Ships Drives

[alex_greene]

You wanted to know which sort of drive people prefer. I prefer:

And having now described what you prefer, you have to let other people tell you what they prefer, even if it means that you, personally, have to suffer in silence.

When someone tells someone else "I'm not going to let you get away with ...," you cross a very large line of forum etiquette. Here, on the forum, you have to let everybody have their say, even if everybody else's opinions were diametrically opposed to yours.

For all you know, Marc W Miller His Own Self [praise be unto him] might decide that, from tomorrow, Traveller ships are not powered by fusion and propelled by M-drives, but are rather pulled along by trained geese. You, personally, would not have a say in that. Though you can have an opinion, and even share that opinion freely.

But you cross the line when you expect others to stop having their own opinions and to fall in behind yours.

 

[phavoc]

My take on the while propulsion question is that it doesn't matter if it's reaction based, or reactionless. But engines still function the sake way. They all act like a regular rocket engine. Turn them on and they push your ship in a direction. Smaller ones are used to turn or rotate the ship using the same method as your primary engines. You still have to accelerate, flip, then decelerate to arrive at zero relative rest at your destination.

Whether or not they function like an EM drive and have no need to expel particles, they act like ion drives, or plates or a Saturn V engine, it's inconsequential to their usage.

Now it does become important if you are for example, talking about their visual or IT footprint and how far away you can spot a ship under power. But the game mechanics have never really taken into account the little fact that you can't have "dogfights" in Newtonian physics. Unless one ship was following the other, two ships or fleets would interpenetrate each other and fire as they passed. It could take hours to simply stop. That's too much crap to deal with for a game, which is why it isn't there.

Beyond that I've always seen ships using anti grav to neutralize gravity, but then using thrusters to spin to maneuver and then engaging their main engines (that all have the capability to slowly add thrust) to actually move. Thrusters work in atmo, too, but are nowhere near as useful or capable as aerodynamic surfaces at speed. Though amy ship at rest can't use their control surfaces until they are actually moving. Vehicles would use anti-grav for thrust, too, but not ships because the ship would not install two parallel systems since it doesn't have the space, nor real need since anti-grav doesn't make the ship any less massive in a grav well, so it still takes a lot of energy to simply make it turn.

In my view that is relatively simple, it works and fits. As a reference or player you can then model your actions based on more or less real world processes. We are already stretching science to create the Traveller univerae, so there's no need to stretch it further without a valid reason and a reasonable payback in utilization.

Now, if we are talking UFO's, 1969s TV series of the same name, ELO album covers or shis based on 80s Simon game machines, then anything is possible. But for Traveller game mechanics that's my interpretation. Which is why I don't like the rule change allowing someone to dock with a starship under power and that's trying to avoid the effort. It would be akin to a fighter trying to refuel from a drogue line behind an aerial tanker that doesn't want to share. Sure the fighter is more maneuvable and faster than that slow tanker, but it's still a somewhat delicate operation that requires effort and cooperation in the best of times.

 

[Tenacious-Techhunter]

Oh, sure, you resolved it... but you didn’t reason about it. You used a roll to avoid reasoning about it. I’m just not letting you get away with what is clearly a dodge, rather than a legitimate response.

On the game table, there is no reasoning in the sense of talking the GM into things that clearly would bend the game system. Resolve by roll or resort to rules. If both fails, apply common sense taking canon setting infos into account. Other than that, out of luck.

The GM and the players both need enough information in order to logically conclude results from physical phenomena. Otherwise, the GM and the players will be at odds over an outcome that should be a purely physical result. Vagueness allowing for more than one interpretation of results from a fixed set of starting conditions is inexcusable; it detracts from players being able to understand their environment enough to make workable plans, and then achieve the legitimate results from those plans, instead of forcing a GM having to make up nonsense on the fly to cover for poorly characterized technology. In case you didn’t understand it before, this is what I mean by “reasoning about” a given piece of technology; it has to make enough sense that player characters can use it in the same way that real world people use real world things, with all the improvisation that that implies.

 

[AnotherDilbert]

My take on the while propulsion question is that it doesn't matter if it's reaction based, or reactionless.
...

Now it does become important if you are for example, talking about their visual or IT footprint and how far away you can spot a ship under power.

Any reaction drive would leave a noticeable wake, as in deadly.

A 200 dT Free Trader has a volume of 2800 m3 and a loaded weight of perhaps 2800 tonnes, to accelerate it at 1 G ≈ 10 m/s2 would take a thrust of 2800000 * 10 ≈ 28 000 000 Newton = 28 MN, roughly the same as the first stage of a Saturn V. A Type T would be about 8 times more. A large ship would be orders of magnitude more noticeable.

Since we do not use most of the ship as reaction mass, the mass we do eject must have a ridiculously high velocity, as in very near light-speed. The M-Drive would be a giant particle accelerator, and anything hit by the wake would take massive radiation damage. No-one would allow you to use it anywhere near an inhabited planet or space-station.


A reactionless drive makes everyone's life easier and you can use it without worrying about killing anyone.

 

[Tenacious-Techhunter]

If you're not fine with this, play another game. There is no - I repeat - no indication, how slight whatsoever, that either FFE or Mongoose are intending of revamping or rebooting Traveller in the next ten years. If you got a problem with that - and apparently you do - then find a game that suits your tastes better. But it really is tiresome to read post after post that you find both the mechanics and the setting crap and how it should be changed when clearly no other wants to do so and is in fact happy the way things are.

If you’re happy with Traveller abandoning the market, consistently running out of players, and dying off as a game, does it even matter what you think? If Traveller is determined to be something so obsolete it will never be viably publishable again, should that really happen without any opposition? Do you love Traveller so little that you are willing to consign it to only the people that already love Traveller, and not newer audiences that demand more?

 

[Tenacious-Techhunter]

That's my go-to description also. 1 cubic meter and 2 tons of drive charged with 1MW of power generate 40 tons of thrust and require a surface are of thrust/200 in square meters. That's all there is to remember (well, the price of MCr1 per unit also). Neat.

Now, see, that’s the kind of material that belongs in a Traveller book. You can easily improvise an Air-Raft with that.

 

[fusor]

That's my go-to description also. 1 cubic meter and 2 tons of drive charged with 1MW of power generate 40 tons of thrust and require a surface are of thrust/200 in square meters. That's all there is to remember (well, the price of MCr1 per unit also). Neat.

Now, see, that’s the kind of material that belongs in a Traveller book. You can easily improvise an Air-Raft with that.

I told you that was in the FF&S book.

 

[Tenacious-Techhunter]

And having now described what you prefer, you have to let other people tell you what they prefer, even if it means that you, personally, have to suffer in silence.

He already stated what he prefers. I am not disagreeing with what he prefers; he can prefer anything he likes, and I’ll have no opinion about that. What I am disagreeing with his insistence that the existing description of drive technology can be reasoned about; that you can draw logical conclusions about what will happen from a set of initial conditions, so that you can form an actionable plan; a very important criteria that enables gameplay. Engineering and Gadgeteering characters have very little to do if they don’t actually have the means with which to do those things.

When someone tells someone else "I'm not going to let you get away with ...," you cross a very large line of forum etiquette. Here, on the forum, you have to let everybody have their say, even if everybody else's opinions were diametrically opposed to yours.

When someone so strongly insists that something I’ve said is wrong, and then I offer a case that proves otherwise, and he goes out of his way to dodge that proof rather than admit being wrong (or at least keeping quiet about it in embarrassment), I’m going to call him out on his failure to defend his point. Allowing people to bring a patently false argument to the table just instigates disagreement.

But you cross the line when you expect others to stop having their own opinions and to fall in behind yours.

That is not what is happening here, and you are misunderstanding what is happening if you think that is what is going on. Please read the thread so as to have a full understanding of the circumstances.

 

[Tenacious-Techhunter]

That's my go-to description also. 1 cubic meter and 2 tons of drive charged with 1MW of power generate 40 tons of thrust and require a surface are of thrust/200 in square meters. That's all there is to remember (well, the price of MCr1 per unit also). Neat.

Now, see, that’s the kind of material that belongs in a Traveller book. You can easily improvise an Air-Raft with that.

I told you that was in the FF&S book.

Which has no bearing on what is published in Mongoose Traveller, 1E or 2E. If you were so aware of it, you could have answered my question.

 

[theodis]

In case you didn’t understand it before, this is what I mean by “reasoning about” a given piece of technology; it has to make enough sense that player characters can use it in the same way that real world people use real world things, with all the improvisation that that implies.

You made that clear. But: to meet this criteria, it is sufficient that a given piece of technology is consistent. It does not have to be plausible in the real world. If a drive unit consists of a box with faeries that push against the front part and you can boost the performance by kicking the box, that's really all that's needed to know. Well that and that the box and the box alone violates conservation of momentum. It's entirely besides a gaming point whether its possible in the real world or not.

 

[theodis]

That's my go-to description also. 1 cubic meter and 2 tons of drive charged with 1MW of power generate 40 tons of thrust and require a surface are of thrust/200 in square meters. That's all there is to remember (well, the price of MCr1 per unit also). Neat.

Now, see, that’s the kind of material that belongs in a Traveller book. You can easily improvise an Air-Raft with that.

I agree. FF&S was a pain in the ass for design sequences, though.

 

[Tenacious-Techhunter]

In case you didn’t understand it before, this is what I mean by “reasoning about” a given piece of technology; it has to make enough sense that player characters can use it in the same way that real world people use real world things, with all the improvisation that that implies.

You made that clear. But: to meet this criteria, it is sufficient that a given piece of technology is consistent. It does not have to be plausible in the real world. If a drive unit consists of a box with faeries that push against the front part and you can boost the performance by kicking the box, that's really all that's needed to know. Well that and that the box and the box alone violates conservation of momentum. It's entirely besides a gaming point whether its possible in the real world or not.

For a fantasy game, I don’t disagree; but, similarly, if the faeries can’t be built as PCs, you’ll need to know how much space a faerie takes up, how much a faerie can push, and for how long; which is just a throwaway number if it’s only used once, but if it’s used for every ship in the game, and other technologies besides, that becomes pretty important!

Earthdawn features paddle-boats driven by steam engines powered by elemental fire... sure, the elemental fire is an arbitrarily magical phenomenon... but once you have the “heat source” mapped out, it’s still a goddamn steam engine! You know how it performs!

 

[theodis]

If you’re happy with Traveller abandoning the market, consistently running out of players, and dying off as a game, does it even matter what you think? If Traveller is determined to be something so obsolete it will never be viably publishable again, should that really happen without any opposition? Do you love Traveller so little that you are willing to consign it to only the people that already love Traveller, and not newer audiences that demand more?

Actually, if I didn't like Traveller I wouldn't be playing it since 1986 (with some pauses in between). But yes, I couldn't care less whether it brings new audiences that demand more because in all likelyhood I will never have a chance to play with them anyway. Where I live, I can find enough people to fill a gaming table or two and that's enough. I'm done missionizing for a long time.
And... Traveller is in publishing for 39 years now, the current license for Mongoose is good for another 9 years (I think) and FFE isn't going anywhere. From where I stand, it looks like Traveller can easily make its 50th birthday just the way it is.

 

[alex_greene]

And having now described what you prefer, you have to let other people tell you what they prefer, even if it means that you, personally, have to suffer in silence.

I am not disagreeing with what he prefers

Good. Then consider the matter closed.

 

[phavoc]

Any reaction drive would leave a noticeable wake, as in deadly.

A 200 dT Free Trader has a volume of 2800 m3 and a loaded weight of perhaps 2800 tonnes, to accelerate it at 1 G ≈ 10 m/s2 would take a thrust of 2800000 * 10 ≈ 28 000 000 Newton = 28 MN, roughly the same as the first stage of a Saturn V. A Type T would be about 8 times more. A large ship would be orders of magnitude more noticeable.

Since we do not use most of the ship as reaction mass, the mass we do eject must have a ridiculously high velocity, as in very near light-speed. The M-Drive would be a giant particle accelerator, and anything hit by the wake would take massive radiation damage. No-one would allow you to use it anywhere near an inhabited planet or space-station.


A reactionless drive makes everyone's life easier and you can use it without worrying about killing anyone.

That's a good point. If Traveller maneuver drives operate along the way, say of how Star Wars ships do (cue the Millenium Falcon blasting out of Mos Eisley spaceport without blowing down any troopers with it's drive backwash).

We do know that rocket backwash in an atmosphere is pretty nasty, especially with bigger rockets. I haven't done much looking into rocket backwash in a vacuum to argue for/against it. The shuttle would use it's thrusters in close proximity to the ISS to undock, but those hyrdazine thrusters weren't particularly powerful, certainly not enough to do much more than low-speed maneuvers.

If we postulate reactionless thrusters, what sort of signature then would they have?

And as far as signatures and reaction mass... with the ability of multi-million ton ships to now have reaction thrusters that can boost them at high-G velocity, you now have your giant particle accelerator drives.

 

[Reynard]

One of the first stories I read about the Man-Kzin Wars was the first meeting of each race. Humanity had been programmed for generation to be non-violent. The Kzin immediately attacked with something like a microwave weapon cooking the inside of the human ship. The humans' panicked not knowing how to react to hostility and turned the ship around to flee. Their drive system acted like a gigantic laser beam tearing the Kzin ship apart. Backwash can kill.

F,F&S (Traveller: TNE) Page 71, Fusion rocket: First, cannot be used in a planetary atmosphere. Second, "Ships passing through its hydrogen wake will generally do so quickly enough that they will not suffer any ill effects unless within very short range (-200KM, referee's discretion). In this case, each crewperson must make a Difficult roll versus [Constitution] to avoid incapacitation by radiation (Average if wearing radiation-protective clothing) and each system on the ship suffers a minor damage result."

F,F&S (Marc Miller Traveller) also states using such an engine used in an atmosphere or a crowded orbital approach is considered and act of war.

"If we postulate reactionless thrusters, what sort of signature then would they have?"

A gravitic signature from within the ship at best. It's not actually creating a gravity well but interacts with them.

 

[wbnc]

One of the first stories I read about the Man-Kzin Wars was the first meeting of each race. Humanity had been programmed for generation to be non-violent. The Kzin immediately attacked with something like a microwave weapon cooking the inside of the human ship. The humans' panicked not knowing how to react to hostility and turned the ship around to flee. Their drive system acted like a gigantic laser beam tearing the Kzin ship apart. Backwash can kill.

F,F&S (Traveller: TNE) Page 71, Fusion rocket: First, cannot be used in a planetary atmosphere. Second, "Ships passing through its hydrogen wake will generally do so quickly enough that they will not suffer any ill effects unless within very short range (-200KM, referee's discretion). In this case, each crewperson must make a Difficult roll versus [Constitution] to avoid incapacitation by radiation (Average if wearing radiation-protective clothing) and each system on the ship suffers a minor damage result."

F,F&S (Marc Miller Traveller) also states using such an engine used in an atmosphere or a crowded orbital approach is considered and act of war.

"If we postulate reactionless thrusters, what sort of signature then would they have?"

A gravitic signature from within the ship at best. It's not actually creating a gravity well but interacts with them.

I'd imagine there would ba a good bit of turbulence from a starship-sized gravitic drive. enough to be noticed and make it a rough ride for any small craft entering the grav wake.since these drives actually produce a direct stream of exotic particles I imagine when they are taking off there would be a down wash, and side spray of particles as they collided with the ground. Enough to generate a good bit of dust and debris being tossed up if they are on unpaved areas, and depending on the particles used perhaps a bit of heat as high energy particles interact with the environment.

 

[Reynard]

Are we still talking Mongoose gravitic maneuver drive? Didn't we establish they are reactionless or is that still vague? High Guard separates gravitic maneuver from reaction drives. If maneuver produces particles (graviton particles?), it is a reaction drive. Then again, if it's using physical particles as thrust it really isn't manipulating gravity for lift and thrust. Not gravitic.

 

[Condottiere]

You could have a nuclear damper act as a catalytic converter for the fusion drive.

 

[phavoc]

Are we still talking Mongoose gravitic maneuver drive? Didn't we establish they are reactionless or is that still vague? High Guard separates gravitic maneuver from reaction drives. If maneuver produces particles (graviton particles?), it is a reaction drive. Then again, if it's using physical particles as thrust it really isn't manipulating gravity for lift and thrust. Not gravitic.

MGT is pretty vague on what the maneuver drive really is. That's part of the discussion. Is it truly reactionless (i.e a bright light), or is there SOME sort of exhaust, say like ions, or is there something more? I think it's not the latter.