Centrifugal Gravity: The kind of Artificial Gravity widely used by larger habitats and even starships, because it is substantially cheaper than faking it using powered vector-control apparatus, not to mention substantially simpler to implement and with fewer things to go wrong.
Notable for its amusing Coriolis side-effects, which is why it’s a really good idea not to bet on any ball games with a spacer until you’re used to how spin gravity affects things in practice…
Okay, let’s talk about paragravity.
First up, a note on nomenclature. Paragravity is one of the two things that an Imperial habtech might be referring to when they talk about artificial gravity, the other being spin gravity. Unlike spin gravity, which is “powered” by good old centrifugal force, paragravity is produced by ontotechnological space magic that does wonderfully complex things involving information physics and grand unified theories and other such things to poke the universe in exactly the right way – basically, one branch of the mass-inertia-and-momentum manipulating vector control.
Which is to say that it is produced by gravity rotors, suitcase-sized boxes with a power connector, a ‘weave connector, and a thermal management connector on the outside, filled with solid-state hardware that is a proprietary product of Mariseth Gravitics, ICC. And into whose internal workings we shall thus respectfully avoid going.
What we’re talking about here is how they work on the outside.
The field of paragravity (the gravity envelope) can only be created between two gravity rotors of opposed polarity. That gets you a straight field (with perhaps some convex distortion at the edges) between the two, which imposes a force functionally identical to mass-generated gravity (i.e., affecting all atoms, etc., equally) on everything with mass inside it. This creates a consistent down direction towards what, for the sake of designation, we shall call the “positive” rotors.
(You have to have a closed envelope, and can’t operate an unpaired gravity rotor even if you wanted to: since the universe is functionally infinite in whatever direction you’re pointing it, energy requirements for the half-field head asymptotically for infinity, at which point the circuit breakers save you from a messy ‘splosion.)
Both momentum and energy are conserved, as they would have to be.
The former is the reason that you gravity rotors should be bolted firmly to the structure of the hab; whatever force they exert is, per Callaneth’s Lemma (or Newton’s Third Law, whatever name you prefer), reciprocally exerted too, half to each rotor in the pair.
While difficult to arrange even deliberately, this does imply that if you can get enough mass in one spot and move it just right, you can get the gravity rotors to tear themselves free and leap in the appropriate reciprocal direction.
With regard to the latter: it takes energy to establish the gravity envelope, but once it’s up and running, maintaining it takes only minimal energy physically speaking. (I.e., it still consumes quite a bit of energy in the rotor while it’s up and going, because rooting the universe ain’t cheap; that energy just doesn’t go into the envelope. It’s this waste that makes paragravity a real expensive thing to run.)
That, however, is only true so long as nothing is moving within it. Falling objects, moving in the down direction of the envelope, take energy from the envelope as they gain kinetic energy. (Likewise, when you lift an object within the envelope against its downforce, that pushes energy into the envelope, which is a surge effect that the hardware has to cope with. Alas, it’s not something that can be harvested in the majority of applications.) You could call this paragravitational potential energy if you like, since it sits in essentially the same place in the relevant equations.
While it takes the rotors a little while to initialize from a cold start (although some of this time is self-diagnostics and the like), once up and running, though, you can change the parameters of the gravity envelope very quickly; and you can generate pretty much any amount of gravity you want up to their capacity so long as you’re willing to spend the energy (which varies proportionately) needed to do it.
This is what lets you use the exact same technology for inertial damping; you just have appropriately oriented gravity rotors cancel out your engine thrust inside the starship – while bearing in mind that this will have certain effects on your structural load. (Likewise, you can use them when grounded – but since they don’t block planetary gravity, if you want 1G in the cabin when landed on a 3G world, you will actually be running the paragravity system at -2G.)
The drawback, however, is that the same lack of “inertia” in operation that lets you change your gravity quickly means that they fail equally quickly – and shut down essentially instantly if the power fails, just like an electromagnet’s field collapses – so failing to keep up maintenance schedules may mean being abruptly smashed to the deck with a force of twelve gravities! Caveat engineer.
No Gravity For You: Subverted, since the knowledge of how to move in microgravity is commonplace, and microgravity-friendly martial arts are almost as commonplace. And, indeed, a majority of spacer habitats and starships run without gravity anyway. Not like they’re a bunch of dirthuggers, y’know?
(And if you are using spin gravity, stopping the spin – which turns off gravity for the whole habitat – is very definitely not something you do this casually.)
If you are using vector-control gravity, however, the attack mode you use isn’t disabling the gravity, it’s reversing the gravity repeatedly and quickly (a maneuver delightfully referred to as “grav pong”) until you’ve bounced the villains into submission. Or unconsciousness.
Handwavium (in General)
I try to write the technology in my universe in such a way that at least 95% of it falls within the laws of physics as we know them, or at least as we mostly know them and assuming that they’re being fairly kind to us when it comes to technologies we haven’t developed yet.
The other 5% is powered by handwavium.
My chosen handwavium, for those who are new and haven’t heard the term before, is ontotechnology, a lovely term for “those technologies which let you reach into the mechanisms underlying reality and poke them in useful ways”. A fully mature ontotechnology would, arguably, be “that technology which you build universes with”; fortunately, what they have in the Eldraeverse is a very, very immature ontotechnology. From an in-world perspective/in the parlance of the Worlds, ontotechnology usually refers to some product of one or more of Information Physics, Matrix Theory, or Ontological Precedence, those three being the leading contenders for the Next Big Thing in physics.
(Unfortunately, the evidence seems to be suggesting that all three of these mutually contradictory theories appear to be true, which most physicists and philosophers take as evidence that (a) the universe is far more complicated than anyone imagined, and (b) may just possibly be having a laugh at our expense.)
From an out-of-world perspective, ontotechnology means handwavium. Specifically, it means one of these:
All of which share certain characteristics, such as having been invented by transsophont geniuses in symbiosis with very large computing facilities, having theories behind them which – in detail – are very hard if not downright impossible for people without rather enhanced brains to understand, and so far as the vast majority of people are concerned, might as well come in black boxes with “Big angelic powers within. No mortal serviceable parts inside.” stenciled on the outside.
Apart from those, it may also mean one of the assorted gap-filling assumptions I’ve had to make in inventing the details of advanced technologies, in re everything from whether P=NP to enough theory of mind to have a decent handle on AI mental architecture; while none of that actively violates what’s known, that I’m aware of, it’s certainly extrapolating well beyond reasonability for anyone except… well, an SF writer.
Here endeth the summing up for newbies, ’cause we’re here to talk about the parameters wrapped around a particular example of handwavium:
Inertial Damping
So let’s talk about inertial damping. The first rule of inertial damping is that you don’t talk about inertial damping —
Ahem. Sorry. The first rule of inertial damping is that there’s no such thing as inertial damping, as a separate technology. There are “inertial dampers”, but they happen to be an application of the same underlying techniques – as a bundle, called vector control – which are your generic mucking-with-the-shape-of-space-time-without-needing-inconveniently-huge-masses tools, and which underlie related technologies such as, say, artificial gravity, techlekinesis, kinetic barriers, tractor-pressor beams, hopelessly inefficient reactionless drives (which aren’t even actually reactionless – in this universe, we OBEY the Law of Conservation of Momentum), and so forth. I prefer not to multiply handwavium beyond necessity, obviously, so I make all of these – and I didn’t actually start with all of them, some were just logical implications – examples of the same family of phenomena.
All inertial damping actually is is… artificial gravity.
This brings with it all the associated limitations. For example: you can only create the a-grav field between matching and opposed sets of gravity rotors. (Well, that’s not technically true – but not having the second one there means you’re trying to attract about half the universe with your a-grav field, energy requirements head asymptotically for infinity, fuses blow, and you’re done here.) It’s basically an internal closed field, with very little spillover at the fringes. Forget a-graving anything in open space or cheating your way to a reactionless drive with them; you need something to mount the rotors on, and that thing is not going to be within the field of effect.
It’s also quite energy-hungry, because it’s not like we’ve repealed the energy conservation laws or the inverse square law, either. That’s why it’s being used to damp only two small habitable areas and not, say, the entire length of the ship so you wouldn’t need all that heavy trusswork supporting the cargo and the fuel against the engine’s thrust; it’d be grossly uneconomic even if you had somewhere suitably strong – they would be holding the whole weight of everything, after all – to mount the rotors. The material construction is essentially always more cost-effective when doing jobs that construction can do. Also, of course, if your spacecraft is primarily held together by an inertial dampening field, under whatever name your universe calls it, then you’re pretty much going for a design that is guaranteed to undergo rapid unplanned disassembly as soon as the power goes out for the first time. Consolidated Mutual Mitigation & Surety aren’t going to write a note to cover that.
(Side note: These associated costs are why, artificial gravity or no, most habitats that want gravity spin to get it, and ships – including the Greed and Mass-Energy use gravity wheels, and so forth. One of my general rules of thumb in handwavium design is that handwavium that reproduces something that can be done comfortably by regular physics tends to be more costly, in one way or another, as roundabout, over-complex ways of doing things often are. In this case, the upshot of that is that artificial gravity is very useful for small-scale applications in the lab and industry, curiosities like the zero-g bed, and interesting spin-off applications like inertial damping and techlekinesis, but if all you need is regular old pretty constant gravity… start spinning.
Meanwhile, if you’re traveling on one of those dirthugger-friendly passenger lines that has gravity in the passenger sections and doesn’t have gravity wheels? There’s a reason you’re paying a damn sight more for your ticket than the people willing to live like spacers for the duration.)
What makes it function as inertial damping is that the gravity rotor network is tied into the engine controller, and the reaction control system, and – were this ship capable of atmospheric flight – the flight data computer, and various other systems which together understand the forces the spacecraft is about to apply to itself, or coming from sources which are reporting to it, and generates the appropriate matching vector on the contents of the damped area – insert assorted technobabble here – such that the net differential acceleration vector between them and the ship they’re in is zero.
The key limitation here is that it can only do anything to compensate for accelerations that it knows about; it can’t read the future or identify force-about-to-be-applied, it just follows in sync with the systems that accelerate the ship. If you’re in a collision, if something explodes unexpectedly on-board, if you’re being shot at, or in other ways you get hit by unknown sources of acceleration, the inertial damping system can’t do a damn thing about that. It gets you comfort, either as a luxury on half-gee freighters or as a practical necessity on twelve-gee fast couriers, but the bridge still needs seatbelts, the corridors still need handholds, and in the event that none of this works out, it may still be chunky salsa time.
Artificial Gravity: The piece of Applied Phlebotinium they call vector control does provide something which is functionally equivalent to artificial gravity, yes. On the other hand, (a) a good plurality of cylinder habitats still prefer to use spin gravity, because it’s much easier on the energy budget; and (b) the vast majority of spacecraft and starships, modulo those passenger liners catering to planet-dwellers, don’t use it, because the 3/5ths of the population that are spacers got used to microgravity, both socially and through pantropic adaptation, a long time before vector control was invented. Microgravity is their native gravity, essentially, so why change it?
They do use vector control quite often to make sure their nice microgravity environment isn’t messed up by thrust gravity, though.