Alternity RPG "gravity induction engines"

[someone_else]

I know, I know, first post and already talking of impossible things related to gravity.
But I wanted a expert's opinion on the effect of the engine, not on its actual workings (that are obviusly made of an handwavium/unobtanium composite). My usable knowledge on gravity stops at newton gravitation, and I know that it is unaccurate.

So, let's talk of its effects from the game's lore: they say that it creates an "artificial slope in the fabric of space" that makes the ship fall in its direction. They say that this gravity well is placed "whithin the engine". They also say that "the gravity well is too short-ranged to effect anything else than the ship itself".

Now, from what little I could get from a few calculations i did in an excel sheet with the newton's law on gravity, the magical gravity well either is extremely close to the ship's center of mass (requiring a ship created like a pusher plate with the gravity well at its center) or it will need to be extremely powerful (i.e. affecting multiple objects in a wide area).

Also, a gravity well placed in the vicinity of the ship (or even in it) should generate dangerous tidal stresses on the ship's frame and crew, just because things "fall" toward a point in front of them (or in various directions).

So I'm able to tag it as "extremely silly" by myself.

I wanted to get a gravity-well-creating engine that, while using pure techno-magic to create the gravity well, had realistic effects. But my knowledge on the subject is limited at best, and this place seems inhabited by people that know more.

Any ideas?

btw, just in case you drop by the only Alternity official forum, I'm someone_else there too. (you can't go wrong, there is only one site that talks about Alternity other than Wikipedia)

[Teleros]

I wanted to get a gravity-well-creating engine that, while using pure techno-magic to create the gravity well, had realistic effects. But my knowledge on the subject is limited at best, and this place seems inhabited by people that know more.

A simple way would be to make one that functions rather like a tractor beam (I've used the idea myself) - think of it as a ship pulling (or with anti-gravity, pushing) on nearby massive objects to get around with graviton lasers or however you want it to work. It wouldn't work well when you're far from such objects and needing to change your course or acceleration, because gravity only propagates at the speed of light.

As for realistic effects... any gravitational field warps light around it a little, to the point where black holes etc can show you what's on their other side (albeit in a distorted fashion). Gravity also follows the inverse-square rule, so unless you have the magitech required to counteract it you may find the gravity on board ship affected by your drive.

The Honor Harrington books by David Weber use gravity for their main drives, although it's something of a technobabble view of gravity. May be worth looking up though.

[someone_else]

A simple way would be to make one that functions rather like a tractor beam (I've used the idea myself) - think of it as a ship pulling (or with anti-gravity, pushing) on nearby massive objects to get around with graviton lasers or however you want it to work. It wouldn't work well when you're far from such objects and needing to change your course or acceleration, because gravity only propagates at the speed of light.

Looks cool, but mostly depends on what does a tractor beam. It is mostly useless technobabble in most explanations i read. Can you explain better this?
Also, having to "brace" my ship on planets and stars to move means that this kind of propulsion system works with decent reacton times only when I'm quite close to a planet or star, so will be very limited even for an in-system drive.

Gravity also follows the inverse-square rule, so unless you have the magitech required to counteract it you may find the gravity on board ship affected by your drive.

And that is why I was thinking of a ship shaped like a pusher plate with the gravity well in its focus, if it is created that way all the things "fall" to the ship's prow.
So the ship will have to look like a dish and travels with the concave end forward.
But even then the crew and other objects will be accelerated in weird directions even if I make the deckplans with the concave end as the ship's "down".

[Cykeisme]

If you have the handwavium ability to generate arbitrary gravity wells and project them into space, instead of projecting a single well in front of your ship, you can instead project a large number of them evenly distributed on a plane perpendicular to your direction of travel.
That should help take care of tidal forces.

[Batman]

Not really. If tidal forces are a problem to begin with, you're STILL faced with the problem of the front end of your ship accelerating faster than the stern...
Also, let's just for the sake of argument assume Wars-level acceleration. You just created a 4 figure g gravity well (gravity plane in your version). That's the gravitational equivalent of FOUR THOUSAND EARTHS moving around in a solar system. I foresee INTERESTING side effects

[joenye]

In accordance with batman, you would probably end up with a ship that looks like a can crinkling to a almost perfect point where your gravity well is, and if you have a sheet of them your gravity waves would interfere and you would end up with a nice wave interference shaped ship, that is if it even stayed in one piece... not a very good thing to be in;)

[Batman]

Err-why?

[joenye]

*sigh* the gravity well would have to be at least of the size to move the ship by pulling over long distances to work, and do you think that putting something that can attract to masses LIGHTYEARS AWAY inside your ship isn't going to attract part of your ship. That part of your ship will crumple and fold into the singularity in the shape of a cone. Now this is the hard part to explain, so feel free to jump in if you have a better explaination for gravity wave interference. So you have a wall of singularities right? Now imagine that each is a stone you have tossed into a pond. The ripples going outward are the gravity waves that move at the speed of light to transmit the force of gravity. Now as those ripples spread, they hit one another, and in the spot where a valley hits a valley the valley gets deeper. Likewise the gravity wave interfere, and in the valley collision spots the gravitational force is greater, so it pulls more. In the spots where a crest meets a crest the opposite happens. Then in every spot it pulls more the cone effect I first described will happen, so instead of just one point, you get more points than you have singularities. So you end up with a spiky crushed ship

[Teleros]

Just trying to think a bit on how you could get it to work...

1. Set up your gravity-well a good distance from the ship, and as gravity weakens over distance, you can stay away and not get crushed. Probably best not used within star systems though.
2. Have a fairly weak one (say 1-2gs acceleration... although why this & not a good old rocket is another matter), and orient your ship such that "down" is towards the gravity well. Your crew can now walk around and such. Well, they might weigh twice as much, but whatever .

The trouble is that gravity is something the effects of which have been quite well documented, so unless you have some really fancy gravity-modifying tech (I dunno, make it follow the inverse-cubed law or whatever ), big gravity wells in star systems can be dangerous to, well, everything else in those same star systems .

[Simon_Jester]

I'm still trying to figure something out: why is this concept worse than the science fiction staple of "artificial gravity" or "inertial compensators?"

If I can generate a 1g field pointing towards the floorboards of my own ship, or a 7g field pointing towards the bow to negate the effect of having the back of my seat accelerated into me at 7g by my ship's overpowered rocket engines,* why can't I design a ship that accelerates itself? Why do I even need to generate planetary-mass gravity wells, given my obvious ability to produce gravitational fields that, against all odds, behave like the magnetic field between a pair of Helmholtz coils or something?

The obvious problem is that it plays hob with momentum conservation... but so do inertial compensators.

*Something like this has to exist in Star Wars, for obvious reasons; if ship accelerations are on the order of thousands of g's, then someone has to be applying a uniform acceleration of thousands of g's to every particle in the ship. The hull frames might be strong enough to survive the tidal forces created by nonuniform acceleration, but the instrument panels probably aren't. And the crew... well, obviously not.

[Teleros]

I'm still trying to figure something out: why is this concept worse than the science fiction staple of "artificial gravity" or "inertial compensators?"

I'm not sure it is worse to be honest, it's just someone_else wants one with realistic effects.

[Buritot]

The only way I can imagine a halfway plausible concept applying gravity propulsion is to arrange it (the handwave) in such a way the gravitational forces dispel way faster than the inverse cube law. This way you'd have a very local plausibly strong well which doesn't effect the rest of the universe too much.

I'll try it this way: my gravitational engine is outside the hull but connected to it via girders or something. Nearly all of the mass is inside the hull. The artificial gravity well pulls on the rest of the ship but the girders instead push the well in the opposite direction. (I think this wouldn't work on the premise of lever-fulcrum-connection).

The tractor beam idea is better though, imho.

I'm still trying to figure something out: why is this concept worse than the science fiction staple of "artificial gravity" or "inertial compensators?"

Apropos internal compensators... let's assume we'd have a forcefield that could counteract the immense forces applied to every single particle/molecule/whatever via acceleration. I think this could work for very thoroughly monitored cases, for example high-g burn phases. The machine knows what amount of force will be acting and can apply an appropriate counterforce. But it would not work under less than ideal circumstances, say during a battle in which explosions and whatnot apply forces the computer doesn't/won't know to the n-th digit.

[Sheridan]

The problem with attaching your gravity-producing generator/singularity/whatever to your ship is that it won't go anywhere.

Try this at home: build yourself a "ship" out of paperclips, and then attach a refrigerator magnet "gravity generator" to it with toothpick "girders" and tape/glue/dried bubblegum/whatever. Does the magnet pull the "ship" along your counter (without the magnet--and therefore the framework attaching it to the "ship"--being moved by you)?

No. Of course not.

You'll still have to accelerate your gravity field generator in order to accelerate your ship. Which begs the question of why you aren't using reaction drives in the first place.

If you have some kind of unobtanium crap that will let you decrease/negate and/or increase the effects of gravity on your ship at will, you can do some interesting things with already-existing gravity sources to move your ship. See the Cavorite in the Orphanage series by Robert Buettner for a decent example. Simply attaching a gravity generator to your ship with a physical structure isn't going to work, though.

[Buritot]

Simply attaching a gravity generator to your ship with a physical structure isn't going to work, though.

Yeah, that's what I figured. It would be an asspull of astronomical proportions, and stupidly wrong, too.

I'm still thinking of regular artificial gravity engines, though. If you've got reasonably high velocity high gravity fields skimming around, wouldn't that kind of unravel the structure of the galaxy? Suppose we've got thousands of ships strafing around our stellar neighbourhood, wouldn't the solar systems be inadvertently pulled apart? For instance, we've got a high traffic route passing our sun at a certain distance, and every ship has a gravity engine, wouldn't the solar system be pulled in the direction of the traffic route? And - given enough time - unravel our spiral arm of the milky way? I'm just trying to think up the ramifications of such an engine, mind you...

[Simon_Jester]

EDIT: I actually tried to rationalize this once myself, when I was a lot more physics-naive (not 100% so, but... pretty close). The best I ever came up with was that the induction drive generated a gravitational field that looked like the magnetic field of a bar magnet, with the ship nestled in the zone of uniform directional gravity at the center. One advantage of this is that I could have the really nasty side-effects of the drive field limited to within a few hundred kilometers of the hull, which meant they could use station-keeping thrusters (or their own drive at extremely low power settings, or tractors) to maneuver out to their minimum safe distance and then fire it up.

Yes, this raises a lot of questions, chief among them being "how did you generate gravity in a shape that violates the Einstein field equations?", but there's really no good answer to this one in any case.

The only way I can imagine a halfway plausible concept applying gravity propulsion is to arrange it (the handwave) in such a way the gravitational forces dispel way faster than the inverse cube law. This way you'd have a very local plausibly strong well which doesn't effect the rest of the universe too much.

On the other hand, you'd have a tremendous tidal effect. You really need a uniform directional field to make this viable. The field may have funky shapes outside the ship, and it still needs to be localized, but without a way of generating uniform directional gravity, this kind of engine shouldn't work even if you can put an inverse-cube or greater decrement on a gravity field.

Apropos internal compensators... let's assume we'd have a forcefield that could counteract the immense forces applied to every single particle/molecule/whatever via acceleration. I think this could work for very thoroughly monitored cases, for example high-g burn phases. The machine knows what amount of force will be acting and can apply an appropriate counterforce. But it would not work under less than ideal circumstances, say during a battle in which explosions and whatnot apply forces the computer doesn't/won't know to the n-th digit.

This makes sense... but if I can build an inertial compensator that magically accelerates particles which are not solidly connected to it (like air molecules in the middle of a room), why can't I just remove the engine and use the inertial compensator as the engine?

[Teleros]

I'm still thinking of regular artificial gravity engines, though. If you've got reasonably high velocity high gravity fields skimming around, wouldn't that kind of unravel the structure of the galaxy? Suppose we've got thousands of ships strafing around our stellar neighbourhood, wouldn't the solar systems be inadvertently pulled apart? For instance, we've got a high traffic route passing our sun at a certain distance, and every ship has a gravity engine, wouldn't the solar system be pulled in the direction of the traffic route? And - given enough time - unravel our spiral arm of the milky way? I'm just trying to think up the ramifications of such an engine, mind you...

One thing I did hear with regards to asteroid impacts was that stars that get close enough to the Kuiper Belt can, when they move away, cause some of the ice and rocks in the belt to head into the system. Add in ships flying within the solar system (asteroid belts anyone?) and it could be a real issue, especially in a war zone where asteroid defences may be destroyed as a threat by the invading warships.

This makes sense... but if I can build an inertial compensator that magically accelerates particles which are not solidly connected to it (like air molecules in the middle of a room), why can't I just remove the engine and use the inertial compensator as the engine?

Doc Smith pretty much did this in the "Skylark" series.

[Simon_Jester]

One thing I did hear with regards to asteroid impacts was that stars that get close enough to the Kuiper Belt can, when they move away, cause some of the ice and rocks in the belt to head into the system. Add in ships flying within the solar system (asteroid belts anyone?) and it could be a real issue, especially in a war zone where asteroid defences may be destroyed as a threat by the invading warships.

Of course, warships are themselves asteroid defenses, especially if they have multiple-g gravity drives. One of those things could probably destroy a comet just by flying in its general vicinity...

This makes sense... but if I can build an inertial compensator that magically accelerates particles which are not solidly connected to it (like air molecules in the middle of a room), why can't I just remove the engine and use the inertial compensator as the engine?

Doc Smith pretty much did this in the "Skylark" series.

Heh. You're right.

"It started with a lab mishap... and three books later the guy's fighting an intergalactic war."
"Some lab mishap."

For everyone not as familiar with Doc Smith as Teleros or me, the man wrote the first FTL travel story using the most naive possible FTL drive: brute acceleration to faster than light speeds, with the only nod in the general direction of Einstein being "welp, looks like he was wrong." Since Smith was publishing in 1928 and setting the story in 1928, this wasn't quite as silly then as it is now.

And yes, the drive worked like that. Basically, he had some kind of weird interaction between copper an a catalyst Element X that induced total conversion in the copper... and somehow generated directional force without need for a normal reaction drive. The reaction was first discovered when a lab chemist's copper tubing accelerated out through the wall at Mach 3 and rising.

[Teleros]

Of course, warships are themselves asteroid defenses, especially if they have multiple-g gravity drives. One of those things could probably destroy a comet just by flying in its general vicinity...

Oh, if you've got the ability to generate and muck around with gravity fields like this I'm sure a few lumps of rock won't be a problem to shoot down. It's just the fact that with a drive like this you'd need to do something about it in the first place.

And yes, the drive worked like that. Basically, he had some kind of weird interaction between copper an a catalyst Element X that induced total conversion in the copper... and somehow generated directional force without need for a normal reaction drive. The reaction was first discovered when a lab chemist's copper tubing accelerated out through the wall at Mach 3 and rising.

You did feel the acceleration of the original drive though, it was the Fenachrone version that applied the acceleration to everything in its sphere of action or however Doc Smith described it.

[Simon_Jester]

Sorry, you're right. The only one in the series I read closely and recently was Skylark of Valeron, which is post-Fenachrone. Never mind.

[Sky Captain]

IMO the best solution is to have a gravity engine that pushes or pulls against natural gravity wells since it don`t break the law of conservation of momentum - your ship accelerates by pushing or pulling against a planet but also accelerates the planet a bit.

[someone_else]

The problem with attaching your gravity-producing generator/singularity/whatever to your ship is that it won't go anywhere.

I know. It violates fundamental physical laws, but I'm trying to "reduce the damage" by at least giving realistic effects after this handwaved assumption: The "gravity generator" is a magic wand that creates a gravity well (or a black hole) in front of the ship.
Still, I can easily adapt the concept. If i state that the gravity wells can be generated by cheap one-shot devices, I can create a Orion-like vessel. Instead of throwing directional nukes on a pusher plate (like Orion) it throws a gravity generator in the front of it, the generator explodes generating a temporary gravity well, thus "pulling" the ship. This way I don't violate the law you stated, or not? The generator "stands still" at the center of the gravity well.
Still, even for this concept, I need to know something more about the power of gravity wells generated.

To avoid the tidal effects I thought of creating a single gravity well at a good distance, so that the "pull" would be about unidirectional (like the Earth's gravity pull on the surface), but due to my naiveness I cannot figure out the power and the distance of the gravity well to do it. If I must create a gravity well powerful as Earth's and place it at 6 thousands odd km in front of my ship to get a 1G acceleration (like Earth's surface)... I'd break havock with planets orbits.

My handwaved gravity well must be strong enough to pull the starship, distant enough to make the pull near-unidirectional to avoid tidal effects on the ship, close (or powerful) enough to extert about the same pull on both ends of the space ship (or even require a flat hull like a "coin-ship"), and be way weaker than a planetoid's gravity well (to avoid screwing with planet's orbits).

Theoretically the fact that gravity follows the inverse square law can help me in this. The ship is close, so it is affected, a planet is far away, so it is not.

And here is where I asked assistence. Is at all possible to have a gravity well like that? (if generated by magic)

Also, this kind of tech makes impossible to create a constant gravity aboard the ship without dangerous tidal effects (or accelerating the ship too), not even by constant acceleration (because both crew and ship "fall" in the same direction when the ship accelerates).
This also does not need annoying Inertial Dampeners if the engine accelerates the starship by 10 or more gees.
This kind of engine should also be dangerous to use close a planet, probably due to tidal effects the planet would feel.
So the ship would require Orbital Thrusters (that would be chemical or atomic rockets) to maneuver in orbit.

IMO the best solution is to have a gravity engine that pushes or pulls against natural gravity wells since it don`t break the law of conservation of momentum - your ship accelerates by pushing or pulling against a planet but also accelerates the planet a bit.

can you elaborate a bit more this concept? Teleros said something similar in the second post but sounded pretty nebulous. That would be a Grav-Sail right? (would not resemble a conventional sail though)
If the thing can give a decent acceleration for pratic interplanetary voyage (while being in interplanetary space), it may be cool.
If it works only in a planet's orbit it is quite useless for my needs. (but technically it becomes THE tecnology that allows humanity to reach the stars by using the planet's own gravity to cheaply push a payload in orbit, that for now it is a MAJOR barrier for human expansion into space)

Edit: Cool, I have been recognized as a real person by mods!

[someone_else]

huh, the "cheap gravity generator" of the Orion-ish ship would probably still violate the conservation of energy, but that is the generator's problem, not the ship's.

It would also be a good weapon of mass destruction. Any propulsion system with a decent acceleration is a WMD.

[Teleros]

Still, I can easily adapt the concept. If i state that the gravity wells can be generated by cheap one-shot devices, I can create a Orion-like vessel. Instead of throwing directional nukes on a pusher plate (like Orion) it throws a gravity generator in the front of it, the generator explodes generating a temporary gravity well, thus "pulling" the ship. This way I don't violate the law you stated, or not? The generator "stands still" at the center of the gravity well.

Provided the momentum from firing the generator isn't greater than the pull from gravity, and that the ship can survive being pulled nearer this monster gravity projector before it breaks down... yeah I guess it'd be okay. And a neat way to blow up continents .

To avoid the tidal effects I thought of creating a single gravity well at a good distance, so that the "pull" would be about unidirectional (like the Earth's gravity pull on the surface), but due to my naiveness I cannot figure out the power and the distance of the gravity well to do it. If I must create a gravity well powerful as Earth's and place it at 6 thousands odd km in front of my ship to get a 1G acceleration (like Earth's surface)... I'd break havock with planets orbits.

Pretty much . You could limit the damage by only using it far from planets, but... yeah. Over long periods of time, and without flights to correct the movements (let's assume you can calculate all this too), Bad Things will happen.

My handwaved gravity well must be strong enough to pull the starship, distant enough to make the pull near-unidirectional to avoid tidal effects on the ship, close (or powerful) enough to extert about the same pull on both ends of the space ship (or even require a flat hull like a "coin-ship"), and be way weaker than a planetoid's gravity well (to avoid screwing with planet's orbits).

Technically, any gravity well will eventually pull the starship towards it, and some things can survive tidal effects better than others, so it's not all bad. You could always I suppose use it "up" or "down" away from whatever imaginary plane the planets are orbiting on, then change directions to head to a star... but really there's no way to use gravity to move ships about reasonably quickly without the potential for causing problems.

Theoretically the fact that gravity follows the inverse square law can help me in this. The ship is close, so it is affected, a planet is far away, so it is not.

No, the planet is just less affected. It might only be a 1nm/s difference in the speed it zips around the star at, but add in a lot of flights, a million years or so, and even these small changes can be disastrous.

And here is where I asked assistence. Is at all possible to have a gravity well like that? (if generated by magic)

Probably not .

Also, this kind of tech makes impossible to create a constant gravity aboard the ship without dangerous tidal effects (or accelerating the ship too), not even by constant acceleration (because both crew and ship "fall" in the same direction when the ship accelerates).
This also does not need annoying Inertial Dampeners if the engine accelerates the starship by 10 or more gees.
This kind of engine should also be dangerous to use close a planet, probably due to tidal effects the planet would feel.
So the ship would require Orbital Thrusters (that would be chemical or atomic rockets) to maneuver in orbit.

Artificial gravity is usually just handwaved away anyway. Inertial dampeners are designed to dampen changes in acceleration, so I don't see why this would eliminate their need. You're also right about the danger of being close to a planet.

IMO the best solution is to have a gravity engine that pushes or pulls against natural gravity wells since it don`t break the law of conservation of momentum - your ship accelerates by pushing or pulling against a planet but also accelerates the planet a bit.

can you elaborate a bit more this concept? Teleros said something similar in the second post but sounded pretty nebulous. That would be a Grav-Sail right? (would not resemble a conventional sail though)
If the thing can give a decent acceleration for pratic interplanetary voyage (while being in interplanetary space), it may be cool.
If it works only in a planet's orbit it is quite useless for my needs. (but technically it becomes THE tecnology that allows humanity to reach the stars by using the planet's own gravity to cheaply push a payload in orbit, that for now it is a MAJOR barrier for human expansion into space)

Think of it rather like using a laser / photon drive fired from Earth to move your ship around. Any course changes you want to make will (aside from the issue of how gravity decreases in strength the further you get from your reaction mass - ie planets & stars), take a while to make themselves felt, because of the speed of gravity. If you can do this with both gravity & antigravity it'll be a lot easier to use, and there should be no reason why you can't point at a distant star & set off. Just don't expect to be able to accelerate well all the way (or even half the way). Accelerate, coast for a few years / decades / whatever, deccelerate, voila.

[someone_else]

and that the ship can survive being pulled nearer this monster gravity projector before it breaks down

If the gravity well has the right strenght and distance, the gravity pull on the ship will be nearly unidirectional, so even if the pull is a hundred thousand G everything will fall in the same direction at once. The same applies to Orion drive vessels: if the directional nuke does not explode in the right place at the right distance (and with the right orientation) you are in a world of hurt.

To avoid the tidal effects I thought of creating a single gravity well at a good distance, so that the "pull" would be about unidirectional (like the Earth's gravity pull on the surface), but due to my naiveness I cannot figure out the power and the distance of the gravity well to do it. If I must create a gravity well powerful as Earth's and place it at 6 thousands odd km in front of my ship to get a 1G acceleration (like Earth's surface)... I'd break havock with planets orbits.

Let's see if I can do some quick (and probably wrong) calculations:
We have an object massing X kg (Earth) that creates a big gravity field, that accelerates all things around it at 6000 odd km radius (Earth's surface) by 1 G (9,8 m/s).
Gravity follows the inverse square law if we go far from the planet's surface right? So it should work in reverse too.
So if we cut the distance by 10 (so we stay at 600 Km from the planet's core) while the planetary mass remains the same, the gravity pull becomes 100 times more powerful right?
A ship would be quite within the Earth to receive this kind of pull, and the Earth's mass breaks havoc with the planetary orbits.
But this means that if we can scale down the mass of the virtual object generating a gravity well and we stand closer to its center, it will pull the ship with the same strenght right?

Now, tinkering with numbers in my spreadsheet with Newton's Gravity law I get that a gravity well created by 1,47E19 kg of mass (half mass of an asteroid called 704 Interamnia) will extert 1 G of acceleration on an object weighting up to 1E16 kg, if said object is placed at 10 kms from the center of the gravity well.
Usually you cannot stay so close to an object due to its bulk, but if the gravity well is magically created (or if it is a very low-mass singularity), you can stay how close you want.
I seriously doubt that a planet will ever notice a so small gravity well. But I'm no expert. I may be wrong.

This sounds cool, but I still need someone to look if:
1. my reasoning is correct
2. my calculations are correct
3. Newton's formula is correct (and it is not completely precise from what I read)
4. determine if the ship is under tidal stress or if the gravity's pull is nearly unidirectional at that distance. And I have no idea on how to do it.

No, the planet is just less affected. It might only be a 1nm/s difference in the speed it zips around the star at, but add in a lot of flights, a million years or so, and even these small changes can be disastrous.

There will maybe the need of periodic "correction" flights by big space tugs with powerful gravity wells. I don't see it so dark though... if the gravity well is so small and is not used in the planet's vicinity it won't get any bad effect.

Artificial gravity is usually just handwaved away anyway.

One thing is to handwave the actual workings of the engine (that is unavoidable in this case), another thing entirely is to handwave the effects.
You cannot state that you move a ship by creating "black holes very close to its hull". That would simply tear the ship apart. That was the thing that annoyed me in the Alternity books.

Inertial dampeners are designed to dampen changes in acceleration, so I don't see why this would eliminate their need.

Speed and acceleration are relative to the frame of reference right?
If the engine uses a gravity well as in my design, it already accelerates both ship and crew (and cargo) in the same direction, they all begin to "fall" toward its center with the same acceleration and speed. So neither crew nor cargo (nor the ship's frame) will experience the "being pushed backwards (or down) when the ship accelerates" effect (should be an effect of inertia).

[Teleros]

Gravity follows the inverse square law if we go far from the planet's surface right? So it should work in reverse too.

In short, no. If you're in the exact centre of the Earth you're more likely to be weightless, due to the mass surrounding you pulling you equally in all directions.

I seriously doubt that a planet will ever notice a so small gravity well. But I'm no expert. I may be wrong.

The danger is that tiny errors add up.

You cannot state that you move a ship by creating "black holes very close to its hull". That would simply tear the ship apart. That was the thing that annoyed me in the Alternity books.

Perhaps they're very small, short-lived ones . Absurdly small ones would have a similarly small event horizon and so on.

Speed and acceleration are relative to the frame of reference right?
If the engine uses a gravity well as in my design, it already accelerates both ship and crew (and cargo) in the same direction, they all begin to "fall" toward its center with the same acceleration and speed. So neither crew nor cargo (nor the ship's frame) will experience the "being pushed backwards (or down) when the ship accelerates" effect (should be an effect of inertia).

Let's assume a change in direction:
1. You're accelerating north at 1g, until you're travelling at a steady 1km/s.
2. You now want to head west, so you pop a new gravity well to the west and remove the one to the north (if you haven't already).
3. Inertia means you're still travelling at 1km/s north, even as the gravity well to the west affects the ship. So if you want a rapid change in velocity without turning the crew to pink mush, you'll need inertial dampeners or something.