garrick lee (
Wed, 27 Oct 1999 08:30:53 -0700 (PDT)


damn, z, you just short circuited my neurons.

i'm not sure i understood all that...and here are a
few stupid questions to prove it.

1) isn't it all as simple as ---> if an object
possesses enough power to fly/hover in atmosphere, it
possesses enough strength to get out of orbit and out
into space (and anywhere in space, given enough fuel)?
 after all, if you're closer to earth, the gravity is
stronger. if you can defy that much gravity, why can
you not escape earth's weakened gravity a few
kilometers above the atmosphere? if you're past the
equal-gravity portion, can't you just ride on the next
gravity pull that's pulling you in? (ok, something
tells me it's not as simple as that...but what am i
thinking wrong?)

and a gundam can hover right? (how about a macross
valkyrie? and what is macross doing wrong? from what
i read, something tells me that macross violates a few
astrophysics laws, i don't know what...)

2) you're telling me that virtually any volume of
space in space is within gravitational pull of one
planet/asteroid/star or another? i'm trying to grasp
that...(which probably explains why i'll never be an
astronaut, heh). is there no region in space that is
absolutely free of gravitational attraction of one
body or another? (i.e. gravitational pull is THAT
strong???) that's not lagrange...but is/would it be
equal to lagrange, for all purposes?

3) what the hell is a spacesuit for? aside from
providing an enclosed oxygenated environment that's
not freezing... what do spacesuits do to help
"withstand the rigors of outer space" (as i seem to
read very often)? what does a spacesuit/flightsuit do
to help against g forces? (what are they made of, for
that matter?)

4) that reentry's atmospheric friction that
causes the burn, right? what if the angle of entry is
so shallow (say, 1 degree)...would that eliminate
reentry problems? (y'know, kinda float around for a
while, before dropping like a rock?)

or is an object that's in "reentry" definitely,
irrevocably caught in the earth's gravity? therefore,
angle of attack doesn't matter, because earth's
gravity will pull you through the atmosphere faster
than you want to and you WILL drop like a rock ANYWAY
(and burn up real quick)?

what about slingshot maneuvers? they utilize the
planet/star's gravity, but aren't caught in

eh...i think i'll stop asking questions now. i'm
feeling dumber by the minute.

damn glad to be on solid ground, where there's less
physics involved :)

--- -Z- <Z@Gundam.Com> wrote:
> Well, no one caught my mistake, so I'm going to have
> to 'fess up myself,
> just so I can get the correction out.
> I was pretty tired last night and, as experience has
> shown, I tend to goof
> up a technical topic when I'm overworked. In my
> reply to the message "How
> Far Can An MS Go?" re the delta-V (change in
> velocity) requirement to
> travel from one orbit to another, I stated that an
> MS probably had enough
> delta-V to go from low Earth orbit to geosynchronous
> Earth orbit, but not
> from GEO to Lunar orbit.
> That's actually just the opposite of what I meant.
> What I had in mind was that an MS probably has
> enough delta-V to go from
> the LUNAR EQUIVALENT of low Earth orbit -- i.e., a
> low Lunar orbit, such as
> the one used by the Apollo astronauts -- out to the
> four nearby Lagrange
> points, but not enough to reach geosynchronous Earth
> orbit.
> Here's how it works. Earth's at the bottom of the
> gravity well that is the
> heart of the Earth-Moon system. It's Earth's
> gravity, offset and combined
> with the Moon's gravity, that creates the Lagrange
> points. The closer you
> are to the Earth, the deeper you are in the well,
> and the greater the
> delta-V to mark any change in your orbit. The
> farther out from Earth you
> get, the less delta-V you need to change orbit.
> (There are correspondingly
> fewer orbits to obtain, but that's a whole 'nother
> story!)
> The Moon has it's own gravity well, but it's much
> shallower than Earth's --
> about 22 km/sec, compared to 8.6 km/sec. Both are
> well beyond MS thrust,
> so you need a mass-driver or booster to get an MS
> off the Moon and a space
> shuttle or HLV to get one off the Earth.
> Once you're in orbit, you're "halfway to anywhere"
> -- nearly all of the
> mighty Saturn V was expended getting the Apollo out
> into orbit, after which
> it pretty much coasted to the Moon and back. The
> external fuel tank (ET)
> and solid rocket booster (SRB) of the space shuttle
> account for over half
> its mass and are used exclusively to get that puppy
> out of the atmosphere
> and into low Earth orbit.
> But LEO is as high as it gets. When it boosts a
> satellite into GEO, it
> does so with a disposable rocket motor called a
> Payload Assist Module
> (PAM). That gives the satellite the additional 3.8
> km/sec delta-V needed
> to rise from LEO to GEO.
> And that figure works both ways. An MS without
> enough gumption to handle
> the Moon's meager 2.2 km/sec delta-V can't traverse
> from GEO to LEO, which
> needs half again as much.
> It should, however, be able to muster the 700 m/sec
> delta-V to get from
> Lunar orbit to L5 or L4 (same delta-V, different
> vector). Similarly, Side
> 3 in L2 should be able to send an army of MS down
> into Lunar orbit and
> slingshot them on to L1 without having to transship
> them in Musai carriers.
> With a few asteroid garrisons like the A'Bao'A'Qu,
> Solomon and Pezun fir
> docking and refueling and a little slingshot effect
> from the Moon, MS
> should be able to patrol the entire diamond-shaped
> area bounded by L1, L2,
> L4 and L5.
> From L4 or L5 to GEO is about 1.7 km/sec delta-V.
> Not as much as getting
> off the Moon, but over twice as much as from the
> Moon to L4 or L5. Can an
> MS do it with just strap-on boosters? Maybe, but it
> would be quite an
> adventure. I'd opt for a full-up booster bed and
> maybe a little
> mass-driver/catapult send-off.
> From L4 or L5 directly to LEO is about 4.1 km/sec
> delta-V -- 300 m/sec more
> than from GEO to LEO. If you can do the latter, you
> can probably do the
> former, but if you can do either, you can go just
> about anywhere in the
> Earth Sphere anyway, because you've gotten over the
> second biggest hump,
> the first being getting off the Earth in the first
> place.
> I hope I've made this all clear now, because I'm
> getting tired again and if
> I go on I'm apt to say something stupid again....
> -Z-
> -
> Gundam Mailing List Archives are available at


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