# GRAV plates and Grav Pong

#### HalC

##### Banded Mongoose
GRAV PONG - a topic being discussed in another Traveller forum elsewhere, but I thought I'd ask the question here to see what people think...

I'm sure that by now, many of you have heard the variation of Grav Pong for the Traveller Universe. Set up some gravity plates in a corridor, such that they are on the walls perpendicular to the normal orientation of walking down the corridor. This way, hijackers who attempt to storm the bridge will without warning, fall sideways. Or, better yet, have plates set into the ceiling and the floor, turn off the one on the floors while turning on the ones in the ceiling. Hijacker falls on his head and is prone on the ceiling. Turn off ceiling, turn on floor again, and hijacker falls to floor, possibly injuring himself. Keep alternating like PONG, hitting the floor, then the ceiling, then the floor, then the ceiling - resulting in a corridor that can't be traversed. Heck, there was even mention of generating up to 6g's of force on the plates - making things worse.

My gut instinct was to say "sounds nice, but..."

What's the but?

Take a single rod of steel, say, 8 feet in length. Anchor each end of that rod into something sturdy - so that it can't come loose. Now. Subject the center of that 8' long rod to a section of gravity that is 6g's for about 2' on either side of the exact center. What kind of stress did we just apply to the rod?

Now, imagine the following scenario: You're kneeling on the floor. Your torso is directly parallel with the ground. Your body is in a 1 G field, as is your neck and your head. But suddenly, because your neck (half of which is in the 1g field area, the other half in the 6g field) is subjected to a massive disparity in grav fields. What happens to the man who suddenly suffers what amounts to whiplash? How severe would that injury be?

Now imagine, a child getting their hands on the controls of the plate and changing the gravity settings INSTANTLY?

Somehow, I just can't see such things being manufactured in a way where carelessness or deliberate misuse could cause injury. I can't imagine that the manufacturers would allow for such a rapid change without trying to build in safety interlocks to prevent such an event from occurring. Last but not least?

How would you feel if your son was walking down a corridor in school, and some joker placed a 6g field plate under the stairs he has to walk down - and instead of a .78 g gravitational field that the planet normally has, it now has a 6.78 g gravitational field JUST as the kid was walking down the stairs. One has to wonder - if one falls 3 feet in a 1 g field, they might have minor issues, possibly even a torn muscle or what have you. But what would that 3 feet distance feel like in a 6.78 g gravitational field?

While it may be amusing or even gratifying to have such a defense aboard a starship - I can't help but think that for the reasons outlined above, grav plates are not designed to be able to change gravity settings quickly, nor to the extreme of 6 g's. In fact? I can't imagine the plates having sufficient gravitational pull past say, 1.5 g's at best - and that only for heavy worlders.

Going back to CT sources I can find no reference to anything but a 1g field for the grav plates and separate acceleration compensation (which would have to be capable of offsetting the ship's maneuvering). I know I am missing something, need to read more thoroughly later.

In the original The Traveller Adventure it is mentioned that the grav plates can be reversed either locally or by the ship's computer.

Switching off the grav plates and acceleration compensators can turn corridors in ships into death traps since the maneuver drive thrust will then dictate which way is down...

Sigtrygg said:
Going back to CT sources I can find no reference to anything but a 1g field for the grav plates and separate acceleration compensation (which would have to be capable of offsetting the ship's maneuvering).

In the original The Traveller Adventure it is mentioned that the grav plates can be reversed either locally or by the ship's computer.

Switching off the grav plates and acceleration compensators can turn corridors in ships into death traps since the maneuver drive thrust will then dictate which way is down...

Probably a good reason to board only when the ship is stationary. On the flip side, can one turn off the acceleration compensators such that it only affects a portion of the hull and not all of it? If so, would not the stresses involved cause problems to the hull itself where portions of its hull is unstressed, while other portions are stressed?

It's vague, since you wouldn't think a commercial variant would exceed two gees, and if there was a hefty cost benefit, why not just install half to four quarters maximum, and let the passengers get a load off their feet.

It seemed very much tied into inertial compensation, when maximum acceleration was six gees, and a side benefit was anti hijacking traps.

You probably have to engage a security override, whose code would only be known to the Captain, possibly First Officer and Security Chief.

Sigtrygg said:
Going back to CT sources I can find no reference to anything but a 1g field for the grav plates and separate acceleration compensation (which would have to be capable of offsetting the ship's maneuvering).

S7 said:
The upper level forward is the passenger deck. Six passenger staterooms line the outer bulkheads while a large central area (26) provides recreational facilities and a galley. The grav plate floor fields for individual staterooms and for sections of the common area may be adjusted from 0.1 to 2.0 G, depending on the preferences of individual passengers.

TTA said:
Special Considerations:
...
Next, quarters for the Ebokin must be conditioned far the their use, with a higher gravity setting, an atmosphere mix simulating Yebab's, and a reddish-orange, dim lighting for each cabin.

Grav plating functions as the inertial compensator for the ship, ergo it would be built with copious redundancy. Otherwise a failure would mean serious injury, likely death, if it failed.

With that being said, being able to deliberately override it may, or may not be possible without a lot of jiggering of the software. Case in point is an airlock. Airlocks are designed to cycle between internal and external conditions, therefore it's pretty damn hard to override that, or should be at least for safety sake (explosive decompress = bad). So there are a lot of safety protocols that would need to be overridden or bypassed to do so.

Grav plating should function the same way. Possible, but not easy to do by design.

On the flip-side, if you are a boarding party, knowing that grav plating can be turned against you, it would be best to have a device that shorted-out - temporarily at least - grav plating to ensure it could not be turned against you. A cable or device that allowed you short out specific sections would be very handy. And if your boarding party was comfortable in zero-g combat, it would provide a bonus to the invaders and a skill check to non-zero g trained defenders.

AnotherDilbert said:
Sigtrygg said:
Going back to CT sources I can find no reference to anything but a 1g field for the grav plates and separate acceleration compensation (which would have to be capable of offsetting the ship's maneuvering).

S7 said:
The upper level forward is the passenger deck. Six passenger staterooms line the outer bulkheads while a large central area (26) provides recreational facilities and a galley. The grav plate floor fields for individual staterooms and for sections of the common area may be adjusted from 0.1 to 2.0 G, depending on the preferences of individual passengers.

TTA said:
Special Considerations:
...
Next, quarters for the Ebokin must be conditioned far the their use, with a higher gravity setting, an atmosphere mix simulating Yebab's, and a reddish-orange, dim lighting for each cabin.
Good catches, I knew I had seen something about higher g, but couldn't find it an a quick skim through.

phavoc said:
Grav plating functions as the inertial compensator for the ship, ergo it would be built with copious redundancy. Otherwise a failure would mean serious injury, likely death, if it failed.
Artificial gravity grav plates are a separate system to acceleration compensators. I have no doubt they are based on the same magic 'gravitics' principles, and may well be linked, but tehy are separate.

You can have ships with grav plates but no acceleration compensation...

Gravity: It is possible to alter the artificial gravity on board. Reducing gravity to zero will limit actions to the level of an attacker’s Athletics (dexterity) skill (see Zero Gravity on page 77). Gravity can also safely be increased up to 3G with an Engineer (computers) check, which will count as high gravity (see page 76).

Sigtrygg said:
phavoc said:
Grav plating functions as the inertial compensator for the ship, ergo it would be built with copious redundancy. Otherwise a failure would mean serious injury, likely death, if it failed.
Artificial gravity grav plates are a separate system to acceleration compensators. I have no doubt they are based on the same magic 'gravitics' principles, and may well be linked, but tehy are separate.

You can have ships with grav plates but no acceleration compensation...

I'd say that you could not create a completely different artificial gravity field w/o tying the two items together. However anything is possible. But at tome point they would need to be integrated, especially since the speed of ships is now far in excess of the old 6G limit.

Turn off the gravity while the spacecraft is accelerating at six gees.

Condottiere said:
Turn off the gravity while the spacecraft is accelerating at six gees.

Hopefully built-in failsafes would not allow for the fields to fail immediately, but gradually, allowing personnel to try and get to a safe place. 6G's is survivable, for short periods at least. But turning off the field instaneously would be deadly to anyone not in battledress or with a personal antigrav device active.

Honestly, unless these artificial gravity fields have a magic cutoff point which goes from Xg to no effect in an instant, they're going to follow the inverse square law. As soon as gravity starts getting high retreat to a safe distance and work out a way around it (assuming gravity takes time to be turned up, of course).

Interestingly, having gravity work like this would mean that a stealth ship would either have to rely on centripetal gravity rings or have the crew suffer in free fall while in stealth mode (what? Traveller ships seem to rarely include radiators to deal with waste heat, so stealth is viable). Gravatic sensors would be able to determine the ship's position from the way the field varies. I suppose this is also how drive signatures work in the OTU.

Also, standard traveller ships have the deck oriented perpendicularly to the engines, which makes little sense (especially for unstreamlined craft and even moreso for distributed craft) unless the engines provide acceleration to the contents of the ship as well as the ship itself. Now this can be explained as the game designers not realising that if your engine is providing 1g of thrust you might as well use that as gravity, but assuming we have an 'acceleration field' drive means that we remove the ability to kill intruders by strapping the crew into acceleration couches and making sudden acceleration and deceleration at 6g until they're just red smudges on the walls.

The first reference to "Grav Pong" I remember was in the Traveller The New Era rules where it was something a Vampire ship (a starship that had been completely taken over by an AI, usually malignant to some degree) doing to the squishy humans inside. Perhaps it comes from an earlier era. I kind of gave it a pass in the TNE timeline as Vampires have essentially corrupted a starship and have had time to get co-opted engineers or something to modify the ship to the necessary level but I still find it to be "narrowed-eyes-Fry-from-Futurama image" worthy.

Regardless, there's a few observations I have about the idea of grav pong:

1) I've always found Grav Pong to be one of those ideas that RPG players think of as some huge (great) exploitable gap that (for me) fails the "Living World" test. The "living world" test, in short, is the concept that an RPG world simulates a world that is full of thinking beings, many of which are at least as intelligent as the players around your table and if your players have thought of it, likely not only someone but someones have probably thought of it before. This is particularly pertinent with something like this. This can't be the first time someone has thought of it. If it works so well everyone would have done it. If it's not being done, it's because there's some reason why it's not being done.

2) As others have pointed out, given how critical grav/g-compensation is for the very survival of everyone on board a starship, I don't think this is the kind of thing that would simply be controlled from the bridge or engineering. You don't want some disgruntled engineer or bridge staff just deciding to turn people into a fine red paste inside your ship. Moreover, the safety engineer in me has to ask: Why would you need to mess with a control like this a ship's normal operation? It seems like it'd be idiot-proofed several times over to prevent tampering, prevent failure, and so on with multiple redundancy to prevent fatal accidents from happening; there's likely safety devices that we haven't even imagined that exist in the Traveller Universe because they've been living with this technology for thousands of years (literally) and have probably had endless accidents and foul play experience to refine their systems.

3) Even if it could be done, I think it'd be about as easy as rigging every every door in a starship to remain open then opening the airlocks to space and ensuring none of the same doors close until the ship is depressurized. It seems to be that ships would be designed so this kind of thing doesn't happen by accident or design. Again, you don't want everyone in a ship at the mercy of just one deranged/disgruntled person.

4) Now it is possible perhaps, that a private ship owner might have sections of hallway modified so that it's not on the automatic safety g-compensation/artificial gravity circuit just so they can do things like this because if player characters are any indication of private starship owners, they're going to paranoid without much consideration of the implications of what they're doing. Perhaps these sections of hallway might have a switch in the bridge that lets you do stuff like this. But unless your Imperium is a very cynical place where life is extremely cheap, I don't think a modification like this would pass yearly starship inspection. In fact the corruption of basic systems like this is usually looked at as somehow more criminal than putting in lethal systems. For instance, just putting in remote control guns behind hidden wall panels in the hallway leading to the bridge and/or engineering (usable from the aforementioned places) is likely to be more easily made legal than a switch can crush people using the ship's own internal gravity.

5) What you can do to them, they can do you. All right, so maybe it is somehow do-able to play grav pong with your ship's internal gravity/g-compensation with little (or a lot) of effort. Here we go back to my idea of the "Living World" ... if we've thought of it, so have millions, perhaps trillions of people in the Traveller Universe. And likely hundreds or thousands who are in a position to do it have tried it. And if it's possible ... wouldn't any shipjackers be aware of this trick too? In fact, if it was so effective and so easy ... it'd be one of the first things shipjackers (and skiptracers) would think of when consider seizing a ship; these people know how dangerous this kind of thing is and are likely to have cased the ship before trying it. This leads to the question: How hard could it be for the shipjackers to hack into this clever "Grav Pong Splatter System" ... and turn it against the crew? They don't have to take the bridge or engineering. If they can remove wall panels or whatever to get into the wiring/cabling/communication system the bridge or engineering use to control this security measure, they could spoof being the bridge or engineering and splatter everyone on the ship (except for them) or shut it down ... or possibly make it send false sensor reports so that the crew thinks the intruders are splattered. When they emerge...nope they're not a fine red paste, surprise. (Meanwhile, Imperial Marines or mercenary boarding parties are going to be similarly familiar with this kind of thing - they're likely going to have some way to depower or deactivate the g-compensation from the outside, you know, by getting the beam-laser on their cruiser to surgically sever stuff, something that's probably likely given a boarding action is probably going to occur pretty close up to the target vessel.)

It seems to me that having such sharp and rapidly changing gravity gradients inside a ship would be very hard on the ship structurally.
Perhaps a hack into the computer controls for such a thing could cause fluctuations that set up destructive harmonics within the hull causing the ship to shake or vibrate apart.

A large part of Traveller is dealing with legacy issues, much like Microsoft has to have some backwards compatibility in their Windows operating system.

Everything used to be tied in somehow, manoeuvre drive, inertial compensation and artificial gravity; for commercial ships, it wasn't a big issue because acceleration was factored in three percent blocks and two was the sweet spot for non military vessels.

Outside of a gym or torture chamber, or a manufacturing module, increased gravity doesn't seem to have much cost benefit.

You have to clarify how inertial compensation is created, if not necessarily how it works,and the excess gravity option will be removed, mostly.

Thinking about this as a Starship Designer, I would have a LOT of failsafes in my gravity system to ensure this kind of event doesn't happen. My grav plates would have an internal battery backup so that when power is lost, the gravity slowly drops to zero over a couple of seconds, not all at once. The opposite would be true too.

In game terms, it takes one combat round for gravity to change from one value to another, up or down. So a Zero-G check prevents any damage.

Having said that - it should also be possible to override such a design. Thus a mini-adventure for the Engineer...

Note, this is NOT how the Inertial Compensators work - they are effectively instantaneous - if there was any lag, the occupants would be goo on the wall in the first combat situation. BUT, the IC system is not connected directly to the internal gravity plates. (lots of hand-waving here). The IC system is part of the Maneuver Drive. The Internal Gravity System is part of the Hull.

If the manoeuvre drive also resolves the issue of compensating for the inertia it creates, it could be considered an inertialess drive.

A question that has plagued the issue of inertial dampeners for a while has always been about the control of gravity by the floor plating (assuming it's in the floors, and not elsewhere). Assuming you can create your own localized gravity field independent of the rest of the universe, would you even need an inertial compensator? Why? Because you have already created an artificial gravity environment separate from the rest of the universe. So, in theory at least, your independent grav environment would be unaffected by your acceleration or maneuvers.

Of course, in order for this to work properly, the grav plating would have to have a field effect that went out in a 360 field. Otherwise you'd be be-bopping along the hallway, enter the access corridor to take the ladder down to the next deck, then you'd splat against the wall when you encountered the 6Gs from being outside the field being emitted from the floor. It could also allow you to toss a ball up towards the ceiling and see it zoom back away from the direction of the M-drive thrust.

Gravimetric Distorter: This weapon creates a distortion field that negates the effect of grav plating. Each gravimetric distorter can effect an area equivalent to one hundred tons of displacement ... This means all crew and items in the area will be subject to zero gravity conditions, unless the ship expends thrust in which case they will be subject to high gravity conditions ... The effect lasts for one round. These weapons are more commonly used by pirates than naval forces although dedicated boarding parties do sometimes make use of them.

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