Acceleration and Space Combat

Discuss the Traveller RPG and its many settings
phild
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Acceleration and Space Combat

Postby phild » Tue Feb 17, 2009 4:54 am

In space combat, acceleration is key to manoeuvreability, because in the absence of an atmosphere in which you can use fins etc., the only way to change direction is to shoot a burst of acceleration in a different direction. This means that although identifying a ship, tracking it and matching speed with it is very difficult, once you have done so, it's very hard for it to get away or avoid being shot unless it is (a) small, and (b) has high G.

It strikes me that the issue is spaceship acceleration. While over a long period of time, even the humble 1G amounts to a very significant acceleration rate, those first 1 or 2 seconds of acceleration amount to very little. Because of this, it strikes me that ships would benefit from some kind of emergency maneuvre thrusters, some kind of ring around the ship which could be triggered in combat to provide a sudden powerful thrust to the side to boost the usual m-drive. The challenge would be to make this thrust as sensor neutral as possible - a series of rocket thrusters, for example, would be immediately detected by passive sensors, and analysed by the ship's computer, and the new position of the target evaluation almost instantly.

Would the normal grav based m-drive be able to provide this sort of additional manoeuvring ability, and if not is there anything in the Traveller canon that might provide this sort of function?
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Postby Rikki Tikki Traveller » Tue Feb 17, 2009 3:53 pm

It can if you want it to.
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Postby Paladin » Tue Feb 17, 2009 4:04 pm

Sounds like a tactic I used to use the old 688 attack sub PC game... If it was near the end of the mission, you could use the emergency ballast system in the sub to avoid a torpedo by forcing the boat to the surface in a hurry. Realistic, probably not. Fun & effective, yup.
Last edited by Paladin on Wed Feb 18, 2009 3:31 pm, edited 1 time in total.
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10harold66
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Postby 10harold66 » Tue Feb 17, 2009 4:09 pm

is vector movement still used for spaceship combat as in CT?
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Postby phild » Tue Feb 17, 2009 5:27 pm

Rikki Tikki Traveller wrote:It can if you want it to.
Why thank you sir. So kind. I'll have a blue one then please :)
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Re: Acceleration and Space Combat

Postby lastbesthope » Tue Feb 17, 2009 7:59 pm

phild wrote: It strikes me that the issue is spaceship acceleration. While over a long period of time, even the humble 1G amounts to a very significant acceleration rate, those first 1 or 2 seconds of acceleration amount to very little.
You mean, one or two seconds of 1G acceleration produces little change in velocity, several seconds produces a larger change. 1G of acceleration only gives you 1G of acceleration, no matter how long you apply it for.

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Re: Acceleration and Space Combat

Postby Shiloh » Tue Feb 17, 2009 8:10 pm

lastbesthope wrote:
phild wrote: It strikes me that the issue is spaceship acceleration. While over a long period of time, even the humble 1G amounts to a very significant acceleration rate, those first 1 or 2 seconds of acceleration amount to very little.
You mean, one or two seconds of 1G acceleration produces little change in velocity, several seconds produces a larger change. 1G of acceleration only gives you 1G of acceleration, no matter how long you apply it for.

LBH
but you *could*, IYTU, allow Engineering rolls to "overload" the M-drive for short periods of time to allow for some sort of ability to escape the predefined volume where an attacker would expect the ship class (if known) to be.
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Re: Acceleration and Space Combat

Postby phild » Tue Feb 17, 2009 9:00 pm

lastbesthope wrote:You mean, one or two seconds of 1G acceleration produces little change in velocity, several seconds produces a larger change. 1G of acceleration only gives you 1G of acceleration, no matter how long you apply it for.
LBH
Indeed. But the point is, for ships of more than 100 displacement tonnes, say, 1G of acceleration provides very little short-term change in lateral velocity if you're trying to evade enemy fire. Manoeuvring away from energy weapons would require significantly greater acceleration in order to achieve a meaningful change in position - perhaps not in a combat round, but a combat round is merely a convenient game abstraction for a turret that is likely to be tracking and firing more frequent than once every 5 seconds.
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Postby kristof65 » Tue Feb 17, 2009 9:23 pm

Keep in mind that a space ship doesn't have to be facing the same direction it's velocity is taking it to. So the ship doesn't really require any type of high power lateral thruster, merely some manuevering thrusters than can spin the ship's axis so the main m-drive is pointing the way it wants to apply thrust.

The higher a ship's velocity is, the harder it's course will be to change, obviously, but the larger range of places along that course it can actually be - because remember that 1G acceleration is up to 1g acceleration.

A ship doesn't have to be constant in it's acceleration, and I imagine that ships will vary their acceleration and facing in order to to try and make their course as unpredictable as possible. This is obviously gong to be harder for a 1g ship than a 6g ship, but it's still a lot of space to cover.
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Postby AKAramis » Wed Feb 18, 2009 4:03 am

Using the "traveller standard g" of 10m/s/s (instead of the 9.8m/s/s terran G), 5 sec is 50m/s, and only half that in positional change...

Rough minimal size for a starship is 1400m^3... a cube of about 11.3m.

Given any reasonabe firing range (which, for lasers, really is about 0.1LS, or 30,000,000m), that gives a 0.2sec, or 2m/s/G vector change, and 1m/G position change.... You are not dodging. (BTW, a focal length of 30Mm is a rather large focal array...)
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Postby barasawa » Wed Feb 18, 2009 5:30 am

Of course, please remember, this is a game.
The real world math and physics would make most gameplay sessions that include a ship based run & gun very boring.
Of course you can do that, but would it be fun and exciting?

I've seen game systems that include over 30 hit locations on a human, tissue damage, bone damage, blood loss, shock, organ damage, and nerve damage. The combat, though realistic in it's results, is a game killer. It always ends up being thrown out by unanimous vote of the group. Never later than the third completed combat, and rarely later than the 4th round of the first combat.

Never forget, you are playing a game, not a reality simulator. If the system is bogged down with too much reality or math, it's not going to be fun for your players. You can take things a bit loose and easy, your players won't mind, it's a sci-fi adventure after all...
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Postby AKAramis » Wed Feb 18, 2009 7:21 am

Barsawa:

I've seen entire campaigns run of Tri-Tac's various games... the detailed combat was no killer at all. It was exactly what that group wanted.

the "Details kill a game" BS is exactly that: bovine excrement.

Details for a group that doesn't want/need them can kill the fun.
Lack of details for a group that does want/need them is just as bad.

This phenomenon is why there are a variety of detail levels in different game engines, and why Leading Edge's and Tri-Tac's designs are still being played. (I have a couple LE designs, and enjoyed their realistic combat. I didn't enjoy TT's, because it was just a cumbersome engine, for me.)

I've had groups where the surreality of Traveller starship combat was sufficient to kill the game for several of the players; one has a BS in Physics, another was an MS in Psych. They both wanted realistic weapons ranges. HG worked for them, as it didn't for me, since range was unspecified, and it was abstract. They were upset with the 0.1LS+ ranges of Traveller lasers, specifically because they knew the formulae correlating wavelength, diameter of primary aperature, and focal length for lasers.
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Postby phild » Wed Feb 18, 2009 8:32 am

barasawa wrote:Of course, please remember, this is a game.
The real world math and physics would make most gameplay sessions that include a ship based run & gun very boring.
Of course you can do that, but would it be fun and exciting?
I actually agree, the system really shouldn't be maths/physics heavy. However, for games that are going for more of a hard sci-fi angle, maths and physics should at least underpin the game assumptions, even if the actual implementation is 'hand-waved' over in the old trusty 2D roll.

So, for example, a hard sci-fi space combat might have fewer gunnery rolls and a lot more pilot and engineering rolls, as the enemy craft fights to match velocity with their opponent. Until they've done so, there is no chance of any beam weapon hits and little chance of missile hits: once they've done so, it becomes less about rolling to hit and more about rolling for damage and reacting with as much damage control as you can muster.

And if this sounds less exciting, then it's just a challenge for the GM. After all, most combat systems feature:
- Some sort of initiative
- Some choice of manoeuvre
- A roll to hit, and possibly a roll to defend
- Some kind of damage determination

You could maintain those four steps very easily, but substituting for:
- Initiative
- Manoeuvre
- Roll to match vectors, and possibly roll to defend
- Damage

It uses slightly different skills, and the rules will need to be different in the detail, but at a macro level you could recreate the tension of a space combat pretty well I think.

You should probably also add additional rolls, for sensors and to hit, which increases the tactical considerations. For attacking ships, piloting and sensors are probably more important than gunnery skill, because if the first two fail, then all the gunnery skill in the world won't help you. And multi-action penalties could really kill you, so while a small fighter is much better at matching velocity because of it's superb acceleration, you're probably going to be minimising sensor activity and concentrating on matching velocity asap and then using your 6G thrusters to spin around your target at pretty close range. A medium-sized ship with a full crew complement has the luxury of being able to do all of the tasks reasonably well, although probably with a lesser M-drive. A large warship is probably designed to cover the vicinity with sand, put all its energy into sensors, and sending fighters out. Capital ships are probably going to stay out of combat, because even with a 6G drive, a 2km ship is pretty much a sitting target!

That doesn't have to be any less fun than a Star Wars style dog-fighting combat. It's just different.

Although this is making me think that Traveller space combat really ought to be run on the basis of 1 second rounds. Which means, if you're not at your post at the start of combat, you should probably forget it! Hmm, although as I think about it, the Hero System 12 second round made up of 1 second Segments would be ideal for this sort of thing, allowing for gun recharges and a damage control check at the end of each round....

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