Rail gun damage?

[tkdguy]

Re: Rail gun damage?

 

back on topic for a second...

 

I had an interesting design for a railgun turret pop into my head in the shower the other day, using a revolver/gatling gun style rotating foreward assembly for rotating a fresh set of rails in place for each discreet "burst" of projectile fire, with fresh rails feeding in from a magazine, and old rails being routed through an automated restoration mill that spits the remachined rails back into the bottom of the magazine.

makes rails a renewable but still expendable resource on a ship, but helps bypass the "the rails get tore up" problem.

I like that one. I thought about a similar thing, except having the rails cooled and reprimed rather than be discarded. IIRC, railguns can currently be fired a few times before they fail altogether, so in your system, perhaps the system will replace the rail after every third shot. On the other hand, having a fresh rail each time would ensure optimal performance.

[Nyrath]

Re: Rail gun damage?

 

yeah, he's solidly in my personal pantheon of demi-gods. His Ogre illustrations were one of the things that got me turned on to military sci-fi.

 

I totally flipped my gourd too when I realized who he was

 

{blush} Thanks!

[SteveZilla]

Re: Rail gun damage?

 

neat post m'man.

 

All this keeps reminding me of a cute paraphrase of Robinson's 1st Law

"Anything moving 2 miles per second or faster is worth it's weight in blam"

 

I just stumbled across this website, and I have to recommend it to everyone here. Extra attention should be given to the page on weapons, given that this thread is about weapons.

[Nyrath]

Re: Rail gun damage?

 

I just stumbled across this website' date=' and I have to recommend it to everyone here. Extra attention should be given to the page on weapons, given that this thread is about weapons. [/quote']

Well, yes. It's my website. I have it in my .sig. See below:

[Thia Halmades]

Re: Rail gun damage?

 

... well, there's your irony.

[SteveZilla]

Re: Rail gun damage?

 

Well' date=' yes. It's my website. I have it in my .sig. See below: [/quote']

 

We have sig?

 

I have a habit of not expolring links in signatures, and came across the site the old-fashioned way (Google). I think mostly because it's just too darned much information to deal with at the time I am usually online.

[AmadanNaBriona]

Re: Rail gun damage?

 

OK, that was amusing, in an Abbot & Costello sorta way...

[Thia Halmades]

Re: Rail gun damage?

 

Who's on First?

[FireTiger]

Re: Rail gun damage?

 

"What's on second?"

 

At tkdguy's suggestion, I'll post something that I'd previously put on my blog page, concerning rules for scaling weapon damages up for Star Hero spacecraft. I was originally planning some conversion work between Hero System and another game that had built-in scaling rules.

 

While taking another look at Star Hero for 5th ed., I found that the book does contain a rule for scaling weapons up to ship sizes. So, I put together a small example based upon this thread, which created the following:

 

The original question concerned scaling these weapons up for starship use. The latest version of Star Hero does have a provision for scaling weapon damages up. The idea is that bigger ships carry bigger guns, so they hit harder (my apologies if I state it too simply).

 

In the 5th edition version of Star Hero, there are listings for human-scale railguns (called gauss weapons in the text; and another term for them is accelerator weapons). These weapons are the Early Gauss Cannon, Gauss Rifle, Gauss Pistol, and Heavy Gauss Gun.

 

Using a bit of information from an older version of Star Hero (2nd edition, 2nd draft) gives us a little expanded information about these particular weapons. (This would also apply to most other weapons as well, but I'm just looking at gauss weapons at the moment.)

 

• Early Gauss Cannon: 2d6 RKA (average 7 BODY) = 0.5 grams of explosives = 2 kilowatts energy output

• Gauss Rifle: 2d6 RKA (average 7 BODY) = 0.5 grams of explosives = 2 kilowatts energy output

• Gauss Pistol: 1½d6 RKA (average 5 BODY) = 0.25 grams of explosives = 1 kilowatt energy output

• Heavy Gauss Gun: 3d6 RKA (average 10-11 BODY) = 4.0 grams of explosives = 16 kilowatts energy output

 

Using the method suggested on pages 217 & 218 of the current version of Star Hero, let us see what results in the following example.

 

An 800-ton Merchant Ship (Star Hero 5E (SH5E), pages 222 & 223), spent 65 points on size. A merchant ship would gain a scale modifier of +13 BODY in damage inflicted upon hulls smaller than 800-tons (65÷5 = 13). Now, if I declare that this merchant ship is carrying a ship-scale gauss rifle, we get the revised listing of:

 

• 800-Ton Scale Gauss Rifle: 2d6+13 RKA (average 20 BODY) = (after rounding) 6d6 RKA = 2 kilograms of explosives = 8 megawatts energy output

 

 

The equivalent weapons could be designed by GMs and players if they wish. The example weapon would then be built as a 6d6 RKA (plus the Armor Piercing, I'd left that out as it was a constant for gauss weapons). Those who don't like the idea of applying the scale modifier in play can still use it to design ship weapons of the appropriate size.

 

Now if I'm lucky, folks might actually find this useful...

[SteveZilla]

Re: Rail gun damage?

 

As a yardstick, I belive it is very useful. Keeping it a yardstick allows specific weapons that are smaller to be on a ship (Anit-aircraft weapons on a battleship), as well as weapons of a larger caliber to be installed on a small vehicle (Millenium Falcon).

 

Or one can incorporate the size/scale difference into the game and keep the attack powers the same. A weapon for a person would be written the same as a weapon for a ship. When shooting at something of a size/scale smaller, every level of size the target is below the attacker imposes a -2 OCV and a +1 Body. When shooting at something larger, just reverse the numbers.

[tkdguy]

Re: Rail gun damage?

 

Thanks for posting the info here, FireTiger. I definitely find it useful.

[FireTiger]

Re: Rail gun damage?

 

It makes the very big ships truely frightening, a 1 petaton hull (300 pts) gets a +60 BODY scale modifier against anything smaller than itself.

 

If we put a ship-scale gauss rifle in one of these monsters, we get:

 

• 1-Petaton Scale Gauss Rifle: 2d6+60 RKA (average 67 BODY) = (after rounding) 19d6 RKA = 1 gigaton of explosives = 4 exawatts energy output (4 quintillion watts).

 

(Woof) So, I think Arthur had the right idea about what to do when faced with these: "Why don't we turn on this Improbability Drive thing?"

[SteveZilla]

Re: Rail gun damage?

 

It makes the very big ships truly frightening' date=' a 1 petaton hull (300 pts) gets a +60 BODY scale modifier against anything smaller than itself.[/quote']

 

I don't agree with this implementation. It doesn't make sense to me that it would to +60 Body to something massing 50 tons all the way up to 0.5 petaton then suddenly drop to "normal" damage with the last size increase (it doubles mass every increment, right?). To me, it would make more sense if the extra BODY damage graduated with the difference in size.

 

If we put a ship-scale gauss rifle in one of these monsters, we get:

 

• 1-Petaton Scale Gauss Rifle: 2d6+60 RKA (average 67 BODY) = (after rounding) 19d6 RKA = 1 gigaton of explosives = 4 exawatts energy output (4 quintillion watts).

 

(Woof) So, I think Arthur had the right idea about what to do when faced with these: "Why don't we turn on this Improbability Drive thing?"

 

Just out of curiosity, how would a 1 petaton vehicle compare, size-wise, to various known Sci-Fi ships?

[FireTiger]

Re: Rail gun damage?

 

I don't agree with this implementation. It doesn't make sense to me that it would to +60 Body to something massing 50 tons all the way up to 0.5 petaton then suddenly drop to "normal" damage with the last size increase (it doubles mass every increment' date=' right?). To me, it would make more sense if the extra BODY damage graduated with the difference in size.[/quote']

 

It is the closest thing to actual scaling rules that I've seen within the rules so far, and it does mention that it only applies to shooting at smaller vessels. Smaller ships at least don't suffer any extra penalties for shooting at craft larger than themselves.

 

Scale Modifier = Points spent to purchase the hull ÷ 5

 

I suppose I could try something I was thinking of previously, which was adapting rules from another system. This kind of thing is easier in games already having different scales for humans and spacecraft.

 

Just out of curiosity' date=' how would a 1 petaton vehicle compare, size-wise, to various known Sci-Fi ships?[/quote']

 

Hmmm... good question. The older version of Star Hero I've got handy only went to 25 megaton hulls. According to the current version of Star Hero, a 1-Petaton ship is 500,000" in length × 250,000" in width.

 

So... roughly about the size of the Unicron from the 1987 Transformers movie or the Zentraedi home base ship from Super Dimensional Fortress MACROSS TV show (which can hold a fleet inside itself). It would be about 200 kilometers longer than the ID4 alien mothership.

 

For anyone who hasn't found it yet, there's a great site for comparing spacecraft from various universes.

 

http://www.merzo.net/

[Nyrath]

Re: Rail gun damage?

 

Just out of curiosity' date=' how would a 1 petaton vehicle compare, size-wise, to various known Sci-Fi ships?[/quote']

A cursory examination shows the original Starship Enterprise had a mass of 200,000 metric tons, which is 0.000000002 petatons.

 

The Death Star II is more difficult to figure. The average value I found was a diameter of 900 kilometers. With an average density of, say, 100 kg/m^3, that would come to about 38 petatons.

[CorPse]

Re: Rail gun damage?

 

... I'm the guy who's constantly complaining that the game does not scale correctly from size to size. I still hold that the system needs an all new' date=' overhauled vehicle system.[/quote']

 

Can I be the other guy?

 

I like the new stuff from TUV, but my sense is that it's a move in the right direction as opposed to a solution.

 

Back to the Thread...

 

Very cool discussion, I'm running into this problem doing conversions.

 

But it all does seem to come down to how one wants to scale things (attack vs. defense) rather than raw firepower. (But I'm sure this has been said here and elsewhere.)

[FireTiger]

Re: Rail gun damage?

 

Back to the Thread...

 

Very cool discussion, I'm running into this problem doing conversions.

 

But it all does seem to come down to how one wants to scale things (attack vs. defense) rather than raw firepower. (But I'm sure this has been said here and elsewhere.)

 

True, true. The small bit of scaling info in Star Hero for 5th ed. can be turned into #d6 values. One could bypass the "only against hulls smaller than themselves" thing in this fashion. That can still cause trouble, as there's no scaling of defenses in either direction, so big guns do very bad things to smaller vessels.

 

The older version I have at hand had a somewhat wider range of weapon scales. It divided ship weapons into Light, Medium, and Heavy without being really clear what those categories were. (But to be fair, the older version I have is a draft of an abandoned revision for the 4th ed. version.)

 

The weapons lists from this older version might come in handy, as the range in damage values isn't as wide as it would be by converting the scale modifier into #d6.

 

(I've also been toying with the idea of building such weapons under Mekton Zeta Plus and then converting them. That'd be cumbersome though, as I'd probably have to filter them through a third game in order to come up with Hero System write-ups.)

[megaplayboy]

Re: Rail gun damage?

 

True' date=' true. The small bit of scaling info in [i']Star Hero[/i] for 5th ed. can be turned into #d6 values. One could bypass the "only against hulls smaller than themselves" thing in this fashion. That can still cause trouble, as there's no scaling of defenses in either direction, so big guns do very bad things to smaller vessels.

 

The older version I have at hand had a somewhat wider range of weapon scales. It divided ship weapons into Light, Medium, and Heavy without being really clear what those categories were. (But to be fair, the older version I have is a draft of an abandoned revision for the 4th ed. version.)

 

The weapons lists from this older version might come in handy, as the range in damage values isn't as wide as it would be by converting the scale modifier into #d6.

 

(I've also been toying with the idea of building such weapons under Mekton Zeta Plus and then converting them. That'd be cumbersome though, as I'd probably have to filter them through a third game in order to come up with Hero System write-ups.)

IIRC, number of kills(up to 11 or so), plus 14 equals the number of damage classes in hero system, at least according to that hybrid game system that dare not speak it's name.

[FireTiger]

Re: Rail gun damage?

 

IIRC' date=' number of kills(up to 11 or so), plus 14 equals the number of damage classes in hero system, at least according to that hybrid game system that dare not speak it's name.[/quote']

 

Well, if I start in Mekton Zeta Plus I've got a built-in scaling system to work with. Even then, it'll be problematic with the really big ships. The big ones will drift into the Excessive Scale of ships — and those are basically plot devices.

 

I could use a straight Mekton to Hero track, but we'd still wind-up with some very large DC values. This path would make it (Kills ×1.5 = DC), so, for example, a Human Scale (1:10) 2d6 weapon—which is roughly what a couple of the guass guns are—started as a 5 Kill Normal Scale (1:1) weapon.

 

From here (1:1) we go up to the next level, Corvette Scale (10:1) and that basic 5 Kill weapon becomes a 50 Kill weapon. A direct cross into Hero would make that 75 DC weapon (25d6). This would still leave Starship Scale (100:1)...

 

Hmmm... you know, folks...maybe I should give up and stop complicating the matter. This idea just seems to make the guns even bigger than they are by using the scale modifier from Star Hero as-is.

[Zeropoint]

Re: Rail gun damage?

 

I've mentioned my take on this before, but it seems relevant to this discussion, so I'll mention it again: the reason that big ships have such piddling body scores is that only things of the same scale can damage the ship's body directly. Human-sized attacks only damage the body of individual hexes. This means that they'd have to do a heck of a lot of damage to seriously harm the ship. Blow relatively (to the size of the ship) small holes in the hull, sure. Wreck internal components, of course. But destroy the ship? That'll take a while.

 

Let's run some numbers.

 

I don't have my copy of TUV with me, but according to 5ER, a Size 20 vehicle is 100 hexes by 50 hexes by 50 hexes for a total volume of 250,000 volumetric hexes and has a mass of 102.4 kilotons, metric. It has 30 BODY, 110 STR, suffers a -13 DCV penalty and has -20 hexes of knockback resistance. That shape makes for an aesthetically unpleasing starship, so we'll take advantage of a clause in the book and re-arrange those hexes a bit, for final dimensions of 200 hexes long, 25 hexes wide, and 50 hexes tall. This gives us a svelte length-to-beam ratio of 8:1, which actually makes for a very thin ship now that I stack up my dice to get a picture in my head, but we'll go with it for now.

 

Let's assume that the USS Target Practice has 20 DEF armor; this seems reasonable for advanced materials on a vessel that has to balance protection and mass. For comparison, 5ER lists a vault door at 16 DEF and "heavy armor" at 19 DEF. I'm picturing this as about a foot of hardened steel, which compares favorably to the beltline armor of WWII battleships. The Iowa Class, for instance, had armor 12.1 inches thick at the strongest point. For another useful benchmark, the maximum damage of a .50 BMG round is 18 Body, and the average damage is 10.5 Body. This gives the Target Practice the ability to blithely ignore standard hardball ammo from a .50-cal; and if we assume that the armor is hardened (which seems reasonable to me) even an AP round from a .50-cal can't do any more than cosmetic damage to the ship.

 

5ER also suggests a value of 8 DEF, 6 BODY for a hex of internal starship wall, and that seems reasonable for a military starship. I'm just going to go with that. Let's assume that the hull itself has 10 BODY per hex. (we can already see one of the issues we're dealing with--how does a ship with 250,000 hexes have a body score only 5 times that of one of those hexes? This is also a clue to the solution of that issue.)

 

Assuming an even distribution of BODY throughout the ship, there are 8,333.33 hexes per 1 BODY, or 0.00012 BODY per hex. One BODY worth of volume is a cube about 20.3 hexes to the side, or a hemisphere with a radius of about 15.8 hexes (diameter about 31.6 hexes).

 

From this, we can see that the damage needed to wreck a hex of hull is 30 Body. According to 5ER, the size of a hole doubles for every +1 Body over that needed to make a single hole (I disagree with this. It works well for comic-book action, but definitely doesn't match my experience in the real world). From this assumption, and noting that 31.6 is conveniently close to 32 (2^5) it's easy to see that by the standard rules, to blow a hole that would do 1 BODY to the ship would require 35 Body of damage from a single human-scale attack. That happens to be the exact average damage of a 10d6 RKA (150 pts). A double AP RKA would only need to do 25 Body to get the same result, allowing you to get the job done with a 7d6+1 RKA (220 pts).

 

However, doing two more Body, for a total 37, quadruples the hole to a diameter of 128 hexes. If we assume a hemispherical damage pattern, we've now damaged 549,033 hexes, which is more than twice as many as the ship HAS and we can assume that the ship has been more or less vaporized. The hole-doubling rule is NOT satisfactory in my eyes for this reason: a mere 7 Body--on ten dice--stand between an annoying but fairly insignificant hole and the complete loss of the ship. Unacceptable.

 

More speculation and number crunching to follow shortly.

[Zeropoint]

Re: Rail gun damage?

 

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]

Re: Rail gun damage?

 

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]

Re: Rail gun damage?

 

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.

 

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]

Re: Rail gun damage?

 

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.

 

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]

Re: Rail gun damage?

 

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