Spaceships - Defensive Munitions
 

in the vein of Traveller Sandcasters...
A defensive weapon mount that launches cannisters of a material which, in essence, confuse targeting systems.
Traveller Sandcasters count as dDR versus Beams.

I want to count them as confusing missile targeting but can't decide whether to use it like ECM (ala smoke), Dodge (substitute gunnery skill for piloting), skeet-guns (MoS = hits) or plain guns (one-shot, one-kill).

Any suggestions?

Re: Spaceships - Defensive Munitions
 

ECM if it works against any number of targets by confusing the sensors and provides a Dodge bonus (but IMO ECM stations are very weak in GURPS). Point defense weapons if they actively shoot down missiles.

Re: Spaceships - Defensive Munitions
 

Yes, the ECCM rules make ECM for smallcraft pretty pointless. Sticking in a system that allows some other kind of defense appeals.

Just realising, though, if I treat it like ECM for missiles, why is it armour v's beams... I guess the skeet-gun effect fits that best: launched "sand", diffuses beams and ravages incoming ballistics. Must be why it's used in Traveller. Or I could just, as you say, give a bonus to Dodge.

I think the basic Traveller sandcaster is a close match for an SM+7 Medium Battery and was going to scale it all from there.

Re: Spaceships - Defensive Munitions
 

Atomic Rockets claims that there's no way a sandcaster can project a dense enough field to make a difference. They don't go into details, but they're usually a reliable source. If you like the idea of sandcasters, go crazy, but if you're looking for realism I thought I should mention it.

Re: Spaceships - Defensive Munitions
 

I think this is a thing that would call for a new rule. Essentially it creates a cloud that will temporarily reduce the damage of lasers firing through it, and reduce the accuracy of missiles on the other side by obscuring the ship using it. Is that right?

Re: Spaceships - Defensive Munitions
 

Wouldn't the cloud prematurely detonate or otherwise scatter kinetic weapons?

Re: Spaceships - Defensive Munitions
 

Most kinetic weapons would not have explosive warheads since the damage of collision would do more damage.

Re: Spaceships - Defensive Munitions
 

Yes, but the same principle that makes kinetic weapons so devastating against ships also means that it takes very little impact with debris to destroy them. Every sand grain hitting the warhead will strike with incredible kinetic force. It might not be a guaranteed kill (missles would need some form of shielding just for random space junk), but it would need to be accounted for.

Re: Spaceships - Defensive Munitions
 

Yeah, and I think it'd take a lower concentration to physically interfere with kinetic projectiles than it would to interfere with their targeting sensors.

Re: Spaceships - Defensive Munitions
 

For the most part, such impacts would basically turn the projectile into scattershot. With active missiles, guidance and/or propulsion might be destroyed. I'd break things into levels.

Minor damage: AP munitions might lose their armor divisor (if dependent on shape). Missile guidance slightly distorted, giving an attack penalty (-2).

Medium damage: Missile guidance damaged, and propulsion system cannot make fine corrections, giving a large attack penalty (-4). If using a volatile* warhead (like antimatter), premature detonation is possible (HT roll for individual missiles; assume 1/2 missiles fail for salvos).

Major damage: Missile guidance is destroyed, and the propulsion system can't do anything beyond making the missile go faster (and it might do this at a decreased acceleration). The missile is effectively "dummyfired," simply going in a straight line to infinity - this imposes a large attack penalty and grants a Dodge bonus (-4; +2). A volatile warhead will certainly detonate prematurely (no roll allowed), and volatile fuel can have a similar effect (HT roll).

Catastrophic damage: The missile is now simply a collection of rapidly-moving projectiles. It has a high RoF, but each hit does less damage (for simplicity, assume x4 and x1/4, respectively). It has the same attack penalty (which may be partially offset by the RoF) and Dodge bonus as in the case of Major damage. If it had any volatiles, these have already detonated.

*Volatile in the Spaceships sense - that is, a system that risks blowing up the ship when damaged


A missile that brushes with the perimeter of a sandcasted barrier suffers Minor damage, one that goes through the area suffers Medium, one that hits near the dead center (or the most concentrated area, if somewhere other than dead center) suffers Major. Going through multiple barriers upgrades damage - going through two perimeters suffers Medium (Minor+Minor), going through a perimeter and a general area suffers Major (Minor+Medium), and going through dead-center and perimeter suffers Catastrophic (Major+Minor).

For a system to determine this, don't give sandcasters an RoF bonus other than that from actual rate of fire (that is, RoF n, not RoF nxm). Each success forces one missile in a salvo through Heavy concentration (Heavy damage), two missiles through Medium concentration (Medium damage), and four missiles through Minor concentration (Minor damage). As you run out of missiles, assign damage to those that have taken Heavy damage first. Calculating what all hits is something I'll leave to someone in a less-loud setting, as I currently can't think straight.

Example: A salvo of 10 missiles is incoming, with a single gunner manning an RoF 3 sandcaster. He fires at full RoF and gets the maximum number of successes possible - 3. This means 3 Major, 6 Medium, 12 Minor. With 10 missiles, this is 3 Major, 6 Medium, 1 Minor, with 11 Minor left over. Those 3 Major get upgraded to Catastrophic, the 6 Medium upgrade to Major, the Minor upgrades to Medium, and there is 1 Minor left over. So, in total, we have 4 Catastrophic, 5 Major, and 1 Medium.