Point defense against Lasers.

[BetterThanLife]

OK Stupid question time. How do Sandcasters work as point defense against a laser?

Since most sensor systems on a starship are lightspeed sensors. Using your passive or active sensors how do you know before the laser hits you that it has been fired at you so you can use Sand in a point defense role. By the time the information that the enemy has fired reaches you so does the shot. How is this supposed to work? Or does sand work against all the lasers targeted at your ship? Which means it was triggered before the enemy actually fired.

Am I missing something or is this one of those wave a magic wand things?

Are lasers two stage weapons, a low powered beam hits the target and determines the range/bearing then the laser is stepped up to the damage producing powersetting and that is how the Sand is triggered?

Just ount a bunch of low powered targetting lasers on your ship and make all your enemies think they are being fired upon at the same time.

 

[womble]

Sandcasters aren't point defense weapons. They're passive defenses which launch a speculative cloud of particles to float between you and the hostile vessel, blocking laser fire (? in both directions, I'd guess ?) until either ship has maneuvered enough that the cloud no longer blocks line of sight, or the cloud disperses.

As you say, active defenses against lasers are not available in most TUs due to the lack of the necessary FTL sensing of incoming fire. Point defenses are usually considered to be active measures.

 

[TheEngineer]

Hi Bhoins !

HighTech ship computers even know, what will happen in near future...

Well in MT, I assume that the enemy fires his beam weapons not only once but as often as these weapons can (ROF).
So, in a 20 minute combat round a target might receive partial hits, which could be used to trigger sandcaster disposal on the targets side.
The effects of these superfical surface hits might be used as additional input for enemies targeting systems.
Its very similar to Your thought about the low powered beams, but I just did not consider to save energy

. (Somehow a high power active sensor pinpoint scan....)

 

[BetterThanLife]

The rate of fire over the period of time is an interesting point. Even if that is the case the first hit it is still going to cause damage.

As for the low powered ranging shot, I would design weapon systems that would either put in a bunch of low powered emmiters to get the enemy to light off his sand and/or not have the low powered initiator. (Recon by fire.) YOu certainly don't want the enemy to know you are firing a weapon he can only detect by being hit.

The use as area defense when you think he is going to fire isn't how the system actually works. At least in my reading of LBB2, LBB5 and MT. I am going to reread T20 and see what it is they are actually saying. But in the original version you got one use of a sandcaster mount for each incoming laser. So for example you have 5 sandcaster batteries and the enemy fires 6 lasers at you then 5 have to penetrate sand and one goes through unmolested. (Even though they all have to pass through the same general area.)

In T20 Sand increases your AC. But I have to see if it is for individual shots or generally.

So much for hard Science. Oh and since MT defines starship sensors as EMS, that means they are lightspeed sensors. The only one that might not be is the densiometer which wouldn't detect a laser. Assuming Gravity is FTL. (Like in David Webbers books.)

 

[Uncle Bob]

In a 10 or 20 minute turn a maneuvering spaceship would get out from behind an unimaginably big cloud of "sand". Therefore a round of sandcaster fire must be a series of bursts, leaving a trail like WWII smoke. By timing carefully it should be possible to return fire during narrow "windows" while remaining effectively protected the rest of the turn.

I don't buy the glancing hits idea. The same rules apply to an armor 0 mylar baloon.

 

[BetterThanLife]

Problem is, given the way they work in the rules, Sand doesn't work that way. It is per individual shots, but I agree you should be able to duck and cover and fire between your own sand, after all you know when it is being launched.

Originally posted by Uncle Bob:
In a 10 or 20 minute turn a maneuvering spaceship would get out from behind an unimaginably big cloud of "sand". Therefore a round of sandcaster fire must be a series of bursts, leaving a trail like WWII smoke. By timing carefully it should be possible to return fire during narrow "windows" while remaining effectively protected the rest of the turn.

I don't buy the glancing hits idea. The same rules apply to an armor 0 mylar baloon.

 

[daibaka]

I may be completely off base here, but I seem to remember that the "sand" in question is actually manipulated to shield the side of the ship facing the incoming fire, and ablates away as it takes or diffuses hits. The sand would retain the angular momentum of its launch anyway, but I think I remember that at lower stellar tech levels the system actually used a ferrous "sand" that could be controlled, via magnetic fields projected from the launching turret, to shield the ship at a short distance. At higher tech levels an improved version utilised gravitics to do the same thing with a more effectively ablative crystalline "sand".

This is all purely from memory, however. I couldn't give you page references without at least a night's worth of research and I could very well be wrong! I'll just add that I haven't read the full T20 starship combat or design sequences yet, so this might not be how these things are done these days!

 

[TheDS]

Daibaka, you are the man! You win for having read the book!

When released, a cloud of sand sticks with the own-ship, and its exact location is controlled by that ship. Its density can also be controlled. The cloud doesn't get disappated unless the cloud gets hit, or the ship enters an atmosphere, or the own-ship releases it (perhaps to make jumping easier?).

A sensor task consists of first seeing the target, then getting a firing solution. The first thing can be done with an omni-directional radar or even by looking at it with your Mk1 Eyeball.

Getting a firing solution involves using ranging sensors, typically LIDAR (Radar with lasers), or at short range, MIDAR (Radar with Microwaves). Such a device gives you range and direction, two detections give velocity, and three detections give acceleration.

When the target ship detects the LIDAR of the firing ship, well, LIDAR is not used for spotting, it's used for getting a firing solution. That's the signal to pop a sand cannister.

Using magnetic or gravitic control (depending on tech level), the cloud is moved to the bearing where the incoming fire is expected. Note that you need 1 sand cannister out there per enemy ship firing on you, and this is generally done by having 1 turret per cannister. I don't know if this is a hard and fast rule, but why else would ships mount more than 1 turret?

Anyway, it takes a few seconds to acquire a firing solution, and this is plenty of time to get the defensive sand out. When hit, the cloud is considered to be destroyed, reducing the incoming shot by its value. Another cannister is immediately popped to intercept the next incoming shot.

Naturally, since your ship is twisting and turning and trying to avoid being hit in the first place, the sand invariably gets out of the way of your outgoing laser shots, so your outgoing fire is not affected, and this also doesn't affect the defensive value. In the books, they say you can make holes in the sand to let your lasers fire out, but realistically, this isn't even needed.

And as one more point of fact, gravity has been found to travel at the speed of light. HeckifIknow how they proved it, but it had something to do with observing occulting stars (stars that cross in front of each other from the perspective of the viewer, in this case, Earth).

 

[TheEngineer]

Hmmm, so a detected active pinpoint scan triggers the release of sandcasters.
Does that LIDAR/MIDAR scan reveal the location of the scanning object in T20, as any active scan does in MT ?

 

[mike wightman]

Sandcasters work differently in the different versions of Traveller.
In Mayday/LBB2 combat the sand cloud is launched as ordnance and the firing ship can lose the protection if it maneuvers away from the sandcloud.
HG and MT abstracted the whole combat system so that sandcasters become a sort of PD weapon. TNE introduced T2300 like shields to the discription of how sandcasters work.
Look at how they are treated in PP:F - that's pretty close to M/LBB2 combat.

 

[TheEngineer]

Its actually the abstraction of those space combat systems, which sometimes make it difficult for me to present players "whats going on" in an - ehm - entertaining way.
Quite well for a board game but perhaps a bit rigid for a RPG session.

Anybody got actual gaming experience with T20 space combat rules ?

 

[BetterThanLife]

So if I develope my firing solution using passives you get no sand? Hell I'll just turn on my active sensors and light you up with tracking radar to get you to launch all your sand. (Intermittently of course.) Then fire on you while you are reloading or when my tracking systems stop causing you to launch sand.

It doesn't jive with the way it is written in HG or MT. Even Mayday. But I haven't messed with Mayday without the HG combat tables in almost 20 years so I may be remembering wrong.

In all of those it is Sand in response to a specific Laser shot at your ship.

I was always under the impression that sand difused lasers not that it was ablated by them.
Which would mean that more powerful lasers would still score but less powerful ones would simply not have enough power to carry through as more than, say a flashlight. Which is why the tables worked the way they do and the roll is to see how much of the sand is actaully in the way.

Originally posted by TheEngineer:
Hmmm, so a detected active pinpoint scan triggers the release of sandcasters.
Does that LIDAR/MIDAR scan reveal the location of the scanning object in T20, as any active scan does in MT ?

 

[etherflyer]

Originally posted by Bhoins:
But I haven't messed with Mayday without the HG combat tables in almost 20 years so I may be remembering wrong.

IIRC, you can launch sand and get the benefits for a while, but they vanish as soon as you accelerate.

They also weren't that substantial. We always preferred to have an extra missile rack or laser -- you ended up taking less damage that way.

 

[BetterThanLife]

Gaming experience solo gaming not as part of a T20 campaign yet. Mostly evaluating the differences between it and MT or HG. You have abstract and mapped. I have already identified the majority of the differences on here in various places. Smaller craft can hit and do damage to each other, further smaller craft can hit and damage larger craft. However, larger craft will mop the floor with smaller craft. Which, IMHO, is as it should be. Once you get into bay weapons especially Meson Bays combat becomes fast and extremely deadly. Multiple Meson Bays will shatter Drednaughts (and we are talking about 3-7 of them). Spinal Mesons will, more often than not, shatter anything in one shot. (And vaporize anything less than 500,000Tons 52.5% of the time with one shot.) As long as you stay away from Meson weapons, and to a lesser extent High Energy weapons (Plasma and Fusion) then combat is well done, easy to GM and fairly balanced the way it should be. (Though Point Defense tends to be hellaciously effective against Missiles.) The problem is exactly how sand works, because it is poorly defined.

Originally posted by TheEngineer:
Its actually the abstraction of those space combat systems, which sometimes make it difficult for me to present players "whats going on" in an - ehm - entertaining way.
Quite well for a board game but perhaps a bit rigid for a RPG session.

Anybody got actual gaming experience with T20 space combat rules ?

 

[TheDS]

Originally posted by Bhoins:
So if I develope my firing solution using passives you get no sand? Hell I'll just turn on my active sensors and light you up with tracking radar to get you to launch all your sand. (Intermittently of course.) Then fire on you while you are reloading or when my tracking systems stop causing you to launch sand.

Good sir, I believe you are over-reading my comment. When an active sensor (like LIDAR) is used, it is obvious from where it comes. Assuming the captain is expecting trouble, a sand cannister is automatically popped out and the cloud takes up residence between the two ships and stays there. Multiple sources from multiple directions will set off more cannisters, I am sure.

I would have to imagine that the obvious cheap trick of moving and illuminating and moving and illuminating again, to appear to be a different ship, would not work against a sensor operator that was not totally green, though I suppose you could figure out how to spoof someone at great expense to you in time and reaction mass.

Meanwhile, you've announced yourself to the other ship, now he's going to illuminate YOU and at the very least will watch you, so being tricky will require a bit of trickiness, so to speak.

A laser cannot be fired accurately on a completely passive bearing against a maneuvering target if the range is greater than about half a lightsecond. (This statement is subject to a number of caveats.) This won't stop you from launching a passively guided missile to avoid the enemy dropping his sand.

Note that the above statement may not be accurately modeled in most games, leading a person to believe that they don't HAVE to illuminate to fire a laser, but here in the real world, in combat you have to have some way to know exactly where the targt is and a pretty good idea of where it will be when your special delivery package attempts to collide with it.

 

[BetterThanLife]

I don't know I think I can get a pretty good read on passives and kill a target. Especially if I have time to track it, it isn't under total EMCON and it isn't doing extensive evasive maneuvers. Over time I can get a really accurate idea of distance, bearing and speed of the target. (It is simple physics.) Then just hose down an area that I figure you will be in when the fire gets there.

I don't need active sensors to fire on a target. Of course Mark-1 eyeball is a passive sensor. (As is a telescopic sight.) Granted in Traveller I don't really expect to be firing starship weapons over open sights... There are always other passive sensors that would work almost as well.