93 replies to this topic

[Owl Cutter]

Kinetic energy and momentum are not the same thing.  They are related, but differ by a factor of velocity- which, in the case of a particle beam, is probably pretty high.  Please, at least read a refresher on primary school-level physics before commenting on realism or phenomenology, the crap that passes for "science fiction" these days is making me sick.  (Heavy Gauss fluff, I'm looking at you...)  A beam of any form of energy is not going to deliver a lot of momentum compared to a shell, rocket or similar that is roughly comparable in effectiveness, at least directly by impact.  

It should deliver momentum indirectly by generating it on-target: dumping its energy into that 5/8 of a ton of armor and blasting it away from the rest of the unit should presumably move enough mass violently enough to produce some serious momentum.  Lasers should be just as good at this as PPC; the mechanism is simply dumping heat into the armor fast enough to make it explode violently away.  Since this is driven by ludicous energy input, not a heavy projectile slamming into the target, momentum of the beam is insignificant in either case.
P.S.  That is, if we're talking about "blaster" lasers designed to incapacitate armored targets by pounding them to pieces, which should not be assumed to be the only approach...  I kinda like the idea of a setting where different laser weapons take different approaches, all the way from heatrays to x-rays...

Edited by Owl Cutter, 03 May 2012 - 11:28 AM.

[Steel Talon]

In urban terrain, ACs are best choice, but i prefer AC/20 over more AC/10 when i can load it
I dont think ammo prices will be canon, for AC/10 is likely to become cheaper while AC/20 the opposite

Edited by steel talon, 03 May 2012 - 02:43 PM.

[Long Draw]

Owl Cutter, on 03 May 2012 - 11:23 AM, said:

Kinetic energy and momentum are not the same thing. They are related, but differ by a factor of velocity- which, in the case of a particle beam, is probably pretty high. Please, at least read a refresher on primary school-level physics before commenting on realism or phenomenology, the crap that passes for "science fiction" these days is making me sick. (Heavy Gauss fluff, I'm looking at you...) A beam of any form of energy is not going to deliver a lot of momentum compared to a shell, rocket or similar that is roughly comparable in effectiveness, at least directly by impact.

It should deliver momentum indirectly by generating it on-target: dumping its energy into that 5/8 of a ton of armor and blasting it away from the rest of the unit should presumably move enough mass violently enough to produce some serious momentum. Lasers should be just as good at this as PPC; the mechanism is simply dumping heat into the armor fast enough to make it explode violently away. Since this is driven by ludicous energy input, not a heavy projectile slamming into the target, momentum of the beam is insignificant in either case.
P.S. That is, if we're talking about "blaster" lasers designed to incapacitate armored targets by pounding them to pieces, which should not be assumed to be the only approach... I kinda like the idea of a setting where different laser weapons take different approaches, all the way from heatrays to x-rays...

Okay, lets make this easy for everyone. Kinetic energy is a measure of the energy level of an object according to its mass and velocity. Momentum is a measure of an object's tendancy to continue in the same direction of movement at the same velocity.

Now, about PPC's causing knock back; This is caused as a result of the extreme temperatures and energy level of the beam which is comprised of electrons/photons (I put the "/" because electrons can move like an electromagnetic wave as well as like a particle). The reason this occurs with an impact with the armor, which undoubtably contains iron is because when you heat minerals like iron to these temperatures, they can burn, just like gasoline. And just like gasoline, if enough of it burns fast enough, you get an explosive force due to the fire displacing the O2 with CO2.

So yes, PPC's do cause knock back, but no, they do not do so through impact damage. This is actually thermal damage, which is why it is considered a thermal weapon when discussed in the real world.

[Ravn]

Sarna does not agree. Recoil here suggest your own mech is dealing with an impulse as well.

Particle Projector Cannon (or PPC) is a unique energy weapon. PPCs fire a concentrated stream of protons or ions at a target, causing damage through both thermal and kinetic energy.As such, despite being an energy weapon, it produces recoil.

Edited by Ravn, 03 May 2012 - 09:00 PM.

[Yeach]

Assumption is that AC10 and PPC both do the same amount damage - 10
Under TT rules they cost around the same to mount 220k C-bills. (see previous posts)

Yet the PPC can be REUSED after the first engagement/mission; assuming AC10 uses all its ammo in the engagement/mission.

What would be a good balance (in terms of C-bills) for a PPC vs AC10 comparison?
Would a PPC costs equalling AC10 costs after 5 engagements/missions (+30k C-bills; 5 x 6k C-bills) be fair?


Autocannons IMO should be cheaper to use than PPC (beam weapons) because they are of a lower level technology.

[Claw55]

PPC should be much more expensive, but make up for it in lifetime ammo savings!

This, for no discernible reason, make me think of buying a hybrid car...

Edited by Claw55, 03 May 2012 - 09:49 PM.

[Rejarial Galatan]

ROFL Claw! Id love to see the map you took to go from PPC to Hybrid

[Fooooo]

If it becomes a big problem I don't see why a "durability" stat for energy weapons wouldn't work somewhat decently.....

Ammo based : You reload after matches (if you need to)

Energy Based : After a certain amount of uses you need to repair the weapon even if it has been destroyed in past matches and replaced, sort of like Diablo I guess. (costs more or = to a destroyed one if at 0 durability)

Not that I really like the idea, but I don't see why it wouldn't work if it was needed.

Edited by Foòóoo, 03 May 2012 - 10:08 PM.

[Rejarial Galatan]

time will tell what really happens

[Ryokochan]

Yeach, on 03 May 2012 - 09:09 PM, said:

Assumption is that AC10 and PPC both do the same amount damage - 10
Under TT rules they cost around the same to mount 220k C-bills. (see previous posts)

Yet the PPC can be REUSED after the first engagement/mission; assuming AC10 uses all its ammo in the engagement/mission.

What would be a good balance (in terms of C-bills) for a PPC vs AC10 comparison?
Would a PPC costs equalling AC10 costs after 5 engagements/missions (+30k C-bills; 5 x 6k C-bills) be fair?


Autocannons IMO should be cheaper to use than PPC (beam weapons) because they are of a lower level technology.

A real world equalvent of the class 10 AC has been around since the late 1960s in the form of the Russian T72 tank gun while there is as yet no real world PPC. Therefore I agree that ACs are lower tech and should cost less both to purchase and to maintain/repair. This would help balance out the game as most new or frugal players would go AC and only richer players could afford to go PPC crazy.

I would suggest AC 10 should cost half as much as a PPC in both inital cost and repair. This would make ammo cost less of a burden over time.

[LackofCertainty]

Yeach, on 03 May 2012 - 05:18 AM, said:

Please let's not use the Solaris Duel argument; use the standard rules assuming 10 pts of damage (for 10 seconds) for BOTH the PPC and the AC10. Why? If you play TT what is the frequency you would use the dueling rules? Lets just stick with the normal TT damages please. Thanks.

I made this comparison on this assumption that the damage was the same; introducing different recycle times just screws up the comparison.

But the Devs have already said that Recycle time is one of the things they're going to be tweaking to translate the weapons from TT rules to FPS rules while keeping them balanced. Things that are balanced in a turn-based game that relies on dice rolls to determine hits are obviously not going to keep the same power levels when you translate them to FPS. >_>


If this is a discussion only allows TT stats for weapons without any considerations for how they'll be tweaked in MWO, then why is this in the MWO general forums instead of the TT forums?


Personally, I'd prefer if ammo-based systems were (in general) a bit cheaper to counteract their long term costs, but the cost balance could easily be maintained by making energy weapon repairs more expensive.

[Owl Cutter]

LD, I was talking about explosive phase change driven directly by dumping lots of kinetic energy into something, not a chemical explosive effect. I think it's safe to assume Battlemech armor is not explosively combustible, and that PPC do not have some mechanism to provide enough Oxygen fast enough to burn it explosively either. Yes, Iron oxidises, but that requires Oxygen, and the atmosphere probably can't provide enough of it fast enough for a chemical explosive effect. I've heard of crazy people pouring liquid oxygen on Iron and Iron-alloy objects and igniting them, with results more incendiary than explosive, so it should be easy to find visual demonstration in a world with Youtube. Maybe you could get it to explode with the right confinement, but battlemechs probably don't fight in liquid Oxygen at abyssopelagic pressures. I suspect I should have been more clear earlier, though, so...

MOMENTUM IS THE PRODUCT OF MASS AND VELOCITY. KINETIC ENERGY IS THE PRODUCT OF MASS AND THE SQUARE OF VELOCITY. In terms of effect, momentum correlates directly with ability to push something around- the amount of force an impact can impart. That's why people trying to bash each other's brains out tend to find heavier masses useful; putting all of your muscle power into hitting something with a heavier tool will exert more force on impact than doing the same with a lighter tool. That's also why a heavier bullet from the same cartridge and gun will produce more recoil and hit harder for similar energy. (optimal propellant efficiency for a given cartridge and gun is also for a given bullet weight, so one projectile choice will probably be more energetically efficient than the other)

Ravn, I don't see how the sarna.net article disagrees, either. I didn't mean to imply that the beam has no momentum, and I thought I didn't need to explicitly point out that you can't have kinetic energy or momentum without the other. I just assume the meaning of that line is that the recoil is measurable, not that it is anything to care about, because that's the easiest way to reconcile that fluff with reality.

Though it might not be in the sarna.net article, PPC are also canonically specified to be kinetic energy weapons. Of course you're going to get some recoil- you can't accelerate particles without imparting some momentum, and momentum is a conserved quantity, but the recoil-coupled momentum will not be what's damaging the target. Kinetic energy transfer will be doing the work, as per canon, whether by producing significant momentum at the site of collision as described earlier, by damaging heat effects, by secondary radiation, or most likely a combination of all those phenomena and more.

PPC are also explicitly, canonically specified to use electromagnetic means to project particles heavier than phota, BUT that specification also establishes the velocities as being in the relativistic range so the practical effect is not _much_ different from a laser in terms of recoil. The formula for kinetic energy can be expressed as momentum times velocity, so accelerating any mass to "nearly the speed of light" means a lot of energy per unit momentum- so much that you will need planet-sterilising orbital bombardment energy long before you have enough recoil for your station-keeping thrusters to have any difficulty with. I'm pretty sure the recoil of a PPC is not a big deal, and the momentum is not what the target should worry about.

I have no problem with any "blaster" knocking targets around without needing worrisome recoil, but if you have a hard time imagining it I suggest inputting "Pulsed Energy Projectile" into your favourite search engine and/or checking the wikipedia for a dramatic example. The idea is to knock a human off its feet with a pulse of light, by exploding a small portion of the human's mass. It ends up being lethally dangerous due to EMP effects from rapidly generating a body of plasma and heating it with the rest of the pulse, which has me suspecting it is a perfect phenomenological model for the PPC. The most obvious difference here between the real laser beam and the fictional heavier particle beam, besides scale of application, is that the latter would not be absorbed by the plasma so efficiently, instead dumping most of its energy into the target directly. This seems like a perfect fit since in Battletech canon, heating is at least a significant part of how all beam weapons damage armor and systems.

Anyway... Gameplay-wise, I think ammo-consuming weapons should overall be much more threatening to offset the various costs. I occasionally lurk around bg.battletech.com and looooongtime players there seem to get the same impression as I, that things are generally imbalanced in favour of beam weapons and against autocannon. Missiles seem to be somewhere in-between, more sensitive to setting, goals, technology and rules, etc. A realtime game represents an opportunity to fix this without messing with any canonical values just by adding neat add-on effects that are not modeled in the source material, and I'm really hoping that PGI are getting it right where those who came before didn't.

I'm not a fan of adding extra maintenance costs for beams, because I see this difference as an opportunity to offer the kind of meaningful choice that reinforces a player's sense of agency. The "roman candle" threat is significant, and so is not being able to take wasteful shots when you only have "low value" targets to shoot at, so I really think there should be a strong reward for taking on those costs. Instead of trying to make the groups more similar by minimising all of those costs, just make those weapons more effective so they are desirable in a fair share of situations and players can feel like they are articulating a preference between two distinct approaches that require very different aptitudes to best use. I like the idea of autocannon and missiles having bonus effects that support each other especially well, so there are options to combine them for greater performance to offset the cost to feed them.

I hope to see all heat generation and dissipation values stay the same, so sustained output is the same, but allow heat-related penalties to apply before dissipating the heat; if I run a flashbulb to avoid the many serious costs of ammo-consuming weapons, which is a sort of thing I tend toward, I should suffer some kind of effectiveness penalty so I don't feel like I'm taking the only viable option. Messing with weight, heat values, etc. would break a lot of canon units, but just adding some consequences for generating a lot of waste heat instead of just for not dissipating it would pretty handily keep our beloved canon units like the Awesome, Flashman, Grasshopper, Hunchback -4P, etc. intact but not cheesy. It could also be a powerful incentive to use lighter 'mechs than otherwise, since those penalties get worse the more high-heat firepower you are cramming on a single chassis in exchange for the mobility of ligher units.

[Tincan Nightmare]

Well one benefit the AC/10 would have over the PPC would be in allowing the Mech to fire more weapons at once due to its lower heat output. In a comparison of the 2 weapons by themselves, the PPC is lighter and does not require ammo but generates more heat and has a slight range advantage per TT stats (as stated in previous posts.) However the AC/10 does offer the advantage of allowing more additional weapons to be fired at once without risk of a heat shutdown or ammo explosion. Look at the original Enforcer, 1 large laser, 1 AC/10, and 1 small laser. If it runs and fires the lg. laser and AC, per TT rules, it is now generating 13 points of heat. If the AC is replaced with a PPC, that would go up to 20. Now you would gain 5 tons from the swap out to the lighter PPC, plus the ammo tonnage, so you could add more heat sinks, but then you could end up with an issue of critical space depending on how this game implements it. If its similar to the TT rules, and you get a set amount of 'free' heat sinks (that you don't have to place in a critical hit location) depending on your engine rating, the more sinks you add the more internal space you may lose on your machine (if heat sinks take internal space like the TT.) This only gets worse if you consider that double heat sinks use 3 slots for IS tech and 2 for Clan tech sinks. If your machine is using Endo Steel or Ferro-fibrous armor, things could get a bit cramped. This would probably be more of an issue on heavy or assault machines, since they usually have more weight availble to mount multiple systems, but an AC/10 could be preferrable if you don't want to add a large number of heat sinks to fire several guns at once. This gets even better with the LBX version, as it fires cooler for further range and is 1 ton lighter than the standard.

Oh and as far as the PPC delivering kinetic energy, heres a quote from a paper written by a Dr. Richard M. Robards.
What Is a Particle-Beam Weapon?

The characteristic that distinguishes the particle-beam weapon from other directed energy weapons is the form of energy it propagates. While there are several operating concepts for particle-beam weapons, all such devices generate their destructive power by accelerating sufficient quantities of subatomic particles or atoms to velocities near the speed of light and focusing these particles into a very high-energy beam. The total energy within the beam is the aggregate energy of the rapidly moving particles, each particle having kinetic energy due to its own mass and motion.

So it seems a PPC would have kinetic impact.

[Pvt Dancer]

8100d 5p4tt3r, on 03 May 2012 - 10:55 AM, said:

The "knock back" is the impact, and then corresponding loss of armor. 20-40(IS), or 30-60(Clan) points is a lot to get hit with and of course you will lose armor. None the less, that is siginificant amount of energy transfer from point of origin to destination and the armor coming off is just a result more then a cause.

The impact alone would cause the pilot and the mech to react and part of that reaction is the loss of armor. Same being said for an LRM barrage. If something of significant size/momentum/density impacts you, even if you lose no armor/flesh it will still transfer it's energy to you.
The PPC isn't like a laser. It isn't like a beam of light, more like a focused stream of lightning. Which usually has a significant impact in and of itself because it is concentrated energy. That is kinetic as well as electrical, and heat damage.

Base rule from Table Top is you make a pilot check at +1 for every 20pts of damage you take. Being hit with an AC 20 is a auto check effectivily. It doesn't matter if it is armor or IS damage. How the MW games of old delt with it doesn't matter, these guys are not those companies and they have stated they would stick as close as they can to table top. Heh... could you imagin if we actually had Piloting skills to grin XP for to stay standing from damage or from other such situations?

But for a responce to the OP, they would have to make ACs very cheap to make them an economicly viable. A excellent post was made as to why stat wise they are viable (when you start looking at more than one PPC or AC 10), but consider an Awesome with 3 AC 10s vs 3 PPCs... What would you really want to run? I wouldn't want to pack enough ammo in that Awesome to make it viable.

That leads me to make sure everyone considers the 'Hidden costs'. Sure, ammo is expensive in the long run, but due to the large amount of Crits of the AC 10, your going to be replacing the AC twice as much as the PPC. Then the additional times you get unlucky and take a critical to the ammo... your replacing a mech, not a AC... or in the PPC's case, a heat sink. That would shoot up the costs over a extended period of time, IMO. Thus they have to make the ACs cost half as much as the PPCs to really make them viable.

To be fair, I would have to say the Large Laser is probably the most economical weapon over both of them.

[Long Draw]

Owl Cutter, on 05 May 2012 - 10:20 PM, said:

Though it might not be in the sarna.net article, PPC are also canonically specified to be kinetic energy weapons. Of course you're going to get some recoil- you can't accelerate particles without imparting some momentum, and momentum is a conserved quantity, but the recoil-coupled momentum will not be what's damaging the target. Kinetic energy transfer will be doing the work, as per canon, whether by producing significant momentum at the site of collision as described earlier, by damaging heat effects, by secondary radiation, or most likely a combination of all those phenomena and more.

PPC are also explicitly, canonically specified to use electromagnetic means to project particles heavier than phota, BUT that specification also establishes the velocities as being in the relativistic range so the practical effect is not _much_ different from a laser in terms of recoil. The formula for kinetic energy can be expressed as momentum times velocity, so accelerating any mass to "nearly the speed of light" means a lot of energy per unit momentum- so much that you will need planet-sterilising orbital bombardment energy long before you have enough recoil for your station-keeping thrusters to have any difficulty with. I'm pretty sure the recoil of a PPC is not a big deal, and the momentum is not what the target should worry about.

That was an excellent post there Owl Cutter! I think a very easy example that we all can use to associate PPC technology to real world technology is a particle accellerator lab. So, when scientists utilize the accellerator to observe particle collisions, they actually propel, using electromagnetic fields, a few particles in each sample source to nearly the speed of light, approximately 99%, which when the particles collide, causes explosive effects in the view of the common person. However, we don't see these collisions causing massive detonations or recoil in these accellerators. If there were significant recoil, it would most likely damage or destroy part of the accellerator itself.

If you go onto sarna.net and read the information about the armor employed on battlemechs during the time period we will be in, you will see that the armor is designed intentionally to "blow off" or explode outwardly. The reason this is done is so that when weapon energy or ammunition rounds impact the armor to cause at least minimal damage, the armor can negate some, if not all, of the damaging energy of the destructive effect.

This can be compared to the CASE system used to "blow off" the explosive energy of ammunition that detonates while still inside a mech.

[Owl Cutter]

Did any one suggest that it would not "have kinetic impact?" Also, light has a measurable kinetic impact which is the basis for the concepts of the solar sail and photon drive. It's just that, for literally any physical phenomenon with a velocity at or near the speed of light, by the time the momentum starts being worth noting, the energy is way more than enough to explode baryonic matter with more momentum by astronomical factors if it is concentrated in a vaguely death ray-like manner. I am not interested in discussing the semantics of whether EM radiation has kinetic energy or not, or for that matter is a pure manifestation of it, but it does in fact impart a kinetic impulse every time it physically interacts with anything that changes its velocity, from creation to reflection to refraction to diffraction to absorption.

I am really torn on whether the AC/10 vs PPC comparison makes more sense due to being ideal for the same targets and having similar-ish ranges, or the AC/20 vs. 6 Medium Lasers due to identical ranges and being ideal for wildly different targets. Scale means a lot here; comparing the HBK-4G to the -4P is not too bad, but if the King Crab instead had 11 Medium Lasers and 19 heat sinks more, who would ever want to trade for twin AC/20? Just for the crit padding to protect the LRM ammo, the lasers would be a huge upgrade.

More relevant to the topic of this thread, beams are generally more useful in BT and are the first choice if you have the space for enough cooling; if the range profile of the AC/10 looks better than the PPC's for a specific design, the Large Laser starts looking pretty appealing too. It's not quite as powerful, but much cheaper and lighter so you can cram more goodies on elsewhere, and free of all those ammo concerns. It just comes out one crit slot behind. The AC/10 is mostly for when you can't fit enough cooling for a[nother] PPC to work. It's a very valid reason, and allows some 'mechs to exist that couldn't without an AC/10, but I myself haven't reached for it yet because I will go for a bracket setup if I can, and that tends to require less heat sinks. I would like for all autocannon to be more than substitutes, though. That does happen outside the late Succession Wars era, but in an Intro Tech setting they feel too much like "poor man's" main beams IMO, so I want them to be boosted somehow so they feel like compelling choices for a primary weapon. In those terms, though, the AC/5 and AC/2 have it much worse since this game will presumably not put a lot of emphasis on anti-air capability at all.

[Connor Macleod]

Here is where I am going to say it really depends on the availability of lostech. You see in classic battletech (between 3000 and 3025), there were no double heatsinks, just single. So yeah, the autocannon weighed more and relied on ammo, but didn't swiftly overheat your mech like the PPC did in that era, so i would choose the a/c 10. However, after double heatsinks were rediscovered, the ppc became more viable (mechs already have 10 heatsinks installed, so with DHS, that's already a heat dissipation of 20) because it costs less even with added DHS's and has no ammo dependance. In fact, aside from the LBX, which can be used both as a hole puncher and as a crit fisher, I prefer the ppc over the a/c 10 any day after the classic battletech era, unless I have the extra c-bills for special munitions. Now as for the ultra version, I'd still go for dual ppcs. Less crit space, same weight (if you include the ammo weight for the ultra a/c 10), same damage potential, no ammo dependance or explosion, and still heat manageable with a few extra dhs installed. Sure it costs more in the short run, but that's a price I'm willing to pay

EDIT: In a twist of fate however, that is really ironic, my favorite mechs are the enforcers and cataphract, two mechs notorious for their autocannons. So I do like using autocannons for sentimental reasons(davion mechwarrior here) but from a practical outlook, I would have to choose the ppc like I said above.

Edited by Connor Macleod, 06 May 2012 - 02:21 AM.

[THELONGSHANKS]

A subject dear to my heart. I have been considering this while decided which mech I want to start out with. I guess it depends on how well the role centered combat works. I am considering playing a lighter class than an Assault, hoping to enjoy being useful and fast for the first time in Mechwarrior history. But whether I find myself pulling of effective ambushes with that AC10, or I end up slogging it out with the heavies is going to be the deciding factor.

[Owl Cutter]

I should have said it explicitly earlier, but I was using Intro Tech as the base assumption, so I wasn't even talking about Doubles...

The difference in heat production between the AC/10 and PPC can be made up by only 7 heat sinks, the complete system ends up being 2 crits bulkier and 1 ton heavier than the AC/10 with a single ton of ammo. Since we're talking about 17 tons vs. 16, that extra mass and bulk looks like a tiny price to pay for all of the benefits a beam weapon offers. If it's really hard to come up with that space and/or I'm already running hot, I must be struggling to fit the weapon in the first place, in which case the Large Laser starts looking really pretty.

It's even more lopsided for me, since I like bracket setups, so that little bit of extra mass and bulk disappears into the huge savings I get from using high-heat weapons relative to autocannon. From a bracket-centric perspective, a weapon that is big and heavy in exchange for running cool just looks super fugly unless it has very long range and no minimum. Since all autocannon come out so far behind here, they ought come out similarly far ahead for the other design approach in order to maintain balance, but they don't. If autocannon were small and light enough that the lower heat let them be more desirable as the first choice for fully cooled designs the way hot weapons are for bracket setups, I think things would be a lot more interesting...

As for Tournament-level, I do like the classic Gauss and LB-10 better than most of the post-renaissance stuff, and CASE is a sight for sore eyes, but don't like how ER PPC and Double Heatsinks minimise their impact. XL engines also tend to encourage changing a lot of 'mechs from "shoot and scoot" plodders to "run and gun" cavalry, which drives up both TMMs and AMMs, making ammo-independence a bit more appealing in addition to the more obvious way they dampen the effectiveness of CASE. Doing so also increases engine ratings, allowing more of those double heatsinks to hide in the engine. It just feels like I can't win here; my preferred aesthetic feels kinda cheesy when glass cannon designers get new difficult tradeoffs while I get nothing but new no-brainer upgrades.

Edited by Owl Cutter, 06 May 2012 - 03:38 AM.

[Hagan]

For me, Energy weapons would cost more than Auto-cannon's purely on the basis that Auto-cannon manufacturers also sell ammunition, where as Energy Weapon manufacturers only get to sell the guns. For me, maintenance costs (if they factor into this game) would mean the Energy Weapons would be more expensive to maintain per battle, and more expensive to repair.

The Auto-cannon's would be cheaper, mainly to do the fact that engineers and mechanics can fabricate mechanical parts easily than they could hi-tech components. Its all swings and roundabouts really, what you gain on one factor, you lose with another. Its all about balance and play-style.