Rail gun damage?

[Zeropoint]

Continuing in the vein of my last post:

Let's try a different approach wherein an attack is required to simply punch through hex after hex in a straight line to total up the damage done. Actually, I can see a major problem with this. the frontal area of the ship is 25*50=1,250 hexes, which means that punching a hole clean through the ship lengthwise would only do 30/1250=0.24 BODY to the ship, but would require (20+10)*2 + (8+6)*200 = 2,860 Body from a human scale attack. For comparison, that's the average damage on an 817d6+1 RKA (12,260 pts). I don't have that many dice and you still have to do that four times to inflict one BODY on the ship. This approach is not going to work, I think.

Real-world anti-ship weapons, such as mines, missiles, shells, and torpedoes all have one thing in common: the letter E, which stands for "explosives". Science-fictional weapons such as lasers and hypervelocity solid projectiles also tend to release their energy as an explosion. Let's see what happens if we use an attack with the Explosion advantage to try to destroy our quota of hexes.

5ER lists an option for RKAs which I'll be using here: subtract 2 points of damage for every hex of expansion. That will make things much easier to calculate.

We can see from the numbers in the last post that to inflict one point of BODY damage on the ship, we need to damage the component hexes of the ship out to a radius of 16 hexes, at which point the damage will be 32 less than the damage at the point of impact. To destroy an internal hex will require 14 Body. Therefore, the damage at the point of impact must be 46 Body, the average result of a 13d6+1 RKA, Explosion (+1/2) (300 pts).

On this same model, a 20d6 RKA, Explosion (+1/2) (450 pts) would do an average damage of 70 Body at the point of impact and would do 14 Body out to a radius of 28 hexes. Assuming a hemispherical damage pattern again, this would destroy 91,952 hexes for a total of 11 BODY to the ship.

It would also appear, at first glance, to pretty much cut the ship in half, but the hole in the hull will "only" be 20 hexes in radius.

Hmm. This has been interesting, but this is too complicated to work out in play, at least without some kind of computer program or spreadsheet formula or something.

I think a table showing Size category on one axis, dice of RKA, Explosion on the other, showing how much body was done in each combination, would be very enlightening right now. I'm going to see if I can figure out how to use a spreadsheet program, because that's a lot of number crunching.

More when I have the results.

[Zeropoint]

Hmm. Game mechanics question here: should the value of the ship's hull armor protect all the internal hexes, i.e. subtract from the damage done to them? I've been assuming that if the blast can penetrate the armor at all, then the full value of the attack gets applied to each internal hex in the blast radius, but that starts looking pretty silly with explosions just barely large enough to penetrate the armor.

[braincraft]

a) Even if it were useful to try to translate real-world physics to HERO mechanics in anything like a literal sense, you should note that that is not how projectiles do damage.

b) If that's what you want in game-mechanical terms anyway, just define the rail gun as an AoE Line attack, with Megascale or however many multipliers, and possibly No Range.

c) That is what intervening objects do to projectiles; they slow them down and they end up doing less damage. Often, the amount of force lost is minimal, but sometimes it is great. It's not out of the question for a rail gun projectile to lose enough velocity penetrating one hull to not have enough force left over to penetrate through the other side.

[Zeropoint]

Braincraft, are you talking to me? I'll assume you are and respond accordingly. If you weren't, then this post is pretty much meaningless.

a) Even if it were useful to try to translate real-world physics to HERO mechanics in anything like a literal sense, you should note that that is not how projectiles do damage.

First, I haven't mentioned real physics at all. This is all HERO math. Second, if you think that simple projectiles don't cause explosions when they hit, I've got four words for you: Tunguska. Barringer Meteor Crater.

b) If that's what you want in game-mechanical terms anyway, just define the rail gun as an AoE Line attack, with Megascale or however many multipliers, and possibly No Range.

c) That is what intervening objects do to projectiles; they slow them down and they end up doing less damage. Often, the amount of force lost is minimal, but sometimes it is great. It's not out of the question for a rail gun projectile to lose enough velocity penetrating one hull to not have enough force left over to penetrate through the other side.

When I mentioned an attack (note that I didn't specify that it was a projectile) punching through the ship lengthwise, I was specifically thinking of something losing a little bit of force with each bulkhead it passed through--that's why I computed the damage that it would have to do to penetrate the hull twice and 200 hexes of internal space.

[Trebuchet]

I thought you guys might be amused to know this thread has been linked on a conservative/military weblog in a discussion of the new 16 megajoule navy rail gun.

http://ace.mu.nu/archives/253630.php

[clsage]

I thought you guys might be amused to know this thread has been linked on a conservative/military weblog in a discussion of the new 16 megajoule navy rail gun.

http://ace.mu.nu/archives/253630.php

Repped !!!

"+6 Vorpal Holy Avenger Shells.

Oooh..."

-Carl-

[SteveZilla]

Repped !!!

"+6 Vorpal Holy Avenger Shells.

Oooh..."

-Carl-

And of course used by a Paladin.

Though they did first use Hero System!

"10d6 Mega RKA + AoE Explosive Effect."

[CorPse]

I thought you guys might be amused to know this thread has been linked on a conservative/military weblog in a discussion of the new 16 megajoule navy rail gun.

http://ace.mu.nu/archives/253630.php

Talk about a case of "build it and they will come."

Dang.

[tkdguy]

I thought you guys might be amused to know this thread has been linked on a conservative/military weblog in a discussion of the new 16 megajoule navy rail gun.

http://ace.mu.nu/archives/253630.php

Cool!

Here's a video of a test firing, which I cross-posted in the random videos thread.

[Merovign]

It's a 32-Megajoule railgun, BTW.

And Ace is the guy who statted out 2004 candidates in D&D terms. There's a little bit of RPG geekage at AoS, along with a whole lot of crazy.

Look today and you'll see an argument over a guest blogger declaring support for Seahorses in the primaries.

Be warned that there's often a fair amount of profanity and some real brain-bleach-needed posts.

There's a reason Ace describes his blog as a "Moronblog."

[FireTiger]

It's a 32-Megajoule railgun, BTW.

Let's see... looking at the old Integrated Damage Class table, a 32 MJ weapon is at the 6½d6 to 7d6-1 line. That makes it slightly bigger than the ship's railgun from Star Hero for 5th ed., found on page 197.

[Markdoc]

Cool!

Here's a video of a test firing, which I cross-posted in the random videos thread.

I was wondering if anyone had posted that. It's a cool video: though it highlights the problems we were talking about upthread - you can see the "gun" self-destructing in a spectacular fashion as the projectile comes out.

cheers, Mark

[tkdguy]

I was thinking about how to circumvent other problems with railguns.

Recoil: There is recoil when a railgun is fired. In space, where there is no friction, it can affect the ship's trajectory (remember, firing an autocannon deorbited an Almaz station). My solution: Fire thrusters to counteract the recoil at the same time the guns are fired.

Range: Railguns would be less effective at long range. If the target is able to move under its own power, it can "dodge" the shells. My solution: The guns will be linked to a tactical computer that is constantly updating the target's trajectory and making the necessary corrections.

What do you think?

[IndianaJoe3]

Range: Railguns would be less effective at long range. If the target is able to move under its own power, it can "dodge" the shells. My solution: The guns will be linked to a tactical computer that is constantly updating the target's trajectory and making the necessary corrections.

Once the railgun shell leaves the barrel, it is on a fixed trajectory. The target can still dodge. There could be guidance thrusters on the shell itself.

[Nyrath]

Recoil: There is recoil when a railgun is fired. In space, where there is no friction, it can affect the ship's trajectory (remember, firing an autocannon deorbited an Almaz station). My solution: Fire thrusters to counteract the recoil at the same time the guns are fired.

Those would have to be pretty huge thrusters. They have to basically put out the same amount of energy that the railgun round contains.

Newton's second law say that F = ma, i.e., momentum is mass times acceleration. If a railgun round of mass x is accelerated at rate a, it will contain xa momentum, which will shove the firing ship with that much force. The thruster will have to emit the same amount of force in the opposite direction to counteract this.

Which means you really don't want to in the thruster's exhaust plume.

Range: Railguns would be less effective at long range. If the target is able to move under its own power, it can "dodge" the shells. My solution: The guns will be linked to a tactical computer that is constantly updating the target's trajectory and making the necessary corrections.

This is a problem with all non-seeking weapons, be they cannons, railguns, laser batteries, or particle-beam weapons. And there is no real solution, short of time travel or telepathy.

Your target has a certain area that represents its possible future locations. The area is determined by the time-of-flight of your weapon from you to the target, the target's initial trajectory, and the target's engines (how much can it change its trajectory within the time-of-flight).

If this area is larger than the target silhouette, you probably will never hit the target.

Possible solutions include making your weapon home in on the target (despite the target's attempts to jam the homing mechanism), and area-effect warheads. Both of which work poorly with railguns.