Antigravity & Inertial Dampening

[phavoc]

Rather than derail another thread I thought I'd start a new one.

Traveller is full of pseudoscience, which makes sense because a) it's a game, and b) just about anything is possible in the future, especially if it's a sci-fi game.

Traveller has an upper limit of ships drives - 6Gs (or at least up to 70 tons). We know that by controlling the gravity within the ship you can negate the effects of acceleration. We know that you can manipulate gravity so that you can move against the local grav field, or generate an artificial one and locally increase gravity.

The only explanations I can recall is that a ships deckplating is where the antigrav fields are generated. Which means you can dial up or down gravity in whatever area you want to. What I have never found though is a more thorough explanation of the whole issue. It's not textbook dampeners because it seems to completely override acceleration by negating it locally and applying it's own little world. It has the same effect, but it's not the same thing. One could easily test this on a ship by dialing back the grav field to zero and seeing if your objects get pasted to the wall in the direction of the acceleration provided by the engines.

If you remember your Star Trek episodes, those ships had intertialess drives. But when they got hit with enough force the bridge crew always went tumbling out of their chairs. So in Traveller when your ship's collapsed matter hull gets smacked with a kinetic strike, does the crew go tumbling out of their chairs too (maybe not... in the 52nd century they re-discovered seat belts)? Where does the energy go? Or by generating an entirely new localized grav field does the energy simply get absorbed, or dissipated back into space?

We know from building battleships and other large structures that the more armor you put on the outside, the stronger the bracing and other internal structures need to be in order to deal with the pressure and channeling of energy. Otherwise while a shell hit on the outside may not penetrate, the facade would cave in without something supporting it. Ships appear to be mostly slab-sided so that energy couldn't be channeled like say an arch would channel pressures.

Thoughts?

 

[simonh]

There are basically two options for how m drives work inns traveller. There are many variations within these categories, but I think these are the high level options.

One is that the drive generates thrust much like a rocket, but without the exhaust. Thus is how thruster plates are described in Mega Traveller. If they work like this, you do need some kind of inertial or acceleration damping because otherwise sustained acceleration at 3+G will kill the crew. I also assume the grav drives in vehicles such as the air raft work the same way, generating thrust.

The other option is some kind of gravity drive that generates a gravity gradient around and across the ship, that cause it to 'fall' in the desired direction. This isn't the only possible form of gravity drive, other variants could work like the type above, but this option pretty much only works using a form of gravity manipulation. This type of drive would not require any kind of acceleration or inertia damping, because the ship and its occupants would not experience any force. I'm Find it hard to believe grav vehicles such as the air raft work this way, because open topped grav vehicles are going to be a bit mad, if not lethal to travel in.

Personaly I think Traveller seems to imply the first type as being the standard, it's the type I prefer to assume in my games, but live and let live.

As to how acceleration/inertia damping works, I assume it's the same principle as used to provide artificial gravity. If grav plates in the floor and ceiling can generate a gravity field for normal operation, plates capable of up to the drive rating in Gs, mounted in the walls, should be able to compensate for the engine's thrust. Thus some of the manoeuvre drive tonnage is actually devoted to dampers.

Simon Hibbs

 

[Condottiere]

Could be a predictor programme, that based on what the ship sensors pick up, calculate likely outcomes and adjust the gravitational fields.

That's why one's that weren't accurately calculated or were unforeseen, throw the bridge crew all over the place.

 

[Tom Kalbfus]

There are basically two options for how m drives work inns traveller. There are many variations within these categories, but I think these are the high level options.

One is that the drive generates thrust much like a rocket, but without the exhaust. Thus is how thruster plates are described in Mega Traveller. If they work like this, you do need some kind of inertial or acceleration damping because otherwise sustained acceleration at 3+G will kill the crew. I also assume the grav drives in vehicles such as the air raft work the same way, generating thrust.

The other option is some kind of gravity drive that generates a gravity gradient around and across the ship, that cause it to 'fall' in the desired direction. This isn't the only possible form of gravity drive, other variants could work like the type above, but this option pretty much only works using a form of gravity manipulation. This type of drive would not require any kind of acceleration or inertia damping, because the ship and its occupants would not experience any force. I'm Find it hard to believe grav vehicles such as the air raft work this way, because open topped grav vehicles are going to be a bit mad, if not lethal to travel in.

Personaly I think Traveller seems to imply the first type as being the standard, it's the type I prefer to assume in my games, but live and let live.

As to how acceleration/inertia damping works, I assume it's the same principle as used to provide artificial gravity. If grav plates in the floor and ceiling can generate a gravity field for normal operation, plates capable of up to the drive rating in Gs, mounted in the walls, should be able to compensate for the engine's thrust. Thus some of the manoeuvre drive tonnage is actually devoted to dampers.

Simon Hibbs

Actually the second kind is a sublight warp drive, basically it accelerates a frame of reference around the starship up to the ship's hull displacement. 3-g's won't kill the crew. Mercury astronauts experienced more than this.

 

[simonh]

Actually the second kind is a sublight warp drive, basically it accelerates a frame of reference around the starship up to the ship's hull displacement. 3-g's won't kill the crew. Mercury astronauts experienced more than this.

It may seem similar to the Alcubiere warp drive concept, but it's actualy different. The apparent similarities hadn't occured to me or I'd have tried to be clearer. In a warp drive local space around the ship is 'flat' and space in front of the ship is contracted, while space behind it is expanded. The vessel itself, or anything else in the bubble, isn't in a gravity field. If you look at the 3D representation of the warp bubble in the Wikipedia article you'll see the interior of the bubble is flat. In a gravity drive, Larry Niven called it the Gravity Planar, the drive generates a local gravity gradient, so the gravity field across the ship is tilted.

I should have been clearer about what I meant by sustained accelerations. Pilots and astronauts routinely experience accelerations from 3G or more for short periods of no more than a few minutes. Traveller assumes ships routinely cruise at their maximum acceleration half way to heir destination, then decelerate again at the same rate for the rest of the journey. 3G or more acceleration for even relatively short interplanetary journeys would cause severe trauma or death.

Simon Hibbs

 

[phavoc]

There are basically two options for how m drives work inns traveller. There are many variations within these categories, but I think these are the high level options.

One is that the drive generates thrust much like a rocket, but without the exhaust. Thus is how thruster plates are described in Mega Traveller. If they work like this, you do need some kind of inertial or acceleration damping because otherwise sustained acceleration at 3+G will kill the crew. I also assume the grav drives in vehicles such as the air raft work the same way, generating thrust.

The other option is some kind of gravity drive that generates a gravity gradient around and across the ship, that cause it to 'fall' in the desired direction. This isn't the only possible form of gravity drive, other variants could work like the type above, but this option pretty much only works using a form of gravity manipulation. This type of drive would not require any kind of acceleration or inertia damping, because the ship and its occupants would not experience any force. I'm Find it hard to believe grav vehicles such as the air raft work this way, because open topped grav vehicles are going to be a bit mad, if not lethal to travel in.

Personaly I think Traveller seems to imply the first type as being the standard, it's the type I prefer to assume in my games, but live and let live.

As to how acceleration/inertia damping works, I assume it's the same principle as used to provide artificial gravity. If grav plates in the floor and ceiling can generate a gravity field for normal operation, plates capable of up to the drive rating in Gs, mounted in the walls, should be able to compensate for the engine's thrust. Thus some of the manoeuvre drive tonnage is actually devoted to dampers.

Simon Hibbs

The SOM described thruster plates as inertialess drives. Except that's always been an explanation that doesn't fit in the other versions of Traveller because if you look at all the travel time tables it assumes a constant specific thrust to the halfway point, then turnover and the application of thrust to come to a zero-zero rest at your destination. Ergo the drives could not be inertialess.

One explanation could be that the maneuver drive itself generates a very localized field and the ship "thrusts" against it, thus generating thrust. There is some form of exhaust, however, as most versions talk about ships being detected at a distance while their drives are active there would be some sort of exhaust. It could be similar to how current ion thrusters work.

The hole in the theory of grav plates doing it all is when you read about how you can locally dial up or down gravity. In the case of dialing it down you would create no field, and thus if you were in the field you should be affected by the thrust of the ship until you encountered another field. Unless this explanation also says that whenever gravity control is turned off locally, the field still exists. Which seems kinda contradictory.

Then there is the idea that some form of inertial compensator field exists forward of the drives and that accounts for things on the ship not being affected by the constant thrust along a single axis.

There are a number of ways it could possibly be explained. Unfortunately it's just not and assumptions are made, all reasonable depending on how you see things.

 

[Tom Kalbfus]

Actually the second kind is a sublight warp drive, basically it accelerates a frame of reference around the starship up to the ship's hull displacement. 3-g's won't kill the crew. Mercury astronauts experienced more than this.

It may seem similar to the Alcubiere warp drive concept, but it's actualy different. The apparent similarities hadn't occured to me or I'd have tried to be clearer. In a warp drive local space around the ship is 'flat' and space in front of the ship is contracted, while space behind it is expanded. The vessel itself, or anything else in the bubble, isn't in a gravity field. If you look at the 3D representation of the warp bubble in the Wikipedia article you'll see the interior of the bubble is flat. In a gravity drive, Larry Niven called it the Gravity Planar, the drive generates a local gravity gradient, so the gravity field across the ship is tilted.

I should have been clearer about what I meant by sustained accelerations. Pilots and astronauts routinely experience accelerations from 3G or more for short periods of no more than a few minutes. Traveller assumes ships routinely cruise at their maximum acceleration half way to heir destination, then decelerate again at the same rate for the rest of the journey. 3G or more acceleration for even relatively short interplanetary journeys would cause severe trauma or death.

Simon Hibbs

Unless they are in water tanks. A water tank converts the gravity pull into water pressure. Under 1 full gravity, every 10 meters is 1 additional atmosphere of pressure, under 3 gs the pressure gradient would be one atmosphere every 3 and 1/3 meters. If you are standing, then the water pressure is greater on your feet than your head, so that prevents te blood from pooling towards your feet. Of course every cubic meter of water has the mass of 1 metric ton.

 

[F33D]

Unless they are in water tanks. A water tank converts the gravity pull into water pressure.

No, it doesn't. When you go under water in a pool your body is STILL experiencing 1 G of acceleration. If you have every been in free fall or under zero G conditions you know that because you lack that "falling" sensation in water. Why? Because your body is experiencing the same acceleration it does while not in the water.

 

[Tom Kalbfus]

Unless they are in water tanks. A water tank converts the gravity pull into water pressure.

No, it doesn't. When you go under water in a pool your body is STILL experiencing 1 G of acceleration. If you have every been in free fall or under zero G conditions you know that because you lack that "falling" sensation in water. Why? Because your body is experiencing the same acceleration it does while not in the water.

But the water exerts equalizing pressure on your body to counter the blood pooling to your feet, So long as you body is mostly immersed in water, you should be alright, so long as you make allowances for breathing, eating and elimination. Probably virtual reality could also help for those people trapped in those tanks for extended periods of time. If you could accelerate at 6 g for 2 months, you would reach the same speed as you would after accelerating for 1 year at 1 g. Why would we do this? In the real world, we probably don't have artificial gravity or reaction-less engines, instead, what we'd use is beamed propulsion, say a laser sail for instance, the problem is, the laser that pushes the sail spreads out as you increase the distance from its source, so you will want maximum acceleration before you get out of range of the sail, so you want to accelerate quickly to achieve maximum velocity.
You probably won't find this in your standard Traveller campaign.

 

[F33D]

But the water exerts equalizing pressure on your body to counter the blood pooling to your feet, So long as you body is mostly immersed in water, you should be alright,

For no more than 2 G's for a medium time. Your organs are still being pulled. Higher than 2 G's and you die in a short time. The blood will still pool as the pressure is EQUAL across your body. Just like out of water...

 

[Tom Kalbfus]

But the water exerts equalizing pressure on your body to counter the blood pooling to your feet, So long as you body is mostly immersed in water, you should be alright,

For no more than 2 G's for a medium time. Your organs are still being pulled. Higher than 2 G's and you die in a short time. The blood will still pool as the pressure is EQUAL across your body. Just like out of water...

A little test, ever get out of bed too quickly and feel dizzy? Your heart has to work a little harder when going from a lying down position to a standing up position, That wouldn't be true if the water pressure equalized your blood pressure.

 

[ShawnDriscoll]

One day, maybe we'll understand what gravity is and how it works. For now, I'm not about to say how it should work in a role-playing game.

 

[Condottiere]

That's why space fighter pilots are called Ariel.

Going from the Mongoose context, inertialess drives are probably the same tech level as hop drives.

 

[Tom Kalbfus]

One day, maybe we'll understand what gravity is and how it works. For now, I'm not about to say how it should work in a role-playing game.

We know what it does.

 

[simonh]

Divers immersed in water aren't in zero-G, it's just that the water supports them very evenly over the lower surface of their body. That's why you don't feel the stomach-churning feeling of the insides of your body floating around all over the place. Thy're still pulled down by gravity and suspended by the membranes and connective tissue inside your body.

http://en.wikipedia.org/wiki/Weightlessness#Neutral_buoyancy

Simon Hibbs

 

[Reynard]

Traveller M drives are reactionless, not inertialess. They use gravitics (HG page 42) to propel without an actual need for Newtonian physics of a reaction engine. The ship still is affected by inertia, the ship and everything within wants to go in a straight line. When a ship changes vector, things within not essentially nailed down would rather continue the way they were going. The greater the forces, the more dramatic the effects. Without gravity fields, which intertial compensators are an extension, the insides of ships would be everywhere. 21st century ships barely register such inertia issues because they move and turn so slooooowly. AG/IC systems most likely parallel M drive development.

"If you remember your Star Trek episodes, those ships had intertialess drives."

I hunted through all my Star Trek tech manuals and the Impulse Drive is not inertialess. They are, in fact. reaction drives fueled by fusion reactor to produce superheated plasma which goes through subspace compression to increase mass then manipulated by vector coils for direction. Traveller M drives are actually more advanced.

The reason the ships crew get tossed is those massive attacks on the ship still get through to momentarily disrupt systems including the AG/IC. Notice the various panels sparking when redshirts fly over railings. Trek ships don't turn on a dime so, when they do make hard maneuvers, they strain every system. Notice they added the seat restraints in the movies.

I have seen images for Traveller with bridge chairs featuring restraints. AG/IC is not perfect.

 

[simonh]

Traveller M drives are reactionless, not inertialess.

Agreed, it's pretty common for the two to be confused with each other. I can't recall if MegaTraveller said the drives were reactionless or intertialess, but thery certainly meant reactionless from the way they described it. Any manipulation of the inertia of the ship, and especialy the people inside it, would have some pretty dramatic effects apart from just making it easier for the ship to accelerate. Many of those effects would likely be highly detrimental to the survival of organic life.

Simon Hibbs

 

[Reynard]

MegaTraveller maneuver (not gravitic) drive is a reactionless. Traveller: The New Era uses a variety of reaction drives. In Marc Miller's Traveller, the reactionless drive isn't available until TL 12.

I could not find mention in either Classic Book 2 Starships or Book 5 High Guard for whether maneuver is reaction or not, however, as pertains to this topic, Classic HG page 17: "Tech level requirements for maneuver drives are imposed to cover the grav plates integral to most ship decks, and which allow high-G maneuvers while interior G-fields remain normal.". Grav field and maneuver drive techs are, in fact, interdependent.

 

[phavoc]

MegaTraveller maneuver (not gravitic) drive is a reactionless. Traveller: The New Era uses a variety of reaction drives. In Marc Miller's Traveller, the reactionless drive isn't available until TL 12.

I could not find mention in either Classic Book 2 Starships or Book 5 High Guard for whether maneuver is reaction or not, however, as pertains to this topic, Classic HG page 17: "Tech level requirements for maneuver drives are imposed to cover the grav plates integral to most ship decks, and which allow high-G maneuvers while interior G-fields remain normal.". Grav field and maneuver drive techs are, in fact, interdependent.

Interdependent, or independent? As I read that quote the grav plates generate their own field that is independent of the maneuver drive. Which is essentially overriding or canceling out the inertia generated by the drive plates. But if it's localized and you can dial it down to zero then the inertia of the drive would be applied, and thus things would go sliding towards the same direction the drive field is going. OR, the field, even at zero-g settings, is still being generated and countering the drive field. I think the latter would make more sense, not to mention be a lot safer.

In classic ST the tv series (no add-on's there), the ships had inertialess drives because they could stop on a dime when Kirk ordered all stop. They could be reactionless, but still be intertialess. However ST still had control over gravity, so there's that added complexity too.

If you recall some of the episodes had their chairs falling over too, except Kirk's. It's good to be Captain!

Thanks for digging those references up.

 

[F33D]

That wouldn't be true if the water pressure equalized your blood pressure.

Correct. which is why standing/lying in water won't save you from being killed long exposure to high G conditions.