inertial dampers

Starships Are Not Boats

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As explained here…

(In short, down, when under thrust, is determined by the direction of your drive axis, and specifically, is the direction your engine is in – because it’s pushing you the other way.)

I feel somewhat bad, sometimes, for violating this one here and there, sometimes quite egregiously, but there’s a reason for that, and it has to do with the fiction in my science fiction. Specifically, the inertial dampers that I talked about here. See, way back in the day before those were invented, from the Phoenix stack on up, spacecraft and then starship design was indeed constrained this way; virtually all designs were tail-landers, with the decks perpendicular to the drive axis, and the only exceptions to that rule being belly-landing vehicles intended to operate in atmosphere and/or land planetside, in which case the need to deal with the planetary gravity field took precedence and those aboard pretty much had to suck it up and deal with the inconvenience when in space and under thrust.

(We omit, for the moment, the complexities of spin gravity and the combination of spin and thrust “gravity” that gave the world terms like thrustdown and spindown and realdown and lots of rather complex gimballing mechanisms.)

But then the inertial damper was invented, thus ensuring that the interiors of starships equipped with it were under microgravity all the time, even when they were under thrust, and naval architects almost immediately split three ways:

  1. The traditionalist school, who had been building tail-landers for a millennium and dammit, were going to keep on building tail-landers, because that’s how spacecraft ought to look, and for that matter, it’s kind of nice to still be able to fire up the drive if your inertial dampers break down, isn’t it?
  2. The convenientist school, who countered that people had been complaining about what a pain in the ass ladders, companionways and elevators were for getting about inside spacecraft for most of that millennium, especially if you’re not under thrust most of the time, that long corridors are much nicer, and that it’s good not to have large pieces of equipment split between a half-dozen decks, and so now that they could build starships as belly-landers, dammit, they were going to.
  3. And the spacer school, who pointed out that if there’s one thing that you could learn from modular and beehive habitat design over all that time, it’s that “down” is a strictly local phenomenon and one only useful under a few circumstances anyway, and that in a microgravity environment not only can you arrange your decks any damn way you please, but you don’t even have to be consistent in doing so, and proceeded to arrange their designs’ interiors in whatever way they felt was useful at the time and place.

In what I think of as the modern era, the spacer school has essentially won the argument, although examples of the other two schools do still show up. (After all, planet-landing craft have to be consistent one way or the other, what with that planetary field to contend with.) Among people who have the relevant technology, at least – the constraint still exists, and applies in full to anyone who doesn’t have fancy ontotechnological physics-editing tech to play with.

 

In Lieu of In Lieu

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Well, I was going to post the second part of The Shipping Trade today, except that writing it didn’t happen because of day job, and so forth. Then, I thought I might post a sketch of the ship involved, just to give y’all an idea of what you’ll be looking at, but then that would require me to go out and hire a scanner. That, and I made said sketch, and then looked at it, and then concluded that I couldn’t possibly inflict such a terrible picture on my readers…

So permit me, please, instead to sketch a verbal picture for you of the

CMS Greed and Mass-Energy

To start with, Greed and Mass-Energy is atypically large for a free trader; in those leagues, which principally deal in small, high-value-to-mass/volume cargoes, lugging around 40,000 tons displacement of cargo is huge. (It’s still not in the major freight line league, though; those guys can use freighters that are million ton-displacement behemoths.) Thus, the shipcorp that owns her (it’s essentially a syndicate of officers, crew, and former crew, with executive power vested in the captain-owner) is pretty prosperous to be able to cover her running costs. Dealing in brokered cargo actually isn’t her main business – she specializes in contracts like the RCS-assembly charter from Kerbol to Kythera she just left, but an empty hold is a hole that drinks money, so you take the cargo when you can get it.

Also, obviously, at a size like that, she’s not streamlined, or built to land planetside (gravity wells being acutely expensive); and is even rather more massy than anything that most stations like to have dock directly to them. Her cargo’s generally ferried to station, or upwell and downwell, by local lighters at each end of the trip. Rather, she’s built very much in the classic mode; a long, relatively thin, open-frame truss structure. Attached to that, going from fore to aft, we find these different sections of the ship:

Right at the bow, sitting on the end of the main truss, is the command capsule, an ellipsoid slightly stretched along the ship’s main axis, relatively tiny compared to the rest of the ship, and containing, for starters, the bridge and associated avionics systems. (The bridge is actually buried in the center of the capsule, for its protection; it’s displaced off to the front end of the ship, however, because the command capsule is also where the primary sensors are housed to keep them out of the way of cargo, fuel, and drive radiation, and this positioning cuts down on sensor lag. It’s still pretty safe; it’s not like anyone’s going to be shooting at them.) The first of the other two notable features it houses is docks and locks, right for’ard on the axis where it’s easiest to match thrust and spin, which usually houses a couple of cutters used for taking the crew ashore and for occasional maintenance, and a skimmer for in-field refueling. (The fuel itself doesn’t pass through here – the skimmer docks aft to offload what it scoops. No fuel for’ard of the support plate, that’s the general rule.) The second, aft by the truss, is the robot hotel for all the little space-rated utility spiders you may see now and them crawling about the structure doing maintenance, thus saving the engineering department any need to get suited up and go outside for routine work, although they still may need to do so from time to time.

Just aft of that, accommodations and secondary systems are housed in a toroidal gravity wheel. This is actually a very unusual design feature in an Imperial ship-class; just about everyone and especially the spacer-clades are genetically adapted to microgravity, and the spacer-clades prefer it, as a rule; but the Cheneos-class architects originally designed her class for near-frontier work, and included this for occasional passenger service. Greed and Mass-Energy only rarely carries passengers, so they keep it geared all the way down, producing only a tenth of a standard gravity, which doesn’t offend the spacer-clades all that much. There’s a second, smaller wheel rotating inside it to null out the gyroscopic effects; it’s used to house some other equipment that likes a little gravity, but for the most part, this one’s just a countermass.

(The wheel does, however, provide enough gravity to let the CELSS Manager run a pretty decent microbrewery in the spare volume, and perhaps more importantly, provides a place where you can drink it off-shift without suffering from a nasty case of the zero-g bloat. [Remember, folks, bubbles don’t rise in microgravity!] And apart from crew morale, having decent beer makes for good PR when traders meet.)

These areas, incidentally, are one of the few places on board where the really high-tech ontotechnological stuff makes an appearance, in the form of inertial damping. The people who built her liked microgravity, and weren’t all that keen on losing that while under thrust, especially since she was built to fly brachistochrones or near-brachistochrones (bulk tankers and ore freighters, etc., are usually built to fly economic minimum-delta/Hohmann transfers; no-one else wants to wait that long for their cargo) and so would be spending most of her time under thrust. The job of the inertial dampers is to apply the thrust of the drives evenly across the entire area’s structure and everything in it, thus ensuring that no-one actually feels any acceleration, and the lovely microgravity environment is preserved. (It also avoids having to come up with some wretchedly complicated gimbal arrangement for the already wretchedly complicated seals-and-bearings for the gravity wheel, no longer having to do which is something that made architects particularly grateful for this innovation.)

Behind this, the cargo. ‘Way back along the truss there is a very large, solid plate, the support plate. The cargo containers are simply stacked “atop” – by which we mean for’ard – of it, in six big blocks arranged around the axis with sixfold symmetry (this arrangement being a reasonable compromise between use-of-volume and convenient straight lines), and are designed to lock to the plate, the truss, and each other to form a solid interlocked structure. There’s no hold or other walls around the cargo; the containers are themselves spacetight when they need to be, and so lighters can just drop them into place and pick them up freely while in port.

The breakbulk cargo, on the other hand, is messy. It has to be podded up individually when not spacetight, and then individually lashed down and made secure atop the cargo container stacks. This annoys the cargomaster, which is why breakbulk is unpopular these days despite the fact that breakbulk shippers usually pay a premium in exchange for you having to do this (the “lash comp”). Actually, what really annoys the cargomaster is that she can punch a button and have the ship automatically query the v-tags on the container cargo for its mass stats, and so forth, whereas for breakbulk she’s got to recall her Academy training, dig out the spreadsheets, and work out the corrections to the center-of-mass-and-moment-of-inertia chart by hand. Well, still by computer, but you know what I mean.

Aft of the support plate, still in sixfold symmetry, you have the bunkerage – fuel tanks, stacked three deep in multiple rows, all filled with slush deuterium, running right to the stern, where they surround the cylindrical shroud of the mostly-unpressurized engineering hull (you can take a crawlway right back along the truss to the small, pressurized maneuvering room back this far, should you need to examine the drives close-up in flight, but the actual machinery space isn’t), which contains the interlinked systems of the main power reactors and the fusion torches themselves, strapped to the aftmost extent of the main truss.

And there are lots of fuel tanks. Even though said fusion torches are miracles of a mature nuclear technology, capable of achieving near-theoretical efficiencies and outputs and delta-v per unit fuel that routinely makes naval architects from less advanced civilizations throw down their slide rules in despair and weep into their terrible coffee-equivalents, the one unchangeable rule of space travel is that your mass ratio is always much, much less favorable than you might want it to be.

Good thing deuterium’s so cheap, isn’t it?

(Edited to add: And I must have been half-asleep this morning, because I forgot…)

…and most prominently of all from a distance – dominating the entire view of the ship from a distance, by area as well as by temperature – sweeping out from among the fuel tanks (although comfortably retracted to sit alongside them, leaving approximately a sixth of their radiative area useful, while idling in dock – the vast panels and pipework of the heat radiators. Because the other one unchangeable rule of space travel is that you always have waste heat, too damn much waste heat, and you’ve got to get rid of it somehow. Especially once you fire up those fusion torches. (The radiators, however, unlike the rest of the ship, have only fourfold symmetry – so that they can be perpendicular to each other when unfolded, because there’s very little point in radiating heat right back at your own radiators.)

 

Handwavium: Inertial Dampers

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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:

  1. The handwavium that enables FTL travel (generating wormholes from entangled singularities, probably very related to type 2);
  2. The handwavium that enables FTL communication (tangle channels of the non-quantum entanglement kind, which implies that the universe is just full of non-local hidden variables); or
  3. The handwavium that enables a decent degree of control over gravity and/or mass (vector control).

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.