Mark Simmons (scorpio@best.com)
Tue, 31 Oct 2000 10:18:43 -0800


Lim Jyue writes,

PROPELLANT SPECS

> Actually, all it did was to restrict their performance to OYW
>levels, didn't it? If they had the same amount of propellant as the supposed
>OYW MSes, their performance would be much higher since their lightweight
>materials lower their full weight while their thrust increases.

  And that's the point. All the Z reference books say that "modern"
mobile suits carry more propellant than their One Year War ancestors,
something made possible by their lightweight construction.

> Which, IIRC, never made it in any show except 0080 -- which was
>absolutely necessary as the JEP reduced most of the 2nd Gen Zeon MSes to
>pitiful ranges.

  Some Zeon mobile suits in 0083, such as the Gelgoog Marine, also have
external propellant tanks... and they don't have much thrust at all.

> Eh? Why? Won't the composite be lighter per ton than titanium alloy?

  I think you mean "lighter by volume." :-) No idea why - I'd just note
that the antique Galbaldy Beta has a lower dry weight than the Hizack and
GM II, which use newer materials.

ALEX SPECS

> Heheh. Unfortunately, counting the two as thrusters will present 2
>problems.
>
> 1) It doesn't account for the foot thrusters.
> 2) It may throw the apogee motor count -- which is getting more and
>more confusing -- out the window too.

  None of the 0080 specs account for foot thrusters. Like I said, that's
a difference in approach between 0080 and 0083. As for the apogee motors
- hey, the Alex still has more than enough to go around. Point being that
this _is_ where the extra two thrusters are supposed to be located.

> Of course, they could call each backpack thruster as 35,000kg, each
>leg thruster as 8,000kg, and the each pair of foot thrusters (2 in each
>sole) as 7,000kg thruster

  They could have, but they didn't. :-) And that would create another
problem - none of the GMs from 0080 have butt thrusters, but they all
have foot thrusters, so all their specs would have to be adjusted to
include the foot thrusters as well.

> Well, we've multiple "official" specs that doesn't agree on multiple
>MS, so a lot of those specs are somewhat suspect too. It gets worse when you
>consider that many books copied from one source, which may have mistakes in
>their specs.. and so the errors goes on down the sources.

  Which, again, is why I always go back to the primary sources. Errors
tend to crop up as you go along and proliferate throughout subsequent
publications. As an example...

  The specs for all the 0080 mobile suits were originally printed in the
laser disc liner notes (among other places). However, when they compiled
the new liner notes for the DVD, they reformatted everything and wound up
screwing up the specs. Now they list total thrust for everything, and I
note that they got the correct total thrust for the Full Armor Alex
(174,000 kg) but wrongly attributed it to the regular mode. Then they
added the extra 42,000 kg for the Full Armor mode and came up with a
grand total of 216,000 kg. One day, some poor schmoe is going to look up
the Alex's thrust and copy those numbers out of the DVD liner notes on
the assumption that they're "official," when really some Bandai Visual
editor just got sloppy and mixed up some ten-year-old specs.

> Frankly, the FA version does not seemed to have supplementary
>thrusters except for the butt-6 pack, which when you consider the space they
>had, seemed to be small thrusters in the main. Having an additional 48,000kg
>of thrust from them is slightly unbelievable..

  42,000 kg total (7,000 kg x 6). You may find those numbers excessive,
and Lord knows I do too, but they _are_ official. That's why people
characterize 0080 specs as excessive.

THRUSTER MATH

> Actually, what *are* reasonable values for thrusters? I don't really
>see a pattern here, since most MSes has wildly varying values for thrusters
>-- and I don't necessarily have separate location ratings for all of
>those MSes.

  It's a moving target, indeed. In general, foot thrusters are spec'd out
at 3 tons or more - the 0083 specs list the Gundam/GM foot thrusters as a
pair of 1,870 kg thrusters (3,750 kg per foot), and the Zaku F2's foot
and ankle thrusters as 3,100 each. The Rick Dom II and Gelgoog Marine are
listed as having 7,000 kg foot thrusters, but then again, the 0083 specs
ignore the skirt and ankle thrusters for these mobile suits, so they have
to credit all that extra thrust to the feet.

  In general, thruster values are pretty arbitrary. I think the specs-
makers tend to concentrate more on the total thrust, then divvy up this
total among whichever nozzles the mecha designer happened to put on his
mobile suit. As a result, there's no real visual difference between a
7,000 kg thruster and a 27,000 kg thruster.

  It is illuminating, however, to look at mobile suits which have
thrusters in their legs and see how much of the total was allocated
thereto. The official specs for the Alex give it 48,000 kg of thrust in
the legs (8,000 kg x 6), which is 36% of its total. This is actually on
the high side of the range; my quick number-crunching indicates that the
fraction is between 20-40% for the most part, with 25-30% being typical.

  For example, the F91 Gundam has 30% of its thrust in its legs. The Nu
Gundam, Gaza D, 0083-version Rick Dom II, and F91-version Jegan all have
25%. Sentinel's Xeku Eins and the CCA-version Jegan are around the 35%
mark, Sentinel's Z Plus and Gundam Mark V at 40%, the Z Gundam at 45%.

  So, if we kept the same fraction of the Alex's thrust in the legs, and
gave it the same 30,000 kg backpack thrusters as the GM Custom (hey,
that's still 25% more than the original Gundam's backpack thrusters!),
then we'd have a total thrust of about 94,500 tons. Subtract 7,500 kg for
the foot thrusters (I'm going by 0083 standards here - count the feet,
ignore the butt), and we have 27,000 kg left over for the six leg
thrusters, or 4,500 kg apiece.

  Just as an example...

-- Mark

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Mark Simmons / scorpio@best.com / http://www.gundamproject.com/
"If you can kill it, it's not a god, just a good old-fashioned monster."

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