Gravity in multiple planes

[Spike]

I understand that Traveller, in all editions, uses reactionless drives in such a way that acceleration forces are not a concern for the crew. I understand, also, that the reactionless drives are gravity based, or simply unexplained (and any engine/nozzle projections to the rear can be explained away as heat sink/projector mechanisms to remove waste heat from the engines...), so it make some sense for the ships artificial gravity to be generated by the drives, or at least by some similar mechanism (it follows thusly: since the ship is in fact accelerating (or decelerating) at any given time and yet no suggesting of fighting 'g-forces' that whatever generates the artificial gravity is not simply confined to a deckward direction, but is actually rapidly tuneable to offset maneuver (reactionless drive being a much more attainable technology than inertialess drive, I should think...).

Thus it is fully possible for the crew to theoretically control the orientation and strength of gravity aboard the ship, perhaps to provide tactical and strategic advantages over boarders?

Where my admittedly amateur understanding fails me is what happens when you have different G forces from different directions simultainiously... in real science. Assume, for the moment that the crew does not turn off the default 1-g deckward gravity but creates a 1-g 'rearward' gravity to put the cockpit at the 'top' of the ship, making an almost impossible climb for boarders without grav belts... or would the deck gravity provide enough force to 'cling'... what about disparate gravs?

IN theory if they put two exactly opposed gravitic planes (floor and ceiling) with the same force... how do you determine the 'safe zone' where the two forces are equally opposed (a flight tunnel?)...

This is purely theoretical noshing here.


Of course, provided the crew is strapped in, and has a sufficently powerful maneuver drive, one might suggest that the simplest solution to boarders during flight is to simply turn off the artificial gravity on board ship all together. With no 1-g 'deckward' force, and potentially (as I understand it) 6g 'acceleration' force, any boarders would be swept into bulkheads with punishing force. Repeat as necessary.


Or is my understanding of Traveller technology and/or gravity flawed?

 

[aramis]

A lot depends upon the assumptions one starts with...

In CT, it's part of the drives.
In MT, Artificial Gravity and Inertial Compensation is separate from Thrusters.
In TNE, thrusters are non-canon... Inertial Compensation is TL limited to TL-9 G's (IIRC), and when not needed to compensate against drives, can be implied to produce artificial gravity. ContraGravity merely blocks natural gravity with 98% efficiency.
In T4, T-plates produce thrust, Inertial Comp is a separate system, and there's ContraGrav... with everything on, one can land a 1G ship on a 50G world.... and take off again...

T20 presumes to be the same as CT.
MGT seems likewise.

Now, mechanism?
I can see several possibilities...
1) Cathode-anode style - some form of particle flow: from plate A to plate B. Possibly a pair of fields whose overlap generates the effect.
2) flow push: Some single emitter produces some invisible particle which interacts with solids generating a force away
3) field push: some single emitter produces a field or wave that emits and forces matter away.
4) Flow Pull: some emitter that, upon it's emitted beam/flow/particle, reacts by return force vectored towards particle/flow/beam source. Practically non-sensicle; Good luck explaining it under current physics models.
5) Field Pull: some emitter that produces a wave or field that causes items to accellerate toward source.

Note that #1 is the only one unlikely to suffer inverse square losses; it's like standing in a closed loop wind tunnel. Flow effects are likely to be limited in direction; field effects are likely to be omnidirectional, needing wide plates.

If using #1, #2, or #4, it's probably possible to build accelerators with them that work really well.

Me, I assume it's a function of the TL10+ Maneuver-drive, and is rated at Drive-G's +1, and is switchable. I have used the 7G paddle effect... it's not a big fall, but it hurts... and armor isn't much use.

 

[the angle]

Even within a single set of rules, there's no reason why this needs a one-size-fits-all answer. Look at traction control in cars: some don't have it; some have it done badly; some have it full-time only; some have it as an on/off option; and some have it with half a dozen or more different settings. It depends on what the car is designed for and how much you're willing to pay. In Traveller, it could depend on what the ship was designed for, where and when it was built, and possibly what sorts of modifications or maintenance issues it's had during its lifetime, which could be quite long.

In other words, it can work just about however you want, and it can be different from one ship to another. Gravity manipulation is one of the least explored technologies in Traveller. Once it becomes possible, coupled with Traveller's unbelievably cheap energy, it's unlikely that the world would look much like the Traveller we all play.

Steve

 

[BlackBat242]

The general default is usually considered that the entire ship internal gravity generation system is an "all-or-nothing" system... it is always the same throughout the ship.

While it shifts to compensate for acceleration, it is designed to only produce perceived gravity in one plane... and the same plane throughout the ship.

It is designed to always "pull" toward the deck plates, in whatever strength is desired.


Custom designs allow for breaking up the ship into sectors, each with its own separate gravity generation controls, and even to having each stateroom with its own variable controls!

It really is up to the designer of the individual ship... and the bank account of the builder, as the more separate controls and subdivision of the gravity generation system you have, the more it costs.

And no, there are no rules I am aware of as to how any of this is done. It is all up to the Ref.

 

[HG_B]

And no, there are no rules I am aware of as to how any of this is done. It is all up to the Ref.

Can't remember the supplement but there was one describing being able to alter the Gs in your stateroom. There was no added requirements for the ship design. If I remember I'll post the info.

 

[Spike]

Gravity manipulation is one of the least explored technologies in Traveller. Once it becomes possible, coupled with Traveller's unbelievably cheap energy, it's unlikely that the world would look much like the Traveller we all play.

Steve

See... thats where I'm coming from. From what I can tell (admittedly I'm a latecomer), Gravity Control is a fundamental technology in Traveller terms. Every ship has some form of gravity control technology, its used for cars, for tanks, for gropos.... it may very well be nigh ubiquitous (heavier weapons certainly use it in part to do their thing...).

Just because it is under-explored at the moment doesn't mean it has to always be. I'm all about exploring the implications, but I'm reluctant to do that in a vacuum (har har...). I'm not a physics expert, nor am I an expert on all things traveller, which is why I open a conversation here... to draw upon the expertise of those who know traveller, and maybe know some of the actual math underneath it all.

So what I know is that Traveller has artificial gravity technology, and specifically it appears they have contra-gravity as well as synthetic gravity (meaning, in my bastardized homemade jargon, that they can negate gravity and gravity like forces, and with some fairly decent fine tuning at that... AND they can create gravity where there is 'none' in relative terms). I also know that Traveller has 'reactionless' drives, meaning that ships do not throw stuff out the back to move, though it is strongly suggested (if not absolutely true) that they do not have any form of inertialess drives... once a ship is moving it keeps moving until something acts to make it stop, though this seems like it could be 'squishy' at some game tables, but the rules themselves don't seem to support inertialess travel at all.

Now, I'm mostly working from MgT, with a side order of Gurps, so my information is incomplete here but: it seems that 'Thrust' is measured in G's, which would be felt accelation from the crew, IF they actually felt it. Here my lack of physics background really hurts me... but I don't think it actually matters for where I am going for this.

Things I don't know but seem likely: It seems highly likely that maneuver drives (reactionless) work using some form of the same gravitic technology that allows ships to lift off from planets without burning their weight in fuel or more. For 'liftoff' we could imagine a technology that creates a 'polarized' field around the ship like a magnet, pushing away the lesser mass (the spaceship) from the opposite polar field of the greater mass (the planet)... but in deep space this doesn't work. Even if we suggest that it is highly tuneable (and presumably controlled by the computer based on desired results from the pilot), the field would still need something to work off of or it would be restricted to straight line travel to/from the nearest stellar body.

So the gravity drive may not be an answer unless the manipulation of gravity allows the ship to 'warp' the fabric of space. Bear with me, I'm outside my comfort zone here... I've read about space being treated like a sheet of cloth, with it being spun around strong gravity wells like black holes, but I'll be damned if I can really get my head around it. Working from the metaphor is problematic but presumably the maneuver drive, if gravitic, would be able to create 'beneficial' warping of that metaphoric fabric in a way that makes sense mathematically. I envisioned it either pushing itself along (a somewhat traditional view based on reaction drives we are familiar with) or or pulling itself along (possibly as a 'car' or 'tracked vehicle'), but given the metaphor I'm confined to by my own incomplete knowledge it could just as well be 'surfing' space, creating a 'slope' that the ship slides 'down' in the direction it wishes to go... I'm vaguely enthralled with the idea of creating a 'gravitic tunnel' in space that it travels along like water in a pipe or clamped to like a cable, but I'll be damned if I can work out 'how' it does that just by manipulating gravity.

This is all theoretical, of course. How does a theoretical, plausible, gravity based reactionless drive actually work? And has this ever actually been touched upon by any existing Traveller works? I mean... my LBB2 actually has what I assume are Real Delta-V equations in it (not that I've looked too closely, sorry), which seems pretty damn hard core to me for a game... but then again, that's why I'm here rather than just handwaving it all away.

If we want to get wonky, we can even use 'gravitic' technology to discuss Jump Drive. My understanding of Jump Drive is that you basically created a miniature wormhole between two points in space, force it full of burning hydrogen to expand it to a useable size, and enter that tunnel/pocket for a week (representing the 'thickness' of the 'subspace fabric' we are 'folding' to join two points... damn thats a lot of quote marks...) and exit out the other side accompanied by a blast of ejected hydrogen as the artificial tunnel collapses behind you. This neatly explains why there is no jump fuel efficiency for higher tech jump drives: The amount of fuel is entirely proportional to the size of the ship, though it does not account for why the length of the jump acts as a fuel multiplier... the 'length' of the tunnel remains fixed regardless of the distance jumped.

So: Fishing.

I obviously need more information, either Traveller specific that I've overlooked or misunderstood, or real world physics/math/whatever that I've overlooked or misunderstood. I'm all about the hard rational universe that is internally self-consistent.


Side question: When using Antimatter Powerplants (TL 17+) would you still require jump fuel? Even using the above explanation I could see it going either way: if the powerplant is powerful enough it can 'brute force' open the tunnel or 'inflating' the tunnel with hydrogen is far more efficent than trying to stretch it by main force (imagine expanding a balloon without 'filling' it... you can stretch it but its a lot harder than just filling it up).


If it helps: I'm not trying to fix or correct anything about Traveller (any traveller) but filling gaps and superstructure... I'm just as happy to fill from canon as make stuff up that fits.

 

[Gray Lensman]

Artificial Gravity can do whatever!

In David Brin's Sundiver novel the ship was a disk protected by a "statis field" , to get from one side of the disk to the other you walked "around a gravity loop".

If you've never read it you should.

 

[hdan]

Sorry for the rambling nature of this post. It's at least sort of on topic.

I actually had part of this conversation with my kid - Traveller M-Drives are (at least post TL-12) essentially Star Trek warp drives in that they manipulate the fabric of space to propel the ship. The difference being that ST warp drives are very fast, and Traveller M-Drives are "normal space" drives.

I suppose it makes sense to view reactionless M-Drives as a sort of proto-warp drive that can bend space enough to propel the ship a few score meters per second squared (1G is defined in Traveller as 10 m/s^2 - slightly "heavier" than Earth's 9.8m/s^2), but not enough to really enable the monsterous speeds in Trek.

I always imagined the space warping tech implied by gravitics was the basis for Jump technology. Some smart scientist noticed when he warped the field hard and fast enough, strange things happened, and the rest is future-history.

I'm coming around to the idea that "modern" ships (star and space, TL10+) use a variety of gravity manipulation technologies in their ordinary operation. Earlier TL ships would have different mechanisms, but I'm specifically talking about the grav-enabled ships you find in the 3I.

First, we have Grav Lifters, based on the same technology you find in an air/raft. These devices can nullify and even invert the force of gravity as caused by mass in relation to themselves. The modules themselves float up or sink, working like "solid state hot-air balloons" to an extent. Not capable of creating their own warp (for whatever reason), they can still finely balance an existing warp to hover, float or sink.

As an outgrowth of grav lifters, we have inertial dampeners which control the gravity environment inside of a given bubble/field that they project. These allow gravity to be experienced inside of a ship and also insulate the occupants from any acceleration due to external gravity or engines.

Higher tech grav lifters can probably extend their "bubble" to the entire ship and provide inertial/artificial gravity controls at the same time. This same technology can make "gravity" point in any useful direction, so acceleration purely by manipulation of gravity becomes possible, as long as there is at least a little local gravity to interact with.

This technology would enable very convenient access to a planet's orbit, and ships and boats could loft up anything they could fit into the volume of their lifter field with very little trouble. (Aside from the probably colossal energy requirements of their drives, but hey, everyone has fusion by this point, right?) Accelerating these satellites to orbital velocity would take a little longer, but once clear of the atmosphere these things are a bit less trouble.

Earlier TL starships might only have these two systems in their M-Drives, requiring that they "boost up" and coast out to 100D, then turn on the attraction to haul themselves back in. These ships could still travel out to the planets in a way similar to modern interplanetary flight, but might carry chemical or ion/plasma thrusters.

Once thruster plates become available, then ships can warp space as if there were a mass nearby, and the gravity based M-drive becomes a truly useful interplanetary drive.

 

[Icosahedron]

Spike, I'm with you in trying to create an internally consistent Travelleresque reality. Unfortunately, many aspects of Traveller don't lend themselves to that ideal and you will have choices to make.
I made a similar enquiry here some time ago (can't find it on a quick search) and I concluded that there must be several (at least four) different types of grav principle, none of which are fully in step with Traveller canon.

Deck Plates and internal gravity/inertia compensation must be some form of local surface effect that work only over a distance of a few metres. Otherwise the inverse square law would wreak havoc with the requirements of the effect within the confines of the deck space. Probably ground-skimming vehicles use this principle too - else why are they limited to skimming?

Free-flight grav vehicles and landing ships must use a different effect that negates or manipulates planetary gravity - else why are they restricted to orbital range? However, they must have some additional limitation applied to prevent air rafts from reaching highports (otherwise why have shuttles?)


Repulsors/Tractors must somehow project a gravity field - good luck on explaining that one, it still escapes me.

M-Drives must somehow push against something other than a gravitational field, since the strength of gravity can vary by a factor of a trillion or more between deep space and the vicinity of a star, which should translate to a similar variation in acceleration!
This still escapes me, but perhaps something along the lines of the Mach Principle or the Alcubierre Drive (both real-world ideas) might cut it when I have time for more research.

Although I like to figure out what the systems do, I try to avoid explaining how they do it. That generally leads to players spending more time rolling on the floor or poking holes in the idea than actually playing the game. Don't play Pandora - keep the black box closed, just tell the players what it does.

The main difficulty with Alcubierre principle is generating enough power to locally warp the 'cloth' of spacetime, of course, you can overcome that with any handwave you fancy...

As for Antimatter, whether you want that to negate your fuel worries or not depends on the type of universe you're creating. Look at the ramifications for travel and make your decision.

Hope that helps.

 

[mike wightman]

IMHO the true magic of Traveller ships is the acceleration compensation system - something that is not explained or explored by the rules very much at all.

The ability to produce artificial gravity fields and acceleration compensation are glossed over but any thought on the matter makes you realise that ships in Traveller are producing force fields that are so much in the background that they are trivialised.

 

[aramis]

Each edition handling it differently is part of what creates the disconnects across canon.

CT:
Gravitic Suspension, which is thrust based (striker)
Artificial Gravity (Bk2)
Repulsor beams (Bk5)
Tractor Beams (Bk5)

MT:
Gravitic Suspension, which is thrust based
Ship T-Plate Maneuver drives (note minimum size)
Artificial Gravity plates
Inertial Compensation
Repulsor beams
Tractor Beams

TNE
Gravity Nullification (Called Contragrav)
Artificial Gravity/Inertial Compensation (same system here)

T4
Gravity Nullification (Called Contragrav)
Artificial Gravity/Inertial Compensation (same system here)
Gravitic Suspension, which is thrust based
Ship T-Plate Maneuver drives (note minimum size)

MGT
Artificial Gravity/Inertial Compensation (abstracted)
Gravitic Maneuver Drives
Grav drives (Vehicle Supplements)
Gravitic Lifters (Vehicle Supplements)

The big disconnect is TNE; TNE doesn't allow gravity manipulation outside the hull, ony disconneting from external gravity. All other editions have some form of gravitic thrust.

All editions have some form of on-board gravity simulation by imparting acceleration to things using some field or beam system. Not one defines how it works. It is implied that Inertial Compensation is a variation on the same technology. In MT, AG and IC are divorced from each other. (MT: AG costs 2x as much, draws 2.5x the power, same volume and mass as IC.)

 

[mike wightman]

TNE and T4 have repulsors and tractors, with their TLs reversed from MT. At very high TLs these are combined into one system.

They also have the miracle tech of grav focussed lasers.

 

[aramis]

TNE and T4 have repulsors and tractors, with their TLs reversed from MT. At very high TLs these are combined into one system.

They also have the miracle tech of grav focussed lasers.

I didn't have my TNE stuff to hand to check. And I hate GFL... but it's the only thing that explains the colimation angles needed.

 

[Spike]

Today I was reminded of a fine detail of Gravity that I had known but either forgot completely or simply glossed over as always.

Gravity is multidirectional. Erg. Look: Right now I am gravitationally attracted to my coffee cup, as it is too me, right?

And what we CALL gravity, with regards to the ship's Thrust is actually just Force (and of course, Gravity is just a Force as well).

FELT Gravity is therefore made up of only UNOPPOSED force... and I sort of realized this when I was talking about the z-gee tunnel in a corridor with opposed gravitational planes earlier. That is exactly what should happen, though the exact placement will vary if the strength is unequal, as distance is squared I believe.

While I had already considered the idea that ships 'Engines' are in the back and look, in some cases, remarkably like thrusters, they are merely placed there with radiation fins to disperse waste heat out the 'back' of the ship for convience and perhaps out of tradition.

If we postulate a 'gravity' drive is is probably more accurate to describe the 'motion' of the ship as FALLING towards an artificial gravity well directly in its path. The crew doesn't feel this because the same field mechanic that is generating the artificial gravity well that the ship is falling towards also isolates them (they are within the projector essentially*), and they are feeling a stronger attraction to the directional pull of 'down'.

Only when the ship is in range of a powerful natural gravity well (in orbit or landed) does the ship not 'fall' in this fashion, as we already know that the primary mechanism here is neutralizing the existing gravity. One wonders if the mechanism is so well tuned that the ship is literally flung out of orbit/off the surface by centrifugal force, like a sling stone being released!


Of course, I'm not sure what, if any, effects this would have on my earlier 'stupid gravity tricks'.




* Actually, that doesn't answer anything at all unless we can somehow postulate that the artificial gravity well only acts on the shell of the ship and not on its contents. Sounds like technobabble to me.

Either way, this does explain why ship's drives must still be more powerful as the ship gets more massive, as the strength of the gravity well must be correspondingly stronger as well, or rather our 'virtual mass' that is generating the gravitic attraction must be more 'virtually massive' to attract the ship properly.

A side effect of this theory would be that maneuvering around the nose of a ship (friendly or otherwise) is problematic, particularly for small craft and missiles, while the back end is merely... warm. Assuming the 'gravity point' is in 'contact' with the nose of the ship, a thrust 6, 100 ton ship has a gravity point of 600 virtual tons... I think. I don't want to do the math at the moment (and of course, we don't have a volume for this gravity point, it could be inestimably small or as large as the projecting ship (or more really), which is an important concern, particularly for missiles (which would be expected to impact the ship to work). I suspect that a sufficently massive ship (capital ships) would have a mass sufficent to provide a 'felt' gravity even not accounting for a multiplier for a 'virtual' gravity.


As an aside, if this is a basic factor of manuevering in space, this might explain why there are no 'gravitic weapons' in use, despite gravity manipulation being obviously well above the rest of the technology curve. Any attempt to build a weapon using gravity directly must overcome the defenses already built in to every ship in the galaxy!

As a second aside, I really wanted to figure out a way to plug 100 diameters into the Law of Gravitation. I would suspect this would require a slight alteration to the existing formula, a refinement based on Traveller Jump physics and so forth, but it seems so close. I just don't have the time to monkey with it right now...

 

[aramis]

If, somehow, one gets a maneuver drive to be projecting a gravity source in front of the ship, then the maneuver drive can not be used for ground takeoffs in the wilderness...

Because, if you do, then you rip a chunk of ground with you, and it stays with you.​

It does, however, mean a gravity gradient aboard ship. That is, if the source produces a 1g center pull*, and is 5L away from the bow, the front is 4.5L and the aft end is 5.5L, so the front experiences 5²/4.5²=25/20.25=1.234G, while the back experiences 5²/5.5²=25/30.25=0.826G, or about 0.408G tidal stress. It also means that, at the front, you are held to the floor at 0.234G, and the back, rearward at 0.174G. The center is at freefall.

*well, the center of pull won't be exactly the center of mass... I ran a quick ss, and got the average pull at 1.03G for a uniform distribution with 1G at 5L.

Alan Dean Foster used such a drive in several novels, but also decided to ignore dilation and the C-limit. And it rubs physicists the wrong way due to the source being perpetually in front of the ship...

 

[Spike]

I did address lift off in my last post, though not for the reason you suggested which is a very good point, btw.

The most efficient method of take off, given the technologies available might be to simply 'negate' the ship's attraction to the orbital body in such a way that the angular momentum of the bodies rotation throws the ship 'out'. I imagine that an early experiment with 'contra-gravity' would involve at least one accident where stuff got 'thrown' accidentally until they learned to control the level of the effect or apply it more universally... which might make contragravity a 'defense' against kinetic weapons interestingly enough. The unintended consequences of easy, powerful and controllable gravity manipulation technologies is... interesting.



Your comments about the gravity gradient are interesting but I think you are using them as opposed forces directly. If the entire ship is in a 5g 'fall' through space, we can call that the X axis, and the 'ship's gravity', that the crew experiences (deck plates... though I imagine we'd really only want one set at the 'bottom' of the ship or subsequent decks would have higher gravities as the pull added up), is a Y-axis attraction. What needs to happen here, and this is, I'm sure, the VERY SIMPLE way of looking at it, is for the inside of the ship to have an opposed 'fall' away from the front towards the back... again on our x-axis. The 'trick' in this case is keeping the backwards fall from affecting the ship (effecting? Damnit!), which is just as problematic as keeping the exterior 'fall' from affecting the inside of the ship... in fact it would just create an additional complication over the first. But assuming we DID use this method, I think the 'felt' gravity at either end would be fairly minor, and in conjunction with the 'y-axis' gravity, would make walking the ship feel like walking a gentle curve (earth's surface? More gentle? Less gentle? I suspect less, but I'm avoiding the math here, and we are discussing notional distances at the moment).

Where my knowledge breaks down is the way this 'y-axis' gravity actually interacts with our 'x-axis' gravity. I know the math is out there, I just don't know it yet. My assumption is that we could increase the y-axis pull to be strong enough to pull the crew to the decks, and the x-axis pull would negate the perceived strength of the deck plate pull (like those spinning rides where the floor drops out, maybe?). The purely notional point is 6g decks provide (notionally) 1g pull against a 5g thrust?

Wildly inaccurate, but am I on the right track?

 

[Icosahedron]

If we postulate a 'gravity' drive is is probably more accurate to describe the 'motion' of the ship as FALLING towards an artificial gravity well directly in its path. The crew doesn't feel this because the same field mechanic that is generating the artificial gravity well that the ship is falling towards also isolates them (they are within the projector essentially*).

I'm not sold on 'gravity drive', but I'm interested in an 'inertia drive' which has many similarities. Your description here fits an inertia drive very well and dispenses with the need for internal 'inertia compensation'. Consider it borrowed.

I suspect that a sufficently massive ship (capital ships) would have a mass sufficent to provide a 'felt' gravity even not accounting for a multiplier for a 'virtual' gravity.

You're suggesting ships large enough to generate a g-field by virtue of their mass alone? Nothing in Traveller is that big - a ship the size of the Moon would have 1/6g...

As a second aside, I really wanted to figure out a way to plug 100 diameters into the Law of Gravitation. I would suspect this would require a slight alteration to the existing formula, a refinement based on Traveller Jump physics and so forth, but it seems so close. I just don't have the time to monkey with it right now...

Not sure what you're asking for here.

which might make contragravity a 'defense' against kinetic weapons interestingly enough. The unintended consequences of easy, powerful and controllable gravity manipulation technologies is... interesting.

Yep, it's called a Repulsor. The ranges at which Traveller repulsors are supposed to work are problematical though.

Your comments about the gravity gradient are interesting

Yes, I was going to mention tidal effects and gradients myself until I saw Aramis beat me to it. This is a problem with gravity drives that disappears with inertial drives.

Where my knowledge breaks down is the way this 'y-axis' gravity actually interacts with our 'x-axis' gravity. I know the math is out there, I just don't know it yet.

It's in LBB2. gravity works on the vector principle.

Incidentally, If I'm reading your earlier description of a zero-g corridor between two opposing grav plates correctly, the setup would create an unstable equilibrium - like balancing on a knife-edge. The slightest movement from dead centre would send you crashing into one plate or the other.

 

[Spike]

I'm not sold on 'gravity drive', but I'm interested in an 'inertia drive' which has many similarities. Your description here fits an inertia drive very well and dispenses with the need for internal 'inertia compensation'. Consider it borrowed.

No problem! Certainly the way a lot of games (and versions of traveller don't seem to be an exception) seem to treat most vehicles as inertialess to one extent or another, but from what I've seen this is less true of Traveller than most. My LBB 2 has the rules for 'turn over' at midpoint and so forth. Strangely, I don't think including realistic inertia into the mechanics makes the game any harder to play from a rules aspect, but it is a frequently ignored aspect of space travel. Hell, I'm a fan of Eve Online, but their insistance on 'water physics' for space travel drove me absolutely buggy the entire time I played! Given that a computer can easily compute microgravity physics at least as easily (if not MORE easily)... there just isn't a good excuse.

You're suggesting ships large enough to generate a g-field by virtue of their mass alone? Nothing in Traveller is that big - a ship the size of the Moon would have 1/6g...

Everything, even my coffee cup, has Gravity. I'm not saying it would be a very strong field, but a ship at rest in deep space would have an orbital cloud of debris, for example. That isn't even controversial. What I forgot when posting earlier is that the gravitational constant is small enough that the 'virtual mass' actually has to be much higher than the ship's mass (for a thrust 6 equivilent it would be 1x10^11 or so... we are talking about a virtual singularity in all probability. At this point it may be easier to suggest that the drive creates a condition where the ship ACTS like it is falling towards a virtual singularity, without actually creating one... which puts us back to the starting point)

Not sure what you're asking for here.

The Law of Gravitation, beginning physics. Everything in the universe is attracting everything else in the universe. The amount of the attraction created the force we know as Gravity (on earth measured as an accelleration of 9.8 m/s2). The equation is relatively simple: G x Mass1 X Mass2 / Radius squared.

Radius is obviously the distance. Since Jump drives are 'regulated' by distance from a major orbital body (that is, one that supplies sufficient gravity to monkey with the jump drive), it seems that something akin to the Law of Gravitation is at work... too much external gravity and the jump gets wonky if it works at all...

Now: Planetary diameters have very little to do with actual gravity (that is a function of mass, so density becomes important), but one can suggest that it is far simpler to use as a guideline than a hard rule. The simplest way to use it would be to count 'Diameters' as a unit of measurement (which is, properly speaking, meters... a much smaller unit), so half the diameter, squared, is the devisor in the equation. That means we divide by...40,000.

A more 'accurate' way of doing it would be, I suspect, to use Earth's Diameter as a base, for a 1g planetary body, as a base, and assume that a similar ratio of diameter to gravity is at play in the galaxy (a bold assertion, I assume, but I know next to nothing about astrophysics and orbital bodies beyond what I've just stated...). From there we plug the numbers into the equation given above (where G is the gravitational Constant of 6.67 x 10^-11) to get the natural gravity a ship can be under when it tries to Jump.

Of course, to do this properly we'd also need a 'standard' ship size, in terms of actual mass (Not displacement... ugh!)... smaller ships could actually be closer to planets than larger ships.

Much to detailed, I am absolutely sure.

Yep, it's called a Repulsor. The ranges at which Traveller repulsors are supposed to work are problematical though.

Hrm. The traveller books I have do not have repulsors that I have seen. Mostly Mong-Trav and Gurps Trav, though I have played in more versions than I actually thought (thinking way back!)

Yes, I was going to mention tidal effects and gradients myself until I saw Aramis beat me to it. This is a problem with gravity drives that disappears with inertial drives.

Tidal effects shouldn't occur if the two points are stationary in relation to one another I thought? Now, if you start manipulating the field so that you get variable gravity at different points in the ship, as suggested re:defensive actions against boarders, then it does become an issue.

It's in LBB2. gravity works on the vector principle.

The LBB2 I have is a slim little pamphlet and I don't recall seeing that in there, though I did see ship's turnover and thrust/speed calculations. I'll check when I get home.

Incidentally, If I'm reading your earlier description of a zero-g corridor between two opposing grav plates correctly, the setup would create an unstable equilibrium - like balancing on a knife-edge. The slightest movement from dead centre would send you crashing into one plate or the other.

Well...yes. I was trying to work out in my head the tolerance of the corridor but I realize now that it is purely a function of how distant the plates are and how strong the attraction is. Now that I'm playing around with the 'Law of Gravitation' (Newton's Law of Gravitation), I'm running into SEVERE problems with the idea of 'Gravity Plates' on decks. As I understand it, gravity on Earth works in part because the Earth is so very massive in relation to us that the effects of distance (which grow exponentially) are mitigated except at extreme distances. A 'deck plate' doesn't have that advantage, though it is creating a '1g' pull by means we can't actually name (being above our tech obviously). What is the 'distance' this 1g is actually calculated at and for how massive an object? Does a 'deck plate' gravity necessarily create a virtual mass equivilency, even though its actual mass for purposes of drives, is negligable? Does then entire principle work on some sort of 'superscience field effect' rather than newtonian attraction or einstienian relativity (which I can say precisely nothing about... at the moment)? The last answer is easiest but also the least satisfying, as handwavium always is.

I think the principle behind good 'hard' science fiction is that the scientific theories behind your high tech must be plausible and explainable, even if the actual engineering and math necessary to actually DO it isn't... and if the math is 'doable' its even better. But no one wants to read engineering blueprints for the heroes laser cannon... (well... maybe. Schlock Mercenary occasionally delves into blueprints quite entertainingly...from time to time).

 

[aramis]

There's a reason my AG is a flow between cathode and anode... it makes the gravity not subject to the inverse square law. It also means absolutely no IC without 4+ faces (tetrahedron) and preferably 6 faces. And no AG without a floor and ceiling.

 

[Icosahedron]

I'm reasonably familiar with gravity physics, but I'm still not entirely sure what you're aiming for with the 100 dia thing. Are you trying to make the jump drives drop out at a certain gravitational field strength? That has been discussed on another thread here, but would require a major upheaval to the rules.

LBB2 combat system uses vectors to calculate accelerations. Since the effects of gravity are accelerations, they work on the same principle: 1G acting toward the rear of the ship and 1G acting toward the floor will result in a net force of root 2 G acting 45 degrees down/rearward, etc.

The way I figure deck plates, using inverse square, is one plate 0.5m under the floor pulling down and another plate 0.5m above the ceiling pushing down (reversed field) They are calibrated to form 1G at 0.5m (at floor and ceiling) and their combined effect will produce around 0.5G in the mid section.
How they produce that field is something I don't discuss, but the same effect (whatever it is) allows vehicles to skim at a ride height of 0.5m from the ground. They can go higher, but fuel use increases by inverse square...