Parking Orbit

How practical is it to tailor a parking orbit for lunar missions that
is reasonably efficent to reach from KSC and precesses at 180 degrees a
lunar month?

Will McLean

On 17 Feb 2006 10:12:33 -0800, in a place far, far away, "Will McLean"
made the phosphor on my monitor glow in such a
way as to indicate that:

How practical is it to tailor a parking orbit for lunar missions that
is reasonably efficent to reach from KSC and precesses at 180 degrees a
lunar month?

What's wrong with 360?

Rand Simberg wrote:
On 17 Feb 2006 10:12:33 -0800, in a place far, far away, "Will McLean"
made the phosphor on my monitor glow in such a
way as to indicate that:

How practical is it to tailor a parking orbit for lunar missions that
is reasonably efficent to reach from KSC and precesses at 180 degrees a
lunar month?

What's wrong with 360?


Nothing. Any multiple of 180 will do. 180 seemed more doable, based on
the orbits I've been able to find information on.

Will McLean

On 17 Feb 2006 12:17:26 -0800, in a place far, far away, "Will McLean"
made the phosphor on my monitor glow in such a
way as to indicate that:

How practical is it to tailor a parking orbit for lunar missions that
is reasonably efficent to reach from KSC and precesses at 180 degrees a
lunar month?

What's wrong with 360?


Nothing. Any multiple of 180 will do. 180 seemed more doable, based on
the orbits I've been able to find information on.

Oh, I misunderstood. You're looking for an actual precession in an
inertial frame? I thought you meant an apparent precession from the
viewpoint of the earth. How does 180 help you? I would think that
360 would be the only one that would give you constant angle with
respect to the earth.

Anyway, what's wrong with L1, other than the performance hit (a
penalty I think well worth paying)?

Rand Simberg wrote:
On 17 Feb 2006 12:17:26 -0800, in a place far, far away, "Will McLean"
made the phosphor on my monitor glow in such a
way as to indicate that:

How practical is it to tailor a parking orbit for lunar missions that
is reasonably efficent to reach from KSC and precesses at 180 degrees a
lunar month?

What's wrong with 360?


Nothing. Any multiple of 180 will do. 180 seemed more doable, based on
the orbits I've been able to find information on.

Oh, I misunderstood. You're looking for an actual precession in an
inertial frame? I thought you meant an apparent precession from the
viewpoint of the earth. How does 180 help you? I would think that
360 would be the only one that would give you constant angle with
respect to the earth.


D'oh!. I meant to say 180 degrees in half a lunar month, or 360 a
month. Or any multiple of that, since I don't require a constant angle
with respect to to the system. I want to arrange the precession so that
every time the lauch window opens to a particular lunar orbit, the moon
is in the plane of the parking orbit.

Anyway, what's wrong with L1, other than the performance hit (a
penalty I think well worth paying)?


Performance hit, the travel time, and L1 is no longer an option with
the current plan.

Will McLean

On 17 Feb 2006 13:29:33 -0800, in a place far, far away, "Will McLean"
made the phosphor on my monitor glow in such a
way as to indicate that:

D'oh!. I meant to say 180 degrees in half a lunar month, or 360 a
month. Or any multiple of that, since I don't require a constant angle
with respect to to the system. I want to arrange the precession so that
every time the lauch window opens to a particular lunar orbit, the moon
is in the plane of the parking orbit.

That makes more sense. But I'm not aware of any way to get a lunar
(and I assume that you want it to be a lunar polar) orbit to do that,
absent continuous thrusting (you could do it with an ion drive, or
perhaps a sail). Of course, if you are aligning it with a bimonthly
launch window, 180 actually would work--it would just be a matter of
entering from above versus entering from below.

Anyway, what's wrong with L1, other than the performance hit (a
penalty I think well worth paying)?


Performance hit, the travel time,

Only an extra day or so, I believe. What's the big deal?

and L1 is no longer an option with the current plan.

Ah, but other people can make better plans.

"Will McLean" wrote in
ps.com:


Rand Simberg wrote:
On 17 Feb 2006 12:17:26 -0800, in a place far, far away, "Will
McLean" made the phosphor on my monitor glow in
such a way as to indicate that:

How practical is it to tailor a parking orbit for lunar missions
that is reasonably efficent to reach from KSC and precesses at
180 degrees a lunar month?

What's wrong with 360?


Nothing. Any multiple of 180 will do. 180 seemed more doable, based
on the orbits I've been able to find information on.

Oh, I misunderstood. You're looking for an actual precession in an
inertial frame? I thought you meant an apparent precession from the
viewpoint of the earth. How does 180 help you? I would think that
360 would be the only one that would give you constant angle with
respect to the earth.


D'oh!. I meant to say 180 degrees in half a lunar month, or 360 a
month. Or any multiple of that, since I don't require a constant angle
with respect to to the system. I want to arrange the precession so
that every time the lauch window opens to a particular lunar orbit,
the moon is in the plane of the parking orbit.

Then I'm afraid you're out of luck. Regression for a 100 nmi equatorial
orbit is nine degrees per solar day (less than 270 degrees per lunar
month), and the effect decreases with both altitude and inclination.


--
JRF

Reply-to address spam-proofed - to reply by E-mail,
check "Organization" (I am not assimilated) and
think one step ahead of IBM.

In article .com,
"Will McLean" wrote:

Rand Simberg wrote:
On 17 Feb 2006 10:12:33 -0800, in a place far, far away, "Will McLean"
made the phosphor on my monitor glow in such a
way as to indicate that:

How practical is it to tailor a parking orbit for lunar missions that
is reasonably efficent to reach from KSC and precesses at 180 degrees a
lunar month?

What's wrong with 360?


Nothing. Any multiple of 180 will do. 180 seemed more doable, based on
the orbits I've been able to find information on.

Will McLean

Why would anybody *want* such a long-duration parking orbit? The craft
could go stale if it is kept in orbit that long -- besides, the only
reason for an earth parking orbit is to extend the launch window from
some 3 minutes to several hours. It costs propellant to insert into park
and then inject into translunar.

On Fri, 17 Feb 2006 21:37:37 GMT, in a place far, far away, Orval
Fairbairn made the phosphor on my monitor
glow in such a way as to indicate that:

Why would anybody *want* such a long-duration parking orbit? The craft
could go stale if it is kept in orbit that long -- besides, the only
reason for an earth parking orbit is to extend the launch window from
some 3 minutes to several hours. It costs propellant to insert into park
and then inject into translunar.

Presumably to establish a propellant depot, which could pay for itself
in terms of the extra propellant for the insertion.

Hello - I am new to this Group - but I do have some insight to this
astonishing Question?

180 Degrees Being the infra-spectrum in which we can see and operate in that
the temperature is fine for working in? - not too much?

Also the indexing of the interior is a advantage in that the interior is
really the importance of the overall in that the indexed interior is a
fundamental in that the overall importance in that the overall input pattern
is a fundamental?

Question though? With the Moon so interconnected and seemingly ineventfully
- connected to the Tide Lines on the planet - could the Moon be a poor
destination in that I believe that the Solar Winds (Geo-magnetical forces)
are the
willing and given in that the overall is very efficient as is!? Very light
craft as landed
before - (as with more propulsion) are event
full enough!?

I hope this answers your Question? I also as my Web Space below serves -
answer Questions about almost anything?

Here is my Web Space Address?

http://www.members.shaw.ca/finitesystems/index.html

Another thing - as I am an experienced Networking Cohesive newsgroup
person? - as I may have Just witnessed a simple thing as I Just read 1
Posting - please do not do that to Me if you did what you did or you will
surely see the other side?

Casper












"Rand Simberg" wrote in message
...
On 17 Feb 2006 10:12:33 -0800, in a place far, far away, "Will McLean"
made the phosphor on my monitor glow in such a
way as to indicate that:

How practical is it to tailor a parking orbit for lunar missions that
is reasonably efficent to reach from KSC and precesses at 180 degrees a
lunar month?

What's wrong with 360?