Skirting Madness

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Skirting Madness

Post by toysdream » Tue Nov 25, 2014 8:21 pm

It's been about a year since my last round of noodling about vintage mobile suit specs, which remains a kind of back-of-the mind obsession. (See previous installments from 2012 and 2013.) In particular, I keep puzzling over the trademark skirt and leg thrusters of the Dom and Gelgoog series, which are seldom listed in official specs and tend to get wildly differing valuations when they are.

Thus, it's been interesting to see these machines revisited in the official setting art for Gundam Unicorn. For the first time ever, we have variants such as the Dom Tropen, Dwadge, Gelgoog, ReGelgu, and Desert Gelgoog - not to mention latter-day descendants like the Dreissen - appearing side by side, and all redrawn to a consistent standard. What can we see when we peek up their skirts, hm?

You know what this means: Time for another lineup graphic! All to scale, naturally. ... lineup.jpg

The most striking thing to me, after all these years of studying toy and model interpretations, is that the leg thrusters of the Dwadge and Gelgoog are really big. To all appearances, they're roughly the same size as the skirt thrusters; certainly they don't seem significantly smaller than the five skirt thrusters of the Rick Dom II, Dwadge, and Gelgoog Jaeger.

In previous ramblings on this subject, I've guesstimated that the combined thrust of the skirt and leg thrusters is probably on the order of 50 tons. For example, this would account for the 54,000 kg difference between the Rick Dom II specs in Gundam 0083 (which only count the back and foot thrusters) and its full output in Gundam 0080. It would also fit the standard Gelgoog, whose four foot thrusters should probably have about the same output as the two 7,000 kg units in the feet of the Gelgoog Marine, leaving about 45-50 tons of thrust to be accounted for.

But if the skirt and leg thrusters are all about the same in terms of output, those are going to be pretty wimpy little engines - based on the above examples, we're looking at roughly 5,000 kg per nozzle. Is this reasonable? Let's tear our eyes away from the One Year War for a minute and broaden our scope.

As you can see, this new lineup graphic includes some later machines from Gundam ZZ and Char's Counterattack which also have skirt or leg thrusters. The Dreissen, as Gelgoog Jager pointed out in this previous thread, has four 9,800 kg thrusters on its skirt - as well as four equally big thrusters in each leg which aren't even counted in its specs. The Sazabi has four leg thrusters of similar size which are counted in its specs, and rated at 9,800 kg apiece - exactly the same as the Dreissen's skirt thrusters. (Aside from the Dwadge and Kaempfer, this is one of the few times the leg thrusters have ever been included in the specs of Zeon mobile suits.)

Also from Gundam ZZ, we have the Bawoo, with two little 6,300 kg thrusters which are used in Bawoo Nutter mode. The R-Jarja has five skirt thrusters which have never been depicted, rated at 11,200 kg apiece - just like the shoulder thrusters of the Hamma-Hamma, so perhaps they're the same type.

If we go further afield, we'll find other examples in the legs and skirts of AEUG and Titans machines like the Zeta Gundam, Re-GZ, Gaplant, and Gabthley. These are all in the range of 11-12,000 kg per thruster.

It seems, then, that an output of about 10,000 kg is pretty typical for a good-sized skirt or leg thruster. It also seems that the leg thrusters are seldom included in the total output, possibly because their limited propellant supply prevents them from being used on a regular basis. So the Dwadge specs, which rate its skirt thrusters at 9,300 kg x 5, seem completely credible.

What about the leg thrusters? Well, since they're roughly as big as the skirt ones, the figure of 8,200 kg x 6 seems credible for these as well. On the other hand, it's unusual for these to be included in Zeon mobile suit specs, and the Dwadge specs rate its back thrusters extremely poorly (a mere 4,300 kg x 2) and ignore the foot thrusters altogether. If its total thrust is 104,300 kg, and 46,500 kg of that is accounted for by the skirt thrusters, it would be more typical for the remaining 57,800 kg to come from the back and foot thrusters - that's only 800 kg less than the equivalent figure for the Dom Tropen.

In case you're curious, I do find this idea a bit of a relief. It's always nice to be able to embrace published specs, instead of trying to rationalize them away, and it was becoming something of a brain-strain to peer up the skirts of the Dom and Gelgoog and try to convince myself that I was looking at a brace of rinky-dink five-ton thrusters. However, this leaves us with new puzzle where the leg thrusters are concerned. More on that, perhaps, in a followup installment...

One other curious thing about the new setting art for Gundam Unicorn: The Regelgu, which had five skirt thrusters in Gundam ZZ, only has three here. As we've noticed, the models and toys have been similarly indecisive about whether the standard Gelgoog has three or five skirt thrusters. None of this seems to affect the overall thruster specs, so perhaps the individual thrusters of the three-thruster version are each exactly 66% more powerful?

-- Mark

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Re: Skirting Madness

Post by balofo » Tue Nov 25, 2014 9:08 pm

Mahq should really consider almost every Sleeved old MS as new machines with separate profiles for UC. Nice research

Going a bit further in the UC timeline: I was really disappointed the HGUC X1 manual didn't have the specs for its leg thrusters. The base X thrusters already have 100,000kg, with the possibility of overloading to 120,000kg. That's already superior to every the late Zanscare unique MS minus the Zanneck(does it count the Zanneck Base?). Sadly we can't compare the Crossbones with the Victory series because of the MF/MD.

As shown in Ghost the X-0 has superior mobility to Zanscare grunts. In the original Crossbone manga the leg thrusters were shown to be really powerful(even having the side effect of heating the hidden knives), So I guess it must have RIDICULOUS acceleration but I've never seen the calculations for its maximum thruster acceleration. I believe we can do it with the known data, but I have no idea which are the correct parameters to do the math.

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Re: Skirting Madness

Post by Evex » Wed Nov 26, 2014 7:03 am

I have a question. If the thrusters are not accounted for in the main thrust could it be that they are considered vernier thruster/apogee motors then, and included in that number ? I know at some point that category disappears in a mobile suits, I guess we can call it an information page. Though if the thrusters are part of the mobile suits regular thrust. I guess that would mean the actual acceleration numbers would be off for the suits.

On the note of the Regelg. Wouldn't the Sleeves downgrade the number of thrusters the suit has, similar to what the delaz fleet did with its Rick Dom IIs ? They are limited on what resources they can use after all. Watching the video of the Regelg on Gundam info the thrusters in its shoulder binders are considered its main thrusters. This mean the skirt armor, and leg thrusters would be considered secondary thrusters. It's possible the propulsion category only takes into account main thrusters. Looking at the Regelgu again it accounts the shoulder thrusters as 6 x 15700 kg and the back pack thrusters as 2 x 28300 kg.

This brings up the question of its ten vernier thruster/apogee motors, which it has ten of. Looking at the suit I can't see any clearly visible. If we think of the gelgoog there are three thrusters in each of its feet, so in theory that is six out of the ten right there. If we assume the skirt armor thrusters are the remainder of the vernier thrusters then that means there is four thrusters under the skirt armor. This would bring the vernier thruster/ apogee motor count to the full ten listed. The only hole in my theory is the two thrusters in each of the suits feet. By my theory that would actually bring the vernier thruster/apogee motor count up to 14, which is four more then the official numbers given.

Looking at the model of the Regelgu on Sd Gundam Capsule fighter online. The skirt armor thruster are shown as three, while its legs have three thrusters each. The feet have two thrusters in them each on the sole of the foot. Looking back at what I wrote earlier the leg and foot thrusters are most likely seen as vernier thrusters/apogee motors. This would only leave the skirt thrusters unaccounted for.

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Re: Skirting Madness

Post by toysdream » Wed Nov 26, 2014 3:28 pm

The original model sheet art for the Regelgu specifically notes that there are five thrusters under the skirt. This was reflected in the 1/144 model kit, too. So the three thrusters in the Unicorn version are a definite change.

As Evex notes, the skirt, leg, and foot thrusters weren't counted in the original Regelgu specs from Gundam ZZ - and indeed, foot thrusters aren't counted in any specs from Zeta, ZZ, Char's Counterattack, or Gundam 0080. So changing the number of thrusters in the skirt wouldn't necessarily affect these specs, and the "true" thrust of the Regelgu would presumably be quite a bit higher. That's not the only weird thing about the Regelgu specs, though. You'll note that it has the same backpack as the standard Gelgoog Marine, but the Regelgu's backpack thrusters (rated at 28,300 kg each) aren't included in the Marine specs, and the Marine version has a pair of 20,500 kg thrusters inserted into the middle of the backpack instead.

On the whole, it seems likely that thruster-looking things would be counted as vernier thrusters if they aren't listed as thrusters. Another obvious example of this would be the Hizack, which is supposed to have ten verniers - most of which must be in its leg booster units. Assuming that all verniers produce at least some amount of thrust, the decision of how to list these could be somewhat arbitrary.

Okay, now for a part two with a bunch of Federation, AEUG, and Titans machines. This is to the same scale as the first one if you want to compare and contrast... ... ineup2.jpg

On the whole, this seems consistent with the previous installment. Most of the skirt thrusters here are in the 11,000 to 12,600 kg range; the Alex's pelvis thrusters, which appear on a lot of Gundam 0083 machines but aren't included in their specs, are rated at 7,000 kg each.

I also note that the Zeta Gundam, Methuss, and Rick Dias II all have 10,600 kg thrusters on their legs, so these may be standard units; although the Rick Dias II seems to have five thrusters on each leg, its specs only list a total of six.

The specs for the Rick Dias's skirt thrusters vary widely from one version to the next. In the Rick Dias II, the main 19,300 kg thrusters are listed as being on the "back", leaving it unclear whether they mean the skirt or the binders. It seems like it would actually make more sense if the skirt thrusters were on the order of 18-19,000 kg; then we could switch the Sturm Dias specs around, saying that the skirt thrusters are 18,300 kg apiece, and the huge binders are the 34,200 kg thrusters. As for the standard Rick Dias, then, its thrust would be split evenly between the skirt and its booster binders (which are currently ignored in the specs).

-- Mark

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Re: Skirting Madness

Post by Gelgoog Jager » Wed Dec 10, 2014 6:32 pm

By the way, I was wondering why not some of these skirted MS, namely the ground use units, took after the Dom's example and used a hovering system on their feet soles rather than traditional thruster?

The ground use Gelgoogs (MS-14D, MS-14G, MS-14GD, etc.), as well as later units such as the Dreissen could have been equipped with hovercraft systems on their feet soles, while relying on their other thrusters (backpack, skirt and calf).

For comparison, we are told that other advanced amphibious units like the Zock and Shamblo relied on hovering systems rather for ground movement.

Considering that the Dreissen was supposed to be mainly a ground unit, maybe the design could have taken the such approach.

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Re: Skirting Madness

Post by MythSearcher » Fri Dec 19, 2014 11:25 am

Some real life design input here, nothing canon, just rational grounds of designing a space combat MS.

Placing any thrusters at the skirt area is not really effective, the same goes for the back thrusters as well.
The best place to place them will be the under foot ones if it is purely for space combat, that is the most effective way to go with the AMBAC functions and easiest to line up your thrust vector with your centre of gravity. With MSs doing AMBAC and the CG moving from the centre line quite quickly, the back and skirt thrusters will be really inefficient in performance and needed many verniers to adjust for attitude.
If you want the MS to be able to do ground combat and is afraid of dust and sand going into your thrusters(not that it really matters since your thrusters are pushing things out and not dragging them in) you can place them in the back or side of the legs.

Some thrusters with further projected structures like the GP01fb, GP02A, GP03S, AGX-04A1, Ex-S, Hi-Nu, etc. are a step above the backpack and skirt, but still lower efficiency than the leg thrusters since the structures only have one DOF, making lining up the CG will only be possible in 2 planes.(you can use other limbs to actively adjust the CG to line up, but that is exchanging your MS's actual functionality to balancing.)

Anything in the back pack or skirt should be sub thrusters or verniers in a more real life sense.

A good rationalization of the unnumbered thrusters can be that they are standard issue of that particular military, and thus they don't really list it in the spec, everyone in that period should know their thrust. Not us though.

Final note, similar sized nozzle does not mean similar thrust, that is a pretty sad fact. The speed of the exhaust and the flow rate along with material technology all changes the most efficient nozzle size and shape of the thrusters, even the place you designed where it should be used matters.
(Shorter in atmosphere since the exhaust pressure cannot fall lower than atmospheric pressure, but longer in space for higher efficiency, yet not too long so the mass of it becomes too high and lowers your fuel efficiency.)

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