collins355
Emperor Mongoose
MegaTrav, which was a 2D6 combat system had the following target size modifiers (note that as these DMs were applied to the defender overall DM the positive numbers are actually harder for the attacker):
Ship Combat
- Thread starter mavikfelna
- Start date
J. L. Brown
Emperor Mongoose
No it absolutely does not. It seems intuitive, and feeds into 'rule of cool', but it makes no sense in terms of the way MGT 2e space combat works,
Let us start with some size comparisons; in terms of meters of diameter for spherical ships.
100 dTons = 13.8 m
1000 dTons = 29.9 m
10000 dTons = 64.4 m
100k dTons = 138.8 m
1000k dTons = 299.0 m
The million dTon ship is 10000 times bigger, but not 10000 times wider, than the 100 dTon ship. This is the square/cubed relationship in action.
What does this mean for gunnery? At one km, a 1m target is 1 milli-radian. A two meter target at one km (2 milli-radians) is a difficult shot, even under perfect conditions. At one km ('Adjacent' range), targets are the same number of milli-radians across as they are meters wide; a 10k dTon ship is a little more than twice as wide as a 1000 dTon ship. For longer ranges, divide the width in milli-radians by the number of kilometers -- so the 1000 dTon ship at 2 km is the same size target as the 10k dTon ship at 4.3 km.
The 100 dTon ship at 11 km is exactly the same size target (1.25 milli-radians) as the 1000 dTon ship at 37.5 km, and the million dTon ship at 375 km -- all of these targets are at 'Short' (+1 to-hit) range.
The importance of size is incredibly exaggerated.
It's probably more relating to the issue of the larger ship needing longer to move it's cross section out of the danger zone. A 100 ton ship that thrusts sideways and displaces 15m is totally gone from where it was. The attacker needs to predict in which direction it went in order to keep a firing solution on the target.
A 1000k ship that thrusts laterally 15m is still substantially square in the danger zone, and the firing ship really doesn't need to know in what direction it moved.
A 1000k ship that thrusts laterally 15m is still substantially square in the danger zone, and the firing ship really doesn't need to know in what direction it moved.
J. L. Brown
Emperor Mongoose
Two points; a 6000 dTon ship has a cross section of 34.32 meters -- only about twice (~2.5x) that of a 100 dTon ship. Somehow, a 100 dTon ship is +0 to-hit due to size, while a ship less than three times the size is +6 to-hit. A million dTon ship is more than eight times bigger than the 6000 dTon ship, but no easier to-hit. The way size is modeled is clearly screwy.
Secondly ships are not stationary, nor starting every turn from stationary. After accelerating at 1G for just six minutes, even a 'slow' ship is moving at 3530 meters per second. Moving the 'end point' of where such a ship will be at the end of a six-minute combat turn is a matter of deflecting only a tiny amount -- even speeding up or slowing down by a tenth of a G will be enough, even for a million dTon vessel. But somehow, the size of the ship can give up to a +6 to-hit bonus -- and yet the speed it is traveling (the number of milli-radians it is slewing across from the point of view of the firing weapon) is completely unimportant.
Secondly ships are not stationary, nor starting every turn from stationary. After accelerating at 1G for just six minutes, even a 'slow' ship is moving at 3530 meters per second. Moving the 'end point' of where such a ship will be at the end of a six-minute combat turn is a matter of deflecting only a tiny amount -- even speeding up or slowing down by a tenth of a G will be enough, even for a million dTon vessel. But somehow, the size of the ship can give up to a +6 to-hit bonus -- and yet the speed it is traveling (the number of milli-radians it is slewing across from the point of view of the firing weapon) is completely unimportant.
MonsterX
Emperor Mongoose
I don't think anyone is arguing for the current size DMs, J.L. If you read the rest of the sentence of mine which you quoted, you will see I argue against those and for a different model. But to quote your earlier post, assuming the target is a sphere, the visible area from the shooting ship is this:
100 dTons = 13.8 m
1000 dTons = 29.9 m
10000 dTons = 64.4 m
100k dTons = 138.8 m
1000k dTons = 299.0 m
Thus, a bit more than double for every x10, which absolutely provides a bigger surface area to hit. However, my argument did not address that part of the equation. Instead, you will find I argue what rinku also argues: that smaller ships are more able to use their thrust to unpredictably move out of the position which fire control would predict they will be. This is because of speed-of-light lag: a target at 30000 kms will have a 1/5 second lag - that is, your fire control see the target where it was 1/10 second ago, you fire your laser, it gets there 1/10 second later - so you are shooting where the ships' location was predicted to be in 1/5 of a second's time. In that time, the ship could move 1m per G rating in completely UNPREDICTABLE directions (it is this unpredictable part that is important- accumulated vector is completely predictable but thrust is unpredictable). If the ship is 300 meters in diameter, this isn't much. If it is 13,8 meters in diameter, there is a good chance you dodged the laser.
We can disregard the ballistic part ships' vectors' for too-hit, as this is the predictable part. An object moving at 500kps relative to you is the same as one moving 10kps for targeting (this is not strictly true, and not at all true for missiles, but pretty much is true for beams). I think we can assume that velocity per se does not have a large systematic effect on to hit.
This analysis ignores inaccuracies in targeting, which will obviously exist too, but just to make the example clearer.
J.L., this time please read to entire post, instead of just taking out a sentence fragment to use as a strawman.
100 dTons = 13.8 m
1000 dTons = 29.9 m
10000 dTons = 64.4 m
100k dTons = 138.8 m
1000k dTons = 299.0 m
Thus, a bit more than double for every x10, which absolutely provides a bigger surface area to hit. However, my argument did not address that part of the equation. Instead, you will find I argue what rinku also argues: that smaller ships are more able to use their thrust to unpredictably move out of the position which fire control would predict they will be. This is because of speed-of-light lag: a target at 30000 kms will have a 1/5 second lag - that is, your fire control see the target where it was 1/10 second ago, you fire your laser, it gets there 1/10 second later - so you are shooting where the ships' location was predicted to be in 1/5 of a second's time. In that time, the ship could move 1m per G rating in completely UNPREDICTABLE directions (it is this unpredictable part that is important- accumulated vector is completely predictable but thrust is unpredictable). If the ship is 300 meters in diameter, this isn't much. If it is 13,8 meters in diameter, there is a good chance you dodged the laser.
We can disregard the ballistic part ships' vectors' for too-hit, as this is the predictable part. An object moving at 500kps relative to you is the same as one moving 10kps for targeting (this is not strictly true, and not at all true for missiles, but pretty much is true for beams). I think we can assume that velocity per se does not have a large systematic effect on to hit.
This analysis ignores inaccuracies in targeting, which will obviously exist too, but just to make the example clearer.
J.L., this time please read to entire post, instead of just taking out a sentence fragment to use as a strawman.
J. L. Brown
Emperor Mongoose
I did not construct a strawman; I disputed the idea that 'ship size' was terribly relevant to starship combat. A ships thrust (and relative heading compared to the firing ship) is far more important, yet entirely ignored. Even the modifiers due to range are far more important than 'ship size'; but they are capable of far less impact on actual to-hit rolls.
And I do not think the argument from light-delay is super relevant; starship combat is not conducted in fractions-of-a-second turns. Whether someone claims that starship-scale weapons fire much slower, or take longer to find satisfactory targeting solutions, or that they produce a saturated area of fire within a cone of effect doesn't really matter; the rules are abstracted in such a way that (outside of 'dogfighting') only the performance of a weapon over six minutes is important. In a six minute turn, ships can vastly change their position -- over scales hundreds of times larger than their own silhouette.
Bonuses to-hit based on ship size are a silly at these scales.
And I do not think the argument from light-delay is super relevant; starship combat is not conducted in fractions-of-a-second turns. Whether someone claims that starship-scale weapons fire much slower, or take longer to find satisfactory targeting solutions, or that they produce a saturated area of fire within a cone of effect doesn't really matter; the rules are abstracted in such a way that (outside of 'dogfighting') only the performance of a weapon over six minutes is important. In a six minute turn, ships can vastly change their position -- over scales hundreds of times larger than their own silhouette.
Bonuses to-hit based on ship size are a silly at these scales.
Sigtrygg
Emperor Mongoose
You have just done the hard part then incorrectly applied the equations of motion.
A 6g ship has 0.2s to not be where it is predicted to be - we are aiming at centre of mass remember. So how far does 6g acceleration for 0.2 seconds get you?
None of those ship sizes can avoid being hit.
Here is a new table
| Acceleration/ms-2 | 60 (6g) | 70 (7g) | 80 (8g) | 90 (9g) |
| displacement after 0.2 seconds /m | 1.2 | 1.4 | 1.6 | 1.8 |
A target ship's initial velocity is effectively zero, your laser can "match velocity" and thus you are only affected by the target's acceleration.
Processing time, correction for vibration in machinery, I estimate that to be limited by computer processing speed and comms lag between the machines... this is what adds up to make rolling dice necessary, but note that inside a certain range you should never miss...
I would say that you should use the correct equations, I think you have used the final velocity equation rather than displacement from original position.
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That's why the chart of target DMs by size is logarithmic and not linear. It makes sense to me. Especially with practical elements like Rinku's allowance for movement, or the fact that - despite the ardent wishes of physicists down through the years - "first, we shall assume that the spaceship/car/racehorse/cow is a perfect sphere" is sometimes less helpful, eg with mainly elongated wedge/rectangle/lozenge objects moving largely in the direction of their long axis.
MonsterX
Emperor Mongoose
No, I don't just guess. I just don't do the multiplication correctly. Except actually I do. 6 gs gets you 60 meters. 0.2 is 12 meters.
I don't just guess by "feel." I might or might not miss a digit. In this case, it was you that missed the digit, but ok. Nobody need to go after anybody for that, we're all human.
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MonsterX
Emperor Mongoose
You did, because you pluck a sentence fragment, in order to be able to portray ME as arguing something entirely different than what I actually was. That is the definition of "constructing a strawman". I say "plucked" as it makes clear it was intentional - I can't say why anyone would do this - but obviously it must be since the SECOND HALF of my sentence changes the meaning from the meaning you attribute to it.
If you want to argue against my argument, then you should argue against MY ACTUAL ARGUMENT, and not against the thing I am also arguing against.
If a body at rest accelerates at 6G for 0.2s it will move 1.18m (or 1.2m as Sigtrygg rounded it to, since we assume 10 m per second per second, not earth’s gravitational constant). Whether or not it starts at rest, that's the change in position due to the 6G in acceleration.
Your answer (12m) makes sense if you are thinking of 60m/s of velocity, but 6G is acceleration (the first derivative).
The real reason why the table for different ship sizes is quite reasonable requires the use of radians, liberal smatterings of sohcahtoa and some vector maths and since this thread is already the traditional trashfire of hostility and blank assertions there's no way I am getting involved in that!
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Sigtrygg
Emperor Mongoose
No, I think you may be using the wrong equation. I apologise for the "feel" comment, it reads way worse than I intended.
displacement is equal to one half of acceleration multipled by the square of the time
s=0.5at2
0.5 x 60 x 0.2 x 0.2 = 1.2m
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Condottiere
Emperor Mongoose
I'm not saying this is standard procedure, but you could salvo multiple ray guns simultaneously in a pattern, where the target might be when they arrive.
One should intersect, even if the target pilot is janking the spacecraft wildly around.
One should intersect, even if the target pilot is janking the spacecraft wildly around.
Sigtrygg
Emperor Mongoose
That's why in HG80 you get a higher to hit number with multiple weapons in a battery, the black globe rules show not all of them hit. A factor 9 laser batter has 30 individual weapons, yet only 9EPs are absorbed by the black globe, so we can infer 21 of them miss even on a successful hit. other explanations are availabel (EP is input energy, BG absorption is based on output energy for example)
Condottiere
Emperor Mongoose
Should be easier to predict position, of a black globe engaged spacecraft.
J. L. Brown
Emperor Mongoose
I responded directly to the idea that I disagree with. Your whole paragraph was 'Modifiers based on the size of a ship are something that are important enough to model; I would do it differently'. Here:
An Imperial Star Destroyer is around 1600 meters on its' longest axis; at 1000 km ('Short' range) it is about the same size (or maybe smaller, for tall people) as a person standing in the open 1 km away. In combat with an arbitrary number of targets, the firing ships weapons must be steady enough (for six minutes at a time) to effectively put fire into that 1.6 milli-radian arc, or utterly miss. The motion of one target, perhaps a maximum of two targets, can be more-or-less compensated for by motion of the firing ship -- but doing so makes the movement of the firing ship more predictable.
Over a turn, a 1G ship can change 'where the enemy expects me to be' by 648 km; a 9G ship can change by 5832 km. These effects completely dwarf 'ship size' on anything smaller than a planet. Modeling 'Ship size' as an important modifier in ship to ship combat is silly; there are far larger effects at play which are completely ignored.
MonsterX
Emperor Mongoose
yes, that is the point I am making. The 1000 to 6000 tons example being presented as my position what I object to. I do in fact think that DMs based on log of tonnage is the way to go and I do not support the position that there should be DMs from 1000 tonnes to 6000 tonnes and not thereafter.
I see the argument you are making, and of course the size of space dwarfs the size of the ships targeted regardless of how big they are at the ranges we are talking about. I still think you are wrong that size does not affect hit probability. Of course, it is a question of how much, and whether it is worth giving DMs; that is always the question traveller.
But if we assume that it is possible to hit a target at that range (i.e. the shooting is not entirely random), but also possible to miss (i.e. the location of the target cannot be predicted with perfect accuracy, and/or the shoot weapon/fire control is not perfectly accurate - so there is some randomness) , the chance of hitting or not is going to be affected by the size of the target, because there will be some error and if there is, whether or not this becomes a hit or a miss depends on how big the target is. The is the case regardless of whether we consider a the volume of fire - some of it is hitting and some missing and the amount hitting increases if the target is bigger because near misses become hits if the target is bigger.
MonsterX
Emperor Mongoose
ok, I see what you mean.
Still, the assumption of only 1/5 second was very conservative absolute minimum theoretical reaction time. And actually 1.2 meter is not nothing for a small ship; it could definitely cause a hit to miss instead: it isn't that significant though for a big ship. Which is my point.
Sigtrygg
Emperor Mongoose
A 10dt fighter is 140cubic metres - 6.44m diameter if a sphere so even a smallcraft can not evade the laser at 30,000km without adding more time for processing, targeting and vibration.
A 5dt fighter is 70 cubic metres so even it has a diameter of 5.1 metres and can not evade if the laser is aimed at centre of mass.
30,000km is in the very long range range band, as you get closer it becomes almost certain the laser will hit.
I think the reaction time has to be extended to take into account the various things I mentioned in order to make weapon fire require a dice roll at all. And the problem remains that if you have a 40% chance to hit at 30,000km, by the time you are at 1000km you are an automatic hit.
A 5dt fighter is 70 cubic metres so even it has a diameter of 5.1 metres and can not evade if the laser is aimed at centre of mass.
30,000km is in the very long range range band, as you get closer it becomes almost certain the laser will hit.
I think the reaction time has to be extended to take into account the various things I mentioned in order to make weapon fire require a dice roll at all. And the problem remains that if you have a 40% chance to hit at 30,000km, by the time you are at 1000km you are an automatic hit.
