. So 1 g does not equal 1 mass of earth.