Getting Tylo to capture me in Jool orbit

[More Boosters]

Hey guys... Is this a thing? I mean from a ballistic transfer straight from Kerbin and not just catching up to Jool from a more or less resonant orbit. I figured that since Tylo is as massive as Kerbin with none of that atmosphere, I might be able to get a gravity assist from it to slow myself down enough for a capture. My alternative is to just go for a Laythe aerobrake, but my only experience with that and Laythe in general was the time when my early game probe that somehow got to Jool got tossed around a bit by the meanie moons before Tylo decided they had enough fun and launched it straight at Laythe with a 90 degree angle of attack. Poor thing got instantly vaporized at the upper atmosphere. :D

[zolotiyeruki]

Yes, and that's generally the most common way to do it. I've only done it once (for a "ssto to laythe and back" challenge), but the ideal is to put your Pe (around Jool) right on Tylo's orbit and time it perfectly so that you meet Tylo at your around-Jool Pe.

[More Boosters]

[quote name='zolotiyeruki']Yes, and that's generally the most common way to do it. I've only done it once (for a "ssto to laythe and back" challenge), but the ideal is to put your Pe (around Jool) right on Tylo's orbit and time it perfectly so that you meet Tylo at your around-Jool Pe.[/QUOTE]

And how do you go about doing that? I currently set up an orbit that gets me 9km close to Tylo and barely bends my trajectory, in fact I'm not sure if it's a way I'd want as the projected orbit once I'm out of the Jool system is smaller than my current orbit; which means I'll slow down with respect to the sun and speed up with respect to Jool. I think.

[Empiro]

It may take some time to properly get the trajectory set up. You need to do it early, and it may require you to speed up or slow down slightly.

However, if you're passing within 9km of Tylo, and your path within Tylo's SOI looks like a straight line, then you're moving way too fast (i.e. bad transfer). If your path does bend a lot in Tylo's SOI, then it's just a matter of entering at the right time and place. Don't forget that Laythe can also be a good target for a reverse assist.

[More Boosters]

[quote name='Empiro']It may take some time to properly get the trajectory set up. You need to do it early, and it may require you to speed up or slow down slightly.

However, if you're passing within 9km of Tylo, and your path within Tylo's SOI looks like a straight line, then you're moving way too fast (i.e. bad transfer). If your path does bend a lot in Tylo's SOI, then it's just a matter of entering at the right time and place. Don't forget that Laythe can also be a good target for a reverse assist.[/QUOTE]

It doesn't look like a straight line but it doesn't bend much until low altitude either, but that should be expected. Maybe I can take a screenshot for you?

[url]http://imgur.com/gallery/bOysg[/url]

[Mastikator]

[quote name='More Boosters']It doesn't look like a straight line but it doesn't bend much until low altitude either, but that should be expected. Maybe I can take a screenshot for you?

[URL]http://imgur.com/gallery/bOysg[/URL][/QUOTE]

You could do a powered gravity assist, and the highest peaks are something like 12km so you could do an even lower flyby for more effect.

[More Boosters]

[quote name='Mastikator']You could do a powered gravity assist, and the highest peaks are something like 12km so you could do an even lower flyby for more effect.[/QUOTE]

Would that be more effective than just getting in a low orbit around Jool and benefiting from the Oberth effect?

[moogoob]

[quote name='More Boosters']Would that be more effective than just getting in a low orbit around Jool and benefiting from the Oberth effect?[/QUOTE]

MUCH. I (with the help of folks here) pulled it off on my last career save. Came in hot (did an extra-fast burn form Kerbin to decrease travel time) and only needed 1000m/s to both capture AND adjust about 9/10s of my inclination to hit Pol.

[Superfluous J]

Nail your Jool encounter way out. Preferably while still in Kerbin's SOI but at the midpoint or AN/DN should be fine. Burn to pass Jool on the right (so you're going the same direction as the moons) and get your trajectory passing right through Laythe or Tylo's SOI. Laythe's good because it's close and Jool's gravity gradient's more pronounced, and Tylo's good because it has more weight to throw (you) around.

Do that burn, and if you're lucky you'll actually get an encounter with that moon, and for a couple decimeters per second you can tweak the encounter (I suggest using a maneuver node to tweak, so you only have to burn once) to enter the moon's SOI from behind, and exit from the side putting you into a Jool orbit. If you're not lucky, no biggie. Just (again, use a maneuver node. Measure twice, burn once as they say) do a burn that is a combination of radial and -grade for - again - a few decimeters per second and you'll get an encounter in no time. Then tweak it as above.

If it's too squirrely (it's hard to do a perfect 2-decimeter burn with a massive hulk of a ship) just go forward about halfway to Jool, and the burn will take more dV and therefore be a bit easier to fudge.

[Geschosskopf]

What usually happens to me is that there's no guarantee Laythe and/or Tylo will be in the correct position for me when I go by on the proper path. And I can find no good way to set up an actual encounter with either from outside Jool's SOI. It seems that the game only handles 1 SOI change into the future when it comes to displaying things. Thus, I have to wait until you're inside Jool's SOI before targeting Laythe or Tylo and the whole display of an encounter with either works.

But here's the thing. It takes about 1 month of game time to go from the edge of Jool's SOI to the vincinity of Laythe, during which time both moons will go around Jool many times. And burns made out in the fringes of Jool's SOI are very, very cheap. So it's usually just a matter of making sure my path is crossing that of Laythe and/or Tylo in the correct place and doing tiny forewards or backwards nudges with RCS to get an encounter in the correct general area.

[Superfluous J]

[quote name='Geschosskopf']It seems that the game only handles 1 SOI change into the future when it comes to displaying things.[/QUOTE]

Actually it's 3, which is ridiculously low for anything other than going to Mun. Open up the settings.cfg file (In your root KSP directory) and find:
[code]CONIC_PATCH_LIMIT = 3[/code]

Change it to something sane. I have:
[code]CONIC_PATCH_LIMIT = 8[/code]

In theory it hurts performance, but I've never noticed.

[Pthigrivi]

Oh thats super helpful, thanks 5th!

[swjr-swis]

[quote name='5thHorseman'][code]CONIC_PATCH_LIMIT = 8[/QUOTE]

Awesome tip, thank you.

[Tatonf]

[quote name='Geschosskopf']What usually happens to me is that there's no guarantee Laythe and/or Tylo will be in the correct position for me when I go by on the proper path. And I can find no good way to set up an actual encounter with either from outside Jool's SOI. It seems that the game only handles 1 SOI change into the future when it comes to displaying things. Thus, I have to wait until you're inside Jool's SOI before targeting Laythe or Tylo and the whole display of an encounter with either works.

But here's the thing. It takes about 1 month of game time to go from the edge of Jool's SOI to the vincinity of Laythe, during which time both moons will go around Jool many times. And burns made out in the fringes of Jool's SOI are very, very cheap. So it's usually just a matter of making sure my path is crossing that of Laythe and/or Tylo in the correct place and doing tiny forewards or backwards nudges with RCS to get an encounter in the correct general area.[/QUOTE]

This is how I did this :

[IMGUR]NgYRb[/IMGUR]

On the first image, look at the green orbit : it's the predicted orbit after a Tylo gravity assist, it can totally capture you into the Jool system.
Of course the trajectory is important, if you do it badly you can get the opposite effect. It depends on which side of Tylo you're coming, but this can be corrected for almost nothing.

[Geschosskopf]

[quote name='Tatonf']On the first image, look at the green orbit : it's the predicted orbit after a Tylo gravity assist, it can totally capture you into the Jool system.[/QUOTE]

Oh yeah, it works like a charm. I'm just saying that because KSP won't show me more than 1 encounter into the future, it's impossible for me to set this up completely from outside Jool's SOI, Jool in this case being the only encounter the game will show me. So from outside Jool's SOI, I can make my path go by to the right of Jool and tangential to Laythe or Tylo no problem. But it's only luck of the draw that I actually encounter either without further ado once I'm inside Jool's SOI. So once I get in Jool's SOI, I have to speed up or slow down a tiny bit to get the actual encounter with Laythe or Tylo.

Is this just me? Is it actually possible to set the whole thing up from outside Jool's SOI? I mean, I can target the individual moons from outside Jool's SOI but my path will not show any encounters with them as long as I'm outside Jool's SOI.

[Superfluous J]

[quote name='Geschosskopf']Is this just me? Is it actually possible to set the whole thing up from outside Jool's SOI? I mean, I can target the individual moons from outside Jool's SOI but my path will not show any encounters with them as long as I'm outside Jool's SOI.[/QUOTE]

I answered this a couple posts above.

[quote name='5thHorseman']Open up the settings.cfg file (In your root KSP directory) and find:
[code]CONIC_PATCH_LIMIT = 3[/code]

Change it to something sane. I have:
[code]CONIC_PATCH_LIMIT = 8[/code]

In theory it hurts performance, but I've never noticed.[/QUOTE]

[Claw]

FYI, you can play "pure stock" and still get more patch limits without editing config files. I actually find that I like the default conics (to keep things decluttered) but then do a little trick when I need more intercepts to show.

So the way you can have the game add more patch lines is by setting up your first maneuver. Then, in a subsequent patch line, add another maneuver node (you don't even need to pull the handles). Another patch line will show up. Keep adding nodes and you can get more lines to show up.

[jwbrase]

[quote name='More Boosters']It doesn't look like a straight line but it doesn't bend much until low altitude either, but that should be expected. Maybe I can take a screenshot for you?

[URL]http://imgur.com/gallery/bOysg[/URL][/QUOTE]

Your screenshots show that you're coming in on the wrong side of Jool. Tylo orbits Jool at about 2 km/s, moving counterclockwise when viewed from the north (all bodies in the Kerbol system have parallel axes, so we can define a universal north for the whole system). Your encounter trajectory passes by Jool moving clockwise. This means you encounter Tylo going 2 * 2 km/s = 4 km/s faster relative to Tylo than you would if you passed by Jool on the opposite side (because you're meeting Tylo head-on instead of catching up from behind). Tylo's escape velocity at the surface is only about 3 km/s, so a 4 km/s difference in your encounter speed will make a *huge* difference in how much deflection Tylo can give you (as a given ratio of incoming velocity to escape velocity at periapsis altitude will give your flyby trajectory a unique deflection angle).

[Tatonf]

[quote name='Geschosskopf'] So once I get in Jool's SOI, I have to speed up or slow down a tiny bit to get the actual encounter with Laythe or Tylo.[/QUOTE]

Yes, that's what my 34.4 m/s node is about.

[PLAD]

There was an [URL="http://forum.kerbalspaceprogram.com/threads/117415-SSTO-to-laythe-and-beyond"]SSTO to Laythe and beyond [/URL]challenge a while ago in which we used lots of flyby tricks to get from LKO to a Laythe encounter. Red Iron Crown came up with a beautiful Tylo capture maneuver, which I later copied. Here is the screenie showing the setup for a Tylo flyby to capture into Jool orbit. My ship comes from below on the dotted line, and since it is going faster than Tylo, comes up from behind and inside and passes around front to get thrown outward into the elliptical orbit that later encounters Laythe.:

[IMG]http://i.imgur.com/QOIEhEh.png[/IMG]

Note some details:
-The Tylo encounter is made while moving almost tangentially to Tylo's orbit, and moving in the same direction around Jool. This way you reduce the encounter speed to the lowest possible value and enable Tylo to make the greatest change to your path.
-I executed the 4.2m/s manuever almost 3 Kerbin years before the encounter. At this distance out you can easily adjust for when Tylo will be where you need it to be. For instance if you make a 1m/s retrograde thrust (so slow down 1m/s), the fact that it is still 30 million seconds to your Jool encounter means you will be about 30 million meters 'behind' when you get there and Tylo will have time to move tens of thousands of Km. You have to compensate for the change to your path that the retrograde adjustment makes by changing your radial and normal velocity a bit as well, but by fiddling with the three you can almost certainly get the Tylo encounter you want.
-I needed to use Mechjeb's maneuver node editor to plan the burn accurately enough (to +/-0.01m/s). Precisenode works too. It is true that you can never make a burn that accurately, but what you are doing is finding that the right path is there and getting close to it. You'll almost certainly need another burn later (if you follow the album you'll see I made a 0.2m/s right after entering Jool's SOI) but it will be smaller that the early one. The sooner you get close to the right path the smaller the final adjustments will be!

If you want to see the whole flights, RIC's entry in that thread is post #69, mine is post #85.

[More Boosters]

Can someone check the imgur album I posted in my earlier post to see if I am doing it right? I do have a Tylo intercept already; well I will after I perform the burn there. The un shown Tylo periapsis is 93km and I'll lower it further later. And precise node lets you change the number of conic patches on the fly so if you get clutter you can just turn it down.

[Red Iron Crown]

[quote name='PLAD']There was an [URL="http://forum.kerbalspaceprogram.com/threads/117415-SSTO-to-laythe-and-beyond"]SSTO to Laythe and beyond [/URL]challenge a while ago in which we used lots of flyby tricks to get from LKO to a Laythe encounter. Red Iron Crown came up with a beautiful Tylo capture maneuver, which I later copied. Here is the screenie showing the setup for a Tylo flyby to capture into Jool orbit. My ship comes from below on the dotted line, and since it is going faster than Tylo, comes up from behind and inside and passes around front to get thrown outward into the elliptical orbit that later encounters Laythe.:

[url]http://i.imgur.com/QOIEhEh.png[/url]

Note some details:
-The Tylo encounter is made while moving almost tangentially to Tylo's orbit, and moving in the same direction around Jool. This way you reduce the encounter speed to the lowest possible value and enable Tylo to make the greatest change to your path.
-I executed the 4.2m/s manuever almost 3 Kerbin years before the encounter. At this distance out you can easily adjust for when Tylo will be where you need it to be. For instance if you make a 1m/s retrograde thrust (so slow down 1m/s), the fact that it is still 30 million seconds to your Jool encounter means you will be about 30 million meters 'behind' when you get there and Tylo will have time to move tens of thousands of Km. You have to compensate for the change to your path that the retrograde adjustment makes by changing your radial and normal velocity a bit as well, but by fiddling with the three you can almost certainly get the Tylo encounter you want.
-I needed to use Mechjeb's maneuver node editor to plan the burn accurately enough (to +/-0.01m/s). Precisenode works too. It is true that you can never make a burn that accurately, but what you are doing is finding that the right path is there and getting close to it. You'll almost certainly need another burn later (if you follow the album you'll see I made a 0.2m/s right after entering Jool's SOI) but it will be smaller that the early one. The sooner you get close to the right path the smaller the final adjustments will be!

If you want to see the whole flights, RIC's entry in that thread is post #69, mine is post #85.[/QUOTE]
Thanks for the props. I wish I could claim that it was careful planning and calculation that got me to that method but it was really more trial and error making minor adjustments to the correction node. I saw that I had almost arranged a Laythe encounter, so I kept fiddling until it worked. The relevant pic from my mission:

[IMG]https://dl.dropboxusercontent.com/u/61004449/KSP/1.0.4/LSSTL/screenshot408.png[/IMG]

My approach to setting this sort of thing up is very similar to PLAD's. My method (pretty much requires a node editor for fine adjustments and viewing the Jool system from angles where the node is not visible):

1. Just get a Jool encounter with the ejection burn from LKO, don't try to be super precise. That will come later in the correction maneuver.
2. Exit Kerbin's SoI.
3. Set a node for an hour or more in the future, so you have no time pressure while adjusting the node.
4. Focus on Jool and view the system from "above". Target Tylo.
5. Adjust the node so that the path touches Tylo's orbit tangentially in the same direction as Tylo's orbit.
6. Now adjust your arrival time so that Tylo is in the right place for an encounter. Make small prograde/retrograde adjustments for timing, then use radial+/- and normal+/- to get the path back at Tylo's orbit. This is the fiddliest part, very small adjustments make significant differences.
7. Once the Tylo encounter is set, refine the resultant orbit. Use normal+/- in small amounts to adjust the inclination, and fine tuning the periapsis will adjust the Ap/Pe of the final orbit. If your destination is another Joolian moon, it's useful to target that moon and see if you can arrange a "free" encounter.
8. Now it's time to execute. This is a precise burn, so I find it useful to dial the main engine's thrust limiter as low as it will go. It doesn't make much difference if the burn takes a long time, but having it change the trajectory slowly lets you prevent overshooting. Focus on Jool in map mode during the burn and watch carefully.

[More Boosters]

[quote name='Red Iron Crown']-snip-[/QUOTE]

As shown in my pictures I did a ballistic transfer during a transfer window but I still don't get a closed orbit like the one you are showing up there after passing very close to Tylo.

[Red Iron Crown]

[quote name='More Boosters']As shown in my pictures I did a ballistic transfer during a transfer window but I still don't get a closed orbit like the one you are showing up there after passing very close to Tylo.[/QUOTE]
You're encountering it almost perpendicular to its direction of travel and from the retrograde direction, you'll get very little in the way of a useful slingshot that way. See step 5 in my list above.