Using mass driver engines as laser defense.

[Lexx]

Ok, anyone here familiar with traveller? If so you already know what a sandcaster is/does.

For the rest, a sandcaster is used to defend against lasers in traveller ship combat by scattering clouds of sand in front of an attacking ship so it's lasers will be degraded by passing thru the sandcloud.

Well, there's no real reason why a mass driver engine in THS can't do likewise.

As I see the mass driver engine (MDE) is uses finely powdered rock dust as a reaction mass and throws it out the rear at unholy speed to propel the asteroid ship it's mounted on.

BTW, even tho this wasn't said in THS, I was assume that by system wide law a MDE is required to ONLY exhaust FINELY powdered rock to avoid creating streams of murderous rock fragments whizzing around at lethal velocities and concentrations. So, at least in my THS setting, MDE's are made to be unable to throw out dangerous sized chunks of rock. This alos eliminates using them as impromptu coilguns and the difficult mechanics of figuring damage for various chunks of rock being spit out by them.

It would likely be a MAJOR crime in the THS solar system to have a MDE that put out anything but fine dust, something perhaps other GMs want to adopt despite the temptations of using MDEs as emergency weapons.

Anyway, back on topic...

As I see it, a MDE could be used like a sandcaster in THS to defend a ship propelled by one from attack by lasers. Since lasers automatically hit in THS (Which is pretty realistic given the facts of realistic space combat.) the issue is how to reflect the effect of tons of rock dust degrading laser fire that passes thru it.

Well, here's what I have. Submitted for your approval:

If a ship with a MDE is attacked by laser fire from another ship or AKV, but not a XRMP, it may try to use it's MDE exhaust as a defense.

In order to do so, it's MDE must face the attacking ship and keep it within a 60 degree conical arc centered on the MDE. It must also use it's MDE at full thrust.

Note that since MDEs are fairly standard, the relative size of one is not important as a smaller MDE will likely be mounted on a smaller asteroid and thus have less ares to cover, while a larger one may put out more dust it has more area to protect, nullifying any advantage it would expect due to the greater volume of dust it outputs.

The pilot of the ship must make a piloting roll or another person on board must make a tactics roll to deploy the cloud effectively. Only one roll is used, even if both skills are present.

The intent to use a MDE as an anti-laser defense must be made at the start of the turn and the ship must be facing the attacker it wishes to screen itself from. If the conditions are met and the piloting or tactics roll is a critical success, a ship firing lasers thru the arc must roll 3 times against his gunnery skill and take the highest result. In case of a critical failure, roll a die: On a 1-4 the result is simply treated as all lasers fired having no effect as they are either absorbed or ablated by the perfectly placed cloud of rock dust. On a 5-6 it's treated as a normal critical failure on the gunnery skill roll.

If the ship using the MDE makes a success on either it's pilot or tactics roll, a ship firing laser at it from within the 60 degree conical arc centered on it's MDE must make 2 gunnery rolls when firing lasers, and take the worst roll with the provisions mentioned above.

If the ship using it's MDE as a laser defense fails the roll, no effect is had on any laser fire.

If the ship using it's MDE as a laser defense makes a critical failure on it's roll, then it gets no benefit against laser fire and suffers the appropriate effect of the critical failure.

A MDE can't defend against any other weapon, including XRMPs as the XRMPs are too fast moving to lay a cloud in front of. Also note that if the ship using a MDE as a laser defense fires lasers thru the arc covered by it's MDE exhaust while using it, it will have to roll for effect based on the results of it's MDE roll just like an attacking ship would as the MDE is venting dust for the full 100 second turn, and a lser shot represents a full 100 seconds of fire.

As this is a suggested optional house rule, I haven't come up with modifiers for damaged drives, but perhaps a -1 to the piloting or tactics roll for each 5% or so of reduced thrust would be fitting. Also note the ship using the MDE must expend power, reaction mass and build up heat as if the drive were running full tilt.

This makes a nice add on to the space combat rules and gives people a reason to occasionally take asteroid ships with MDE. Please use or ignore this proposed optional rule in the friendly spiirit it was offered in.

[Phil Masters]

Mass drivers are certainly illegal in Earth orbit, whatever size chunks they eject. In, say, the Belt - who cares about a few more lumps of rock moving at high velocities? Got lots of those already, and they're lost in all that volume.

("Space is big.")

Anyway, mass driver throwing dust as defense:

Mass driver ejects dust. Dust expands forming cloud.

If opposing ship has any lateral acceleration relative to the target to speak of, it ignores this fact and carries on shooting. If not, it uses a nudge from lateral thrusters to acquire such velocity, then starts shooting again. Cloud of dust is almost certainly soon left behind the fight. Laser beam may clip edge of cloud, perhaps losing 1% of intensity.

Remember, a space combat turn lasts 100 seconds. What do you think happens to that dust cloud in 100 seconds? And how far is the fight likely to move?

Trav sandcasters don't work, I'm afraid.

[Lexx]

Originally Posted by Phil Masters

Mass drivers are certainly illegal in Earth orbit, whatever size chunks they eject. In, say, the Belt - who cares about a few more lumps of rock moving at high velocities? Got lots of those already, and they're lost in all that volume.

("Space is big.")

Anyway, mass driver throwing dust as defense:

Mass driver ejects dust. Dust expands forming cloud.

If opposing ship has any lateral acceleration relative to the target to speak of, it ignores this fact and carries on shooting. If not, it uses a nudge from lateral thrusters to acquire such velocity, then starts shooting again. Cloud of dust is almost certainly soon left behind the fight. Laser beam may clip edge of cloud, perhaps losing 1% of intensity.

Remember, a space combat turn lasts 100 seconds. What do you think happens to that dust cloud in 100 seconds? And how far is the fight likely to move?

Trav sandcasters don't work, I'm afraid.

The ship is constantly ejecting the dust, it's not just one cloud, it's a constant smokescreen effect.

Also, if the distance is large enough, the firing ship won't be able to shift laterally enough to shoot around the screen effect.

[Phil Masters]

Put it this way; if a mass of matter N is effective laser defense when scattered across cubic miles of space, wouldn't it be more effective plated over the ship's hull as armour?

At the very best, some of the mass you eject gets in the way of the beam. The beam - which is presumably capable of punching through non-trivial amounts of spacecraft hull structure - vaporises it, and much of its energy continues on the way to the target.

I notice that Trav sandcaster descriptions include all sorts of doubletalk about (specially formulated) prismatic crystals to scatter the beam. Despite which, they're still considered one of that line's less plausible features.