-Z- (z@gundam.com)
Mon, 30 Oct 2000 21:03:42 -0800


> -----Original Message-----
> From: owner-gundam@1u.aeug.org [mailto:owner-gundam@1u.aeug.org]On
> Behalf Of Rodrick Su
> Sent: Sunday, October 29, 2000 10:45
> To: Mobile Suit Gundam Mailing List
> Subject: [gundam] Axis movement 0086-> Zeta
>
> Question: Did Axis moved a bit too fast on its way back from the asteroid
> belt?
>
> The OYW Zeon remnant fleet took 18 months to get to the asteroid.
>
> Axis took 20 months to return to Earth Sphere, while being several order of
> magnitude more massive than any spaceship. With that much mass to be
> displace, does it take more time to get it up to speed? And one thing I
> keep on noticed in animation as well as in live action: Acceleration get
> more screen time than deceleration. We never get to see Axis decelerate
> (except being deflect by Gate of Sedon and the colony laser).

Technically speaking, Axis didn't get "back" from the Asteroid Belt, because the
asteroid Axis was always out there. The spherical gravity block habitat Mauser
(or Mowsa, if you prefer) and the apogee motors were attached to the asteroid,
which then became a waystation for the Jupiter Energy Fleet, in UC 0072.

I don't have a departure date for the Zeon refugees, but we can assume it was
sometime after the fall of A'Bao'A'Qu (31 December 0079) and prior to the
conclusion of the Granada Treaty (14 January 0080). They arrived at Axis on 28
March 0081, so their transit time was about 15 months.

Dozul Zabi's widow died on 5 May 0081 and Maharajah Khan became Regent for
Mineva Lao Zabi, which put him in command of the Axis forces. The Delaz Fleet
and Axis confirmed their alliance in November 0081. Maharajah Khan died on 9
August 0083 and was succeeded as Regent by his then-16 year old daughter, Haman,
two days later.

The Axis Advance Fleet arrived in the Earth Sphere at 02:23 on 10 November 0083.
I don't have a date fro its departure from Axis, but it couldn't have been
before November 0081, because there was no Axis/Delaz alliance prior to that
date. It must've left while Maharajah Khan was still Regent, because Haman
didn't succeed him until just 90 days prior to the Axis Fleet's arrive -- much
too short a time for such a transit. If the Axis Fleet left on the day the
alliance was confirmed, it's transit time would've been almost exactly two years
(24 months). Assuming that the transit time must be at least the 15 months it
took the Zeon refugees to go out to Axis, the latest the Axis Fleet could've
departed Axis was 10 July 0082.

Axis began its journey to the Earth Sphere on 6 February 0086 and arrived on 2
October 0087. Although we donít know where Axis might actually have been
situated in the Asteroid Belt, this is consistent with the transit time to and
from the asteroid 1 Ceres, which works out to 1.84 years (22 months).

So the question is less how long it takes Axis to move from the Asteroid Belt to
the Earth Sphere, because that one-time transit has a fixed start and end date,
as it is how long it takes a Gwajin or Gwanban class battleship to make the same
transit.

Here's where it becomes important to know that Axis was in the same relative
position as Ceres, because transit time is determined by the delta-V required to
change orbits, not by the amount of physical distance between two points. To
hold a particular place in the Asteroid Belt, an object must be traveling at a
certain orbital velocity. It's the difference between that velocity and Earth's
orbital velocity that must be overcome to make the transit.

Assuming that the transit is via Hohmann minimum-energy orbit, we can estimate
the transit time as a differential between the two orbital periods. For
example, a Hohmann transit from Earth, which has an orbital period of 12 months
(365 days), and Mars, which has an orbital period of 22.9 months (687 days),
would take 8.5 months (259 days). A transit to Jupiter, which has an orbital
period 11.86 years (142.2 months), would take 2.6 years (33 months).

Asteroids are a bit different, however, in that their orbits are more eccentric.
  In the 3.7 years (44.4 months) that it takes 1 Ceres to go around the Sun, it
also moves inward and outward nearly the full width of the Asteroid Belt. As it
gets closer, it slows down; as it moves away, it speeds up -- "higher" orbits
have greater velocity that "lower" orbits. To go from Axis to Earth, one must
decelerate the entire distance, The 22 month transit time cited above is for
Ceres at its mean distance from the Sun. At apogee, it can take half again as
long -- nearly as long as a transit to Jupiter. At perigee, the transit time
would be just under double that of a trip to or from Mars -- about 14.4 months.

It appears, then, that the Zeon refugees traveled to Axis when Axis was nearing
perigee, that Axis itself made the transit when it was near the mean and that
the Axis Advance Fleet made its transit somewhere between perigee and the mean.

-Z-

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