Anti-gravity <> anti-mass

[phavoc]

To the best of my understanding of various Traveller versions (with some exceptions), vehicles equipped with anti-gravity devices are able to only make it to low orbit before their drive mechanisms no longer function. Which leads me to believe that their anti-gravity capabilities require an actual grav field to resist. Which explains the idea that starship and spaceship drives are still reaction(ish) based.

Also, the anti-grav drives counter the effect of gravity, but they don't have any effect on mass. Mass is something that nearly all versions of Traveller (with the exception of GURPS) ignored. Ships were concerned with displacement tons, which makes perfect sense. This is more of an academic discussion than anything else.

So if that's the case in deep space you have to use standard drives and thrusters to maneuver. And to move some of these ships in combat would require pretty energetic thrusters. Mass still matters and you need energy to effect it (LOTS of it if we are talking multi-thousand ton warships armored with collapsed matter plating).

In a planetary environment, I would assume that ships anti-gravity is used to raise/lower it, but it still requires its maneuver drives and thrusters to turn and move forward/backward.

Thoughts?

 

[Reynard]

One thing brought up in various versions of Traveller is vehicular AG devices are terribly weak compared to similar starship units. There is mention that mongoose maneuver engines are reactionless gravitic drives in contrast to the alternate reaction drive also available. Gravitic drives use a system's various gravity wells to grab onto.

I can't remember which offhand, T5 and/or maybe MegaTraveller, describing maneuver drive as manipulating quantum forces to move anywhere while lower tech gravitic drives were confined to near planetary orbit.

In each situation, the unit pulls or pushes on a powerful force and drags the volume attached to it along.

 

[Condottiere]

Which is where the old question as to whether the drives create a field effect comes from, which I would suppose imposing their own pseudo gravity field and/or well on the universe, that they perpetually fall into.

 

[dragoner]

Which is why I say they create a negative curve:

Hyperbolic n-space, denoted H^n, is the maximally symmetric, simply connected, n-dimensional Riemannian manifold with constant sectional curvature −1. Hyperbolic space is the principal example of a space exhibiting hyperbolic geometry. It can be thought of as the negative-curvature analogue of the n-sphere. Although hyperbolic space H^n is diffeomorphic to R^n, its negative-curvature metric gives it very different geometric properties.



(Stolen from wiki)

 

[Anonymous]

Hyperbolic n-space, denoted H^n, is the maximally symmetric, simply connected, n-dimensional Riemannian manifold with constant sectional curvature −1. Hyperbolic space is the principal example of a space exhibiting hyperbolic geometry. It can be thought of as the negative-curvature analogue of the n-sphere. Although hyperbolic space H^n is diffeomorphic to R^n, its negative-curvature metric gives it very different geometric properties.

But that doesn't make any sense to me... it probably doesn't make a whole lot of sense to anyone!

:shock:

Thoughts?

If we assume that the anti grav technology for vehicles and ships is based on the same theory I think we need to lay down some ground rules. I'd really like for the upcoming Traveller Companion to do this as I think it's a setting detail that impacts greatly on how players interact with the setting but I have a funny feeling that Mongoose is happy to let players choose what's right for their games. (This kinda goes back to that idea we were batting around about a MgT wiki. I would like to see a consensus on how these aspects of tech in the MgT setting work but I'm not sure how easy that would be to get).

MgT manoeuvre drives don't consume fuel, they're powered by the ship's power plant and therefore aren't a reaction thruster. If in the absence of a significant gravity well you move to reaction thrusters then you need to make a lot of space on a ship for fuel especially if you want to give the kind of accelerations that we're used to. 6G takes a heck of a lot of energy to sustain with reaction drives. If, as I believe is a popular interpretation and Condo has already mentioned, the manoeuvre drive is some kind of a field effect then I can see a field being projected in any direction. Some will say that the deck plans all have the drives at the rear and so this isn't "true" to which I say, the people drawing up deck plans didn't have any directives as to how the ships worked and simply drew them as aircraft from the 20th century and people have continued to do so ever since.

Now maybe, just maybe, the anti grav modules on a ship are able to negate a percentage of the ships mass and by doing so it takes considerably less energy to push the ship forward. The higher the drive rating, the more mass it can negate and the greater the acceleration the ship is capable of. We're currently developing drives like the VASIMR that use argon as a propellent that's super heated to plasma and shot out the back, takes a fair bit of power to do this and the amount of argon fuel is less than the reaction drives we've come up with so far. Who's to say how efficient the drives have become in the far future? And just like todays spacecraft and satellites, small thrusters and momentum wheels are used to control the craft's attitude.

 

[dragoner]

Hyperbolic n-space, denoted H^n, is the maximally symmetric, simply connected, n-dimensional Riemannian manifold with constant sectional curvature −1. Hyperbolic space is the principal example of a space exhibiting hyperbolic geometry. It can be thought of as the negative-curvature analogue of the n-sphere. Although hyperbolic space H^n is diffeomorphic to R^n, its negative-curvature metric gives it very different geometric properties.

But that doesn't make any sense to me... it probably doesn't make a whole lot of sense to anyone!

:shock:

Except math people - https://en.wikipedia.org/wiki/Hyperbolic_space :wink:

In simple terms, the drive creates a negative curvature in space that pushes it, the opposite of normal gravity.

I also kind of like the propulsion proposed that squeezes space through a venturi type quantum structure, one of the hypotheticals linked to in the NASA page.

 

[Anonymous]

It's hard (for me!) to imagine that a ship equipped with such gadgetry would look akin to the ships in Traveller which are basically aircraft.

Did you ever postulate on where on the ship such drives would be and how it might change the appearance of the ship?

 

[dragoner]

It's hard (for me!) to imagine that a ship equipped with such gadgetry would look akin to the ships in Traveller which are basically aircraft.

Did you ever postulate on where on the ship such drives would be and how it might change the appearance of the ship?

If the effect of the negative curvature is created behind the ship to propel it, then I guess the "drives" (now that is a term I'm not too fond of) would be in the rear of the ship, even the glow emitted could be part of the effect. Just to be simple, as you can see by going to the actual page, the idea behind it, and things like the Riemannian manifold: https://en.wikipedia.org/wiki/Riemannian_manifold aren't easy to visualize; as a negative curvature of space isn't actually a reverse of a normal curvature in n-space, like drawing a line in another direction.

The paragraph is hard to understand, and for what it is worth, that ability to manipulate space time, is also the prerequisite for the jump drive, which in my Traveller 'verse, is a False Vacuum Metastability event combined with quantum tunneling and bubble nucleation. It isn't simple, it shouldn't be simple, it is to us today, ultra-high technology, however to people in the future, it is just colloquial terms like the "m drive" or "jump".

 

[Anonymous]

I didn't make the question clear enough, does this negative curve also allow the ship to ignore the effects of a planet's gravity well and assuming that places the machines on the "underside" of the ship, did you tweak deck plans or just say it was built into the hull?

And, what should we call the heavy machinery at the back of the ship that pushes us forward?

:wink:

 

[dragoner]

What we call it now, a propulsion unit, I'm not even sure where "drive" enters into it.

The negative curve would create it's own effect, how it interacts with another source ... conjecture of the conjecture? I could see there being an effect and there being no effect, the effect being independent of the planetary gravity. IMTU there are also lifters, which basically reverse polarity of the native gravity environment, that is not as a good explanation though. I'm more comfortable thinking about hyperbolic n-space. I suppose the propulsion unit could create a bubble, or that the ships has landing lifters. The layout of ships could be descendent of aircraft, just to give people the fuzzy feeling of familiarity, same as they could eliminate windows on aircraft today but people would hate it.

My problem with the whole game-ism of tech levels, is that if I went back two thousand years, I could build a diesel engine to run off vegetable oil with what they had there, just with a little update to their casting ability. Business in fact calls technology "Knowledge Capital", which is fundamentally correct, as engineering deals with processes and systems that don't have an analogy to tech levels. On the other hand, I don't know how to replace that concept in game, at best I say it is just an arbitrary scale imposed by TL 15 Imperial Bureaucrats.

 

[Sigtrygg]

CT 77 - mdrive was hinted at being a reaction drive
CT HG1 - mdrive was defined as a fusion rocket
CT HG2 - mdrive not defined, spare EP grant agility which starts to imply electrically powered reactionless drive tomfoolery
CT 81 - mdrive not defined and hints at reaction drive removed
MT - reactionless quantum gravity handwavium bollocks
TNE - a deliberate return to reaction drives (HEPlaR) as was the intention in CT according to interviews
T4 - you can build reactionless drives or HEPLaR take your pick (the reactionless drives have a slightly different quantum gravity based handwavium)
T5 is a complete mess
MgT defines the mdrive as being some sort of gravitic reactionless drive without much in the way of quantim gravity handwavium.

IMTU the m-drive reduces the inertial mass of the ship (hence the volume requirement of the mdrive) and a reaction engine provides the thrust, hence the need to burn fuel and the illustrations of thrusters on the back of ships.

 

[Tom Kalbfus]

I didn't make the question clear enough, does this negative curve also allow the ship to ignore the effects of a planet's gravity well and assuming that places the machines on the "underside" of the ship, did you tweak deck plans or just say it was built into the hull?

And, what should we call the heavy machinery at the back of the ship that pushes us forward?

:wink:

All gravity, whether positive or negative obeys the inverse square law with distance, a planet is a much larger object than an antigrav vehicle, so you will have to travel a lot further from a planet that you would from an antigrav vehicle to diminish its gravity by the same amount. I would say that a grav vehicle flies because it pushes down on matter mostly that is close to it, so long as their is matter nearby, it can continue to ascend, whether that matter is air or ground or water, it doesn't matter, but when the matter surrounding it diminishes to a vacuum, then that antigrav vehicle has reached its operational height, it can maybe push itself into orbit, but that's it, it can't travel any farther without a maneuver drive.

That would also mean that grav vehicles can't fly as high above vacuum worlds like our Moon, than it can above planets with atmospheres, so there should be a chart which determines the operation height of a grav vehicle that varies with atmosphere type.

 

[phavoc]

Well, the drive could be a reaction-style drive, but it just consumes very tiny quantities of fuel. NASA is working on one of those now (a xenon drive I think), that has a very low specific impulse but it consumes tiny amounts of fuel, thus making it potentially feasible for constant propulsion. Traveller drives could operate on a similar principle, but be far more energetic.

Or not.

But I'm still curious about the mass part. If you can put enough power out of your drive units you can overcome any mass issue. But to be able to maneuver the ship requires equally powerful thusters that can spin the ship on any axis. And from all the illustrations the big drives are only mounted in the rear. The rest of the Traveller universe seems to adhere to standard Newtonian physics. I've always been of the opinion that the larger ships shouldn't be as nimble as they are sometimes made out to be. Otherwise there's conflicting descriptions of the technology and how it works (gasp!).

 

[Reynard]

"TNE - a deliberate return to reaction drives (HEPlaR) as was the intention in CT according to interviews"

TNE reverses what Mongoose does, making a reaction drive the official engine while thruster plates is an alternative.

"T5 is a complete mess"

To the unbiased, T5 is just fine, official and works well. Marc had the sense for an all inclusive book to include all the diverse maneuver drive types from all the past and present editions with great detail. I consider it a valid, authoritative source as ay other Traveller product. I actually own the book and know what I'm talking about.

 

[Anonymous]

Sigtrygg,

Thanks for the summary, I've not got access to CT or T4 these days and I didn't own MT it was good to read it all in one place.

What was written on the differences between anti grav on ships and vehicles?

Were any limits placed on grav vehicles in terms of altitude or manoeuvrability?

CT 77 - mdrive was hinted at being a reaction drive
CT HG1 - mdrive was defined as a fusion rocket
CT HG2 - mdrive not defined, spare EP grant agility which starts to imply electrically powered reactionless drive tomfoolery
CT 81 - mdrive not defined and hints at reaction drive removed
MT - reactionless quantum gravity handwavium bollocks
TNE - a deliberate return to reaction drives (HEPlaR) as was the intention in CT according to interviews
T4 - you can build reactionless drives or HEPLaR take your pick (the reactionless drives have a slightly different quantum gravity based handwavium)
T5 is a complete mess
MgT defines the mdrive as being some sort of gravitic reactionless drive without much in the way of quantim gravity handwavium.

IMTU the m-drive reduces the inertial mass of the ship (hence the volume requirement of the mdrive) and a reaction engine provides the thrust, hence the need to burn fuel and the illustrations of thrusters on the back of ships.

 

[Sigtrygg]

In CT grav vehicles are moved by null grav modules later shortened to grav modules. These provide lift against the local gravity and can be used to reach orbit, but it takes time.

Ship drives are much more powerful but are not mentioned as having the grav module 'lifters'.

In MegaTraveller it was spelled out that contragravity - the old CT grav vehicle grav modules - and the m-drive are different grav manipulation systems. Once agin though ships wouldn't mount both.

In TNE that changed - grav modules no longer provide movement only lift and so a secondary drive is required - a jet engine, rotors, sail even Ships can now use contragrav lifters to overcome gravity while their HEPlaR drive provides thrust. (Note a ship with 1g HEPLaR will struggle to lift from a 1g+ world without being built as a lifting body or having c-g lifters.

T4 maintained TNEs model.

T5 is a mess of confused drive types - NAFAL drives (STL drive to the rest of us), m-drive, contra grav, grav drives, reaction drives....

 

[phavoc]

"TNE - a deliberate return to reaction drives (HEPlaR) as was the intention in CT according to interviews"

TNE reverses what Mongoose does, making a reaction drive the official engine while thruster plates is an alternative.

"T5 is a complete mess"

To the unbiased, T5 is just fine, official and works well. Marc had the sense for an all inclusive book to include all the diverse maneuver drive types from all the past and present editions with great detail. I consider it a valid, authoritative source as ay other Traveller product. I actually own the book and know what I'm talking about.

TNE was a more rough-and-ready style system. I think had Traveller been TNE from the start it would have had more adventure possibilities insofar as the background tech and stuff. Though it would have had a continuity issue with building such a large space empire with the tech as such. And the whole idea of raiding to scavenge. And virus.. ah hell, there goes that theory..

T5 - Umm, well, I think opinions of T5 are mixed at best. I happily contributed to the kickstarter and once I got my very large book and had some time to go through it I just sighed and put it on the shelf where it's since rarely ever been taken down. I had thought that Marc was going to make the ultimate version, but it seems he never learned from his previous mistakes. One would have assumed that with the debacle of T4 and the really fine GURPS version he would have come up with something better. T5 is a really hot mess. It has lots of promise, but it's still a mess. And I'm basing that on someone who also owns the book and has owned every print version (except D20's) since the LBB's came out. And many other game systems.

I won't say T5 sucks (that's a valid opinion too) simply because I don't want to get into a flame war. But I will NEVER buy another Miller production sight unseen again - ever. From a game publisher perspective that's like the kiss of death.

 

[Condottiere]

The equivalent of marine diesels for cruising, though I'd suppose that would be more appropriate for the jump drive.

 

[phavoc]

The equivalent of marine diesels for cruising, though I'd suppose that would be more appropriate for the jump drive.

Starfire tackled this concept with splitting engines up into two types - military and civilian. To use a speed analogy, civilian drives traveled at a speed of 4, and military drives could do 6. But civilian drives were designed for constant use, while military drives required more maintenance time when running.

Tactically a military drive was superior. But strategically a civilian drive was better. That's kind of the same thing we see today. Civilian ships poke along at a decent speed mixing fuel consumption and speed, whereas military drives need to do high-speed, fuel guzzling at times, and much lower consumption for cruising from A to B. That's why when you read some ship descriptions and it lists their range it sometimes puts their cruising speed in there to indicate that the longer range is at cruising speed only.

 

[Anonymous]

Modern civilian shipping is faster than most people think. Before the recent fuel price increases, container ships were being designed for a service speed of 25 knots which isn't that far removed from the 30(ish) maximum you would expect from a warship: they're also several times heavier than a carrier.

Those 5 knots will make a big difference if the torpedo chasing you is only doing 30 knots like they used to, but the real difference is in agility and acceleration. (EDIT: Although the miltiary don't like azipods (directional thrusters) for some reason (they probably feel they are too vulnerable to damage), so I'm not actually sure about the agility issue... though a destroyer is like 1/40th the mass, so likely more agile despite the lack of azipods...)

Strategically a naval task force is as fast as the diesel-powered support ship carrying its fuel and ammo.