Do Minmus-Kerbin cyclers take into account the Mun?

[FlamingPuddle01]

I've just recently learned about the Aldrin cycler and I've been looking for resources on how the mechanics of one works and how to make one yourself, while I found plenty of explanations of what it does, but nothing goes in enough depth to teach me how to make one myself. I would really like to make a Minmus-Kerbin cycler but I don't know if the Mun's gravity will end up messing with the orbit. Is it possible to account for that? Thank you in advance!

P.S. I have taken basic college level physics and calculus, so while orbital mechanics of this game have been extremely complicated for me, I've been able to handle the math side of things so far, but I might be overconfident in my abilities with this scenario. No need to explain the basics of kinematics or anything, I just want to know the steps I can take to create this kind of orbit. Thank you again!

[Geonovast]

Moved to Gameplay Questions

[Spricigo]

A Kerbin-Minmus Cycler don't need to take in account the Mun's gravity while it stays away of Mun's SoI. Avoiding get into Mun's SoI can be quite tricky in itself.

 

 

[bewing]

The Aldrin Cycler is a 3 body gimmick. The craft is in orbit of the Sun, and visits two bodies orbiting the Sun during the cycle.

7 hours ago, FlamingPuddle01 said:

I would really like to make a Minmus-Kerbin cycler

So you could make a cycler in Kerbin orbit, going between Minmus and the Mun. But Kerbin is the primary in this case, so it's not theoretically possible for it to be part of an Aldrin cycle -- unless your craft is in orbit of Kerbol, going between Kerbin and another planet (Duna, Dres, Jool, Eve, etc.).

 

[FlamingPuddle01]

3 minutes ago, bewing said:

The Aldrin Cycler is a 3 body gimmick. The craft is in orbit of the Sun, and visits two bodies orbiting the Sun during the cycle.

So you could make a cycler in Kerbin orbit, going between Minmus and the Mun. But Kerbin is the primary in this case, so it's not theoretically possible for it to be part of an Aldrin cycle -- unless your craft is in orbit of Kerbol, going between Kerbin and another planet (Duna, Dres, Jool, Eve, etc.).

 

Ah, I had a misunderstanding of what an Aldrin cycle was then, the place I first heard of describing it suggested doing one from Kerbin to the Mun, so I had assumed that it was an 2 body orbit that used  the gravity of the orbiting object (Mun in this case) to modify the trajectory of the ship so that it would return to the orbit of the orbiting object at the next position.  Thank you for clearing up that misunderstanding, it makes sense now why I couldn't find any more info on Aldrin cycles to the Mun or Minmus! But followup question, is there any type of cycler that can go from Kerbin to the Mun so that I can do an Aldrin cycler from the Mun to Minmus, making a sort of spacial pony express?

[Spricigo]

1 hour ago, FlamingPuddle01 said:

Ah, I had a misunderstanding of what an Aldrin cycle was then, the place I first heard of describing it suggested doing one from Kerbin to the Mun,

Oh well... there is the Aldrin_cycler and there is the Aldrin_cycler  

1 hour ago, FlamingPuddle01 said:

so I had assumed that it was an 2 body orbit that used  the gravity of the orbiting object (Mun in this case) to modify the trajectory of the ship so that it would return to the orbit of the orbiting object at the next position.

A cycler is nothing more than a craft that have periodic encounters with body A and body B while maintaining its trajectory. For a Minmus-Kerbin Cycler that is just an orbit with low periapsis, high apoapsis and a bit of synchronicity to be there when  Minmus show up*. 

There is  a bunch of reason why that may be a good idea in real life but  not so many reason why it would be a good idea stock KSP. 

*not necessarily  every time, just 'often'

 

[FlamingPuddle01]

39 minutes ago, Spricigo said:

A cycler is nothing more than a craft that have periodic encounters with body A and body B while maintaining its trajectory. For a Minmus-Kerbin Cycler that is just an orbit with low periapsis, high apoapsis and a bit of synchronicity to be there when  Minmus show up*. 

Oh, and would doing this make it repeatable? because ultimately I would like to set up a station moving between both bodies that I can hitch a ride on whenever I need to do a tourism quest

[king of nowhere]

7 hours ago, FlamingPuddle01 said:

Oh, and would doing this make it repeatable? because ultimately I would like to set up a station moving between both bodies that I can hitch a ride on whenever I need to do a tourism quest

i have to calrify first, a cycler does NOT save fuel.

sure, the cycler will keep moving between both bodies, at no cost, but to dock with the cycler you have to match its speed, which is already equivalent to the speed needed to reach the other body. quoting from wikipedia,

Quote

Once the orbit is established, no propulsion is required to shuttle between the two

but that doesn't mean anything. once you make your ejection burn and enter the hohmann transer orbit, no propulsion is required. once you already made your manuever, no propulsion is required.

in fact, i dare say a cycler wastes more fuel. though in real life you have the advantage that you can make it bigger, and you only need the extra speed for the probes that will dock with it. so you can have a massive space station where your astronauts can live during the several months of transfer, while the probes needed to get to the station are smaller and can skip most basic necessities, since they will only be inhabited for a few days. in ksp your astronauts can live forever in an external seat, so you have no such limitations.

 

that said, a cycler between kerbin and mun would orbit kerbin with low periapsis, and its apoapsis would get close to mun. it should stay out of mun sphere of influence, or th eorbit would be perturbed. and it would need to have the orbit syncronized so it will get close to mun at each apoapsis - it doesn't help if you're at the same apoapsis if mun is on the other side of the orbit. for minmus i'd say it's impossible to stay syncronized with minmus while avoiding mun entirely; eventually you'll end up in mun SoI, and the gravity assist will kick you off trajectory.

[paul_c]

I'm not an expert on space travel but getting to the Moon by bicycle is going to take ages!

[Spricigo]

9 hours ago, FlamingPuddle01 said:

Oh, and would doing this make it repeatable? 

It is supposed to stay in the same orbit forever.  You just need to avoid being throw out of course by the Mun or even by Minmus.

Just make sure you understand the  drawbacks of hitching a ride with the cycler.

• Higher deltaV cost
• Longer wait time
• Longer travel time

1 hour ago, paul_c said:

I'm not an expert on space travel but getting to the Moon by bicycle is going to take ages!

Silly me! Expected that going on a bicycle would just take two cycles. 

[king of nowhere]

1 hour ago, paul_c said:

I'm not an expert on space travel but getting to the Moon by bicycle is going to take ages!

well, armstrong was a famous cyclist, and he went on the moon. while playing jazz, no less!

 

(for those who don't get it, there are three famous armstrong, and i'm conflating them into the same person)

[paul_c]

You mean, he went to the Nevada desert to shoot the pictures and video for the fake moon landing?

[FlamingPuddle01]

On 12/6/2020 at 5:50 AM, king of nowhere said:

i have to calrify first, a cycler does NOT save fuel.

sure, the cycler will keep moving between both bodies, at no cost, but to dock with the cycler you have to match its speed, which is already equivalent to the speed needed to reach the other body. quoting from wikipedia,

Thank you for clearing this up, I totally did not think about the relative velocity of the ships, which is a really important thing to consider. Whoopsie.

 

On 12/6/2020 at 5:50 AM, king of nowhere said:

in fact, i dare say a cycler wastes more fuel. though in real life you have the advantage that you can make it bigger, and you only need the extra speed for the probes that will dock with it. so you can have a massive space station where your astronauts can live during the several months of transfer, while the probes needed to get to the station are smaller and can skip most basic necessities, since they will only be inhabited for a few days. in ksp your astronauts can live forever in an external seat, so you have no such limitations.

 Ok, at this point I'm just grasping for straws to have *any* reason to make the space station with a funny orbit (I guess I don't even want it to be a cycler, but I'll make a better description of what I'm trying to do in the next paragraph), but if I made the station big enough to house more kerbals than would be realistic for a single rocket, have a few really big landers attached to the station, and take a crap ton of tourism quests that require landing on the moon, and then basically take multiple trips to fill up the station with relatively small SSTOs that go and dock with the station, undock and then return home in one piece, then use those big landers to land and then return to kerbin with as little fuel as possible. I ask this knowing that the answer is probably that I'm just making a reusable rocket ship with extra steps and a big hunk that I'll never get the funds returned from because it is constantly in orbit, but I'm hoping that I'm missing something. 

Anyways, now to describe the orbit that I was thinking of making originally that apparently isn't a cycler. What I want to do is make an orbit that goes from Kerbin to the Mun, uses the Mun's SOI to alter its tragectory by a small amount, just enough so that it will return to Kerbin, go around it and then when it is reaching its heading towards apoapsis again, BAM! there's the Mun, rinse and repeat. The orbit would end up looking like a sort of flower if I'm imagining it correctly and I have to believe that with a delicate hand and enough elbow grease it could be done. I'm pretty sure that this way it wouldn't take nearly as much time as a normal cycler since it is constantly moving from Kerbin to the Mun, all I really need to figure out is if it breaks any laws of physics to do so since I'm not confident enough in my knowledge of orbits to figure it out with any degree of certainty, since I keep finding myself wanting to put it all in terms of a linear plane.

[FlamingPuddle01]

Actually wait one second. If I set up a lunar colony and kept the SSTO docked, what I could do is set up some mining for refueling, have the lander wait a cycle to be picked up again and then refuel the SSTO entirely, making the entire trip cost only the delta v it takes for the SSTO to get back into Kerbins orbit (less than 1000 delta  v if I wanted a super smooth descent, even less if I make my ship capable of handling harder descents). It's a bit complicated and of course the easier way to do it is cut out the space station with the fancy orbit and just have a SSTO with a lander that does the same thing, but I think the important thing to keep in mind is that I'm looking for a reason to justify using the space station with a fancy orbit instead of building the space station with a fancy orbit for a specific reason.

[vv3k70r]

On 12/5/2020 at 5:58 PM, FlamingPuddle01 said:

I would really like to make a Minmus-Kerbin cycler but I don't know if the Mun's gravity will end up messing with the orbit. Is it possible to account for that?

N-body problem is hard to implement in a game. It would not be much playable after a while. So rails are implemented in game.

In game You can do something that resemble this cycle in its simplified mechanics for some loops. But in game it would not be a good idea as it is in reality.

[Zhetaan]

On 12/5/2020 at 11:58 AM, FlamingPuddle01 said:

I've just recently learned about the Aldrin cycler and I've been looking for resources on how the mechanics of one works and how to make one yourself, while I found plenty of explanations of what it does, but nothing goes in enough depth to teach me how to make one myself. 

Try this and see what you think.  It's not exactly a step-by-step guide, but it does a decent job of both elucidating the theory and examining the extent of the possible solution space.  There are several different kinds of cyclers, of which the Aldrin cycler is but one.  I'll help you to begin:  to even start establishing a cycler, you'll need the synodic period of the two bodies that you want to visit.  Since Kerbin is its primary, the Mun has no synodic period with Kerbin and so a cycler between Kerbin and the Mun in the traditional sense is not possible.  However, and with respect to others who have said that, there's nothing keeping you from establishing a cycler anyway.  One way to do this is the take the degenerate case of the synodic period of a body with its primary:  that's just the orbital period.  You can establish an orbit that is some rational multiple of a Mun orbit, time it so that you don't lithobrake, and, so long as it is not thrown out of that orbit by Mun gravity, there you go.  Resonant orbits are useful for all manner of things, and the cycler is simply a case of resonance extended to three bodies instead of two.

Alternatively, and I suspect that this may be closer to your intent, you can establish a cycler between the Mun and something in Kerbin orbit that does have a synodic period with the Mun.  It's doesn't need to be Minmus.  You can put up a way-station, refuelling stop, heat shield, escape pod, funeral pyre, or nothing in some orbit of Kerbin and establish a cycler between that and the Mun.  If your design is to set up an Aldrin cycler, then the starting orbit will have a minimum orbital altitude that is probably a bit above your typical low Kerbin orbit, owing to the fact that the cycler, with its eccentricity, will have a periapsis lower than the orbit you pick.

On 12/6/2020 at 12:07 AM, Spricigo said:

There is  a bunch of reason why that may be a good idea in real life but  not so many reason why it would be a good idea stock KSP.

On 12/6/2020 at 10:55 AM, Spricigo said:

Just make sure you understand the  drawbacks of hitching a ride with the cycler.

• Higher deltaV cost
• Longer wait time
• Longer travel time

Per usual, @Spricigo raises good points.  The chief benefits of a cycler have to do with reusable habitation space, launch costs, and travel time--but only travel time in the sense of the wait between two adjacent 'stops' on the cycler line.  Because the cycler is typically eccentric enough to extend out far past the target body, travel time on an outbound or inbound leg between the two points of interest is shorter--potentially much shorter--than it would be on a Hohmann transfer orbit.  Once past that second point of interest and near the apoapsis, the time that the cycler craft spends out there is, ideally, while it is uninhabited (the crew departed to do experiments on Mars or what-have-you), and then the crew returns aboard for the relatively short journey home.

Cyclers may not become necessary, per se, but they do begin to make a lot more sense when you run mods such as Kerbalism that simulate radiation, food and water requirements, and other health-related issues, because those mods both require and reward short trips with heavy radiation shielding.

The heavy shielding is where I make my third point.  @Spricigo is absolutely correct in saying that it takes more delta-V to operate a cycler.  That was always going to be the case; it's not a Hohmann transfer or any of the other minimum-propellant transfer orbits.  A cycler does not meet the target tangentially, and as such will never be the most efficient in terms of delta-V.  However, a cycler takes advantage of the fact that there is another way to look at cost.  Consider, for a moment, that you are sending a vessel to the Mun.  It is a small, un-crewed probe of perhaps a half-tonne fully fuelled.  How much delta-V does it take to go to the Mun from low Kerbin orbit?  By the map, it will cost 860 m/s.  Consider now that you are sending a one-megatonne station on the same orbit.  How much delta-V will it cost then?

Still, it will cost 860 m/s.  But how much will it cost in tonnes of propellant and Funds?  Well, that's another story.

Let's get away from mods for a moment.  Let's say that you want to send a full crew, and with the upcoming update, a few crates of spare parts, along with a mobile processing lab, a fuel processing plant, and because why not throw in the kitchen sink, a comm array that lets homesick Kerbals telephone their mothers.  All of this needs to to go the Mun (for a certain highly subjective value of need, of course), but it doesn't need to stay there, which means that for the slightly increased cost of rendezvous for a low-mass lander or shuttle, you can send all of that equipment once and get repeated use out of it for so long as you want to use it, and you don't need to worry about braking burns or otherwise getting it safely to Mun orbit.

On 12/5/2020 at 7:59 PM, FlamingPuddle01 said:

But followup question, is there any type of cycler that can go from Kerbin to the Mun so that I can do an Aldrin cycler from the Mun to Minmus, making a sort of spacial pony express?

You'd be best situated to set up a cycler that runs from the Mun to Minmus first, and then finding something resonant that runs from low Kerbin orbit to the Mun.  It should be possible, but it may not be pretty.  What you describe is likely only useful as a novelty, but I don't doubt that it can be done.

On 12/7/2020 at 8:27 PM, FlamingPuddle01 said:

Ok, at this point I'm just grasping for straws to have *any* reason to make the space station with a funny orbit (I guess I don't even want it to be a cycler, but I'll make a better description of what I'm trying to do in the next paragraph), but if I made the station big enough to house more kerbals than would be realistic for a single rocket, have a few really big landers attached to the station, and take a crap ton of tourism quests that require landing on the moon, and then basically take multiple trips to fill up the station with relatively small SSTOs that go and dock with the station, undock and then return home in one piece, then use those big landers to land and then return to kerbin with as little fuel as possible. I ask this knowing that the answer is probably that I'm just making a reusable rocket ship with extra steps and a big hunk that I'll never get the funds returned from because it is constantly in orbit, but I'm hoping that I'm missing something.

You are; a cycler is a reusable rocket ship with extra steps.  That's the point.  In many ways, it's an elaboration of the more traditional method, for example sending a vessel that has been optimised to send lots of tourists to low orbit (and return them safely), meeting a transfer vessel there, and sending that to make rendezvous with an optimised lander in Mun orbit that can take those tourists to the surface (and return them safely, too).  What you want to do is essentially to combine the transfer vessel with space stations at either end of the Mun transit leg into one craft that also allows you to take your SSTO (or whatever launch-to-orbit vessel you send) and lander along without needing to worry (much) about the extra propellant costs of sending all of that hardware on that journey.  It's a perfectly valid way to do it, and it has the added benefit of being both a difficult challenge and elegant in its implementation when you get it right.  Is it the most propellant-efficient way to do it?  Not at all.  Is it more cost-effective than sending single-use delivery rockets to get your reusable landers to Mun orbit?  Quite possibly.  Is it more fun?

Try it and find out.

 

 

On 12/8/2020 at 4:34 AM, vv3k70r said:

N-body problem is hard to implement in a game. It would not be much playable after a while. So rails are implemented in game.

True, but if you ever are intested in N-body physics, I leave you with this.

On 12/6/2020 at 11:04 AM, king of nowhere said:

well, armstrong was a famous cyclist, and he went on the moon. while playing jazz, no less!

That's not without controversy; there's a persistent rumour that he was taking pure oxygen and laxatives the entire time.

Edited December 9, 2020 by Zhetaan

[Spricigo]

26 minutes ago, Zhetaan said:

Per usual, @Spricigo raises good points. 

 I try.  Didn't had the time to elaborate (busy with real life) but your post cover pretty much everything I had to add.

I think we can summarize as: there are several different kinds of cyclers; they are somewhat complex to setup and operate and they may be a viable (dare I say, even effective) option given the right circumstances (just those circumstances are not the most obvious)

21 hours ago, FlamingPuddle01 said:

Actually wait one second...   ...what I could do is...

You can do many thing and is up to you, and just you, to decide what exactly will be done. Though, we can provide some ideas, thou.

My first assumption was that you wanted to do it because of "cool", it seem that cost and practicality was more your concern.  If that is the case, a dedicated but regular spaceship that can do the Mun-Minmus 'cycle' when required is likely to be a better option than a true cycler. The station may acts as transshipment staging post or given a different use (or no use. If it looks cool enough, why not?)

[vv3k70r]

9 hours ago, Zhetaan said:

True, but if you ever are intested in N-body physics, I leave you with this.

I programed some simulations wiht n-body, to set a long term stable planetary system You get a very empty system (like our) or there is a lot corection behind the phy to keep it on track, or it is not stable before and after. Every orbit is in long term chaotic and it came from chaotic state. Current ilusion of "stability" is just an event. I guarantee that pleyer would play back and forth such a system and see diferent path of timelapse.

[Zhetaan]

6 hours ago, vv3k70r said:

I programed some simulations wiht n-body, to set a long term stable planetary system You get a very empty system (like our) or there is a lot corection behind the phy to keep it on track, or it is not stable before and after. Every orbit is in long term chaotic and it came from chaotic state. Current ilusion of "stability" is just an event. I guarantee that pleyer would play back and forth such a system and see diferent path of timelapse.

Oh, certainly.  I don't think that the Principia people guarantee the long-term stability of the system.  I know that they needed to make a lot of adjustments just to keep it stable in the short term, but insofar as total system longevity is concerned, well, suffice it to say that the KSP solar system was never designed to be realistic.  I think that the design paradigm is essentially to establish a system that is pseudo-stable for a long-enough period of time to avoid unmitigated chaos during a typical career save.

On the other hand, realistic or not, if you run enough mods then your computer's CPU can simulate the heat death of the Kerbal universe on its own.

[Corona688]

On 12/5/2020 at 4:55 PM, Spricigo said:

A Kerbin-Minmus Cycler don't need to take in account the Mun's gravity while it stays away of Mun's SoI. Avoiding get into Mun's SoI can be quite tricky in itself.

Some days the mun just doesn't want you to go anywhere.

 

[king of nowhere]

On 12/8/2020 at 3:00 AM, FlamingPuddle01 said:

 I think the important thing to keep in mind is that I'm looking for a reason to justify using the space station with a fancy orbit instead of building the space station with a fancy orbit for a specific reason.

well, you could download the kerbalism mod, that would add concerns like food and radiation shielding that will justify the fancy station...

[Spricigo]

2 hours ago, Corona688 said:

Some days the mun just doesn't want you to go anywhere.

At this point maybe is better to try to avoid Minmus SoI and make it a Mun-Kerbin cycler. 

[vv3k70r]

5 hours ago, Zhetaan said:

Oh, certainly.  I don't think that the Principia people guarantee the long-term stability of the system.

Can they guarant any if players start throwing asteroids?

5 hours ago, Zhetaan said:

I know that they needed to make a lot of adjustments just to keep it stable in the short term, but insofar as total system longevity is concerned, well, suffice it to say that the KSP solar system was never designed to be realistic.

It is why it is playable. Realistic mean over 10k dV to get away from homeplanet.

5 hours ago, Zhetaan said:

I think that the design paradigm is essentially to establish a system that is pseudo-stable for a long-enough period of time to avoid unmitigated chaos during a typical career save.

Players are significant chaos factor.

5 hours ago, Zhetaan said:

On the other hand, realistic or not, if you run enough mods then your computer's CPU can simulate the heat death of the Kerbal universe on its own.

Most simulation I runned where peuudo stable when almost empty (like our world) or after changing some values (to scale it down) it was hard to find starting state that could deliver anything pseudo stable.

Of course there could be some phy cheating making static  keplers adjustment (mostly adjusting rotation to speed and distance of the body) to dynamic state, but players will notice that and exploit for magic gravity asists.

And it is not that instability colapse it in long term - when domino starts it go fast and disasemble whole system. Mostly throwing everything away after passing near central star.

So if they would put anything intresting like binary planet (say planet and moon of similiar mass) there would not be any room for dynamics. Pin it to rails and forget about physics.

 

There is a workaround I used - I justr throwed gigantic number of celestial bodies and wait until it get stable. Most were thrown away, Oort has formed, asteroid belts has formed, but distances were realistic (just more eliptical orbits), so playability would be hard.

4 hours ago, Corona688 said:

Some days the mun just doesn't want you to go anywhere.

Let say it is a perfectly adjusted manouver?

Edited December 9, 2020 by vv3k70r

[Spricigo]

@vv3k70r AFAIK Principia mod only uses n-body calculation for the orbits of the craft while keeping the celestial bodies bound to their perfectly ellipitical orbits.  I also suppose, asteroids still counts as craft and thus not affecting other craft orbit even f the player gather  bnch of those in the same place.

maybe someone with more interest may check in the mod's thread to be sure (i'm fine with just what my flawed memory tells me)

[vv3k70r]

8 hours ago, Spricigo said:

AFAIK Principia mod only uses n-body calculation for the orbits of the craft while keeping the celestial bodies bound to their perfectly ellipitical orbits.  I also suppose, asteroids still counts as craft and thus not affecting other craft orbit even f the player gather  bnch of those in the same place.

Obviously. To calculate nbody You have to read in every body from the list for every body and stack vectors to execute positionchange before You execute next loop. There is a lot of room for exploits because some asteroids have a significant mass that can be dropped during gravity assist.

I sugest to use massless Sun (just jump over it in calculations) and bodies would draw beautifull epicycles around mass centerpoint.

There could be no reasonable, exploits/bug free solutions for curent computing power avilable at home for playable game pourpose.