How does Traveller handle artificial gravity on ships

[atpollard]

I've always taken the maximum thrust vs tech level (first seen in CT High Guard) to represent not the limits of thrusters, but the limits of the life support gravitics to perform inertial compensation.

Trouble with that approach is that there are non-gravitic ways of mitigating maneuver Gs. Even if the grav-plates can only nullify/create 1G (minimum for "normal" operation) that only leaves 5G to compensate for, and there are rollercoasters that throw that at you (briefly). Fighter jockeys pull 8G turns without blackout, using reclined seats, G-suits and special breathing techniques.

Even if you reckon the maximum G-force that can be sustained for hours is 2 or 3, that means the minimum thrust rating would be 3 or 4, if the internal gravitic compensation was the limiter.

G tolerance beyond minutes of exposure is extremely low. Prolonged 2G exposure will kill some prople and extended 3G will kill most people. The heart cannot pump blood to the brain and the veins cannot return it from the legs.

Except for brief military-maneuvers, hyper conditioned crews, or augmented people - the uncompensated upper limit for travel will be less than 2G.

 

[Shiloh]

I've always taken the maximum thrust vs tech level (first seen in CT High Guard) to represent not the limits of thrusters, but the limits of the life support gravitics to perform inertial compensation.

Trouble with that approach is that there are non-gravitic ways of mitigating maneuver Gs. Even if the grav-plates can only nullify/create 1G (minimum for "normal" operation) that only leaves 5G to compensate for, and there are rollercoasters that throw that at you (briefly). Fighter jockeys pull 8G turns without blackout, using reclined seats, G-suits and special breathing techniques.

Even if you reckon the maximum G-force that can be sustained for hours is 2 or 3, that means the minimum thrust rating would be 3 or 4, if the internal gravitic compensation was the limiter.

G tolerance beyond minutes of exposure is extremely low. Prolonged 2G exposure will kill some prople and extended 3G will kill most people. The heart cannot pump blood to the brain and the veins cannot return it from the legs.

Except for brief military-maneuvers, hyper conditioned crews, or augmented people - the uncompensated upper limit for travel will be less than 2G.

So *compensated*, closer to 3 than 4 at minimum. Fine. I don't have the tables to hand, but I'm pretty sure they start at 1. And "maximum" has to cover "sprint" abilities. A high G escape to Jump distance is quite short, and if you know your crew is fit, strapped into acceleration couches (which can do so much more for you than current fighter seats) then you might even be able to sustain "Compensation + 4" Gs for useful durations. Such assumptions are not unreasonable for military or non-risk-averse (like adventurer) crews.

Indeed, if augmentation would help, you'd expect militaries with only 2-G compensators to be augmenting their crews with blood shunts for plugging into their life support couches so they can pull 6Gs for combat operations.

The whole approach just sets up more questions that you need to answer before you let people wander onstage. Is 6G the limit of the propulsion, or of the compensation? If the latter, and augmentation/wierd science can help with g-tolerance, then *all* spacegoing militaries will have augmented combat crews. I'm not saying those questions can't be answered, but they'll repay consideration.

 

[klingsor]

It seems safer to assume that 6G is a limit on the drives - and very probably the compensators as well in case anyone gets too clever.

With the layout of most ships even 1G acceleration without compensators is very nasty - suddenly the aft bulkhead wants to be the floor.

 

[Patron Zero]

Then to toss a monkey wrench into the discussion, can or do grav plates also operate as inertia dampers like such presented in the Star Trek universe ?

 

[collins355]

So *compensated*, closer to 3 than 4 at minimum. Fine. I don't have the tables to hand, but I'm pretty sure they start at 1. And "maximum" has to cover "sprint" abilities. A high G escape to Jump distance is quite short, and if you know your crew is fit, strapped into acceleration couches (which can do so much more for you than current fighter seats) then you might even be able to sustain "Compensation + 4" Gs for useful durations. Such assumptions are not unreasonable for military or non-risk-averse (like adventurer) crews.

Indeed, if augmentation would help, you'd expect militaries with only 2-G compensators to be augmenting their crews with blood shunts for plugging into their life support couches so they can pull 6Gs for combat operations.

The whole approach just sets up more questions that you need to answer before you let people wander onstage. Is 6G the limit of the propulsion, or of the compensation? If the latter, and augmentation/wierd science can help with g-tolerance, then *all* spacegoing militaries will have augmented combat crews. I'm not saying those questions can't be answered, but they'll repay consideration.

Not necessarily disagreeing with your points, but do remember that space combat is not air combat. In MGT a single space combat turn represents six minutes (in earlier editions of Trav it was even more per turn). So any personal tolerance to G is going to have to be pretty extraordinary even for the 'short sprint' you envisage.

 

[klingsor]

I believe they also act as compensators but I cannot recall a specific reference for this. However it is obvious that they must because the axis of acceleration is usually at right angles to the deck so any acceleration would be dangerous – lethal in the case of a long passageway. Unless of course the drives are inertialess which for me at least is a hand wave too far, that way lies Star Trek.

The comparison with G forces in aircraft is interesting but I fear basically irrelevant for the reasons succinctly posted by collins355, as well as the mismatch between axis I mentioned above. The difference between fighters where the crew are stripped in to an acceleration couch and a starship where you might need to walk about and do repairs or worse reload a missile rack is great indeed.

 

[GypsyComet]

I believe they also act as compensators but I cannot recall a specific reference for this. However it is obvious that they must because the axis of acceleration is usually at right angles to the deck so any acceleration would be dangerous – lethal in the case of a long passageway. Unless of course the drives are inertialess which for me at least is a hand wave too far, that way lies Star Trek.

Star Trek "gets away with it" through a combination of things, at least one of which (internal inertial compensation) is also part of Traveller. ST ships only put out a little in the way of actual thrust that has to be compensated. The rest, including the FTL component, is done via a mechanism closer to 2300AD's Stutterwarp, which effectively multiplies the small real thrust many times (orders of magnitude) with respect to the galactic frame of reference. As such, they are only slightly more of a handwave than Traveller already has in its Jump Drive. That's not to say ST doesn't do a LOT of handwaving, but that's a discussion for another time and place.

I know some of those who have fallen victim to the "Lies, Damn Lies, and Science Lessons" phenomenon will continue to complain, but honestly, as long as the referee and the Engineering player speak somewhat compatible technobabble, it really doesn't matter where the compensation is occurring. Game.

 

[Commander Drax]

I've always assumed that artificial gravity on board ship, is an artificial effect that simulates gravity, not the actual thing, certainly Traveller canon materials have always indicated that a ship's G field was local to the environment within the ship, i.e. it didn't extend outside it. the 50 K reference was for gravitic drives (which they all were in MegaTraveller) and was only relevent to sensors detecting gravitic drives (i.e. thrusters) and densitometers performing density scans on the aforementioned ship. My memory is getting fuzzy now, it's been years since I've looked at the Starship Operator's Manual, (excellent publication) which is where I get my 'facts' from.

An interesting alternative is to have grav plates mounted on the ceiling as they appear at the approximately the same time as repulsor technology, so objects are pushed away from the ceiling and stick to the floor as they would in a gravity field. Such a field would represent anti-gravity and be tuned to remain within the confines of the ship's hull and not be a threat to any planets nearby as they would quite naturally repulse from a strong gravity source, like opposite magnetic poles, the largest mass being most resistant to change (and therefore staying put).

They would need negative mass

Handwavium at the moment, ho ho...

 

[Gee4orce]

I read something really interesting not long ago: one of the great unknowns of physics is what gives us momentum ? Momentum is more fundamental than mass, and can be thought of as the resistance to movement that an object has. The higgs-boson is thought to have a part to play momentum.

Now...what if objects have momentum because they are moving through some universal field that 'drags' on them. The more mass an object has, the more 'drag' it experiences, and the more momentum it appears to have.

Gravity can be thought of as a warp in space time - so even though you are standing still on the surface of a planet, space itself is flowing past you, therefor you are moving through this momentum field, and you experience gravity.

If momentum is caused by the interaction of mass and a universal field, it raises that possibility that it might be possible to shield an object from the effects of the field (giving it very low, even zero resistance to movement - therefore highly efficient and huge potential accelerations, and 'anti-gravity' effects).

Also, what if you could generate an artificial version of this field ? Yup - artificial gravity !

For me this IS the way anti gravity and M Drives work in Traveller - and what's fascinating this is actually a plausible explanation for them !

 

[EDG]

I think you're referring to inertia there, not momentum. Inertia is resistance to change of motion and an inherent property of mass, momentum is (mass * velocity squared).

 

[Rikki Tikki Traveller]

Bless you and your idea. (waving arms frantically)

If it works for you, then it is done.

It really comes down to "it works just like the Referee wants it to. Just be consistent.

 

[EDG]

I think I've heard the idea that inertia is a kind of drag caused by the mass moving through space-time itself, as if space-time has "friction" or something (probably what geeforce was thinking of). Which makes a kind of sense if you use the 'rubber mat' analogy of space-time, where massive objects make dents in the mat - if they move then they have to deform the mat as they move too.

If that's so though, then to reduce the inertia you would also have to reduce the depth of the 'dent' in the mat, which means that you effectively reduce the mass. Reduce the dent to zero and you effectively have reduced the mass to zero too in terms of motion - you'd have an inertialess drive, which means you can turn on a dime and do all sorts of wacky manoeuvres. (I'm not entirely sure what an inertialess drive means for conditions inside the ship - would the occupants still be subject to acceleration?).

Another option would be to reduce the 'friction' effect of spacetime. So the 'dent' remains the same, but the spacetime around it becomes more 'pliable' and behaves as if the ship has lower mass/makes a smaller dent. Sorta like an icebreaker, I guess. That would have the interesting effect of affecting things around the ship as well though.

 

[daryen]

Well, no matter how you slice it, you are "breaking" science.

So, just pick you favorite break and run with it!

 

[rust]

Well, no matter how you slice it, you are "breaking" science.

In our setting the humans bought their gravitics technology from an alien
species.
Human engineers have learned to duplicate the devices, but human scien-
tists still do not understand how they work.
According to the physics known to humans, these devices are impossible,
but the Sosdrabo insist that their children can understand the theory. On
the other hand, the Sosdrabo never managed to comprehend the human
concept of religion.

 

[saundby]

Reduce the dent to zero and you effectively have reduced the mass to zero too in terms of motion - you'd have an inertialess drive, which means you can turn on a dime and do all sorts of wacky manoeuvres. (I'm not entirely sure what an inertialess drive means for conditions inside the ship - would the occupants still be subject to acceleration?).

When I was using inertialess drives with traveller, I had it as a field that removed inertia effects between the objects inside the field and outside. Mainly because when I started to think of designing a ship and keeping people functional in an environment with no inertia I decided it was too much work. There would still be inertia in the ship, so things acted normally within that frame of reference. But they weren't subject to the effects of acceleration of the ship (enclosed in its field) with respect to the rest of the universe.

I had some fun with the physics of the universe, occasionally building plot lines out of things like tired light and sapient dark matter critters that could only interact with normal matter through gravitational effects.

 

[Gee4orce]

I think you're referring to inertia there, not momentum. Inertia is resistance to change of motion and an inherent property of mass, momentum is (mass * velocity squared).

Damn, you're absolutely correct.

The way I read the theory was that mass is a side effect of matter's interaction with the inertia field. If you were able to totally shield an object from this field you'd have zero inertia and effectively zero mass. This would cause practical problems though, as your starship would instantly zoom off at light speed on the solar wind... :?

For Traveller applications, I was thinking that the explanation is that a technology has been developed which can partially shield an object from this field - allowing these fantastic technologies like reactionless drives and AG.

For some reason, as long as there's a halfway plausible explanation for this stuff it sits better with me, and I'm a lot happier as I zoom around the 2-dimensional galaxy :roll:

 

[hdan]

Maybe the ship's reactionless drive can also push "forward" inside the ship's hull? Combine that with "grav plates" that push down from the ceiling, and you get most of the effect you need. Plus, your crew still gets thrown around by collisions.

(That could also lead to some strange situations in the engineering room!)

I dunno, just an idle thought.

 

[AKAramis]

I think you're referring to inertia there, not momentum. Inertia is resistance to change of motion and an inherent property of mass, momentum is (mass * velocity squared).

Damn, you're absolutely correct.

The way I read the theory was that mass is a side effect of matter's interaction with the inertia field. If you were able to totally shield an object from this field you'd have zero inertia and effectively zero mass. This would cause practical problems though, as your starship would instantly zoom off at light speed on the solar wind... :?

And EE 'Doc' Smith figured out how to cope with it quite well enough in his Lensman series.

 

[Supplement Four]

So these plates actually generate gravity?

Yes, through manipulation of the graviton, not unlike grav belts or air/rafts.

 

[Supplement Four]

Maybe the ship's reactionless drive can also push "forward" inside the ship's hull? Combine that with "grav plates" that push down from the ceiling, and you get most of the effect you need. Plus, your crew still gets thrown around by collisions.

The best description of this I've seen is found in MT's Starship Operator's Manual.

Reactionless thruster plates work by manipulating the "sign" of ions, changing postive ions to negative ions and the reverse.

This manipulation makes the ions repell from each other, not unlike like poles of a magnet.

The plate can be placed inside a ship, but heat becomes a real problem (which is why they are usually mounted externally).

A gyroscope is used in the center of the ship, encased in a sphere of T-Plates, all pressing towards the center. This gives the ship a point at which it can "push off" from, steering the ship in a given direction.