Mark Simmons (scorpio@best.com)
Mon, 30 Oct 2000 12:55:16 -0800


Lim Jyue writes, on various subjects...

PROPELLANT SPECS

> Considering the need of the Zeon military to create an equalizer to
>the large numbers of warships the Federation had, the large amounts of
>propellent may be necessary for Zeon MS tactical use.

  Note a bad theory, but the Z-era mobile suits are repeatedly described
as having more propellant capacity than their One Year War equivalents.
In particular, this claim is made for the Rick Dias (thanks to its
lightweight Gundarium Gamma armor), so logically it should have more
propellant than the Rick Dom.

  Not to mention that the Galbaldy Beta should be a good indicator of One
Year War technology, since it's based on a Zeon design with virtually no
modifications.

> Why did the Z-era MSes need more propellant? With the majority of
>these Z-era suit operating from MS carriers (as opposed to the "fixed"
>asteroid bases of Zeon OYW), I do see the need for more propellant (mainly
>to get back home), but Zeon MSes may had a need for larger propellant for
>longer range operations.

  They didn't _need_ more propellant per se - it's just that the more,
the better, and their lightweight materials allowed them to carry more of
it without sacrificing performance. (Otherwise you end up with exactly
the problem seen in the Zeon specs under discussion, i.e. pitiful thrust-
to-weight ratios.)

  And at any rate, the Zeons _did_ come up with a workaround for longer-
range missions - external propellant tanks.

WEAPONS PAYLOAD

> Maybe not. You may have discounted the weapons weight -- after all,
>weapons development have progressed quite a bit in the short (5+) years
>between OYW and Z. Hence, it is possible the beam rifles carried by both the
>Galbaldy Beta and the Gelgoog are of differing weights.

  Possible, but unlikely - the Galbaldy Beta's rifle _is_ a Gelgoog beam
rifle. :-) Ditto the Hizack's machine gun.

> Furthermore, we do know that armour material has improved over the
>years, so that shield of the Gelgoog might have been substantially higher
>weight than the Galbaldy's. All these will not have been included within the
>base weight, but within the full weight.

  True. But again, the Galbaldy is made of One Year War-era materials
(namely plain titanium alloy). In terms of specs, performance, and
armament, it's supposed to be a good indicator of OYW technology. Newer
mobile suits like the GM II and Hizack use the better titanium-ceramic
composite, but if anything, this ends up making them _heavier_.

ALEX SPECS

> The specs I obtained from the actual 0080 series model kit's manual
>is as follows:
>
> Thrusters: 35,000kg x2, 7,000kg x 2, 8,000kg x6. (6 8,000kg
>thrusters!)
> (Doesn't state if the values are for the NT-1, or the FA.)

  That's for the regular Alex. You'll note they total to 132,000 kg.

> If we peg the big backpack thrusters as the twin 35,000kg thrusters,
>and each leg's three exhausts are the 6 8,000kg thrusters, we are left with
>the problem... which are the 7,000kg thrusters?

  They're in the butt. :-)

  Note that the specs for 0083's mobile suits ignore the butt thrusters,
but _do_ count the foot thrusters. I've written before on this conflict
in thruster-accounting...

  Anyway, nice work with your thrust-tallying scenarios. Unfortunately
the official specs are quite clear in this regard, but you're making a
good start at brainstorming _unofficial_ specs. My first impulse would be
to start with the specs of the GM Custom, which after all has identical
backpack and feet; ignore the two butt thrusters, in keeping with 0083
practice; and then come up with reasonable estimates for the six leg
thrusters, say halving them to 4,000 kg apiece. That comes to 91,500 kg,
for a thrust-to-eight ratio of 1.26 - high, but not inconceivable.

> Let me guess; The MS Encyclopedia also listed the Normal Mode as
>"35,000kg x 2, 8,000kg x 6"? Went along with my Scenario B.. =)

  Nope - 35,000 kg x 2, 7,000 kg x 2, 8,000 kg x 6. Which is actually
correct, for a change.

Ez8 SPECS

> Okie.. that'll explain it, as I don't have that kit. So you do
>consider model kit manual's specs as "official"?

  Not necessarily, but in this case all the third-party publishers seemed
to. :-)

GOUF FLIGHT TYPE

> The Gouf will still need jet fuel to run those jets, correct?

  Not given the way Gundam-world thrusters work. Most mobile suits have
"thermonuclear rocket engines," which circulate liquid reaction mass
through the reactor core and then vent the superheated propellant to
create thrust. The jet engine version of this, pioneered in the Gouf
Flight Test Type and Dom, sucks in air and then superheats it to get
thrust; unlike a conventional jet engine, you don't even need to use
combustible fuel to ignite it. The operating time of such a jet engine is
theoretically unlimited.

ACCELERATION MATH

> Wait a minute.. Since I'm a bit rusty with my physics, I'll like to
>run through the process with you to make sure I got it right.
>
> To determine acceleration, I'll just use the simple F=ma formula.
>Now, F needs to be in Newton (S.I, unit), m in kg, and a in ms^-2.
>
> In this case, T is our force, but it's in kg instead of N. Hence, we
>need to multiply by G, approximately 9.8 (by your assumption in another
>mail). This furfills the F unit requirement (to be in Newtons). The mass is
>already in kg, so we don't worry about that. So, basically:
>
> T[kg]*G[ms^-2] = m[kg]*a[ms^-2] -- which is unit consistent on both
>sides.
>
> Manipulating both sides, we get: T/m [no unit] = a/G [no unit].
>
> Hence, the T/W (more accurately, T/m) ratio I derived is essentially
>the straight line acceleration [in G] of the MS? Is this correct?

  Exactly. So, if the a/G ratio equals 1.000 - i.e. a = 9.8 m/sec^2 -
then you're pulling exactly one gee.

FLIGHT TIMES

> This also probably means that the MS's effective combat time in
>space is only about 10 minutes or less.

  Not necessarily - just its _acceleration_ time. The idea is to launch
from your ship, burn propellant for a few minutes until you reach
cruising speed, and then try to stay at that speed without speeding up
and slowing down all that time. A lot of stops and starts will use up
most of your limited propellant, possibly leaving you without enough to
re-accelerate and catch up with your mothership.

MAGNET COATING

> Actually, I don't get this. Magnetic coating is supposed to reduce
>friction in the joints, correct? While this will enable the MS to position
>the apogee motors faster, a 50% increase seems a bit excessive.

  Yeah, it's a weird choice for the computation, but I guess they had to
factor it in _somewhere_. :-)

-- 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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