Dragon Lady, on 03 March 2012 - 08:17 PM, said:
I can't deny that with real-world technology, Battlemechs are improbable. But then we're talking about {reverb}future technology{/reverb}, so I'm willing to let a few of the improbabilities slide.
By my rough calculations, a 12m tall atlas would have an interior volume of 35 m
3. 120 LRMs weigh one ton, or about 8kg per missile. The closest real-world equivalent I could quickly find via a google search would be
this one. 120 of these missiles
could fit into a magazine of 1 cubic meter. So the Atlas' 12 salvos of LRMs would take up about 6% of its internal volume if they were the same size as the Bantam... and I sincerely doubt that 30th century missile technology would be the same as 1950's technology. SRMs, having a higher ratio of warhead to propellant, probably takes up less volume than LRMs.
If you had 120 Bantam missiles they would have a volume of 120*(0.85*[pi*0.11]) = 3.9 cubic meters, not including the gaps between the round fuselages. Rounding up for the gaps between missiles the volume would be closer to 4 or more cubic meters per "ton" of ammo.
Now we know that SRMs are man portable and unguided, so I'm going to use the rocket launcher I trained on and deployed with in the Marine Corps for a comparison. The
SMAW rockets are almost exactly the length of the launcher (760mm) and have a diameter of 83mm. The volume of a SMAW rockets would exceed, 0.016 cubic meters (from 0.76*[pi*0.083m^2]) with 100 missiles per "ton" of SRM 2/4 and 90 missiles per "ton" of SRM6 ammo, you have 0.16 cubic meters and 0.14 cubic meters .
However SRMs pack more punch and in artwork are much larger than the SMAW. If we use the
Javelin or the
TOW which appear to be much closer to the proper size and are still manportable we get even larger numbers.
Javelin: individual missile = 0.056 cubic meters, LRM "ton" = 6.7 cubic meters, SRM "ton" = 5.6 cubic meters
TOW: individual missile = 0.084 cubic meters, LRM "ton" = 10.1 cubic meters, SRM "ton" = 8.4 cubic meters
Keep in mind that the missiles we see sticking out of the tubes in most of the artwork are even larger than this, so by using modern missiles as comparison we're actually lowballing the volume not highballing with inferior "modern" tech.
Dragon Lady, on 03 March 2012 - 08:17 PM, said:
Looking up the equivalent of an Autocannon/20 round was tougher, but based on
this article, a ton of AC/20 ammo shouldn't need more than 0.16 cubic meters. Thus the Atlas' AC magazine shouldn't take up more than 1% of its internal volume. Altogether, no more than 10% of its volume is needed for its ammo
***uming a cold-war era level of technology. Personally, I think that {reverb}future technology{/reverb} should be able to cut that volume at least in half due to its superior materials science.
Ac/20s are actually the easiest weapon to calculate the volume for. Sarna tells us that there is one AC/20 that fires 10 150mm rounds per shot, which means 50 150mm per ton of ammo. We also know that there is a 203mm AC/20, using a ratio of rounds per "shot" and the caliber we find that a 203mm cannon would need roughly 7.5 rounds per shot. In order to get a more fair (ie smaller) approximation I'm going to assume each shot only fires 7 rounds.
The closest thing I could find quickly for a 203mm shell was
this article. Using the smaller length we get 0.74m^3 (from 7*[pi*203mm^2]*813mm) per shot. 1 "ton" of AC/20 ammo would then take up 3.7m^3 not including the empty space where they circular shells don't meet. Even if we assume that future materials science and the fact that the shell isn't ship based and halve the length you still get 1.85 cubic meters per "ton" of AC/20 ammo.
Dragon Lady, on 03 March 2012 - 08:17 PM, said:
Curiosly, the 5 critical slots used by the Atlas' ammo are about 9% of its total critical spots.
5 critical slots for ammo ranges from 9.25 cubic meters at the lowest (all AC/20 ammo) to 50.5 cubic meters at the highest (all LRM ammo using TOW missile dimensions. Without the Atlas's ammo numbers sitting in front of me I can't tell you what the total ammo volume is, so the min/max will have to suffice to get my point across.
If your calculated volume is correct then the lowest possible ammo volume is more than 25% of the Atlas's total volume, if the largest possible ammo volume is correct then it is almost 1.5 times larger than your calculated volume for the Atlas.
Dragon Lady, on 03 March 2012 - 08:17 PM, said:
I will grant you that there is obviously some streamlining of things for the sake of the game, especially weapon ranges, but one of the things I've liked about the original Battletech game is that, with the aid of {reverb]future technology{/reverb}, the 'Mechs were at least plausible.
(edit: forgot to add second link)
See this is my gripe and why I'm in this debate, none of it is plausible. Everything is rule of cool with wildly too small 'Mechs, to big missiles, and way to little mass. The game is fun, enjoy the game, but do not try to accuse it of being "plausible" because it's the furthest thing from.
RogueSpear, on 04 March 2012 - 12:05 AM, said:
Correct me if I'm wrong, but wouldn't pouring molten metal into the lattice defeat the point and weld it in place? I only named Ferrofibrous because it's the only one that I actually know how the armour is put together - I don't know details about the rest ><
Well what I was thinking was that ceramics have a very high melting point and vaporization point. When using ablative armor against lasers the concept is that as the beam strikes the armor some of it is vaporized creating a cloud of gas that diffuses the rest of the laser spreading it out and weakening the effect. So when defending against lasers it makes more sense to have a material with a lower vaporization point. So I'm thinking the majority of the armor would be metal.
HEAT rounds are a shaped charge which create a "jet" of heat and pressure to defeat armor. Shaped charges (and by extension HEAT rounds) need a certain "standoff" from the target to achieve their full effect. Rule of thumb when we made improvised shaped charges in the Marine Corps was 2/3s the diameter of the charge for the stand off distance.
According to that wiki article on Chobham armor you linked the hardness of the ceramic causes the channel carved by the explosive jet to be uneven disrupting the geometry of the jet severely decreasing its effectiveness. So by creating a framework (lattice) of ceramic and filling it with metal you have the "jet" moving through the overall armor at different speeds severely decreasing its effectiveness. Since its mostly metal it would have a lot of material for laser strikes to ablate into vapour to defeat the laser. All of this would account for the homogenous rather than layered behavior of the armor, while still being incredibly effective against HEAT rounds.
FF armor would take this basic concept and bulk out the armor by adding a matrix of carbon nano-tubes to further decrese the effectiveness of a HEAT round's "jet" by giving yet another material with different behavior. It would also vaporize fairly easily under a laser strike to help with the defeat of laser weaponry. Carbon nanotubes are very light and could account for the increase in bulk without an increase in weight. Though "ton" is more likely a rating of effectivenss per mass rather than an actual weight.
RogueSpear, on 04 March 2012 - 12:05 AM, said:
On the tanks and guns thing, since we're talking realistically about how a tank is better, ealistically where does a tank have space for extra guns? One/two weapons in the turret (Most likely a twinlinked version of the same weapon) due to space issues unless you're building a superheavy, one in the hull (removing the ability to have a forward mounted engine), sponsons, and maybe mounting an LRM rack on top of the turret á la
http://en.wikipedia....alliope]Sherman Calliope[/URL]. Plus in a tank, every weapon needs more space (So crew can move around it) and an extra gunner (Excepting twinlinked weaponry). The battlemech has a huge advantage in the targetting computers they use due to how they manage the weaponry. As for a single gunner doing the same with the same compute, I imagine it's harder to coordinate two sponsons, turret weapon (And a coaxial weapon?), hull mounted cannon and a missile rack since they all cover different firing arcs (Excepting the turret weapons and LRM racks, and sponsons obv have the ability to also cover the front).
To answer this I'm going to link a series of tanks and other AFVs that have multiple weapons.
The
Mark VIII and other WW1 Tanks: These tanks had 2 primary weapons mounted on the side of the tank in sponsons. This kind of mounting would force a tank to be taller than modern tanks, but could still be done.
The
Neubaufahrzeug, the
T-35, the
Vickers A1E1, the
SMK, the
T-100 and the
Type 95 are all examples of multi-turreted tanks with multiple weapons. These designs were ultimately discarded because they were to heavy for the engines and suspension available and because of the complexity which with BTech technology wouldn't be a problem, after all 'Mechs and tanks in universe carry multiple weapons all the time.
The
M3 Lee is an example of a tank which had a hull mounted heavy weapon and a turret mounted medium weapon. The design suffered from the same flaws as a tank destroyer or self propelled gun and its turret mounted weapon wasn't sufficently powerful enough to deal with more agile targets that evaded the main cannon. Imagine an urban fighting tank with this style configuration, Hull mounted AC/20 turret mounted Large Pulse Laser and an SRM 6 launcher mounted like the TOW's on the M2 Bradley.
The
M2 Bradley IFV is a modern example of multiple weapon systems. Its primary armament is a turret mounted 30mm chain gun and a turret mounted TOW launcher with two TOWs ready to launch (SRM 2 anyone?).
The
B-29 is linked here because of its fire control system. The B-29 had four independantly rotating turrets which could be controlled from any of four gunners positions. If they could do it in the 1940's I'm pretty sure they can do it in the 3040's.
Yes you would need more room for additional crew and you would probably have to move the engine to the rear. However did you know that the Panther, which was the most advanced tank of WW2 and the precursor to the MBT, had a rear mounted engine and transferred the power to the front.
Oh interesting side bar to all those who say tanks are extremely cramped and mostly solid, the Panther's fighting compartment (crewspace) was 67% of the entire volume.
Anyway my point is, that it is possible to mount multiple weapons on tanks. Yes your primary turret would probably have twin linked cannons and a coaxial anti-infantry weapon. That is mostly due to ammo loading constraints though and you could probably mount additional lasers in the turret as well. SRMs/LRMs mounted to either side of the turret like the Bradley and perhaps a vertical launch system for LRMs on the back of the turret. Hull mounted, secondary turret and sponson mounted weapons are also a possiblity and with remote aiming you could have all the gunners arranged within the main fighting compartment.
And yes I agree that the anthromoporhic nature of BattleMechs and placement of weapons on them is probably easier for one person to cordinate. However with a tank the gunner can call off target assignments to specific gunners and they can devote their full attention to hitting that target, ie no targeting penalty. In fact this is historically supported by the fact that the T-34 was less effective for having its vehicle commander also be the gunner.
The crew for a BattleTech tank could be: driver and radio operator/hull gunner positioned forward and the hull gunner has a MG or a small pulse laser to deal with infantry. Vehicle commander and primary gunner positioned in the main turret with a twin Gauss rifle, coaxial small pulse laser or mg, SRM/LRMs mounted on either side of the turret, LRM mounted VLS style on the back of the turret. Two secondary gunners positioned back to back in the fighting compartment remotely controling two or sponsons secondary turrets remotely each turret with a Medium Laser and a small pulse laser. Add 4 heat sinks to handle the extra laser weapons.l
RogueSpear, on 04 March 2012 - 12:05 AM, said:
Also in the BT universe due to the extreme cost and difficulty of production of fusion engines and low priority on tracked vehicles, very few tanks have fusion engines and stick to internal combustion. My point on the turn circle was more that a 'Mech is able to counter it's own turn circle due to the articulated legs, and can change direction at a greater angle, etc. I wasn't referring to fighting circle strafing, which the tank may have the edge in (Not sure how easily birdjoint and less flexible humanoid mechs [ie, ones without ball joints in the hips, etc] would be able to turn around on the move).
Fusion engines actually seem to have been fairly common on Star League era tanks and are coming back after the Helm Memory Core and the Clan Invasion. However yes during the Succession wars tanks were less likely to get fusion engines, which puts them at a disadvantage.
I'm still confused as to what you mean by "counter its own turn circle." Are you referring to turn radius? Because even there I think tanks would have the advantage as they can spin their tracks in opposite directions, litterally turning in place.
RogueSpear, on 04 March 2012 - 12:05 AM, said:
Aye you did say bottom armour

Combined arms is always going to be important, but unsupported 'Mechs do have the advantage over traditional armour.
Perhaps over the traditional single turret tank, but I think multi-turret tanks with their ability independantly target would be on par. I still think the only real advantage 'Mechs have over tanks is their strategic one, hot dropping and quick loading.
RogueSpear, on 04 March 2012 - 12:05 AM, said:
Sorry for not quoting you as I go here, I haven't figured out how to use the multiquote feature yet...

Multi-quote allows you to quote multiple posts. If you want to quote me the way I quote you, you have to get a little tricky.
1. copy the [ quote blahblah blah ] before my post
2. place [ /quote ] after the section you want to address
3. paste the open quote section ahead of the next section of quoted text.
Hope that helps!