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Classic Traveller Discussion on the granddaddy of them all, Classic Traveller!

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Old April 29th, 2017, 01:43 AM
Carlobrand Carlobrand is offline
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Default So, why are lasers missing?

We've talked about this before, I think. Take a ship laser, aim it at a target as big as an office building at a range of about a light-second. In the two seconds it takes for the light from the target to reach you and your own shot to reach him, a target doing 6G can move 120 meters on the axis of its engines (or 30 meters perpendicular to that if you like MT Starship Operator's Manual's look on things and port that over here). At a half light-second range, we're talking 30 meters on the engine axis (or 7.5 meters perpendicular).

At a light-second, an object 1.5 kilometers long covers a bit more than an arc-second. An Azhanti High Lightning's shortest dimension is about 1/40th of that, it's longest dimension is a bit under 1/4 of that (4/15ths, actually). Takes 3.65 seconds for an AHL sized ship doing 6G to change its vector by its entire length. I'm not sure how accurate our modern tools are at centering something on a target at that fine an angle, whether they can move quickly enough or accurately enough to track an object changing vectors at a quarter arc-second per second, but when we're talking ships at TL9-15, I'm pretty sure somewhere along that line they acquire that level of accuracy.

So you aim your one laser, you shoot ... and you miss. With no agility, you miss 58% of the time. With full agility, you may have no chance at all. How did you miss?

Well, maybe you didn't.

Let's say a laser hits pretty much whatever they're pointed at within a light-second or so, at least on the scale of a ship. Overall, you miss 58% of the time, but when you hit, you get a surface damage result: a weapon, a bit of fuel, maybe some drive damage. You don't penetrate, you can't reach the computer, can't hit the power plant or the jump drive (which are fairly large targets within the ship), can't hit stuff within the hull. Basically, sometimes you get lucky and hit a weapons port or turret ring, or the exposed portion of the maneuver drive, or a hit over a fuel tank will radiate heat from the hull into the tank and force the tank to vent fuel to keep from rupturing, but you're not burning through the hull even on an unarmored ship.

The ship's moving as you hit it - as much as 30 meters during a one-second burn - and it might also be spinning to distribute any hit over a larger area, and your ability to penetrate depends on your ability to track his changes with fraction-of-an-arc-second adjustments over the course of the burn. So, most of the time you're hitting, but the ship's hull disperses the beam without effect. You only get an effect when you're lucky enough to hit something exposed, like that weapons port, or hit over a fuel tank. In that paradigm, agility is less about dodging the hit entirely and more about making it harder for them to get a bead on the vulnerable parts of your ship's surface. With a one-second delay, holding a beam accurately on something as small as a turret is a lot trickier than holding it on something the size of a ship.

Why would a computer rating affect that? I don't know. Maybe the computer controls some sort of camouflage pattern on the ship's surface intended to make it more difficult for those targeting the ship to discriminate between turret and flat surface, but that shouldn't save the maneuver drive or fuel tanks.

On the subject of lasers, I'm about set to say that that shipboard lasers are x-ray lasers at TL7 and gamma lasers at TL13, at least IMTU. We're doing x-ray lasers now, though in an experimental way and at vastly lower power levels, so TL7 might be pushing it but they'd certainly be a possibility for TL9. I figure I can justify a 2 cubic meter 250 Mw ship-mounted laser to be able to achieve it, and it makes the range thing easier.

Yes, I'm a bit too compulsive about verisimilitude; that's my curse, though it does offer some interesting educational benefits. Yes, there've been suggestions about accomplishing light-second ranges at lower wavelengths with gravity lenses, but I can't see where the power for that comes from when it's delivering 250 MwS at the target.

A useful side effect is that it gives me a handy explanation for why lasers aren't useful for attacking surface targets from orbit: x-ray is blocked by atmosphere. (I have enough trouble keeping those minor colonies alive without worrying about them getting carved up by orbiting pirates trying to pry a ransom out of them.) It also limits the application of ship's lasers groundside, if you have players inclined to indulge in such things: half-value layer in air for photons at 100 KeV is about 35 meters, which I think means you've got a 125 million joule flash of heat and light going off on a line 35 meters out from the laser turret, hot enough to cause lethal burns out to 14 meters perpendicular to that line (and out to 10 meters for the next 35, and out to 7 meters for another 35, ...), but you're not actually likely to do damage to something you aim at unless it's within about a football field's length of you, and it's probably hot enough at the point of emission to damage the laser emitter. That last one is likely to discourage players from trying to carve up the starport from their ground berth: you might fry a boarding party at close range but you won't do a lot more than that, and you'll kill the weapon in the process.
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Comments made are for the purpose of offering alternative campaign settings for consideration. The writer acknowledges that Traveller is intended to emulate certain common science fiction tropes and that, in the course of emulating those tropes and providing a better playing experience, some liberties must be taken with science. No statement by the writer should be interpreted as constituting a criticism of the game on that basis ... except for that bit about Virus. Dude, really?!
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