Best Movement System for Starships in Traveller is CORE RAW: Change my Mind.

[phavoc]

Take out inertia and you have Star Wars handbrake turns... innn ssppaaaccceeee

no, just no.

SW movement came from Lucas wanting to emulate dogfights, as small craft were the heart and soul of the movie universe. Never did we see capital ships behave in any other than what you would expect large ships to behave like (with the exception of the silliness of the SSD falling straight down when an A-wing crashed into it's bridge).

But Traveller also posits fighter "dogfights" and strafing runs... in a universe full of inertia... innn ssspppaaaccceeee. So you already have the silliness baked into the game.

The way to sidestep this would require a bit of handwavium - which isn't really as much of one considering. Some already argue for the magic of the M-drive, so why not simply add to the magic and make it so the drive emits a field around the ship that lets it do the silly things such as perform 180 degree turns to fire a spinal mount and spin back to it's original heading w/o losing any thrust movement for its' turn. This field also acts a sump of sorts for maneuvering. And by manipulating the field you can absorb your inertia and come to a full stop on turn zero, and then thrust in a totally different direction in turn one. This would mean you give up all your inertia, and a pursuing ship could quickly close the gap as it's inertia is not affected - though in practice it, too, would have to dump speed or else overshoot it's prey. To keep the rules cheaters from exploiting it too much, one could also implement a maximum breaking effect in the field, so that it would be akin to deploying flaps to slow your forward speed down, and it may take multiple turns to come to a stop. That's one way to do it.

A similar, simpler, way would be to say that the M-drive creates the field that reduces the mass of the ship to allow the gravitic thrusters to move the ship, and that with the field down the efficiency of the ships movement is greatly reduced - allowing for intertia, but also simplyfing the movement aspect of things.

In any case, if you put inertia in the game you should take out the idea of "random" ship encounters as there is no way in hell you can lie doggo at the 100D mark and intercept an inbound ship that already has a much higher delta-V than you can generate to intercept it from a standing start. And since you cannot detect an inbound jump ship (or intercept one that's been building delta-V for hours), piracy goes out the window. The argument that a ship could "coast" along known inbound jump routes works - but fails because the same ship would have to brake and halt its forward movement or else be discovered by planetary sensors and/or patrol ships and lose any pretense of surprise (and again you don't know when an inbound ship will appear, so the odds of interception piracy actually being successful drop close to nil).

So it really doesn't matter how much one like or dislikes different forms of movement, they all have massive gaps in believability if you still want to have any sorts of interaction between ships in a gaming universe where the sole method of moving between stars is jump drive using Millers rules as they are written. Keeping the same heading and velocity coming out of jump space as you had going in, interceptions simply aren't practical.

 

[MonsterX]

SW movement came from Lucas wanting to emulate dogfights, as small craft were the heart and soul of the movie universe. Never did we see capital ships behave in any other than what you would expect large ships to behave like (with the exception of the silliness of the SSD falling straight down when an A-wing crashed into it's bridge).

But Traveller also posits fighter "dogfights" and strafing runs... in a universe full of inertia... innn ssspppaaaccceeee. So you already have the silliness baked into the game.

The way to sidestep this would require a bit of handwavium - which isn't really as much of one considering. Some already argue for the magic of the M-drive, so why not simply add to the magic and make it so the drive emits a field around the ship that lets it do the silly things such as perform 180 degree turns to fire a spinal mount and spin back to it's original heading w/o losing any thrust movement for its' turn. This field also acts a sump of sorts for maneuvering. And by manipulating the field you can absorb your inertia and come to a full stop on turn zero, and then thrust in a totally different direction in turn one. This would mean you give up all your inertia, and a pursuing ship could quickly close the gap as it's inertia is not affected - though in practice it, too, would have to dump speed or else overshoot it's prey. To keep the rules cheaters from exploiting it too much, one could also implement a maximum breaking effect in the field, so that it would be akin to deploying flaps to slow your forward speed down, and it may take multiple turns to come to a stop. That's one way to do it.

A similar, simpler, way would be to say that the M-drive creates the field that reduces the mass of the ship to allow the gravitic thrusters to move the ship, and that with the field down the efficiency of the ships movement is greatly reduced - allowing for intertia, but also simplyfing the movement aspect of things.

In any case, if you put inertia in the game you should take out the idea of "random" ship encounters as there is no way in hell you can lie doggo at the 100D mark and intercept an inbound ship that already has a much higher delta-V than you can generate to intercept it from a standing start. And since you cannot detect an inbound jump ship (or intercept one that's been building delta-V for hours), piracy goes out the window. The argument that a ship could "coast" along known inbound jump routes works - but fails because the same ship would have to brake and halt its forward movement or else be discovered by planetary sensors and/or patrol ships and lose any pretense of surprise (and again you don't know when an inbound ship will appear, so the odds of interception piracy actually being successful drop close to nil).

So it really doesn't matter how much one like or dislikes different forms of movement, they all have massive gaps in believability if you still want to have any sorts of interaction between ships in a gaming universe where the sole method of moving between stars is jump drive using Millers rules as they are written. Keeping the same heading and velocity coming out of jump space as you had going in, interceptions simply aren't practical.

Inertia doesn't make dogfights unrealistic. It just changes the techniques and makes them look pretty crazy and wild to our eyes. Some episodes of Battle Star Galactica give this vibe, though they weren't very consistent about it. The Expanse episode where the Rocinante attacks the space station is a good example of a dogfighting in space sequence. It is not a matter of taking this fun thing away by insisting on boring science: rather it is a matter of knowledge of how this fun thing would actually work in space, (or not knowing and doing it wrongly (which actually makes it a less of a fun thing in the end) ) . The main thing to get a dogfight started is that you need to be on close to identical vectors and in close proximity. This you can do if you have a lot more thrust than your opponent and don't get shot down on the apporach.

There is no reason ships couldn't spin to point their weapons at their targets, shoot and then spin back regardless of heading. In fact, that's what they usually do in Traveller, to judge from the RAW. RAW ships shoot all their weapons every turn at any target they choose in range regardless of firing arc, which implies they are spinning around as needed. It is what happens in the Expanse when ships shoot each other, and it looks really cool and exciting.

Nobody has a "standing start" ever. The concept is meaningless. Each ship has a vector or an orbit around some object, unless it is sitting on the object. What that vector is, is a part of figuring out if you can intercept another ship - just like it's distance from your ship is. This doesn't change the overall possibilities of interception - it just means that you have to know two things about each ship: their location and vector.

There is no such thing as a "known jump route". This idea also makes no sense. Planets are the usual destination for ships and they are always in motion. So what would a "jump route" be? Any point in space or route where a jumping ship might appear to fly to a given planet will be in a very different location relative to that planet tomorrow, and a year from now it will be outside the star system in question entirely.

There is hope for aspiring pirates however, Finding ships in interplanetary space is difficult, but they come to gas giants and other fuel sources, where you can intercept them. Also, if you know where they are going and how fast they are thrusting you can find them by doing the math. Pirates need spies, sensor buoys and small craft scouts. Intelligent pirates don't pop up in well patrolled parts of well patrolled systems.

Erasing inertia somehow via technology raises all kinds of issues and questions which would have to be worked through, and these are really problematic for maintaining an interesting setting. All the physically impossible magic future techs in the game raise issues of how they interact with the game universe - witness all the discussions about jump drive's preservation of momentum or not, and m drives smashing asteroids into planets. These techs , or ones like them, are needed for the game to make the space opera work, though, so we have to do the work of figuring out how they interact with the rest of physics. Magic inertia erasers, however, don't add to the game, and so we don't need to do this work.

 

[MasterGwydion]

More or less I just ignore space combat. In Traveller it is basically like two ships of the line travelling parallel to each other and firing at each other. Combat in an atmosphere is way more fun and dramatic. Without air/water resistance dogfighting is basically impossible.

 

[phavoc]

Inertia doesn't make dogfights unrealistic. It just changes the techniques and makes them look pretty crazy and wild to our eyes. Some episodes of Battle Star Galactica give this vibe, though they weren't very consistent about it. The Expanse episode where the Rocinante attacks the space station is a good example of a dogfighting in space sequence. It is not a matter of taking this fun thing away by insisting on boring science: rather it is a matter of knowledge of how this fun thing would actually work in space, (or not knowing and doing it wrongly (which actually makes it a less of a fun thing in the end) ) . The main thing to get a dogfight started is that you need to be on close to identical vectors and in close proximity. This you can do if you have a lot more thrust than your opponent and don't get shot down on the apporach.

One typically does not "dogfight" a stationary object. BG cheated the hell out of the inertia by doing basically SW maneuvers - Cylons and Vipers would be accelerating towards one another and then instantly flip and accelerate in the other direction.

It's quite true that dogfights with inertia would be much different than we would expect. The only way TO have a dogfight would be to have similar courses and speeds and then to have the two side interpenetrate. To stay in range one, or both, sides would have to not attempt to radically change velocity or heading.

A better comparison would be sailing ships with cannons at close range, just slugging it out. There would be no real "dog fighting", nor strafing runs of inbound fighters on enemy starships - they would have a moment of time where they were within weapons range and then the two sides would be past one another.

There is no reason ships couldn't spin to point their weapons at their targets, shoot and then spin back regardless of heading. In fact, that's what they usually do in Traveller, to judge from the RAW. RAW ships shoot all their weapons every turn at any target they choose in range regardless of firing arc, which implies they are spinning around as needed. It is what happens in the Expanse when ships shoot each other, and it looks really cool and exciting.

Only the fact that you have, in some cases, extremely large ships trying to rotate on their axis like they were dainty and nimble craft. That's where the Traveller mechanic fails. And this also ignores the fact that you cannot continue to thrust along your course while doing so. In order to maintain your baseline course you'd have to stop your thrust along your current axis, spin, fire, spin, then resume thrust. All the while the ship pursuing you would be continuing to maintain it's thrust, thus if the two ships have similar thrust ratings the ship in pursuit would catch up due to the simple fact it's never had to stop thrusting.

I'm aware the rules don't take into account that weapons, aside from spinal or fixed mounts, can be brought to bear on any target within a 360 degree sphere. I was pointing out the fact that there is a built-in fallacy to this using the rules as written (i.e. inertia). One can simply hand-wave aside the fact that maneuvering thrusters are extremely powerful, or else ships have very little mass, thus they are able to perform like ballerina's in space. These concepts seem at odds.

Nobody has a "standing start" ever. The concept is meaningless. Each ship has a vector or an orbit around some object, unless it is sitting on the object. What that vector is, is a part of figuring out if you can intercept another ship - just like it's distance from your ship is. This doesn't change the overall possibilities of interception - it just means that you have to know two things about each ship: their location and vector.

True, everything in the universe is in motion at all times. However you are ignoring the fact that there is relative motion and universal motion. Objects in our solar system rotate around our sun, which itself is rotating in our galaxy. Ergo all things have motion, but it's also relative to the location you are at. Thus if you are at a "standstill" relative to the system you are in, you will remain in that location until some other objects gravity affects you. Thus you are at a "standstill". I figured that is implied when talking about such things, but obviously that was not how it was taken.

You seem to ignore the fact that in addition to location and vector, one also must account for acceleration. A ship exiting jump space, per RAW, maintains the heading and velocity that it entered jump space. Thus a ship lying doggo (for you that means a ship that is not under acceleration in the local system and essentially is drifting) must begin accelerating to catch the ship that exited jump space. Assuming said ship had been accelerating for hours to reach the 100D jump radius, the ship trying to intercept has very little chance of success before the arriving ship is able to make planetfall, or at least get within range of planetary assistance.

There is no such thing as a "known jump route". This idea also makes no sense. Planets are the usual destination for ships and they are always in motion. So what would a "jump route" be? Any point in space or route where a jumping ship might appear to fly to a given planet will be in a very different location relative to that planet tomorrow, and a year from now it will be outside the star system in question entirely.

Sigh... Yes, all things are in motion. Again you miss the point of the statement. I'm assuming you understand space is pretty big? And the volume of space at the 100D limit or beyond is also rather large? Which means it should be nigh impossible for ships to ever be caught by a pirate since inbound ships can choose their arrival locus? A clever pirate though can also run a navigational plot to know that ships inbound from a particular system tend to arrive in a general area, and they can also backplot a rough route that ships departing the other system tend to take. Whether or not ships would prefer to arrive above or below the elliptical plane is a guess for anyone to make - its not discussed. I tend to think that it's possible to narrow down such a volume of space.

Those known points will always be somewhat known since ships in jump follow a linear path from origin to destination - and any ship can plot the masses large enough to bring them out of jump space, ergo you can narrow things down to the most common/likely emergence area. Inbound ships still have to deal with the 100D limitation of their arrival planet, which gets back to the idea of where exactly they may choose to emerge. Per your previous point, an inbound ship would most likely want to emerge at a location where it can take advantage of the planets movement and minimize having to "catch up" to it while flying along the same orbital path. Or at least emerge at a location where it is relatively neutral for orbital velocity. This doesn't address the fact that the emerging ship already has a heading and built-up thrust vector, but that's an entirely different discussion.

There is hope for aspiring pirates however, Finding ships in interplanetary space is difficult, but they come to gas giants and other fuel sources, where you can intercept them. Also, if you know where they are going and how fast they are thrusting you can find them by doing the math. Pirates need spies, sensor buoys and small craft scouts. Intelligent pirates don't pop up in well patrolled parts of well patrolled systems.

But do they really take days out of their schedule to go get free gas giant fuel when they can buy all the water they want at a starport and refine it themselves? Simple math tells you that the time spent travelling to a gas giant, refuelling, and then moving out to the 100D limit of the gas giant is woefully uneconomical from an operational perspective.

Once you take the other parts of the rules into account, piracy becomes less and less likely from a pure surprise perspective. There are just too many strikes against it. Not to mention that paying for the spies, sensor buoys and scouts makes it more like a business than a "arr, avast ye mateys!" type of operation.

Erasing inertia somehow via technology raises all kinds of issues and questions which would have to be worked through, and these are really problematic for maintaining an interesting setting. All the physically impossible magic future techs in the game raise issues of how they interact with the game universe - witness all the discussions about jump drive's preservation of momentum or not, and m drives smashing asteroids into planets. These techs , or ones like them, are needed for the game to make the space opera work, though, so we have to do the work of figuring out how they interact with the rest of physics. Magic inertia erasers, however, don't add to the game, and so we don't need to do this work.

Aside from players thinking that smashing objects travelling at fractional C velocities is a good way to wage war, I don't see much in the game that speaks to that thing. The idea of inertia and preservation of momentum going into/out of jump space is just fine - but that also means you have to throw it out the window when the rule book states that when having an encounter the two ships are now at essentially zero velocity. Thus your fat and bumbling merchants will always get caught by pirates.

I think it's far better to resolve these things within the core structure of the game. Doesn't really matter if you have magic intertia erasers or not - so long as the gaming universe remains consistent and you don't argue up a storm in defense of the system while poo-pahing criticisms of where it breaks its own rules. As you say, it's space opera, thus it's already outside of the realm of today's existence. Thus if you have jump drives and anti-gravity and all other kinds of theoretical science, there's nothing inherently wrong with making the rest of the system live within the boundaries you have already defined.

 

[Condottiere]

If we switch to six second rounds, we'll have what could be termed, microaccelerations.

Which at the potential velocities involved, could place the spacecraft at quite a distance at the end of six seconds, from the start of six seconds.

And if you manage to maintain relative motion neutrality, could make the spacecraft comparatively agile.

 

[Fluffy Bunny Feet]

How many g would you pull on a Tigress when it spins 180 degrees to fire in no more than 6 seconds?

 

[rinku]

Unless you're doing a high velocity fly past, the assumption that moving between the range bands is orbit *matching*, and takes into account slowing down to intercept, is fair.

And if you DO want to do that flypast, just double the thrust used and apply it to increasing range immediately after you've closed. Simple.

 

[rinku]

How many g would you pull on a Tigress when it spins 180 degrees to fire in no more than 6 seconds?

Most likely the G plates would cope with any rotational side of things. By definition Traveller M-Drives don't affect the passengers, regardless of thrust orientation.

For that matter passengers on a reaction drive ship that does the same would also only experience 1G acelleration towards the floor before and after the flip. There might be a little lateral from the flip, but unlikely to be an issue.

 

[Condottiere]

You can jink around every six seconds, instead of going in one direction for six minutes.

Which should make a spacecraft harder to hit.

And provide that Top Gun vibe.

 

[Sigtrygg]

How many g would you pull on a Tigress when it spins 180 degrees to fire in no more than 6 seconds?

Zero, the internal acceleration compensation cancels out all pseudo g forces and the acceleration of the m- drive.

Traveller ships are incredibly agile, probably because they are based on displacing the volume of the ship rather than the mass...

 

[Sigtrygg]

You can jink around every six seconds, instead of going in one direction for six minutes.

Very true, and with basic maths you can calculate how far you can be displaced from your predicted position with 6 seconds of acceleration, giving a sh[her of potential location.

Which should make a spacecraft harder to hit.

That depends on sensors, fire control, weapon speed and range.

At 10,000km a laser takes 1/30th of a second to reach you, how far have you displaced your ship in 1/30th of a second due to acceleration? This is easily calculated.

And provide that Top Gun vibe.

Top Gun would look very different with light speed weapons...

 

[MonsterX]

One typically does not "dogfight" a stationary object. BG cheated the hell out of the inertia by doing basically SW maneuvers - Cylons and Vipers would be accelerating towards one another and then instantly flip and accelerate in the other direction.

There are no stationary objects. But I think you are referring to the Expanse space station? A space station is just a big spaceship with weak thrusters. No difference. Yes, BG did cheat the hell out of inertia sometimes, but not in the example you give - flipping and accelerating in the other direction is what would happen.

It's quite true that dogfights with inertia would be much different than we would expect. The only way TO have a dogfight would be to have similar courses and speeds and then to have the two side interpenetrate. To stay in range one, or both, sides would have to not attempt to radically change velocity or heading.

No, only the side with higher thrust would have to want to stay in range - accelerating straight out would just get you followed, on your tail.

A better comparison would be sailing ships with cannons at close range, just slugging it out. There would be no real "dog fighting", nor strafing runs of inbound fighters on enemy starships - they would have a moment of time where they were within weapons range and then the two sides would be past one another.

Because the fighters have more thrust (or rather, if they have more thrust), they can in fact do strafing runs, as long as the other ship doesn't outmaneuver them. Why wouldn't they be able to? Their main limit would be that to keep pace, they need to use as much thrust as the other ship do to that, and the remaining thrust might not be enough to keep from getting hit and because they are small a hit is usually a kill.

Only the fact that you have, in some cases, extremely large ships trying to rotate on their axis like they were dainty and nimble craft. That's where the Traveller mechanic fails. And this also ignores the fact that you cannot continue to thrust along your course while doing so. In order to maintain your baseline course you'd have to stop your thrust along your current axis, spin, fire, spin, then resume thrust. All the while the ship pursuing you would be continuing to maintain it's thrust, thus if the two ships have similar thrust ratings the ship in pursuit would catch up due to the simple fact it's never had to stop thrusting.

Grav plates.

I'm aware the rules don't take into account that weapons, aside from spinal or fixed mounts, can be brought to bear on any target within a 360 degree sphere. I was pointing out the fact that there is a built-in fallacy to this using the rules as written (i.e. inertia). One can simply hand-wave aside the fact that maneuvering thrusters are extremely powerful, or else ships have very little mass, thus they are able to perform like ballerina's in space. These concepts seem at odds.


True, everything in the universe is in motion at all times. However you are ignoring the fact that there is relative motion and universal motion. Objects in our solar system rotate around our sun, which itself is rotating in our galaxy. Ergo all things have motion, but it's also relative to the location you are at. Thus if you are at a "standstill" relative to the system you are in, you will remain in that location until some other objects gravity affects you. Thus you are at a "standstill". I figured that is implied when talking about such things, but obviously that was not how it was taken.

No you won't be, unless you are at a Trojan point, in which case you will stay there relative to the object whose Trojan point it is (while still moving relative to everything else.). In a star system, you're either in orbit, on some sort of solar escape trajectory, or falling into something. Or sitting on something.

You seem to ignore the fact that in addition to location and vector, one also must account for acceleration. A ship exiting jump space, per RAW, maintains the heading and velocity that it entered jump space. Thus a ship lying doggo (for you that means a ship that is not under acceleration in the local system and essentially is drifting) must begin accelerating to catch the ship that exited jump space. Assuming said ship had been accelerating for hours to reach the 100D jump radius, the ship trying to intercept has very little chance of success before the arriving ship is able to make planetfall, or at least get within range of planetary assistance.

The word for heading and velocity is vector. A ship exiting jump in a system will have a vector that is essentially random in the local frame of reference from the perspective of an aspiring pirate waiting in ambush - because each star system has its own heading and velocity and the vector of ships exiting jump space will reflect this, as well as any factors which might cause that ship to acquire a vector in the system it is jumping from - the planet it left, the need to exit the jump shadow, anything else the ship might be doing, or even the ship's plans in the destination system (if the captain is thinking ahead, and the astrogator is capable). Your pirate ship might be in a position for an easy intercept, or not, depending on how all these factors add up. It is still up to chance, just like it always was. For example, suppose your ship solar orbit at 2 AU detects a ship decelerating in fast from the outer system. If you detect them very early, you can accelerate to match velocity, but if not you have a long stern chase ahead of you - though maybe you could get close enough for a potshot as he sped by. If you also happened to be headed toward the inner system, and had a substantial vector but less than your target, then you get a short stern chase.

Sigh... Yes, all things are in motion. Again you miss the point of the statement. I'm assuming you understand space is pretty big? And the volume of space at the 100D limit or beyond is also rather large? Which means it sh ould be nigh impossible for ships to ever be caught by a pirate since inbound ships can choose their arrival locus? A clever pirate though can also run a navigational plot to know that ships inbound from a particular system tend to arrive in a general area, and they can also backplot a rough route that ships departing the other system tend to take. Whether or not ships would prefer to arrive above or below the elliptical plane is a guess for anyone to make - its not discussed. I tend to think that it's possible to narrow down such a volume of space.

Not sure what your point is. You seem to be arguing that to be fair to the pirates, merchants should try to restrict themselves to predictable traffic lanes. I see why the pirates would want that, but I am not sure what's in it for the merchants.

Those known points will always be somewhat known since ships in jump follow a linear path from origin to destination - and any ship can plot the masses large enough to bring them out of jump space, ergo you can narrow things down to the most common/likely emergence area. Inbound ships still have to deal with the 100D limitation of their arrival planet, which gets back to the idea of where exactly they may choose to emerge. Per your previous point, an inbound ship would most likely want to emerge at a location where it can take advantage of the planets movement and minimize having to "catch up" to it while flying along the same orbital path. Or at least emerge at a location where it is relatively neutral for orbital velocity. This doesn't address the fact that the emerging ship already has a heading and built-up thrust vector, but that's an entirely different discussion.

But this could be anywhere on the 100D limit, unless we take moons and minor objects into account. Carryover vector from the jump would affect where you want to come out, but the pirates would have no way of knowing in advance what that would be.

But do they really take days out of their schedule to go get free gas giant fuel when they can buy all the water they want at a starport and refine it themselves? Simple math tells you that the time spent travelling to a gas giant, refuelling, and then moving out to the 100D limit of the gas giant is woefully uneconomical from an operational perspective.

Not all mainworlds are good destinations, sometimes you just fuel up and jump again.. Sometime merchanteers are cheap. And sometimes they don't want to go to the mainworld because their creditors will see them there. Pirates don't get to be pirates everywhere, only in certain places where there are good opportunities.

Once you take the other parts of the rules into account, piracy becomes less and less likely from a pure surprise perspective. There are just too many strikes against it. Not to mention that paying for the spies, sensor buoys and scouts makes it more like a business than a "arr, avast ye mateys!" type of operation.

Crime never pays. Unless you have a good business model. Indeed, planning and forethought does increase the success rates of pirates. Considering the extremely high value of capturing a spaceship, crew and cargo, and the considerable loss you incur by screwing it up, planning your heist is probably a better idea than just flying around in deep space and hoping to run into something.

Aside from players thinking that smashing objects travelling at fractional C velocities is a good way to wage war, I don't see much in the game that speaks to that thing. The idea of inertia and preservation of momentum going into/out of jump space is just fine - but that also means you have to throw it out the window when the rule book states that when having an encounter the two ships are now at essentially zero velocity. Thus your fat and bumbling merchants will always get caught by pirates.

Magical zeroing the velocity also creates problems. And do you suddenly tell the players that their plan won't work because your velocity is zero now the pirate has detected you? How does that work? Is it a kind of magic lasso that pirates can use for stopping evading ships? And why does it only work at the start of an encounter? If they can do it at the start, they can also use it when their prey tries to get away.

I think it's far better to resolve these things within the core structure of the game. Doesn't really matter if you have magic intertia erasers or not - so long as the gaming universe remains consistent and you don't argue up a storm in defense of the system while poo-pahing criticisms of where it breaks its own rules. As you say, it's space opera, thus it's already outside of the realm of today's existence. Thus if you have jump drives and anti-gravity and all other kinds of theoretical science, there's nothing inherently wrong with making the rest of the system live within the boundaries you have already defined.

It is inherently inconsistent. If you want to make it consistent you need to do a lot of work with it, like figuring out how ship encounters will interact in a way that doesn't get absurd. When do the vectors zero? Will a sensor detection stop an enemy ship in its tracks? Can I use this as a tactic to slow enemies down? Can I use it to slow myself down? (i.e. I want to get from A to B faster, so I don't decelerate - I just plan to engage in combat at the end of it.; that will bring me down to zero instantly on the beginning of the encounter) Or are we actually all speeding up to the ship with the most vector? If so, can we use this to gain velocity?

I'll just stick with letting everybody keep their vectors at the start of combat. That way, the things the players do affect the universe, and it is possible to figure out how that works.

 

[rinku]

For ships to even attempt combat they need approximately matched vectors. But that is indeed what they will have if they are close to a world or a station, because if they have NOT matched vectors with that point of reference they will not remain close to it for very long. And that usually means velocities that are much lower than you might expect. The Earth orbits at just under 30 kilometres per second; any ship approaching from far away or 100D will need to match that particular solar orbit, then transition to one orbiting the planet. In almost all cases the rough travel time formula will suffice for constant thrust ships; it may not be actually travelling at 1G, flipping, and decelerating at 1G, but the series of burns needed to match orbits as fast as possible will be similar.

You CAN escape combat by hitting the burners if you have enough thrust, but that is also going to prevent you staying with the station or planet, unless you have scope to decelerate

 

[phavoc]

There are no stationary objects. But I think you are referring to the Expanse space station? A space station is just a big spaceship with weak thrusters. No difference. Yes, BG did cheat the hell out of inertia sometimes, but not in the example you give - flipping and accelerating in the other direction is what would happen.

Stationary = relative to your solar system. One can be stationary relative to objects within the solar system and still have angular momentum. That's how all this works. Space stations have a different name for a reason - they don't go flying around. Thrusters are meant for station keeping (i.e. staying in the place it was built) and are not meant to fly around a star system. Otherwise they'd be called space ships.

And BSG cheated the hell out of inertia by flipping and cancelling all their momentum nearly instantaneously. That's not how it happens. If you are thrusting in one directly for 60 seconds at full burn, to flip and go the opposite directly takes 60 seconds at full burn to simply stop (relatively, since you keep saying there are no stationary objects) and only THEN could you begin maneuvering in the opposite direction. It's TV so nobody wants to see a star fighter decelerating to a (relative) stop and then start moving again. I get the TV action. I'm just pointing out that's not how inertia works in reality.

No, only the side with higher thrust would have to want to stay in range - accelerating straight out would just get you followed, on your tail.

In theory, the side with the higher thrust ratings gets to determine how long the engagement lasts - within reasons. One still has to consider their total velocity and how long each side has been under accelerating. You may have 10x the thrust rating as your target, but depending on their velocity and your two courses, your engagement window may be small, extended, or a single pass.

But let's be honest here, modeling this for a game is just very un-fun in my mind. It's something you'd prefer to have a computer run a track of and show you the various points in the engagement where you could maneuver and either stay in range or else disengage. Weber's Honor Harrington series did a good job of describing such tactics for fleet engagements (which were mostly missile) - I thought a few of his "space fighter" descriptions failed when he described making passes at ships already under thrust for many hours. You'd get a sing pass, but you can't come back and do it again without massive deceleration curves. And time under thrust triumphs every time.

Because the fighters have more thrust (or rather, if they have more thrust), they can in fact do strafing runs, as long as the other ship doesn't outmaneuver them. Why wouldn't they be able to? Their main limit would be that to keep pace, they need to use as much thrust as the other ship do to that, and the remaining thrust might not be enough to keep from getting hit and because they are small a hit is usually a kill.

In a word - momentum. For a fighter to run around and 'strafe' it has to kill off its velocity and momentum. That takes time and every second your target continues to build velocity in the same direction. That's not how things work in reality. Again, an idea that sounds cool in a game, but in reality where inertia and momentum exist, not so much. Also said little target makes itself all the more vulnerable when it's decelerating since it becomes easier to hit. If it's maneuvering to stay a tiny target it can't cleanly decelerate since it's angular momentum is all over the compass. Makes a harder target to hit but plays merry hell on accomplishing the goal of "strafing".

Grav plates.

How does this apply to anything? Internal grav plates allow the passengers in the craft to not experience the maneuvers. It does nothing to actually having to spin a large and heavy object that requires energy to maneuver.

No you won't be, unless you are at a Trojan point, in which case you will stay there relative to the object whose Trojan point it is (while still moving relative to everything else.). In a star system, you're either in orbit, on some sort of solar escape trajectory, or falling into something. Or sitting on something.

Trojan points only exist between two or more objects. And this only applies to the gravitational attraction between the object(s) you are neat. The Trojan point cancels out the gravitational pull between the objects. But, like you said, there are no stationary objects. You will continue to have angular momentum for the system you are in as well as the angular momentum from your location in the galaxy you are in.

The word for heading and velocity is vector. A ship exiting jump in a system will have a vector that is essentially random in the local frame of reference from the perspective of an aspiring pirate waiting in ambush - because each star system has its own heading and velocity and the vector of ships exiting jump space will reflect this, as well as any factors which might cause that ship to acquire a vector in the system it is jumping from - the planet it left, the need to exit the jump shadow, anything else the ship might be doing, or even the ship's plans in the destination system (if the captain is thinking ahead, and the astrogator is capable). Your pirate ship might be in a position for an easy intercept, or not, depending on how all these factors add up. It is still up to chance, just like it always was. For example, suppose your ship solar orbit at 2 AU detects a ship decelerating in fast from the outer system. If you detect them very early, you can accelerate to match velocity, but if not you have a long stern chase ahead of you - though maybe you could get close enough for a potshot as he sped by. If you also happened to be headed toward the inner system, and had a substantial vector but less than your target, then you get a short stern chase.

Technically there are 6 items that make up a spatial objects movement for tracking purposes, but that's way more detail than we need here. Per MWM a spacecraft exiting jump space retains it's original vector (i.e. course and velocity) that it had when leaving the other system. Since two separate systems are going to have different angular momentum, a ship may or may not be heading in the right direction upon emergence. This is a good reason why ships should try to come to a relatively stop in their departure system to minimize the differences between system angular momentum. There will always be some, but any ship with 1G or greater thrust can easily accommodate this in the arrival system.

What would actually make for a more reasonable system for interceptions to occur would be for the greater your vector at the time of jumping, the greater your variation for your emergence point. Meaning if you wanted to be able to arrive within a few thousand KM of your calculated emergence destination point, the slower you need to be going when entering jump. A ship that's been boosting for hours to the 100D limit could potentially arrive multiple AU from it's planned point under that model. IF you had such a thing, then it would make it far easier for piracy to occur in both departing and arriving systems. Though ships would still happily have to spend an extra day in N-space vs. getting boarded by pirates, it does allow for more opportunities to interact with other ships. And a reason why you may see some going slow, or slogging away to their destination.

You are entirely correct about in-system travel. In fact you'd probably have regular (though constantly changing) shipping lanes for ships to travel between in-system destinations. Orbital mechanics will force ships to constantly update their paths, however everyone would know what the current path is from Point A to Point B. Most ships would prefer to travel these paths as if there is an emergency there is a greater chance to find assistance as well as encounter patrols or even navigational buoys. Many paths would be along the plane of the eliptic as that's where most everything else is located as well (but nothing to prevent a ship from travelling above/below). Regular paths also make it more likely for ship-to-ship encounters - which makes for believable reasons for intercepts.

Not sure what your point is. You seem to be arguing that to be fair to the pirates, merchants should try to restrict themselves to predictable traffic lanes. I see why the pirates would want that, but I am not sure what's in it for the merchants.

For the most part, yeah. Merchants and passenger liners tend to want to take regular routes that others take. And, usually, these routes tend to be the most effecient ones. They also are the least risky since you're more likely to encounter other vessels in case there is a problem. And, true, it's more helpful to pirates as well if their prey tend to take the same roads. But that's been the nature of commerce since commerce existed. Same reason why animals use game trails instead of always striking off in their own directions - it's easier and more effecient.

But this could be anywhere on the 100D limit, unless we take moons and minor objects into account. Carryover vector from the jump would affect where you want to come out, but the pirates would have no way of knowing in advance what that would be.

To some extent, but not totally. We know that a ship can't emerge on the other side of the planet, or travel through the 100D limit - it would bounce off the grav well. And we know that jump travel is fairly linear. Assuming that a ship from System A wants to arrive at the 100D limit of a planet in System B, and taking into account all the gravitational objects in both systems that it has to thread, that greatly narrows down the area which it can emerge. Then if you assume the emerging ship will want to spend the least amount of time in flight TO the planet (which is bipping along at it's own angular velocity). it would be less flight time to emerge in front of it's orbital path. Though you may have orbital infrastructure close to the 100D limit, thus your emergence points can vary, depending on many other circumstances). Still, while the volume is still rather large, you can eliminate some big chunks and hope to get lucky. If not you just have to wait for the next potential victim to enter your web.

Not all mainworlds are good destinations, sometimes you just fuel up and jump again.. Sometime merchanteers are cheap. And sometimes they don't want to go to the mainworld because their creditors will see them there. Pirates don't get to be pirates everywhere, only in certain places where there are good opportunities.

That's true. Though from pretty much all the published literature the Imperial starport is, typically, the primary destination. I supposed a system might have the largest amount of commerce and population on a moon or station orbiting an gas giant, but in that case your ships would not be travelling TO the gas giant, they'd pretty much already be there. And, frontier refuelling is supposed to be somewhat standard, but still somewhat dangerous. Even a cheap merchant would find it more economical to pay for fuel purifiers and buy unrefined fuel.

The problem here is that the game originally posited a BIG cost savings to go to the gas giant (500Cr/ton vs 100Cr/ton), and also at first only military ships had the necessary mechanisims to use unrefined fuel. Over time fuel purification plants have become the norm, and cheap, and it's the odd duck who'd actually go out of his way to bother to go save some money getting free hydrogen. This is one of those instances that the original concepts have not kept up with the changing game mechanics.

Crime never pays. Unless you have a good business model. Indeed, planning and forethought does increase the success rates of pirates. Considering the extremely high value of capturing a spaceship, crew and cargo, and the considerable loss you incur by screwing it up, planning your heist is probably a better idea than just flying around in deep space and hoping to run into something.

The cost of piracy is, well, high. Owning and operating a pirate ship ain't cheap. Paying for all the aforementioned small craft, sensor and spies makes it more expensive AND more likely for someone to rat you out. And, as you point out, the potential payback is huge - assuming you don't take too much damage, you don't have to fire a bunch of expensive ordanance, etc. A fence won't pay you even going used value for a stolen starship, so that 80Mcr ship you just liberated from its crew might bring you a measly 10Mcr from a fence (hey, we all have expenses...). Assuming you get a decent cargo haul AND someone has the Cr to ransom the crew, you might make enough to continue your existence for a while. But most pirates probably don't have retirement plans for a reason, and they don't plan much for in the future. So long as everyone is ok with that you have a (possible) pirate problem.

Magical zeroing the velocity also creates problems. And do you suddenly tell the players that their plan won't work because your velocity is zero now the pirate has detected you? How does that work? Is it a kind of magic lasso that pirates can use for stopping evading ships? And why does it only work at the start of an encounter? If they can do it at the start, they can also use it when their prey tries to get away.

I'm not saying that, that's the rules as written. Personally I think it's poor and lazy rule writing. This is why I prefer the game mechanics to be written in such a way that you don't have these silly hand waviums or rules that fly in the face of the other stuff you are trying to do. It's hard to keep a straight face and say "SCIENCE fantasy-fiction" and then explain away a silly rule like this. These things can easily be accommodated by making the underlying rules reflect a reasonable explanation. Example - a ship emerging from jump space does so at speed zero - now all ships have to start from zero in order to get anywhere. A sneaky pirate might be stooging along or lying doggo inside the 100D limit knowing that prey have to come near them to get to the planet. Add in things like jump flashes to broadcast to the system it's arrival and you gain more ways to make it possible to be found in the vastness of space (and no magical gravitational sensors either). It's not hard, one just has to think through the mechanics and provide some reasonable reason for how things work.

It is inherently inconsistent. If you want to make it consistent you need to do a lot of work with it, like figuring out how ship encounters will interact in a way that doesn't get absurd. When do the vectors zero? Will a sensor detection stop an enemy ship in its tracks? Can I use this as a tactic to slow enemies down? Can I use it to slow myself down? (i.e. I want to get from A to B faster, so I don't decelerate - I just plan to engage in combat at the end of it.; that will bring me down to zero instantly on the beginning of the encounter) Or are we actually all speeding up to the ship with the most vector? If so, can we use this to gain velocity?

I'll just stick with letting everybody keep their vectors at the start of combat. That way, the things the players do affect the universe, and it is possible to figure out how that works.

As I mentioned above, it doesn't have to be inconsistent. That's just lazy and poor rule writing. Traveller has been around for a very long time, and gone through many interations, yet we still have many of the same problems that have never been corrected. Good rule writing takes away the absurd and explains how things work - and being sure that all your rules stay consistent to the rules detailed in the game makes for a (in my opinion at least) better playing universe. Personally I don't understand why some publishers refuse to correct things once they are pointed out as violating the game rules (prime example is the Gazelle escort, which upon publication violated the drop tank rule by giving it 4 hardpoints. And just how many decades later did it officially get fixed?). Things like that bug me in a game system.

At the end of the day Traveller is what it is. People are going to keep, add, delete, etc as much or as little as they want.

 

[rinku]

Even with the frame of reference of a solar system, nothing is stationary. The stars and planets orbit each other, although in the usual case of a single star its orbit may be inside its photosphere.

As it happens, the barycentre for Sol/Jupiter lies close to, but above the Sun's surface.

Everything is in orbit. At best you might be in something like a surface synchronous one so that you appear to be above the same spot of a planet... but both you and the planet are just spinning around in synch. Lagrange points aren't fixed points - they themselves are in orbit around both the two massive bodies that cause that effect.