Ships Drives

[fusor]

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

There's something in FF&S (p76) about how "gravitic displacement lifters" (another alternate tech) on vehicles or ships would displace the mass of the vehicle downwards. So a ship hovering at 10 metres above the ground would still crush everything beneath it - the effect reduced with height somehow (being 'spread over a wider area'), so a ship 1,000 or 10,000 metres up wouldn't affect much on the ground, but that means that ships coming into land have to come in very specific flightpaths (usually over water, where they'd still make a big wake as they got lower) to avoid damaging anything.

But those aren't Thruster Plates. Maybe there'd be Cerenkov radiation in the atmosphere (a blue glow), but in space I don't think that wouldn't happen so there'd be no visible effect.

 

[Reynard]

A 'bright light' is actually proven to be another form of a reaction drive. Solar sails use bright light to move a object and lasers can use concentrated photon particles to push. The reactionless aspect is normally described as interacting with gravity wells figuratively grabbing or pushing against gravitational force. Ship maneuver drives are MASSIVE compared to lifters. Lifters in other editions have been described as negating gravity locally (contra-grav) and allows other thrust sources to manipulate a nearly weightless craft which is why 1g still works in +1g gravity wells. One edition (Marc Miller's Traveller?) also says the contra-grav can produce some lateral thrust. I think this one is the basis for how grav-belts work.

Nice thing about contra-grav and maneuver drives, no supersonic or hypersonic shock waves when coming to a ground landing. Floats like a butterfly.

 

[fusor]

Nice thing about contra-grav and maneuver drives, no supersonic or hypersonic shock waves when coming to a ground landing. Floats like a butterfly.

Also takes forever to land .

 

[alex_greene]

Nice thing about contra-grav and maneuver drives, no supersonic or hypersonic shock waves when coming to a ground landing. Floats like a butterfly.

Also takes forever to land .

Depends on the length of the backing track.

 

[Tenacious-Techhunter]

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.

Any good starship is also necessarily a good Faraday Cage (to keep out dangerously powerful natural and artificial RF sources), which should outright prevent anyone on a vessel from being killed that way.

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."

While a fusion rocket certainly could, in theory, be used in a planetary atmosphere, it would, in principle, be outlawed on planets slated for habitation. I wanted to find the relevant material on Atomic Rockets, but I couldn’t find it (it’s there, though).

 

[Tenacious-Techhunter]

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.

Or do they emit anti-gravitons, which, while particles in the strictest sense, wouldn’t produce any meaningful drag... but would “shove away” anything they hit.

 

[Tenacious-Techhunter]

A 'bright light' is actually proven to be another form of a reaction drive. Solar sails use bright light to move a object and lasers can use concentrated photon particles to push.

Strictly speaking, the sails themselves are reactionless, but they depend on a reactive source, such as nearby light sources. I would hardly describe the light itself without the sail a complete drive.

Lifters in other editions have been described as negating gravity locally (contra-grav) and allows other thrust sources to manipulate a nearly weightless craft which is why 1g still works in +1g gravity wells.

You either have more than 1g of Thrust, or you don’t. If you have another source besides your 1g contra-grav, you have more than 1g of Thrust. If you have 2g of contra-grav on a 1g world, you have 1g remaining with which to accelerate in any given direction. If your craft is a lifting body design, you then have some additional lift, and can apply the remaining acceleration laterally.

Nice thing about contra-grav and maneuver drives, no supersonic or hypersonic shock waves when coming to a ground landing. Floats like a butterfly.

This is not inherently true. If you enter with enough initial velocity, your contra-grav or maneuver drive isn’t going to decelerate you fast enough, and you will run into shockwaves. Admittedly, this sort of circumstance is a bit unusual, but they do happen. In the case of a smuggler in a streamlined ship trying to evade the authorities by “ditching to atmo”, for instance.

 

[wbnc]

A 'bright light' is actually proven to be another form of a reaction drive. Solar sails use bright light to move a object and lasers can use concentrated photon particles to push.

Strictly speaking, the sails themselves are reactionless, but they depend on a reactive source, such as nearby light sources. I would hardly describe the light itself without the sail a complete drive.

Lifters in other editions have been described as negating gravity locally (contra-grav) and allows other thrust sources to manipulate a nearly weightless craft which is why 1g still works in +1g gravity wells.

You either have more than 1g of Thrust, or you don’t. If you have another source besides your 1g contra-grav, you have more than 1g of Thrust. If you have 2g of contra-grav on a 1g world, you have 1g remaining with which to accelerate in any given direction. If your craft is a lifting body design, you then have some additional lift, and can apply the remaining acceleration laterally.

Nice thing about contra-grav and maneuver drives, no supersonic or hypersonic shock waves when coming to a ground landing. Floats like a butterfly.

This is not inherently true. If you enter with enough initial velocity, your contra-grav or maneuver drive isn’t going to decelerate you fast enough, and you will run into shockwaves. Admittedly, this sort of circumstance is a bit unusual, but they do happen. In the case of a smuggler in a streamlined ship trying to evade the authorities by “ditching to atmo”, for instance.

Anything that involves a force acting on an object is a reaction drive. unless you are talking about something like Traveller 2300 Stutter drives one force acts on the object to move it. Solar Sails work because the object is moved as a reaction to the impact of particles on the sail. The ship itself isn't generating the propulsive force but there is one, the object moves as a result of newtons laws...

technically speaking even a Warp/Alcubierre drive is a form of reaction drive. The ship is propelled by being pushed or pulled by the contraction or expansion of space. it's riding a shockwave to move, even if the shockwave is just a distortion in timespace. Or timespace outside the field is pushing the distortion along.

II think the issue with M-drive is more accurately is a ship ejecting mass or energy to achieve propulsion. or is it using outside forces to move?

Contra/Anti grav uses local gravity to move. The field is propelled away from the ambient gravity field. the ambient gravity field acts like wind on a sail to move the object.

A graviton based drive ejects exotic particles that have the effect of a reaction mass. The ship uses no fuel in addition to the reactors fuel supply since the system creates it's own reaction mass by converting electricity/electrons into gravitons.


If a ship could manage to unfold spacetime around it and negate the effect of its own mass on spacetime, or better yet expand space to produce a negative mass which would then attempt to move to a location with an equal negative mass..The field would move away from the mass/gravity of a planet or star, and the ship could surf that field using spacetime itself as a reaction force.

 

[fusor]

Anything that involves a force acting on an object is a reaction drive. unless you are talking about something like Traveller 2300 Stutter drives one force acts on the object to move it. Solar Sails work because the object is moved as a reaction to the impact of particles on the sail. The ship itself isn't generating the propulsive force but there is one, the object moves as a result of newtons laws...

https://en.wikipedia.org/wiki/Reactionless_drive

If it obeys the law of conservation of momentum then it's a reaction drive. Solar sails are "quasi-reactionless" in that they don't involve reaction mass but still obey conservation of momentum. An Alcubierre warp bubble is an oddball since no thrust is actually involved.

M-Drives as described in Traveller (i.e. "Thruster Plates") are explicitly reactionless - they convert power into motion without any reaction, thus violating the law of preservation of momentum. You just put energy in, and you get motion out.

 

[Tenacious-Techhunter]

Anything that involves a force acting on an object is a reaction drive. unless you are talking about something like Traveller 2300 Stutter drives one force acts on the object to move it. Solar Sails work because the object is moved as a reaction to the impact of particles on the sail. The ship itself isn't generating the propulsive force but there is one, the object moves as a result of newtons laws...

O.K., yeah, maybe the Sail is a Reaction Drive, transfer of momentum and all... but the light source is the active component.

technically speaking even a Warp/Alcubierre drive is a form of reaction drive. The ship is propelled by being pushed or pulled by the contraction or expansion of space. it's riding a shockwave to move, even if the shockwave is just a distortion in timespace. Or timespace outside the field is pushing the distortion along.

After double-checking with Atomic Rockets on the subject of “what constitutes a reactionless drive”, and by the same token, what doesn’t, I’m pretty sure that the lack of momentum transfer in Warp Drives and Alcubierre Drives pegs them as reactionless.

Honestly, I’m more inclined to call Soft Science-Fiction Drives bad and be done with it, so I’m underprepared for this argument.

 

[Tenacious-Techhunter]

If it obeys the law of conservation of momentum then it's a reaction drive. Solar sails are "quasi-reactionless" in that they don't involve reaction mass but still obey conservation of momentum. An Alcubierre warp bubble is an oddball since no thrust is actually involved.

That was certainly my take on it when I initially posted it.

 

[alex_greene]

Honestly, I’m more inclined to call Soft Science-Fiction Drives bad and be done with it, so I’m underprepared for this argument.

There is an awful lot of what looks like bad science in Traveller. Just as fantasy roleplaying games have a weird idea about how magic should work within the constraints of the fantastic settings in those roleplaying games.

Traveller, like all science fiction roleplaying game settings from Stargate to Star Trek to Star Wars, from Doctor Who to Firefly, is inherently handwavey when it comes to the science. Half the tech the settings take for granted would either fail or blow up in their faces if someone tried to build the equipment.

You may not like it, but bad science is an occupational hazard because each of these science fiction settings is predicated on technologies (warp drives, impulse engines, Stargates, Tardises) which modern scientific principles have declared to be impossible.

And Yet ...

You just have to accept that, somehow, settings such as Traveller take the what if, the and yet, the nonetheless, and make them work - to the point where the principles are so well-understood as to be taken for granted. The Engineers of the Far Future take M-Drives for granted, the scientists can explain how M-Drive works, and it's as simple to many of them as the workings of the internal combustion engine are to a car mechanic of the year 2016.

Tenacious, I sympathise that you just don't like the science, and you think it's rubbish. But on this forum, some folks have to accept that they're in the minority. You wouldn't wander into a D&D forum and tell them that magic is bunkum, for instance; it's a fantasy setting. It's like Star Trek's "Heisenberg Compensators," a key technology in transporters. When asked by Time Magazine in 1994 how they worked, Michael Okuda replied "Very well, thank you."

 

[-Daniel-]

Honestly, I’m more inclined to call Soft Science-Fiction Drives bad and be done with it, so I’m underprepared for this argument.

There is an awful lot of what looks like bad science in Traveller. Just as fantasy roleplaying games have a weird idea about how magic should work within the constraints of the fantastic settings in those roleplaying games.

Traveller, like all science fiction roleplaying game settings from Stargate to Star Trek to Star Wars, from Doctor Who to Firefly, is inherently handwavey when it comes to the science. Half the tech the settings take for granted would either fail or blow up in their faces if someone tried to build the equipment.

You may not like it, but bad science is an occupational hazard because each of these science fiction settings is predicated on technologies (warp drives, impulse engines, Stargates, Tardises) which modern scientific principles have declared to be impossible.

And Yet ...

You just have to accept that, somehow, settings such as Traveller take the what if, the and yet, the nonetheless, and make them work - to the point where the principles are so well-understood as to be taken for granted. The Engineers of the Far Future take M-Drives for granted, the scientists can explain how M-Drive works, and it's as simple to many of them as the workings of the internal combustion engine are to a car mechanic of the year 2016.

Tenacious, I sympathise that you just don't like the science, and you think it's rubbish. But on this forum, some folks have to accept that they're in the minority. You wouldn't wander into a D&D forum and tell them that magic is bunkum, for instance; it's a fantasy setting. It's like Star Trek's "Heisenberg Compensators," a key technology in transporters. When asked by Time Magazine in 1994 how they worked, Michael Okuda replied "Very well, thank you."

If this forum had a thumbs up system, I would give you one for this post. Well done.

 

[Tenacious-Techhunter]

There is an awful lot of what looks like bad science in Traveller. Just as fantasy roleplaying games have a weird idea about how magic should work within the constraints of the fantastic settings in those roleplaying games.

You’re missing my point. My point was, since I often dismiss “handwavium” for the uselessly unactionable mess that it is, I so infrequently put myself in a position of caring whether something is so completely nonsensical that it qualifies as a “reactionless drive”, that I wasn’t fully prepared to defend whether Solar Sails qualify as “Reactionless”; apparently, it may depend on just how much scrutiny you’re applying, and at what scope you are considering the issue. But, since you went so far as to open the topic of the legitimacy of handwavium for discussion, I’ll bite.


There’s a big tremendous difference between enjoying the fantastic and having to depend on those fantastic things. Characters in books, graphic novels, T.V. shows, and movies, they understand those things for us, and sometimes we enjoy it when they screw up. PCs don’t get that luxury.

Now, it’s all well and good if you describe a fictional system to such an extent that a player can meaningfully interact with it; disassemble it, repair it, upgrade it, and reassemble it, all on his own terms. If a player has everything they need to apply a fictional piece of technology to any real-world problem it could conceivably be used for, that’s fine; it doesn’t matter how nonsensical it is, so long as it is a complete system that can be used everywhere the real things it replaces can be used for. But, here’s the problem... Traveller canon has built itself on using handwavium to avoid that necessary level of precision. All these drive technologies we’re discussing? Predominantly nothing but weak empty words that sure sound nice, but aren’t actionable. You can’t reason about these things, because they’re so poorly specified; they’re all vaporware!

I like Hard Science Fiction. I really do. Because, by default, everything is actionable. You don’t need to learn a new law of physics; the ones you know work perfectly fine. You don’t run into any “invisible walls” of what a technology is supposed to do, or how it is supposed to work, because it’s all just pure fact. But I have no problem with fantasy, either, so long as it’s a legitimate system. My favorite fantasy RPG is Earthdawn. It has cute little systems for everything, all integrated together in a way that makes sense. And I have no problem with “Space Opera”, in principle...

But what I sincerely do have a problem with is when game designers cover up the holes in their work with meaningless flowery words instead of giving players the material they need to work with the technologies they’re describing; how to think about it, how to apply it to a problem it should be able to solve, and so on. It doesn’t matter how bad the science is, so long as it doesn’t take all of science down with it in the process. Because, after those flowery words dry up into earwax, the player has to be able to use that technology, just as if it were any other technology on his desk, or in his garage.

You just have to accept that, somehow, settings such as Traveller take the what if, the and yet, the nonetheless, and make them work - to the point where the principles are so well-understood as to be taken for granted. The Engineers of the Far Future take M-Drives for granted, the scientists can explain how M-Drive works, and it's as simple to many of them as the workings of the internal combustion engine are to a car mechanic of the year 2016.

Tenacious, I sympathise that you just don't like the science, and you think it's rubbish. But on this forum, some folks have to accept that they're in the minority. You wouldn't wander into a D&D forum and tell them that magic is bunkum, for instance; it's a fantasy setting. It's like Star Trek's "Heisenberg Compensators," a key technology in transporters. When asked by Time Magazine in 1994 how they worked, Michael Okuda replied "Very well, thank you."

If an RPG system isn’t making those fictional technologies in it as simple to the players as an ICE is to a car mechanic, it’s failing those players; because the players need to use that technology every bit as bad as the mechanic does.

But, ultimately, if you’re going to take the responsibility to do this sort of job right, it’s a hell of a lot easier to start from a Hard Science Fiction foundation, because at least then you know what physical laws you’re operating by.

 

[alex_greene]

You’re missing my point.

No ... it is you who is missing the point.

The point is, everybody else hears your words and acknowledges that you've got an opinion.

AND WE DON'T CARE.

 

[Reynard]

Quite frankly yes Alex. If T-T made a ounce of sense with his statements, every form of science fiction would have died out before it ever existed. His description of acceptable SF is pretty much drama set a year in the future. There is not one book, movie, tv show or RPG that can stand his rigorous standards. He can't actually be playing Traveller and may have read it just to point out it's totally unplayable. I'm sure every other SFRPG has met the same fate because no science fiction can meet the standards we've heard over and over. We're hearing a self appointed preacher determine to spread the word science fiction is the devil.

 

[madmike]

For all his pontificating, I have not yet seen a design or a published work of his exacting standards.

 

[Condottiere]

If I recall correctly, if we remove artificial gravity and it's associated technologies, we'd end up with a CoDominium flavoured setting.

 

[rust2]

If an RPG system isn’t making those fictional technologies in it as simple to the players as an ICE is to a car mechanic, it’s failing those players; because the players need to use that technology every bit as bad as the mechanic does.

This is where I think you miss the difference between the real world physics and the use of fictional physics in a roleplaying game. The players do not have to use the fictional technology at all, they do not have to repair gravitic engines and so on, they only have to describe the use of the fictional technology, and for this purpose the technology and the physics behind it can remain a "black box". The players only need to know what this "black box" does, not how it does it and what is inside - while this may be important for you, it is rather irrelevant for the majority of players, mainly because for them it does not provide any additional fun, and fun -and fun only - is why people play roleplaying games.

 

[phavoc]

In any event, regardless of the drive types, it seems to be accepted by most that maneuver drives operate under many of the same principles as reaction drives, with the primary difference being they have little to no exhaust (of if they do, it's not like a true reaction drive). So the engines are generally going to be in the rear of the ship pushing it forward, or perhaps located on sponsoons (like Serenity from Firefly).

If they are on gimballed arms, then it would indeed be possible to swing them forwards, dorsally, ventrally, or to the rear and provide thrust. Though Traveller doesn't take that sort of agility into account, so the issue would be relatively moot beyond aesthetics.