Laser Point Defense Against Missiles

[MrMorden]

Let's say a missile attack is launched at a ship from long range, and it will take the missiles three turns to close on the target to hit.

Does the defending ship get three rolls for missile point defense, or just one? If just one, at what point is the roll taken? Also, if only one roll...why? It seems if I can hit a missile or salvo with a laser, why not start early and keep firing as long as you can?

Thanks.

 

[Valarian]

I'd say that the laser would get a roll for each round that the missile is in range and hasn't yet hit the target.

 

[MrMorden]

At the risk of hijacking my own thread, a couple of more questions:

1) What is the roll to hit/shootdown a missile salvo?

2) For nukes, what does a damper have to roll to defeat the missile? I looked hard for the answer to that one last night and could not find the answer. Is it a separate roll? Adds to the defender's AC vs nukes?

 

[stofsk]

Originally posted by MrMorden:
Does the defending ship get three rolls for missile point defense, or just one?

If there are three rounds available then you get three combat actions. Which means three shots of the lasers. Your lasers can't be used against the enemy ship though, unless you have the double fire offensive program installed in the ship's battle computer. (and even there, you have to have excess energy)

Originally posted by MrMorden:
1) What is the roll to hit/shootdown a missile salvo?

2) For nukes, what does a damper have to roll to defeat the missile? I looked hard for the answer to that one last night and could not find the answer. Is it a separate roll? Adds to the defender's AC vs nukes?

1) Page 163 under Gunner Actions.

Point defence laser: 1d20 + Gunnery Skill + (computer USP/UVP) + Weapon UVP/USP.

Missile's defence: 16 + Missile USP/UVP.

2) Dampers don't work the way you think they do. Page 268: "In combat the USP rating of the screen is used in place of the armor rating of the ship where appropriate."

Thus a nuclear damper provides damage dice reduction rather than a bonus to AC.

Now it's my turn: how many clicks does a missile travel per minute?

 

[MrMorden]

Thanks for the info!

As for missile speed...since they are constantly accelerating, like a ship, you can't say how "fast" they are (since it changes second to second), only how fast they accelerate.

If you assume 60m/sec (6G) acceleration, since velocity = (acceleration * time), you get:

0 seconds = 0 m/s

60 seconds = 3600 m/s

120 seconds = 7200 m/s

and add another 3600 m/s for each additional minute of acceleration.

Clearly at the end of a space combat turn of ten or twenty minutes, any missile will be really hauling ass. With velocities in the tens or hundreds of kilometers per second, it is unlikely an explosive warhead is even necessary to cause extensive damage on impact.

 

[stofsk]

Ah, Traveller. Do math, for fun! (then die in character gen)

 

[MrMorden]

You got that right, brother.

 

[BetterThanLife]

Originally posted by MrMorden:
Thanks for the info!

As for missile speed...since they are constantly accelerating, like a ship, you can't say how "fast" they are (since it changes second to second), only how fast they accelerate.

If you assume 60m/sec (6G) acceleration, since velocity = (acceleration * time), you get:

0 seconds = 0 m/s

60 seconds = 3600 m/s

120 seconds = 7200 m/s

and add another 3600 m/s for each additional minute of acceleration.

Clearly at the end of a space combat turn of ten or twenty minutes, any missile will be really hauling ass. With velocities in the tens or hundreds of kilometers per second, it is unlikely an explosive warhead is even necessary to cause extensive damage on impact.

Only if you actually generate a solid hit and it assumes the target isn't moving away from the missile. At those speeds a non-square impact is at least as likely to deflect away as it is to cause serious impact damage. Further since the target is maneuvering and not stationary, at those ranges some of that accelleration is going to matching the vector changes of the target. Further if the missile is coming in to fast it is prone to miss due to a late jink by the target and just go scorching by.

I personally only allow PDL in the first range band of the Point defense weapon or the turn of impact if the weapon would cross the range band due to speed and impact from outside the first range band. This also sets limits for other craft providing point defense for a ship other than themselves (who don't get the one roll against a very high speed missile crossing through their engagement envelope that fast.).

Actually IMTU ships are limited to one range band of the weapon or three range bands of the sensors whichever is lesser. Provided you know it is coming. I never allow initial sensor readings of an enemy outside the initial range band of the sensors unless the enemy, somehow gives away their presense.

 

[princelian]

A little off-thread, but...

Ah, Traveller. Do math, for fun! (then die in character gen)

If you fail the survival roll in Prior History, you don't die. In CT you are forced into another career (or to muster out, depending on interpretation) and in T20 you roll on the mishap table.

 

[stofsk]

The joke is less funny when you point that out.

 

[BetterThanLife]

Originally posted by princelian:
A little off-thread, but...

</font><blockquote>quote:</font><hr />Ah, Traveller. Do math, for fun! (then die in character gen)

If you fail the survival roll in Prior History, you don't die. In CT you are forced into another career (or to muster out, depending on interpretation) and in T20 you roll on the mishap table. </font>[/QUOTE]Actually in CT you did die (LBB1). In later books, I forget which one it was, I think it might have been LBB5, they added an optional rule that you, Referee's discretion, mustered out and took a loss to some characteristic.

That was formalized as an optional rule in MT. In T20 you don't die but you do roll on the mishap table. (Which can't kill you but can definitely hurt.

)

 

[mike wightman]

The optional rule to not die on a failed survival roll appeared in the revised edition of CT and its derived works, the Traveller Book and Starter Edition.
In MT death was the optional rule.
At no time in CT revised or MT does failing a survival roll cost you anything attribute wise.

 

[BetterThanLife]

I thought I remembered something in there about some kind of disfigurment or permament damage, but it has been years since I played those rules.

I knew someplace back there they added the optional rule about survival roll not being fatal, but I also remember it was an optional rule and the mainline rules were a failed survival roll was death. I also knew in LBB1 was before the optional rule.

Thanks for the fact checking Sigg.

 

[archhealer]

in T20 there is possibility of permanent ability damage. Also, if I remember correctly, you can die in the army prior history, but I think they're the only one, and you have to be pretty damnably unlucky.

 

[BetterThanLife]

Originally posted by Archhealer:
in T20 there is possibility of permanent ability damage. Also, if I remember correctly, you can die in the army prior history, but I think they're the only one, and you have to be pretty damnably unlucky.

Death isn't in my copy of the THB for any class. But failure of the survival roll is not pretty, in most cases, the biggest loss in terms of failure of the survival roll is, IMHO, the 4 years older and no XP.

 

[veltyen]

As far as I can tell the only way you can die under canon generation from the THB is by starting with Con 3, and getting an injury.

Possible? Yes.
Likely. No.