GU-11 or GU-12?

[Jefffar]

Well, there seems to be some confusion about the difference between pointing out something us implausible with realistic physics and saying something is impossible in a fictional universe. The result was a tangential but related discussion in which there was an attempt to argue based on realism that the fictional item would work as depicted forcing those who pointed out the implausibility of the item to defend their points.

Its somewhat unfortunate that the topic is repeatedly diverted by attempts to proove something fictional is realistically plausible.

Its also important to point out that no-one has indicated the item couldn't exist in a universe that doesn't adhere to realistic physics, despite claims to the contrary.

[ShadowLogan]

It would take quite the shrink down. I'm not sure if the rounds and cartridges were spheres no bigger than the diameter of the weapon bore we could meet the listed ammunition loads of some of these weapons.

Well if the propellant (and explosive material if present) is more energetic than conventional materials one could theoretically reduce the size of the round though w/o loss of performance, provided the replacement material has similar physical density (actual mass and volume) but packs a lot more energy into the same physical space.

How much of a shrink down are we talking about here though? More energetic materials are possible, I've read that NASA and the USAF have looked at them in the past w/re to rocket fuel. Some are supposed to be more practical than others. Given the SDF-1 arrival also brought in SLMH technology (apparently), other more energetic materials may also have arrived (we do have MD SLAP/HEAP rounds for pistol/rifles).

I'm not advocating sphere shape, just more advanced materials.

[guardiandashi]

It would take quite the shrink down. I'm not sure if the rounds and cartridges were spheres no bigger than the diameter of the weapon bore we could meet the listed ammunition loads of some of these weapons.

Well if the propellant (and explosive material if present) is more energetic than conventional materials one could theoretically reduce the size of the round though w/o loss of performance, provided the replacement material has similar physical density (actual mass and volume) but packs a lot more energy into the same physical space.

How much of a shrink down are we talking about here though? More energetic materials are possible, I've read that NASA and the USAF have looked at them in the past w/re to rocket fuel. Some are supposed to be more practical than others. Given the SDF-1 arrival also brought in SLMH technology (apparently), other more energetic materials may also have arrived (we do have MD SLAP/HEAP rounds for pistol/rifles).

I'm not advocating sphere shape, just more advanced materials.

I realize that it doesn't fit "other aspects" but one of the ways some universes have gotten away with compressing ammo volumes is by going with things like binary liquid propellants (of course those units do NOT have shell casings being ejected" this of course also gives them the capability of dynamically varying the charge of propellant on an as needed basis which also does not appear to be an option with most robotech/Macross weapons. which tend to be "all or nothing" weapons in most cases.

[Jefffar]

It would take quite the shrink down. I'm not sure if the rounds and cartridges were spheres no bigger than the diameter of the weapon bore we could meet the listed ammunition loads of some of these weapons.

Well if the propellant (and explosive material if present) is more energetic than conventional materials one could theoretically reduce the size of the round though w/o loss of performance, provided the replacement material has similar physical density (actual mass and volume) but packs a lot more energy into the same physical space.

How much of a shrink down are we talking about here though? More energetic materials are possible, I've read that NASA and the USAF have looked at them in the past w/re to rocket fuel. Some are supposed to be more practical than others. Given the SDF-1 arrival also brought in SLMH technology (apparently), other more energetic materials may also have arrived (we do have MD SLAP/HEAP rounds for pistol/rifles).

I'm not advocating sphere shape, just more advanced materials.

Well, let's look at the GU-11 for example. We know it fires 55mm APFSDS ammunition. Now the dart of the APFSDS needs a length to diameter ratio of somewhere between 10 to 1 to 20 to 1 for optimal effectiveness. Now if the projectile was full bore, that would mean between 550 and 1100mm long just for the projectile, not including the casing and propellant.

But APFSDS ammunition uses a smaller, narrower projectile to allow the propellant to accelerate it to a far higher speed, giving it greater kinetic energy which, when combined with it's high sectional density, should allow it to punch through armour.

Looking at some modern APFSDS rounds, we can approximate come up with a rough calculation. For example, the M829 120mm APFSDS round has an actual penetration diameter of 27mm. With the same ratio, the 55mm APFSDS round would have a penetrator of 12.375mm in diameter and 123.75 to 247.5mm in length. For those working in imperial units, that's a projectile about 5 to 10 inches long.

Scaling the same ratio up to the Defender's 78mm weapons we see the pentrator for the Defender's APDS rounds probably has a diameter around 17.55mm and an overall length of 175.5 to 350.1mm in length. Again for the metric deficient, that's about 7 to 14 inches long just for the projectile.

Finally, using the same ratio for a 100mm APFSDS for the GU-12 (theoretical, but it's the only way to get good armour penetration without a blast radius), we should get a projectile about 22.5mm in diameter, with a length of somewhere between 225mm and 450mm. This means a projectile between 9 to 18 inches give or take a few.

But the projectile is only a part of the problem, there's the length of the complete round, which is considerably greater. For example the 100mm 3BM25 APDS round fired from D-10 tank guns, but they have eluded me, but the overall length of the complete round in that case is 978mm (about 3 ft, 3 inches) , with a considerable portion of the penetrator extending beyond the front of the casing.

Now the investigations into the LSAT program have determined that using caseless telescoped ammunition (with the projectile mostly or completely in the propellant block) they can shrink the length of a cartridge by about 30% while improving it's effectiveness. So, with the current cutting edge technology, selecting the longest penetrator for maximum effectiveness, we'd see a 100mm cartridge that's 684.6mm long containing a projectile up to 450mm long. That's still a complete round over 2 feet long.

Even if we edged things a bit in favour of alien technology, and cut the cartridge length in half to 489 mm (just over 18 inches) we could still fit that long rod penetrator in. However, any smaller than that and the length of the penetrator begins to decrease and so does its effectiveness.

This also doesn't touch on cartridge diameter. Most cartridges are significantly larger around than the bore diameter of the weapon. Best case scenario would be alien technology allowing a completely straight 100mm case, but a figure 10 or 20 percent larger than that is certainly realistic.

So, how much space do you need for 100 rounds at least 100mm in diameter and 489mm long? Can those be put into a gunpod along with a 100mm cannon plus a feed system capable of handling over 200 rounds per minute? I honestly don't think it's a realistic expectation without the magazine that resembles a police call box.

[Alrik Vas]

and what 7kg a round? so 1400kg if just ammunition in a gun pod. that's about 2 tons right?

can the robot strength of the VF lift that? :O

[Jefffar]

Well, the 100mm APFSDS rounds for the D-10 come in at approximately 20 kg (± 2 kg depending on the specific shell model). So, probably closer to 10kg apiece.

The autoloader that slings those at over 200 rounds per minute is going to be one heck of a machine.

[ShadowLogan]

and what 7kg a round? so 1400kg if just ammunition in a gun pod. that's about 2 tons right?

can the robot strength of the VF lift that? :O

1kg =2.2lbs
1400kg = 3080lbs

VF-1 PS is Giant Robotic PS of 38 (per Macross Saga SB, manga size) so PS x25 (per TSC main book, at 40 it would be x100) = 950lbs (if we use the x100 instead it works out to 3800lbs, but that is "bending" RAW, though IMHO giant robot PS needs some revision due to scale and other animated feats, might require using the Zentreadi full-size PS which is x600 unless one wants to adjust the PS scores instead)

[Alrik Vas]

I'd just use x100. i don't think they intended the VF's to actually be stronger/carry more than a Zentradi, but i'd be okay with it if they did.

[13eowulf]

and what 7kg a round? so 1400kg if just ammunition in a gun pod. that's about 2 tons right?

can the robot strength of the VF lift that? :O

1kg =2.2lbs
1400kg = 3080lbs

VF-1 PS is Giant Robotic PS of 38 (per Macross Saga SB, manga size) so PS x25 (per TSC main book, at 40 it would be x100) = 950lbs (if we use the x100 instead it works out to 3800lbs, but that is "bending" RAW, though IMHO giant robot PS needs some revision due to scale and other animated feats, might require using the Zentreadi full-size PS which is x600 unless one wants to adjust the PS scores instead)

In the alternative one could assume that the weight of the gun-pod is already factored in as a built-in weapon system, and the reason that they are so weak is because they are already carrying so much, this is what is 'left over'.

[glitterboy2098]

palladium's PS system has some logical disconnects in general when it comes to large robots.. most lack the PS to carry any handheld weapons they're issued.. pretty much all of them are too weak to push themselves back up after falling down.

when you start running the lift/carry numbers for them, it becomes increasingly clear that PB's system is optimized for human size characters, and anything much bigger than that starts to break the logic of the system a bit.

it also doesn't help that PS is tied directly to physical combat damage.. you can't just double or triple or x100 the PS without the mecha ending up doing more damage via fists and feet than by it's guns.

so increasing the lift carry multipliers is probably the best way to go.

[Seto Kaiba]

Its somewhat unfortunate that the topic is repeatedly diverted by attempts to proove something fictional is realistically plausible.

If the assertion that it's not is contradicts the facts, well... that kind of diversion is all but inevitable.

Reading back, there have been a lot of false parallels citing to real world equipment of the wrong class.

Well, let's look at the GU-11 for example. We know it fires 55mm APFSDS ammunition.

No it doesn't... per both the OSM and RT2E Macross Saga sourcebook, the GU-11 fires explosive armor-piercing ammunition.

It's possible you may be confusing it with the guns of some of the destroids in the RT2E Macross Saga sourcebook, which ARE said to fire APFSDS. Variable Fighter Master File did identify an APDS-DU round for the GU-11 as a pre-first space war option, but it's not something that was used during the war with the Zentradi.

Now the dart of the APFSDS needs a length to diameter ratio of somewhere between 10 to 1 to 20 to 1 for optimal effectiveness.

Actually, the norm for ammunition from the 90's and later is 30:1 or 35:1. The M829A2 and later are 35:1 scale penetrators, IIRC.

So, how much space do you need for 100 rounds at least 100mm in diameter and 489mm long? Can those be put into a gunpod along with a 100mm cannon plus a feed system capable of handling over 200 rounds per minute? I honestly don't think it's a realistic expectation without the magazine that resembles a police call box.

I don't think anybody here has attempted to defend the idea of the gun's payload... grossly overstating what a given volume can hold, ammo-wise, is something that unfortunately happens a lot in the Palladium Robotech/Macross II line.

Ammunition fitting into weapons has never been a strong point of this universe (Mac II I am looking at you!) Why would we assume that this weapon is any different?

They payload of 78mm cannon shells on the Defender is a tad high and the magazine for the 180mm anti-mecha mortar of the Spartan and Tomahawk is also a rather difficult one.

Just more proof that the Robotech universe doesn't bother with things like realistic physics.

'fraid not, my friends... for the numbers being cited as "proof" of Robotech not bothering with realistic physics don't come from any official source and are purely the product of Palladium's writers. The same is true for the even more absurd numbers that were found in the Macross II book. The official figures (where they exist) are much more reasonable.

the recoil of a useful anti-armor 55mm round fired at over a thousand rds-pm still has staggering engineering implications for the VF-1..

though to be fair, i suspect the original creators of macross just didn't think about recoil.

To be fair, the existence of the VF-1 has staggering engineering implications all on its own... never mind what we see them do in the show.

As far as rate of fire, many aircraft-mounted rotary cannons have the ability to do a variable rate of fire. The OSM spec indicates the GU-11[A] was almost never fired at 1,200rpm (much like the GAU-8/A is practically never fired at its maximum either), and the RPG rate of fire seems to bear this out just fine (it's even within the range of variable fire rates in the OSM).

The math actually does bear out the VF-1 being perfectly capable of firing the GU-11 in flight at lower rates of fire without fear of a disruption to the flight path (assuming proper rotary cannon firing discipline is observed). The VF-1 and A-10A are actually close in mass when loaded for bear, and the VF-1 also has 5.6 times as much engine power to compensate for the recoil force, while firing about 1/5th as fast. That's not assuming the presence of any kind of special recoil-damping system that may exist.

EDIT: Of course, we seldom see them fire in flight because the gun is fixed and the coaxial laser isn't... which makes it a far more practical option that has the great virtue of being recoil-free.