What's wrong with L4?

It just occurred to me today that whenever I've seen people talk about
space colonies orbiting the Earth-Moon Lagrange points, it's always
assumed that the first colony will be at the L5 point (trailing the moon
in its orbit) rather than the L4 point (ahead of the moon).

Is this just sort of a cultural tradition (homage to the L5 society?) or
is there some technical/economic reason why L5 would be a better location?
Is there any delta-V difference between Moon-to-L4 and Moon-to-L5
missions, for example?
---
Roy Stogner

Roy Stogner wrote:
It just occurred to me today that whenever I've seen people talk about
space colonies orbiting the Earth-Moon Lagrange points, it's always
assumed that the first colony will be at the L5 point (trailing the moon
in its orbit) rather than the L4 point (ahead of the moon).

Is this just sort of a cultural tradition (homage to the L5 society?) or
is there some technical/economic reason why L5 would be a better location?
Is there any delta-V difference between Moon-to-L4 and Moon-to-L5
missions, for example?
---
Roy Stogner

Wow, that's a weird coincidence. On April 11 Peter Knutsen started in a
thread in rec.arts.sf.science entitled "Why Always L5"

"I just checked out some of the sci.astro FAQ, which got linked to in
the "green stars" thread. One of the questions dealt with the five
Lagrange points.

"According to those diagrams, L4 and L5 are the two trojan points, 60
degrees ahead or behind the smaller body's orbit around the larger body.
So how come I always hear much more about L5 than about L4, in science
fiction and in RPGs?

"Is there something that makes L5 easier, or more desirable, than L4?"


If the rassers came up with a good reason L5 was more commonly used, I
missed.

--
Hop David
http://clowder.net/hop/index.html

As I recall from my early L5Soc days, L5 was more convenient as the receiver
zone of moon-launched canisters of materials -- but I forget what the
dynamic reason was, probably had something to do with the location of the
catapult on the lunar surface.

Does that ring any other rusty bells?



"Hop David" wrote in message
...


Roy Stogner wrote:
It just occurred to me today that whenever I've seen people talk about
space colonies orbiting the Earth-Moon Lagrange points, it's always
assumed that the first colony will be at the L5 point (trailing the moon
in its orbit) rather than the L4 point (ahead of the moon).

Is this just sort of a cultural tradition (homage to the L5 society?) or
is there some technical/economic reason why L5 would be a better
location?
Is there any delta-V difference between Moon-to-L4 and Moon-to-L5
missions, for example?
---
Roy Stogner

Wow, that's a weird coincidence. On April 11 Peter Knutsen started in a
thread in rec.arts.sf.science entitled "Why Always L5"

"I just checked out some of the sci.astro FAQ, which got linked to in
the "green stars" thread. One of the questions dealt with the five
Lagrange points.

"According to those diagrams, L4 and L5 are the two trojan points, 60
degrees ahead or behind the smaller body's orbit around the larger body.
So how come I always hear much more about L5 than about L4, in science
fiction and in RPGs?

"Is there something that makes L5 easier, or more desirable, than L4?"


If the rassers came up with a good reason L5 was more commonly used, I
missed.

--
Hop David
http://clowder.net/hop/index.html

According to "Space Settlements - a Design Study", NASA SP-413, page 55:

"There do exist, however, large orbits around both of the remaining
libration points, L4 and L5. These have been shown to be stable (refs.
27, 28). A Colony in either of these orbits would be reasonably
accessible from both Earth and Moon. One of these libration points, L5,
is chosed for the location of the first space colony. This choice is
somewhat arbitrary for the differences between L4 and L5 are very
slight."

The mass catcher was to be placed at L2 (page 59).

JimO wrote:

As I recall from my early L5Soc days, L5 was more convenient as the receiver
zone of moon-launched canisters of materials -- but I forget what the
dynamic reason was, probably had something to do with the location of the
catapult on the lunar surface.

Does that ring any other rusty bells?

"Hop David" wrote in message
...


Roy Stogner wrote:
It just occurred to me today that whenever I've seen people talk about
space colonies orbiting the Earth-Moon Lagrange points, it's always
assumed that the first colony will be at the L5 point (trailing the moon
in its orbit) rather than the L4 point (ahead of the moon).

Is this just sort of a cultural tradition (homage to the L5 society?) or
is there some technical/economic reason why L5 would be a better
location?
Is there any delta-V difference between Moon-to-L4 and Moon-to-L5
missions, for example?
---
Roy Stogner

Wow, that's a weird coincidence. On April 11 Peter Knutsen started in a
thread in rec.arts.sf.science entitled "Why Always L5"

"I just checked out some of the sci.astro FAQ, which got linked to in
the "green stars" thread. One of the questions dealt with the five
Lagrange points.

"According to those diagrams, L4 and L5 are the two trojan points, 60
degrees ahead or behind the smaller body's orbit around the larger body.
So how come I always hear much more about L5 than about L4, in science
fiction and in RPGs?

"Is there something that makes L5 easier, or more desirable, than L4?"


If the rassers came up with a good reason L5 was more commonly used, I
missed.

--
Hop David
http://clowder.net/hop/index.html

On Wed, 05 May 2004 19:35:24 -0700, Hop David wrote:

Wow, that's a weird coincidence. On April 11 Peter Knutsen started in a
thread in rec.arts.sf.science entitled "Why Always L5"

That's not a weird coincidence, that's just an indictment of my Google
skills. A search for '"why l5" l4' doesn't turn up that thread, and
apparantly none of the other search terms I guessed were any better. I've
found it now, though; thank you.
---
Roy Stogner

One thing that you might should know is that later on, they decided that a
circular orbit about halfway to lunar orbit was more advantageous than
either L-4 or L-5. I usually just say "HEO".

But if we ever bring all (or a sizeable piece) of an asteroid into cislunar
space, it might placate the more paranoid if we park it in one of these two
points, since they're kind of sticky.

--


Regards,
Mike Combs
----------------------------------------------------------------------
We should ask, critically and with appeal to the numbers, whether the
best site for a growing advancing industrial society is Earth, the
Moon, Mars, some other planet, or somewhere else entirely.
Surprisingly, the answer will be inescapable - the best site is
"somewhere else entirely."

Gerard O'Neill - "The High Frontier"

"Mike Combs" wrote in message ...
One thing that you might should know is that later on, they decided that a
circular orbit about halfway to lunar orbit was more advantageous than
either L-4 or L-5. I usually just say "HEO".

But if we ever bring all (or a sizeable piece) of an asteroid into cislunar
space, it might placate the more paranoid if we park it in one of these two
points, since they're kind of sticky.

Even though firing a piece of rock so as to hit the Earth is much
easier from L4 or L5 than from a 200,000km altitude.

Do you have any references for this decision? I've also seen
suggestions of HEEO (Highly Eliptical Earth Orbit).

L4 is harder to make nicknames from.

L5 can be pronounced 'Elf Hive'.

"JimO" wrote in message
...


L4 is harder to make nicknames from.

L5 can be pronounced 'Elf Hive'.

Elf Ore -- What Snow White's dwarfs dug.

Alex Terrell wrote:
"Mike Combs" wrote in message ...

One thing that you might should know is that later on, they decided that a
circular orbit about halfway to lunar orbit was more advantageous than
either L-4 or L-5. I usually just say "HEO".

But if we ever bring all (or a sizeable piece) of an asteroid into cislunar
space, it might placate the more paranoid if we park it in one of these two
points, since they're kind of sticky.


Even though firing a piece of rock so as to hit the Earth is much
easier from L4 or L5 than from a 200,000km altitude.

Do you have any references for this decision? I've also seen
suggestions of HEEO (Highly Eliptical Earth Orbit).

One advantage of an HEEO station is a ferry from LEO through the Van
Allen Belt.

Here is a HEEO I've been playing with:
Periapsis = 6678 km (300 km above earth's surface)
a = 184800.245 km
e = .96386368
Period = (Moon's period)/3

The apoapsis of this HEEO (362922.5 km) is just 335.5 km short of the
Moon's periapsis (363258 km)

Set this HEEO's line of apsides so it passes by L4 (or L5) point that is
363258 km from earth's center and this will make a L4 nice fly-by
every 27 days or so.

This HEEO will also fly by the L5 each 27 days (but not as closely since
the L5 an extra 120 degrees qill put the L5 a little further than
384,400 km from earth's center). It will also fly by the Earth-Moon L3
point.

Here is a pic:
http://www.clowder.net/hop/etc./HEEO.jpg

Alex, does my memory serve me correctly that you were talking about Moon
harmonic earth orbits awhile back? I believe this orbit is your
invention although it's a pretty good bet someone's thought of it before
you.

--
Hop David
http://clowder.net/hop/index.html