are certain sizes of missile rack more efficient?

[beachhead1985]

This sounds like something that might work out in the math, but I can't figure it.

So i'm looking at the missile hits table and wondering if maybe certain sizes are more likely to roll better on the hits table?

Obviously Streaks kinda skip this whole issue.

I know there are other questions in terms of throw-weight/per tonnage/heat, but I am just wondering about the missile hits table itself

[Colt Ward]

Of the IS LRM racks, the LRM5 is more efficient by weight . . . which is all that really matters when you start rolling to see number of weapon system hits.  The higher the number of chances, the closer to the statistical average you will stay.

[Xotl]

I had this lying around from when I was rebalancing weapons for my own campaign.  The average damages of the 4 LRM racks are:

LRM 5: 3.167 (0.6334 damage per missile)
LRM 10: 6.3062 (0.63062 damage per missile)
LRM 15: 9.501 (0.6334 damage per missile)
LRM 20: 12.6957 (0.634785 damage per missile)

So the LRM 20 wins by a very slight margin, and the LRM 10 is the worst, also by a very slight margin.  The variances are so small as to be pretty much insignificant.

SRM 2: 2.8376 (1.4168 damage per missile)
SRM 4: 5.2904 (1.3196 damage per missile)
SRM 6: 8.0168 (1.333467 damage per missile)

The SRM 2 is the best, while the SRM 4 is the worst.

[Colt Ward]

Problem is I can fit 5 LRM5 for a single LRM20 . . .

[Paul]

Cool, you use the same method I use to analyze missile racks.

Anyway, yeah, as CW points out, there's more to look at than missile table performance alone.

I kinda hoped they would create a bias on the missile tables that'd favor the larger racks in TW, but it wasn't to be. I tend to 'fix' LRM5s in my campaign by making them do 3 heat. Makes them less overwhelming a replacement for pretty much any larger LRM rack.

Paul

[Colt Ward]

Yeah, as far as min/max outlook, the only reason to go with a LRM20 is for mine-clearing or laying those auto-PSR Thunder fields.

With that said, after a long ago (sheesh, YEARS) discussion about the Lao Hu which caused a huge LRM rack size discussion . . . I sort of took it as a challenge to NOT use banks of LRM5s when doing refits just for flavor.  Now MMLs have sort of made that thinking obsolete . . . except perhaps creating reasons TO use LRM racks instead of MML.

I supposed Swarm LRMs for really bunched up masses of enemy units might be another advantage of larger racks, IF you have a pilot with good gunnery.

[SteelRaven]

The SRM 2 is the best, while the SRM 4 is the worst.

??? I know your math is correct, I just don't see fire twice as many missiles at the same target giving you less chance of hitting said target. Maybe it's my ignorance regarding the 2D6 bell curve. 

[Colt Ward]

Again, another thing to look at is that firing 2 SRM2s is better than firing 1 SRM4, greater chance of hitting because your firing more.  Which is why 2 SRM2s do more damage than a single SRM4.

[SteelRaven]

Again, another thing to look at is that firing 2 SRM2s is better than firing 1 SRM4, greater chance of hitting because your firing more.  Which is why 2 SRM2s do more damage than a single SRM4.

...oh :))

[wundergoat]

Smaller racks are significantly less heat efficient.  Also, larger launchers are more 'swingy' than banks of smaller ones.  The LRM20 has a decent shot of hitting for 20 damage and causing a PSR per hit, while a bank of LRM5s would trend more towards the average damage but are much less likely of getting to 20 damage.

[Colt Ward]

I think your missing the math?

5 LRM5 racks, which are the same weight as the LRM20, will do a bit over 15.5 damage on average with a possible 25.  Your single LRM20 will do a bit under 12.7, with a max possible of 20.

[SteelRaven]

Keep in mind these numbers are also averages, the actual dice rolls are going to be all over the place no matter what rack you go with but all and all; Colt Ward has given the best answer.

[wundergoat]

No, I got the math right.  Its just comparing straight averages hides the swingyness of the 20.  Depending on the THNs, you have to hit with at least 4 launchers, 5 if you want reasonable chances.  Then you have to get high enough cluster rolls (5 average for 4 hits, 4 average for 5), which becomes highly unlikely.  The LRM 20 just needs to get 11 or 12 to cause a PSR.  Lower average damage, higher variance.

An analogy is 2d6 vs 1d12.  2d6 rolls higher (7 average vs 6.5) while the d12 is much more likely to get a 12 (1/12 vs 1/36).

[Paul]

An analogy is 2d6 vs 1d12.  2d6 rolls higher (7 average vs 6.5) while the d12 is much more likely to get a 12 (1/12 vs 1/36).

... And 1/12 chance of getting a 1.

Having many weapons is good when the to-hit numbers are 8 or higher the majority of the time.
Having few weapons is good when the to-hit numbers are 7 or lower the majority of the time.

Paul

[Charlie Tango]

Problem is I can fit 5 LRM5 for a single LRM20 . . .

Yes, but you have to hit with 4 of them to potentially do the same damage that I only need to hit once to do...

[mutantmagnet]

Even though these aren't missiles they still rely heavily on the cluster table.

From the calculations I did HAG 40s are marginally better than HAG 20s at each of the three range brackets before you take fitting requirements into account. I haven't done calcs for HAG 30s.

[wundergoat]

... And 1/12 chance of getting a 1.

Having many weapons is good when the to-hit numbers are 8 or higher the majority of the time.
Having few weapons is good when the to-hit numbers are 7 or lower the majority of the time.

Paul

Indeed.  I guess my point is that there is more to "most efficient" than raw damage, like heat, 'swingyness', ruggedness, Artemis efficiency, etc. that make picking the most efficient not particularly black and white.

*edit, forgot the quote

[Xotl]

Problem is I can fit 5 LRM5 for a single LRM20 . . .

The original poster only wanted to know if some columns on the missile hit table were better than others.  Everyone already knows the usual stuff about which racks are better on a ton-for-ton basis.

The LRM 10 definitely still sucks.  This just makes it even worse.

[Colt Ward]

Yes, but you have to hit with 4 of them to potentially do the same damage that I only need to hit once to do...

Yes, and I will have 5 chances to hit each turn while you have a single chance.  With 2d6 bell curve, it means I am going to hit more often than you, the rest is up to the cluster table.

'Swingyness'?  Are you talking about the variable damage output for each hit?  The only way the LRM20 wins out is with heat, and its not a heavy enough penalty to really matter.  5 LRM5s win out on the crits- which makes them more rugged.

5 LRM5s will hit (some of them) more often than a LRM20.  They will do more damage on average over the course of a battle than a LRM20.  The 5 LRM5s combat ability (ruggedness) will degrade slower than a LRM20, since a single crit results in the loss of a single LRM5 rack than the full LRM20 rack.

[Charlie Tango]

Yes, and I will have 5 chances to hit each turn while you have a single chance.  With 2d6 bell curve, it means I am going to hit more often than you, the rest is up to the cluster table.

No, I will miss with all 5 while you will hit with the 1.  It's called dice luck.

[wundergoat]

Yes, and I will have 5 chances to hit each turn while you have a single chance.  With 2d6 bell curve, it means I am going to hit more often than you, the rest is up to the cluster table.

'Swingyness'?  Are you talking about the variable damage output for each hit?  The only way the LRM20 wins out is with heat, and its not a heavy enough penalty to really matter.  5 LRM5s win out on the crits- which makes them more rugged.

5 LRM5s will hit (some of them) more often than a LRM20.  They will do more damage on average over the course of a battle than a LRM20.  The 5 LRM5s combat ability (ruggedness) will degrade slower than a LRM20, since a single crit results in the loss of a single LRM5 rack than the full LRM20 rack.

But my point is a LRM20 is more likely to score 20 damage than 5xLRM5s.  8.3% of the time, the LRM20 will force a PSR off its single hit.  Just assuming for the sake of argument that all 5 LRM5s hit (which is unlikely), just off cluster rolls its roughly 3.15%.  Factor in actually hitting with all the launchers and that number goes down the toilet.  However, you are correct that 5xLRM5s average more damage per volley.

[rlbell]

Yes, but you have to hit with 4 of them to potentially do the same damage that I only need to hit once to do...

That is a wash.  In all situations, LRM20's and LRM5's have the same hit probability and very near, if not identical, damage per tube.  It is only within a single turn that the swings get noticed.  On any turn that the twenty hits, the four fives are very unlikely to do the same damage.  However, any turn that the twenty misses, even shooting at a TN of 12 gives a ten percent chance of at least one of the fives hitting.  If you were to take careful notes of the TN and damage for each salvo, over multiple tons of expended ammo, you would probably notice that there is no difference between any of the LRM launchers.

The only bad rack sizes are among the MML launchers (unless there is an ATM9, which also bites chunks)-- the '7' column is not very good and the '9' column is the absolute worst.  I have been meaning to write my own cluster table, leaving the '2' column* alone and fiddling all of the others to average two thirds of the cluster hitting (a quick and dirty method is to fix the '3' column and the '4' column and use linear combinations to get all of the other columns-- '5' = 2x'4'-'3').

* The only fixes for the two column either set a roll of three to no missiles, or a roll of eleven to only one, or maybe setting a roll of eight to one missile, and a roll of four to two missiles.  The first is bad because a hit was rolled, and none of them are visually unappealing.

[Belisarius]

There are several reasons to want bigger launchers over smaller ones, but it is technically true that the smallest launchers are more efficient. An optimized design uses lots of little launchers. That said, I have been frustrated of late by the near absolute lack of LRM20s on recent machines. There are banks of twin fifteens and tens, many fifteens, MMLs and LRM15s, but I can't think of a Jihad-era fire support machine with more than one LRM20. Am I missing something?

I love the minefield option, the swarm option, and the fact that using one LRM20 makes my opponents much happier than having to roll five times for the same thing.

[ArtieAnole]

I can think of one situation where it is much better to have larger racks of LRMs vs. grouped LRM 5's.  Going against units with BAR 5 commercial armor...  Or wait... Do you have to do above the BAR to have a possible crit or just at the BAR?

[Neufeld]

You can not compare LRM5s vs LRM20s and ignore heat load.

LRM20 = 3 ton heat (DHS) + 10 ton launcher + 2 ton ammo = 15 ton
4xLRM5 = 4 ton heat (DHS) + 8 ton launcher + 2 ton ammo = 14 ton
5xLRM5 = 5 ton heat (DHS) + 10 ton launcher + 2 ton ammo = 17 ton

So, while the LRM5 is slightly more efficient than the LRM20, you can not fit 5xLRM5 without having to add more heat sinks.

[Cybra]

You need to exceed the BAR. Additionally, missiles only do 1 to 2 damage per missile (unless your firing thunderbolts, which are a different kettle of fish). As the lowest BAR is 2, meaning that your missiles will detonate on the armour, with no chance to blow through and cause critical damage.

Unless I got it wrong and you take the cluster size and compare it against the BAR?

[foxbat]

Problem is I can fit 5 LRM5 for a single LRM20 . . .

True, but that single LRM 20 will deal only 6 heat, while the 5 LRM 5 will cause 10. If you take heat into account, the LRM 5 advantage cancels out IMO.

[mutantmagnet]

Then there is whether or not you choose to use Artemis enhancements.

[Blackjack Jones]

That said, I have been frustrated of late by the near absolute lack of LRM20s on recent machines. There are banks of twin fifteens and tens, many fifteens, MMLs and LRM15s, but I can't think of a Jihad-era fire support machine with more than one LRM20. Am I missing something?

Well there isn't just one reason, but off the top of my head.

-Artemis IV. LRM-15+A4 has the same average on the cluster chart as the 20 w/o A4 , so looking at it from an average damage standpoint, the LRM-15+A4 is more weight efficient.
While of course you could put A4 on the 20 rack, it gets hard to stack them for both weight and space reasons.
-Related to above, the relative lack of Narc/iNarc designs, as unlike A4, it tends to favor each size of missile rack equally, as long as you're not the one carrying the Narc Launcher.
This doesn't negate the base efficiency of the launchers themselves, but it would put the 20's on a better footing compared to the Artemis situation above.
-Ammo efficiency / safety. Taking a 10 or 15 requires two tons of ammo for the average scenario, where the 20 requires three tons. Reducing the number of explodey critical slots
of course  can be seen as improving a design.
-It's just plain easier to make designs fitting a lot of bells and whistles with a LRM-10 or LRM-15, compared to the space hog that is the 20 rack. It gets a bit worse with ammo and Artemis IV,
as an IS LRM-20+A4 plus three tons of ammo can just about eat up an entire location on a 'Mech.
-MML's. A little bit of smart designing by replacing SRM's in designs that needed range, and quite a bit of New Toy Syndrome.

You need to exceed the BAR. Additionally, missiles only do 1 to 2 damage per missile (unless your firing thunderbolts, which are a different kettle of fish). As the lowest BAR is 2, meaning that your missiles will detonate on the armour, with no chance to blow through and cause critical damage.

Unless I got it wrong and you take the cluster size and compare it against the BAR?

The rules in TW just say "damage", but of course that can be a little vague.

I'd have to say you need to take it against the cluster size. Otherwise we start to get in the  fluff vs. gameplay territory, and that rarely ends well.
Such as a HMG throwing a ton of small shells being able to penetrate BAR 2, where a full cluster of 5 Long Range Missiles striking a similar sized area can't.

[Belisarius]

All true. But all also besides the point. I'm mostly interested in indirect uses which, as pointed out with the NARC tend to favor the heavier launcher. I don't need much in the way of bells and whistles, although I must admit, Guardian would be nice. The Capellan Archer gets close, but not quite (the lack of fists on an Archer is just reprehensible). I'm not too proud to use old school LRM carriers and Archers, I was just expecting a greater effort to make use of semi-guided and NARC guided LRMs through this proliferation of otherwise more-optimized designs (compared to previous ones). There aren't many pieces of tech out there that let you fire at the enemy without them getting a chance to shoot at you. This is a key capability that I think is often underrepresented.