Do MGT Traveller ships have anti-gravity for lift?

[phavoc]

Rather than disrupt the Tug thread I thought I would open this up here.

A question was raised that deserves an answer I think because it seems so fundamental to spacecraft operations.

Do you consider Traveller starships to have built-in anti-gravity/contragravity capabilities such that by using their antigravity alone they can ascend to orbit or descend from orbit without using their main drives?

If you answer NO to the above, then please state your understanding of this and how ships are able to land at a starport or anywhere in a gravity well.

 

[phavoc]

To answer my own question:

Yes, I believe all starships have an inherent antigravity capability that allows them to counteract gravity and maneuver without using their main thrusters. I believe starships have the ability to hover at will, and their main drives provide thrust to accelerate. Smaller thrusters spaced around the hull allow them to rotate, raise/lower their nose, etc. Their antigravity capabilities allow them to ascend/descend vertically, but otherwise do not provide any form of locomotion.

And their antigravity systems require a gravity field to work in, thus they are useless in space, or at least outside a planetary bodies gravity field. Their capabilities are inverse to the planets gravity, up to a certain level (whatever that is), at which point they would be overwhelmed and fail. So too far into a gas giant and you get squished no matter what.

 

[wbnc]

Thanks for the new thread. The question is key to that design being feasible but it needs to be discussed in detail.

do not know what the canon is for this question. But it would seem to be inferred that ships have some sort of gravitic drive system as part of their design. there are no illustrations that give ships the vertical thrusters needed to make a pure reaction drive based landing on a world with gravity and atmosphere. also illustrations show structures and other objects close to landing areas...this would be prohibited by the side wash fro a reaction drive.

assumptions based on artwork are fraught with flaws I admit but it does give some hints....caution: always remember assumption is the mother of screw ups.

 

[fusor]

I've quoted what TNE's FIre Fusion and Steel says about it a few times (that's probably the most in-depth that any canon product has gone about how the tech works in Traveller).

From FF&S pg 75:

The standard lifter used in Traveller is the contra-gravity device found on most spacecraft.
[...]
Contra-Grav
Many spacecraft have contra-grav (CG) lifters as fuel-efficient means of landing and taking off from a planet surface, and CG lifters are also used on grav vehicles. CG lifters do not provide thrust and so cannot physically lift a craft or vehicle. Instead, they neutralize most of the gravitational attraction of a world (approximately 99% of gravitational force, beyond which power use becomes prohibitive). This, combined with atmospheric pressure, will provide buoyancy in very dense atmospheres and so allow the craft to float at low altitudes, but usually CG is used only as an adjunct to the ship's thrusters. By neutralizing most of a world's gravitational field, a ship with only 1G of thrust can still escape the world's gravity well. Note that CG does not reduce the mass of the ship, and so a 1G thruster will still only produce 1G of acceleration; CG merely negates the gravitational vector of a world.

And this is on top of Thruster Plates, which work differently:.

Thruster Plates (FF&S pg 73):

Maneuver drives in previous editions of Traveller were explained as related to the same body of theoretical physics which allowed artificial gravity and damper fields, which is to say manipulation of gravitational force and the strong nuclear force. Artificial gravity was defined as a force which could either push or pull and which acted on the gravitational field of a mass. Clearly, this would not be an efficient means of travel outside of a gravity well, and so a further advance was postulated which allowed the force generated by the drive to push on the actual thruster plates of the ship itself, propelling it through space and achieving a true reactionless drive.

So that's what TNE says at least. Unless MGT says otherwise, maybe it'd be best to assume this is true in MGT too?

 

[AnotherDilbert]

I do not think that it is necessary.

I have used the MegaTraveller convention for a long time. It has M-Drives and Contra-grav, but starships do generally not have Contra-grav. SSOM describes how ships can land using just the M-Drive, the M-Drive can be overdriven for short periods of time and the trust can be vectored.

 

[-Daniel-]

I have always assumed they did, but now the question has been raised I realized I am unsure why I believed that was the case. Lacking any hard answer I think I will continue in that belief so I stay consistent. Then once we have a definitive answer I will adjust my thinking to fall in line with canon.

I will say, thanks for this very interesting conversation. It is a good thing to question things like this once in a while.

 

[AnotherDilbert]

I've quoted what TNE's FIre Fusion and Steel says about it a few times (that's probably the most in-depth that any canon product has gone about how the tech works in Traveller).

So that's what TNE says at least. Unless MGT says otherwise, maybe it'd be best to assume this is true in MGT too?

TNE also did not use M-Drives, but HEPlaR rockets, by default.

 

[AnotherDilbert]

MT Referee's Manual. Not a book I own. So going by what I do own, the HG both 1e and 2e, I would not have known it was a option in a non-core book. Curious and interesting.

This conversation has taken a very interesting turn. :mrgreen:

Referee's Manual is a core book in MegaTraveller (MT).

(I hope you don't mind i moved the answer to this thread.)

 

[-Daniel-]

MT Referee's Manual. Not a book I own. So going by what I do own, the HG both 1e and 2e, I would not have known it was a option in a non-core book. Curious and interesting.

This conversation has taken a very interesting turn. :mrgreen:

Referee's Manual is a core book in MegaTraveller (MT).

(I hope you don't mind i moved the answer to this thread.)

No I don't mind.

And yes, I didn't word my answer very well. I meant a core Mongoose book. Sorry. I went from CT to Mongoose for the most part. I have bought a few of the other books as folks have suggested them though. But I do realize this means I have missed some good back ground stuff, just like this.

 

[wbnc]

I've quoted what TNE's FIre Fusion and Steel says about it a few times (that's probably the most in-depth that any canon product has gone about how the tech works in Traveller).

So that's what TNE says at least. Unless MGT says otherwise, maybe it'd be best to assume this is true in MGT too?

TNE also did not use M-Drives, but HEPlaR rockets, by default.

If i remember right TNE was a setting where advanced tech was far less common than the Third Imperium setting.

 

[fusor]

I have used the MegaTraveller convention for a long time. It has M-Drives and Contra-grav, but starships do generally not have Contra-grav. SSOM describes how ships can land using just the M-Drive, the M-Drive can be overdriven for short periods of time and the trust can be vectored.

SSOM should be completely ignored for canon purposes (sadly. It's a good book, but it's DGP, and therefore not official canon).

And yes, HEPLaR was the default tech in TNE, but FF&S explicitly describes Thruster Plates as being the M-Drive used in previous versions of Traveller, which is what I quoted. It's as valid a description of the canonical tech as what's in MT, just more detailed.

If MGT doesn't go into detail about what ships have, then what are you to do? Leave it vague and unknown, make it up yourself, or go with whatever was described for it in previous editions? I'd rather do the last option myself.

 

[SSWarlock]

A possible circumstantial proof of MgT ships having inherent anti-grav lift ability is the Detachable Bridge option. Per HG 2e, page 38, "...emergency thrusters give it basic manoeuvring capabilities, equivalent to Thrust 0. A detachable bridge is even capable of soft–landing on a planetary surface."

Seems to me that aerodynamic design isn't usually part of a bridge's layout. So a soft-landing capability would be easiest explained as being due to anti-grav lift, which would function more like a parachute. Or at least that's my opinion. But if detachable bridges can do it, why wouldn't spacecraft? However, I'd assume some thrust is required to lift off. Thrust 0 just won't allow craft on a planet surface to achieve orbit.

Just my 2 CrImp's worth.

 

[AnotherDilbert]

SSOM should be completely ignored for canon purposes (sadly. It's a good book, but it's DGP, and therefore not official canon).

I have been given another impression over on COTI. I wouldn't know if it's canon, I just use it because it's a good resource. I will stop quoting it if you do not like it.

If MGT doesn't go into detail about what ships have, then what are you to do? Leave it vague and unknown, make it up yourself, or go with whatever was described for it in previous editions? I'd rather do the last option myself.

If it is left open to interpretation, your view is as good as anyone else's.

I do not use the TNE model since TNE used a completely different technological base for propulsion.


Thruster Plates (FF&S pg 73):

Maneuver drives in previous editions of Traveller were explained as related to the same body of theoretical physics which allowed artificial gravity and damper fields, which is to say manipulation of gravitational force and the strong nuclear force. Artificial gravity was defined as a force which could either push or pull and which acted on the gravitational field of a mass. Clearly, this would not be an efficient means of travel outside of a gravity well, and so a further advance was postulated which allowed the force generated by the drive to push on the actual thruster plates of the ship itself, propelling it through space and achieving a true reactionless drive.

I can't see that this says anything about the need for contra-grav. It just says that Thruster Plates produce thrust, it's no more detailed than the info in MT.

 

[AnotherDilbert]

A possible circumstantial proof of MgT ships having inherent anti-grav lift ability is the Detachable Bridge option. Per HG 2e, page 38, "...emergency thrusters give it basic manoeuvring capabilities, equivalent to Thrust 0. A detachable bridge is even capable of soft–landing on a planetary surface."

I read it the other way, "thrusters" are generally M-drive. Thrust 0 is even a M-Drive rating in MgT2.

 

[fusor]

SSOM should be completely ignored for canon purposes (sadly. It's a good book, but it's DGP, and therefore not official canon).

I have been given another impression over on COTI. I wouldn't know if it's canon, I just use it because it's a good resource. I will stop quoting it if you do not like it.

AFAIK it's not canon because Roger Sanger owns it (unless something has changed in the past couple of years?). I love the DGP books, but if you're talking about canon then those aren't part of it.

I do not use the TNE model since TNE used a completely different technological base for propulsion.

The "different technological base" is the default HEPLar rocket that TNE uses. The Thruster Plates in FF&S may be alternative tech for TNE, but they are explicitly there to represent the reactionless drive used in other version of Traveller. Therefore they are a canonical explanation for how those work (and it's pretty much as described in MT anyway).

I can't see that this says anything about the need for contra-grav. It just says that Thruster Plates produce thrust, it's no more detailed than the info in MT.

It doesn't. I just quoted the Thruster Plates section to show what that says. The Contragrav quote is what says that most ships have CG as well as an M-Drive.

 

[AnotherDilbert]

Effect of Gravity
When fighting in the presence of a significant gravity field that field acts as an additional “thrust” on the craft fighting within it.

This explicitly says that ships do not have contra-grav. If they had they would not be affected by the gravity field.

This is the same movement system as in LBB2, so CT ships do not have contra-grav either.

 

[phavoc]

Effect of Gravity
When fighting in the presence of a significant gravity field that field acts as an additional “thrust” on the craft fighting within it.

This explicitly says that ships do not have contra-grav. If they had they would not be affected by the gravity field.

This is the same movement system as in LBB2, so CT ships do not have contra-grav either.

If that's the case then how does the classic Scout or Free Trader land? Traders and scouts are supposed to be land anywhere on planets to do their job. This goes against all the illustrations and concepts these ships stand for.

I have never assumed that they do NOT have contragravity capabilities. I will have to look at my GURPs books to see what they say.

 

[AnotherDilbert]

AFAIK it's not canon because Roger Sanger owns it (unless something has changed in the past couple of years?). I love the DGP books, but if you're talking about canon then those aren't part of it.

I thought Traveller canon was unrelated to copyright, see: http://www.travellerrpg.com/CotI/Discuss/showthread.php?t=35735


From FF&S pg 75:

The standard lifter used in Traveller is the contra-gravity device found on most spacecraft.
[...]
Contra-Grav
Many spacecraft have contra-grav (CG) lifters as fuel-efficient means of landing and taking off from a planet surface, and CG lifters are also used on grav vehicles. CG lifters do not provide thrust and so cannot physically lift a craft or vehicle. Instead, they neutralize most of the gravitational attraction of a world (approximately 99% of gravitational force, beyond which power use becomes prohibitive). This, combined with atmospheric pressure, will provide buoyancy in very dense atmospheres and so allow the craft to float at low altitudes, but usually CG is used only as an adjunct to the ship's thrusters. By neutralizing most of a world's gravitational field, a ship with only 1G of thrust can still escape the world's gravity well. Note that CG does not reduce the mass of the ship, and so a 1G thruster will still only produce 1G of acceleration; CG merely negates the gravitational vector of a world.

This says that contra-grav is used to save fuel for the ship's thrusters, i.e. HEPlaR. M-drives does not use reaction fuel, so have no need for contra-grav.


Contra-grav is also specific to TNE, no other edition use it. Other editions use anti-grav that not only negates weight, but also produces thrust somehow.

I have used contra-grav, when I mean anti-grav, in this thread, sorry.

 

[fusor]

This is why I hate how Traveller defines drives and speeds. You need to know the thrust, and for that you need to know the mass (which is ignored in all but TNE). "G-rating" doesn't really help much.

 

[AnotherDilbert]

This is why I hate how Traveller defines drives and speeds. You need to know the thrust, and for that you need to know the mass (which is ignored in all but TNE). "G-rating" doesn't really help much.

I believe it's an obvious simplification. If the size of the drives are dependant on all other systems, the design system becomes iterative and fiddly. It's simpler to allow you to determine the size of the drives by hull size only.

I think the CT Striker vehicle design system based drive performance on actual mass. It works.