Re: Transit times between L4 and Moon

" They are racing to reach the Moon. "

"Flip a coin" doesn't enter into it, the result is a tie. :-)

Always amusing when someone wants to sound knowledgeable when they
babble "relativistic orbital velocity", but then say "likely", and funnier
still when they say:
"The other consideration you failed to pay notice to..."


"Timothy Partee" <tpartee@xxxxxxxxxxxxx> wrote in message
news:rIqdnWC0GNFbeBLanZ2dnUVZ_gCdnZ2d@xxxxxxxxxxxxxxxx
|
| Given that ship A and ship B start from stable orbits in the precise
| center of the L4 and L5 gravitational pockets (i.e. their motion in
| orbit around the sun is in a precise 1:1 frequency with Earth) and have
| precisely the same mass, engines, fuel, etc. - they would arrive at a
| theoretical point perpendicular to Earth's orbital trajectory at the
| precise same time. This is due to conservation of angular momentum and
| relativistic orbital velocity of the three bodies.
| However, if they are in a theoretical "dead motion" state (relative
| to the Sun) at the beginning of this conjectured model, they would not
| only experience free-falling toward the sun, but would also experience
| perturbations from the L4 and L5 points around them respectively that
| would likely launch them into any number of potentially chaotic paths,
| requiring careful compensation by any engines and navigation systems in
| order to reach Earth. Since you're speaking purely hypothetically, we
| may as well get really crazy.
| The other consideration you failed to pay notice to when you were
| thinking about the moon's orbit and one ship approaching the moon sooner
| than the other due to the time it takes them to move toward it, the
| moon's orbit is changing is: the ships may take more than one lunar
| orbit to arrive, and therefore the advantage could be given to EITHER of
| the ships depending on the time it takes them to travel to the general
| vicinity of Earth. Without knowing the precise chronology that this
| "race" begins and the precise details of the mass, thrust and
| capabilities of these craft, it's impossible to guess which will arrive
| first. Flip a coin. =)
|
| - Timothy Partee


|
|
| Aztec50 wrote:
| > Spaceship A is at L4.
| >
| > Spaceship B is at L5.
| >
| > They are racing to reach the Moon. Each has the same engines, and
| > will go at the same speed.
| >
| > Question #1: which will arrive first? Question #2: if I didn't have
| > much energy (and these ships weren't the supersleek dragsters they
| > undoubtedly are), what would be the optimal/energy-efficient orbital
| > "route" from each libration point to the Moon?
| >
| > I.e., what I'm trying to figure out here is whether the fact that L4
| > is "ahead" of the Moon's position in orbit is an advantage or
| > disadvantage vis-a-vis L5's position "behind" the Moon's position in
| > orbit. My first thought was that Spaceship A will win easily (vis-a-
| > vis Question #1), because while it moves toward the Moon, the Moon is
| > moving toward it. But then I reflected that Spaceship A, in going
| > "backward", still has to compensate for the forces that are propelling
| > it "forward." And then I reflected that Spaceship A, in entering a
| > retrograde orbit, will actually start to move in toward the Earth.
| >
| > And then I decided to put the question to all your brainiacs out there
| > in the hopes that someone will actually know the answer to this #$#
| > thing.
| >
| > Just so we're all on the same page, this is the libration point
| > topography. (This map has the Sun at the center, but substitute the
| > Earth for the Sun, and the Moon for the Earth, and we're golden.)
| >
| > http://en.wikipedia.org/wiki/Image:Lagrange_points.jpg
| >
| > thanks!
| >
| > FA

.

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