[HN Gopher] Novel Stable and Low-Energy Earth-Moon Cycle Orbits ...
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Novel Stable and Low-Energy Earth-Moon Cycle Orbits [pdf]
Author : mmastrac
Score : 19 points
Date : 2025-10-06 14:51 UTC (8 hours ago)
(HTM) web link (ross.aoe.vt.edu)
(TXT) w3m dump (ross.aoe.vt.edu)
| araes wrote:
| Cool paper. No propulsion, stable, cyclic orbits between the moon
| and Earth, with times of 45 days (1,1), 84 days (2,1), 64 days
| (3,1), and 74 days (3,2). Also, (3,3) were identified with no
| findable timeframes shown.
|
| All the orbits are also somewhat relaxed, with relatively large
| windows of acceptable trajectories and distances for the later
| families. Perilune altitudes ranging from 750 km to over 6,000
| km. The (1,1) and (2,1) are somewhat restrictive (0.1 km).
|
| Makes a lot of interactions with the moon, exploration, resupply
| much less severe. It looks like you can leave Earth, at ~0.4 or
| ~0.6 moon orbit radius, doing some relatively low velocity, and
| hit a stable resonance orbit. You just have to stay out of GEO
| satellite orbit window where Earth is the dominant gravitation.
|
| Also, may imply that such orbits exist with pretty much every
| single moon around every single planet. Implies there's a Sun-
| Earth orbit family group that's very similar. Probably some
| multi-moon orbits with places like Mars and Jupiter.
|
| Also, implies that there may also be a bunch of objects (rocks,
| meteoroids, dust, asteroids, comet remains, ect...) already
| orbiting in these types of cyclers, since they're relatively
| accepting of variations on a basic theme. (3,1) is a ~250 km
| window, (3,3) is a 2000+ km window.
| Tuna-Fish wrote:
| I really don't understand why you'd use these instead of direct
| ascent. The practical orbits here are in the scale of months,
| while the moon is 3 days away if you just go there directly.
|
| Unless you have a massive space habitat to hang out in, a
| cycler is worse for logistics than just direct ascent. For
| interplanetary transits cyclers might some day make sense if
| you want to move a lot of people around and want to make a huge
| artificial gravity habitat for the journey. But the moon is
| just 3 days away, you can just go direct.
| araes wrote:
| Resupply is a common case. Large amounts of material that you
| "only" need to take out to 0.4 radius. Or that you can "park"
| at 0.4 radius and then pick up later.
|
| Persistent shuttle / subway / bus that you can meet somewhere
| with lower fuel and then tag along for the rest of the ride
| is another. Sure, its faster to drive somewhere direct with
| your car, yet its convenient if there's already a known
| cycling bus / subway route. Go to a known location, tag
| along. Like a bus / subway, it's also enabling. Maybe you
| don't want to / can't pay for a Saturn V project.
|
| Cyclic activities that require more than just a one-way or a
| single round trip. Trash / waste, and similar activities on
| Earth are an example. Put your trash at some known meeting
| spot, it gets picked up and taken away.
|
| The entire satellite economy is another, since it's a
| completely different orbital regime with completely different
| coverage, vantage points, and observational characteristics.
| Example, long term telescope that does a constant Earth-Moon
| cycle every 64 days and has baseline coverage star pattern
| footprint of ~500,000 miles in a relatively short time frame
| for observations (along with observations over the entire
| yearly orbit)
|
| You can also add slowly and keep adding, cause it won't fall
| out of orbit.
|
| Also works with stuff like slow LEO to GEO transfers using
| high ISP engines and long orbit raising spirals. (You have to
| go to 100,000 vs 22,000 miles, yet similar idea).
|
| Speed's not the only metric. No fuel / no propulsion is
| rather compelling. Low energy, low cost, long term stability.
| Tuna-Fish wrote:
| You can't just deliver stuff to the path of a cycler and
| magically have it pick it up with a velocity difference of
| kilometers/s. You need to match orbit with it, which in
| fuel terms is no cheaper than flying the entire path. And
| this orbit matching is generally more expensive than flying
| directly. (Especially because you need to raise and then
| lower your perigee, so a "shuttle" flying between the
| ground and the cycler earth end would have to burn much
| more delta-v than a direct ascent stage that can always
| keep it's perigee down and just raise apogee until it
| intersects with the moon.)
|
| Again, cyclers make sense when you have something heavy you
| want to perpetually travel between the endpoints, and do
| relatively light transfers at the ends. But you don't need
| anything like that for the moon. For the moon, you can just
| take the stage that would have matched orbits with the
| cycler and fly to the moon with it, it's just 3 days, you
| can pack people like sardines for 3 days.
| Alive-in-2025 wrote:
| I was just about to add that last point you raise, must be some
| great stuff floating around in one of these that we haven't yet
| discovered. I wonder if there's a rich horde of dust all in a
| narrower place.
|
| Good summary, by the way. This paper could lead to an eternal
| reference to their name! We have Lagrange orbits, like L2, now
| we will have RRT orbits.
|
| Grad students, it's not all discovered!
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