OTU Only: The Limits of Traveller Space Combat

[whulorigan]

besides, speed limits. no-one anywhere will want ships moving at 20 miles per second anywhere in their system let alone anywhere near inhabited areas and especially never ever not while vectored towards a major port. ever.

Keep in mind 2 things:

1) When you say something is moving @ 20mi/sec, you must define relative to what;

2) The planets in a star system are all moving at that order of magnitude already, so ships transiting between them already have similar velocities. Earth is moving around the sun at about 30 km/sec, Mars @ 24 km/sec, and Jupiter @ 13 km/sec. Anything leaving or entering their orbits will be moving at these velocities already (relative to the sun). Transiting from Earth to Jupiter would require altering the initial vector (30km/sec) to the destination vector (13 km/sec) over the course of the journey (a difference of 17 km/sec).

Apollo 11 was traveling (I believe) at about 10 km/sec after leaving Earth orbit on its way to the moon.

​

But you are right in that it would probably be standard protocol to not vector directly at a world, but at a slightly skewed angle, and adjust accordingly as the velocity slowed into an orbital vector.

 

[atpollard]

There is no SINGLE spot. Every second any "spot" changes. There is no jump accuracy measured in centimeters. Like I said, you have NO idea of how big space that is.

Let me take a stab at this ... my knowledge of physics is better than my knowledge of biology, which admittedly is not setting the bar all that high.

First, heck yeah, space is big ... on the other hand, Traveller starships are pretty fast.

Any given world probably has one or two significant trading partners. Most ships are only J1 or J2, so that limits the traffic pool for most worlds, and Ag Worlds are probably not swapping a lot of produce with each other. So each world has a finite number of worlds that incoming ships are likely to come from and outgoing ships are likely to go to. There will be exceptions, but this will probably hold for most of the world's traffic. For the sake of argument, let's assume some world has two major trade partners which represent 60% and 30% of the traffic to/from the system respectively (the other 10% could be to/from anywhere else within 6 parsecs on almost any heading). Our wanna-be pirate can probably concentrate on 1/8 of the 100 diameter sphere and target 60% of the traffic. Still a really big area.

For any pair of worlds, at each moment, there is probably one optimal jump course between the worlds. Of course, this optimal exit point will continuously vary from moment to moment as both the world of origin and the destination world move. But the optimal exit point exists for each and every moment. Plotting these moments and exit points and connecting the dots will yield a path through space that represents the most likely exit point for 60% of the arriving merchant traffic.

As we all know, time in jump space is unpredictable, so some ships may appear at a point on the optimal arrival curve before the optimal time and other ships may appear later than the optimal time. The existence of this path of optimal exit points, will serve to narrow down the great vastness of the 100 diameter sphere into something that gives a ship bent on interception a fighting chance.

Near that point is where to station those anti-piracy SDBs if you have them.

 

[HG_B]

For any pair of worlds, at each moment, there is probably one optimal jump course between the worlds. Of course, this optimal exit point will continuously vary from moment to moment as both the world of origin and the destination world move.

That's the thing. Angular velocity (between two worlds moving different directions) changes every second. The velocity of the two planets AND their star system velocity difference (added together that LOTS of KM/sec) + jump inaccuracies = HUGE distance entry point differences. And not any single idea jump point really exists. People just head out to 100D and depending on what heading they took, aim for a helpful entry point. All different.

p.s. - the species thing is hard to grasp initially because it is a very loosely defined area. There is fudge factor involved. It is less scientific than many areas you & I are familiar with.

 

[atpollard]

That's the thing. Angular velocity (between two worlds moving different directions) changes every second. The velocity of the two planets AND their star system velocity difference (added together that LOTS of KM/sec) + jump inaccuracies = HUGE distance entry point differences. And not any single idea jump point really exists. People just head out to 100D and depending on what heading they took, aim for a helpful entry point. All different.

Entry point probably have more options to them ... anywhere on the hemisphere is probably good enough.

Exit points on the other hand are probably taking a stab at matching general direction and velocity with the orbit of the target planet. Ignoring the question of pirates completely, you probably don't want to arrive at solar escape velocity on a course opposite the orbit of the world and having just overshot the planet because you exited jump late. So the stream of exit points, while varying from moment to moment, probably form a nice irregular orbit through the solar system. The actual arrival point for inbound ships will be some volume of space along that irregular orbit.

It does not allow for a precise determination of exit time and location, but it sure narrows down that 100D sphere a lot.

 

[flykiller]

Every second any "spot" changes.

correct. but every incoming ship is going to be tracking a particular spot and aiming for it. some overlap is inevitable.

There is no jump accuracy measured in centimeters.

correct. but if you precipitate in at ten miles a second relative you really ought to think in terms of hundreds of miles instead of centimeters.

Like I said, you have NO idea of how big space that is.

incorrect. how big space is overall everywhere out to the furthest reaches of the oort cloud is irrelevant. the issue is where everyone will try to go - and THAT space is not so big.

When you say something is moving @ 20mi/sec, you must define relative to what

given the audience here I would have thought that would be assumed. of course it's relative to source/destination, and also relative to conditions. no-one will care how fast a ship is moving in the oort cloud, but from inhabited planet to inhabited moon everyone will care a great deal.

game input. imagine the debris cloud left over from a large space battle littering a system for decades afterward ....

People just head out to 100D and depending on what heading they took, aim for a helpful entry point. All different.

yeah. and at ten miles a second quite possibly just a gasp and scream away from each other.

inhabited systems will have designated jump precipitation regions with a required entry vector of 0. incoming vessels will then be required to clear precipitation to a designated path for inbound traffic. anything else will result in a penalty ranging from a speeding ticket to confiscation of the vessel.

 

[HG_B]

Entry point probably have more options to them ... anywhere on the hemisphere is probably good enough.

Exit points on the other hand are probably taking a stab at matching general direction and velocity with the orbit of the target planet. Ignoring the question of pirates completely, you probably don't want to arrive at solar escape velocity on a course opposite the orbit of the world and having just overshot the planet because you exited jump late. So the stream of exit points, while varying from moment to moment, probably form a nice irregular orbit through the solar system. The actual arrival point for inbound ships will be some volume of space along that irregular orbit.

It does not allow for a precise determination of exit time and location, but it sure narrows down that 100D sphere a lot.

Yes. Now it would be good to know roughly velocity differences. For an Earth sized planet, a 1G ship going to the 100D point (accel/decel) reaches 112 km/sec at midpoint. So, a ship has the capability to compensate for differences pretty easily by just choosing what they do at mid-point.

 

[Supplement Four]

If feasible, I suppose the tactic would have to be to try and target the M-Drives on a called shot, and then take the time to match vectors.

Called shot? Which edition of Traveller uses "called shots"? Or, are you referring to specific targeting?

In CT, the Select program will allow for general targeting.

Not true in all editions... TNE ships only carry 5-13 hours of reaction mass. They coast almost all the way. Which makes piracy both easier and harder.

I have TNE, but I never read it. Didn't like that game from the moment I saw it in the store. I don't know why I bought so much of that edition--stuff has sat around for years, just collecting dust.

I need to put the stuff on eBay.

So...with TNE, the Travel Forumula is different than the one used in CT, eh? It has to be if what you say above is correct (and I don't doubt that it is).

This begs the question, where do you station your limited number of SDBs (considering poor backwater system)?

I bet that poor, backwater systems don't have SDBs. They're too valuable. The Duke has them protecting the rich, populated, well traveled worlds.

Keep in mind 2 things:

1) When you say something is moving @ 20mi/sec, you must define relative to what;
​

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I've wondered about this before. I'm sure there's some generally accepted method (galactic plane). Maybe the system's star, or the main world.​

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[whulorigan]

Called shot? Which edition of Traveller uses "called shots"? Or, are you referring to specific targeting?

In CT, the Select program will allow for general targeting.

I meant targetting using the Select program. Target the Engineering Section.
Poor choice of words on my part.

Originally Posted by whulorigan
Keep in mind 2 things:
1) When you say something is moving @ 20mi/sec, you must define relative to what;

I've wondered about this before. I'm sure there's some generally accepted method (galactic plane). Maybe the system's star, or the main world.​

For Jumps between systems I would normally presume the destination system star. For in-system travel, the system star makes a good reference point for general purposes. But you could also choose the destination world if it suits your purpose as well.

The key point as far as the conversation is concerned, however, is that I never presume a reference point in a conversation about velocities in space. I always make sure the reference is defined clearly so that everyone is on the same page in the discussion.

 

[Supplement Four]

SDB patrols must be hell in systems where the main world is masked by the system's star.

It would take multi-thousands of SDBs to patrol the entire sphere created by the 100 diam limit of the system's star. And, if we're talking about a binary or trinary system...sheesh!





I think the key to Corsairs is disguise. Fake transponders. A wolf among the sheep.

Like running up the black flag, it's only when a ship shows its true colors as a pirate that victims realize that they are in trouble.

 

[robject]

There ought to be a wide variety of ways a pirate might try to steal its supper.

The one that springs to my mind is that a pirate's "base" can be on-planet, where a corsair is waiting for the right ship to arrive or leave.

 

[Timerover51]

I guess that I figured that one reasonably good means of avoiding possible interception would be to depart a planet on a course 90 degree to the plane connecting the departure and arrival stars, boost at 1-G for 75 minutes, giving a velocity of 100,000 miles per hour, coasting to the safe jump range, executing the jump with the objective of coming out 90 degree to the plane at the arrival system at somewhere around the 120D distance, killing velocity vector, and then heading to the destination planet. I do not view the 100D arrival distance as at all sacrosanct.

 

[HG_B]

I guess that I figured that one reasonably good means of avoiding possible interception would be to depart a planet on a course 90 degree to the plane connecting the departure and arrival stars, boost at 1-G for 75 minutes, giving a velocity of 100,000 miles per hour, coasting to the safe jump range, executing the jump with the objective of coming out 90 degree to the plane at the arrival system at somewhere around the 120D distance, killing velocity vector, and then heading to the destination planet. I do not view the 100D arrival distance as at all sacrosanct.

Moving that slow you'd be a sitting duck on the outbound leg.

 

[Supplement Four]

I guess that I figured that one reasonably good means of avoiding possible interception would be to depart a planet on a course 90 degree to the plane connecting the departure and arrival stars, boost at 1-G for 75 minutes, giving a velocity of 100,000 miles per hour, coasting to the safe jump range, executing the jump with the objective of coming out 90 degree to the plane at the arrival system at somewhere around the 120D distance, killing velocity vector, and then heading to the destination planet.

I don't think all that maneuvering will get a ship anywhere in the way of hiding from pirates. Safe jump is a sphere, 100 diams out, so it doesn't matter if you zig-zagged to a point on that sphere or if you took the shortest route.

The only thing I can see as a benefit is if a ship didn't take the shortest route to the 100 diam limit, instead going to a point on the sphere that takes longer and not being where a tracking ship might expect your ship to be before it goes to jump.

Even that, though, will probably be of little help. It's easy to track a ship with its M-Drive pushing it at max velocity to the jump point.

Likewise, the target vessel will probably notice an incoming intercepting ship long before that ship is able to match vectors.

The question is--can the defending ship do anything about it?

 

[robject]

Likewise, the target vessel will probably notice an incoming intercepting ship long before that ship is able to match vectors.

The question is--can the defending ship do anything about it?

If they find you a bitter pill to swallow -- i.e. you can unleash a formidable volley of nukes -- they may back off.

If you can stave 'em off with sand and beams long enough to reach the jump point, you're golden.

If you can correctly guess the psychology of the captain, then a skilled PC has a chance to manipulate him over the comm lines, but that's a long shot (worth a try, though).

If you can divert them with a plausible ruse ("Wash, activate the CryBaby(tm)"), then you're good.

 

[Supplement Four]

If they find you a bitter pill to swallow -- i.e. you can unleash a formidable volley of nukes -- they may back off.

If you can stave 'em off with sand and beams long enough to reach the jump point, you're golden.

If you can correctly guess the psychology of the captain, then a skilled PC has a chance to manipulate him over the comm lines, but that's a long shot (worth a try, though).

If you can divert them with a plausible ruse ("Wash, activate the CryBaby(tm)"), then you're good.

I'm hearing music....

So you feel like you ain't nobody
Always needed to be somebody
Put your feet on the ground
Put your hand on your heart
Lift your head to the stars
And the world's for your taking
Are you ready to save the world
Yeah

So you feel like it's end of story
Find it all pretty satisfactory
Well I tell you my friend
This might seem like the end
But the continuation is
Yours for the making
Yes, you're a hero
Ooh, yeah

Flash, a-ah
Saviour of the universe
Flash, a-ah

He's for everyone of us
Stand for everyone of us
He saved with a mighty hand (he saved with a mighty hand)
He saved with a mighty hand (he saved with a mighty hand)
He saved with a mighty hand (he saved us)
Every man, every woman, every child, he's a mighty

Flash, a-ah

 

[Timerover51]

Moving that slow you'd be a sitting duck on the outbound leg.

I take it that you assume pirate/corsair ships are sitting in orbit around the planet waiting for ships to take off?

 

[Shonner]

Something I was just thinking about myself; I will be starting a group new to Traveller next month, and I am relatively new to it, too.

I assume that to go into Jump space, a ship wants to be heading in the direction of its target system, and have some velocity already? That might make it easier for both pirates and patrollers: say a system in which there are two likely jump routes, both would want to hang out near the 100d limit between the ports along the likely exit/entry vectors, no?

Groups new to Traveller are cool.

What I've been doing lately is... whatever direction/velocity/orientation a ship is doing at the point of jump, it comes out of jump with the same values. If it's upside-down and backwards when it engages its jump drive, it comes out of jump space still upside-down and backwards.

 

[Supplement Four]

What I've been doing lately is... whatever direction/velocity/orientation a ship is doing at the point of jump, it comes out of jump with the same values. If it's upside-down and backwards when it engages its jump drive, it comes out of jump space still upside-down and backwards.

That's canon, according to the SOM.

 

[aramis]

I have TNE, but I never read it. Didn't like that game from the moment I saw it in the store. I don't know why I bought so much of that edition--stuff has sat around for years, just collecting dust.

I need to put the stuff on eBay.

So...with TNE, the Travel Forumula is different than the one used in CT, eh? It has to be if what you say above is correct (and I don't doubt that it is).

It goes unused.

The G-burn generates a 0.2LS/hour vector (1 hex per turn at 30,000 km per hex and 30 min per turn), tho it really could be 32,400km/0.5hour, or 31,752km/0.5hour...

Instead, tho' not explicitly given, it's the simpler to work on the fly
T=5 D/B
Noting that T is in hours
D is in LS
B is "burns" of 30 G-minutes

And 0.2B=LS/Hr

 

[leo knight]

That's canon, according to the SOM.

What is the SOM?