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What is the trick to getting into Jool orbit useing a Tylo assist?


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I am trying to do a Laythe mission using only  about 1000 MPS  of Delta-v and gravity assists to get to laythe from LKO, but I just can seem to get a good gravity assist with Tylo.   I think that I am missing something, but I don't know what it is.   Does anyone have any tips?

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it's easy, really. all you need to do is, when you are entering jool's sphere of influence, to pass in front of tylo. In fact, just make sure to get a tylo intercept, and see how it changes your trajectory. Move around a bit, you should find a gravity assist to get captured by jool even just by accident. Just make sure you pass close to the equator, otherwise you'll end up in some horribly inclined orbit.

Here are some examples

the first two use laythe, but it's the same principle. Look at where is periapsis compared to the planet's orbit

RhBBpAj.png

wKF99T0.png

in this second case, it looks like the periapsis is in the wrong side. but if you can account mentally for the fact that laythe will be on a different place during flyby, you'll see it works.

but i repeat, you just have to try move your periapsis around

IO0tRdD.png

finally an example with tylo. though this one is from a certain distance, not very visible

Edited by king of nowhere
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Patience and practice.  It’s not difficult once you’ve seen it work a few times, but at first it can be very frustrating.  Here’s my tips, for what they’re worth.

You will need to plan and execute at least two separate burns, one from LKO to Jool intercept, and then a second burn to fine-tune your arrival.

  • From ‘LKO’.  First, I do departure burns from 150-250 km above Kerbin.  At the end of your departure burn, you are looking for a Jool intercept, with a PE as low as you can get it.  Don’t worry if the PE isn’t as low as you’d like, this will be fixed later.  
     
  • Your second burn will be a ‘mid-course correction’.  This burn will take place when your ship is about halfway between Kerbin and Jool.  This second burn needs to be planned in advance using maneuver nodes.  Place a maneuver node about halfway to your Jool intercept, and start playing with it.
  • While playing with the maneuver node, focus your view on Jool.  Make small changes to the vectors, to slowly bring your course to a Tylo intercept.
  • I like to start with Normal/Anti-Normal adjustments to get my path at Jool roughly equatorial.  Next I make small changes to Pro/Retro-Grade or Radial In/Out to get a Tylo intercept.
  • Eventually you should end up with a Tylo intercept, with a course departing Tylo’s SOI that stays within Jool’s.

Tylo is so big, and orbits Jool so quickly, that it’s actually kinda hard to miss.  However, it IS possible your arrival will not produce a favorable Tylo intercept.  In that case, you need to adjust your arrival date/time at Jool.  Playing with the Pro/Retro grade and Radial In/Out vectors (while at your mid-course maneuver..) can easily accomplish this.

Try not to get frustrated.  It is easy after you’ve done it a few times, but until you’ve seen it work it can be confusing, and certainly NOT easy.   

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On 8/25/2021 at 2:06 PM, Tundra said:

I am trying to do a Laythe mission using only  about 1000 MPS  of Delta-v and gravity assists to get to laythe from LKO, but I just can seem to get a good gravity assist with Tylo.   I think that I am missing something, but I don't know what it is.   Does anyone have any tips?

The minimum dV needed to reach Jool SOI directly from LKO is about 1900 meters per second. 1000 m/s seems to be not enough.
I'm not sure at 100% but If you want to use less dV you could try with an Eve or Kerbin slingshot, is quite complicated at least for me,
I think you also have to do a burn while in Eve or Kerbin SOI. To be honest I never did it.

What kind of Laythe mission you want to accomplish? a flyby? get into orbit?

Anyway, this is the method I use to reach Laythe's orbit or surface:

On these kind of Tylo gravity assist brake maneuvers, in order to reach Jool's SOI,
I prefer to use Astrogator instead of MJ cause it put you into an orbit that match Jool's Eq. plane, much more than MJ's "fine tune" does.
The advantage is that since Tylo has an inclination of 0.2° and Laythe has inc of 0°, when you will fine adjust the maneuvers,
it will be easier to intercept Tylo and Laythe if your inclination is close to the Jool's Eq. plane.
The little disadvantage using AG is that it needs an extra node and a bit more of dV depending on your Kerbin position relative to Jool around the Sun,
it may vary from about 50 up to 250m/s or more.

By the way now I'm gonna use MJ only.
It's a bit more arduous cause since you arrive at Jool' SOI with an inclination, you need to deal with Normal/AntiNormal much more in order to intercept Tylo.


AG maneuvers comparison: 1884+74=1960m/s

0%20AG%20maneuvers%20put%20you%20into%20



MJ only method:

1 - MJ advanced transfer: 1887m/s

1%20mj%20adv%20transfer.png?dl=1

 

2 - Intercept Jool SOI, it does not matter if the orbit is inclined and retrograde.

2%20intercept%20jool%20soi.png?dl=1


3 - MJ "fine tune closest approach to target" node - "Approximate final Pe" 62500 km, cause is the Tylo's SMA.

3%20fine%20tune%20maneuver.png?dl=1


4 - Jool's Pe about 62500 km. Orbit is now prograde and close to Jool's Eq. plane.

4%20jool%20Pe%20about%2062500%20km.png?d


5 - Select Tylo as target, Tylo's intercept indicators are far, if your lucky they will be closer.

5%20tylo%20intercept%20indicators%20are%


6  - Use Precise Node Rad and Pro to approach indicators.

6%20use%20PN%20rad%20and%20pro%20to%20ap


7 - Intercept Tylo SOI at Jool's Pe.

7%20intercept%20tylo%20soi%20at%20jool%2


8 - Intercept Tylo SOI

8%20intercept%20tylo%20soi.png?dl=1


9  - Use PN Normal to approach Tylo Pe close to Tylo Equator plane.

9%20use%20PN%20normal%20to%20approach%20


10 - Jool's Ap can be too high.

10%20jool%20Ap%20can%20be%20too%20high.p


11 - Use PN Pro and Rad to reduce Jool Ap.

11%20use%20PN%20pro%20and%20rad%20to%20r


12 -  Use PN Normal to match Jool's Eq. plane.
Do you see how the red dotted line is inclined? Then adjust the inclination by eye with PN Normal to match Jool's Eq. plane.
You may have to repeat steps 11 and 12 several times until Pe is close to Laythe's orbit.


12%20use%20PN%20Normal%20to%20match%20Jo


13 - Set Laythe as target - Intercept indicators are far.

13%20set%20laythe%20as%20target%20-%20in


14 - Use PN Pro/Nor/Rad to intercept Laythe SOI until the orbit is as similar as possible to Laythe orbit.
This part is quite hard but
you have the advantage that Tylo and Laythe have an orbital sync of 4: 1, so Laythe will always be in the same place relative to Tylo.


14%20intercept%20laythe%20soi%20until%20


15 - You're now in Laythe SOI.

15%20laythe%20soi.png?dl=1


16 - Use PN Pro/Nor/Rad to match laythe eq plane, and choose at what altitude you want Laythe Pe to be.

16%20use%20PN%20to%20match%20laythe%20eq


17 - MJ Circularize - Total dV spent from LKO to LLO = 2400 m/s. Only about 1900/2000 m/s if you're planning to aerobrake and/or land.

17%20circularize%20-%20total%20dV%20spen


Note:

- since given the precision of the maneuvers with which you interact, and the floating point calculation errors inherent in the game itself,
plus MJ's burns "inaccuracy errors", every time you perform a maneuver or enter/leave a SOI, you will have to finely adjust the trajectories each time using the mini RCS.

- an easier way could be that to enter Jool's orbit with a fairly high Ap, like about 200M Km or more, the Pe close to Laythe's orbit and the An/Dn close to and before the Ap,
so that you can first perform an MJ "change inc" and then an MJ "hohmann transfer" maneuvers, both close to the Jool's Ap, so you save a bit of dV,
but this obviously will cost more if you have to enter Laythe's orbit, in any case you can aerobrake.

Edited by antipro
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5 hours ago, antipro said:

The minimum dV needed to reach Jool SOI directly from LKO is about 1900 meters per second. 1000 m/s seems to be not enough.
I'm not sure at 100% but If you want to use less dV you could try with an Eve or Kerbin slingshot, is quite complicated at least for me,
I think you also have to do a burn while in Eve or Kerbin SOI. To be honest I never did it.

What kind of Laythe mission you want to accomplish? a flyby? get into orbit?

I am getting a encounter with Eve from LKO, which is about 1000 m/s then fine tuning it so that it will get me another gravity assist with Kerbin which puts me on a Jool intercept course.    I recently tryed something new though.    I just waited for a Jool transfer window, then burned in the direction for a Jool encounter until I got an Apoapsis that was more then 1 year away.  I found that 1 Year and 24 days sets you up for a good encounter.   You then burn Retro until you get a Kerbin encounter and tweak it until you encounter Jool.     This got my Space Plane to Jool with about 1000 m/s.       

 

 Thanks for the help by the way.   I was very thorough and helped me save a lot of Delta-V! :D 

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1 hour ago, Tundra said:

I am getting a encounter with Eve from LKO, which is about 1000 m/s then fine tuning it so that it will get me another gravity assist with Kerbin which puts me on a Jool intercept course.

and how did you calculate this double/triple gravity assist? and which year/day was the first LKO burn?

Edited by antipro
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8 hours ago, Tundra said:

I am getting a encounter with Eve from LKO, which is about 1000 m/s then fine tuning it so that it will get me another gravity assist with Kerbin which puts me on a Jool intercept course.    I recently tryed something new though.    I just waited for a Jool transfer window, then burned in the direction for a Jool encounter until I got an Apoapsis that was more then 1 year away.  I found that 1 Year and 24 days sets you up for a good encounter.   You then burn Retro until you get a Kerbin encounter and tweak it until you encounter Jool.     This got my Space Plane to Jool with about 1000 m/s.       

 

 Thanks for the help by the way.   I was very thorough and helped me save a lot of Delta-V! :D 

so you are telling me you can perform those very complex kerbin-eve-kerbin-jool multiple gravity assists... but you can't use a single gravity assist to get captured at jool?:confused::confused::confused:

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2 hours ago, king of nowhere said:

so you are telling me you can perform those very complex kerbin-eve-kerbin-jool multiple gravity assists... but you can't use a single gravity assist to get captured at jool?:confused::confused::confused:

I was gonna say, I can capture into Jool orbit using Tylo just by fiddling with maneuver nodes, but a multi-assist in Sun orbit to get to Jool I wouldn't even try with a guide!

I guess they're different skill sets?

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On 8/26/2021 at 10:19 PM, Superfluous J said:

I was gonna say, I can capture into Jool orbit using Tylo just by fiddling with maneuver nodes, but a multi-assist in Sun orbit to get to Jool I wouldn't even try with a guide!

I guess they're different skill sets?

All you have to do is basically just pull back on retrograde until you get a Kerbin encounter and tweak it to get a Jool encounter.     I was just having trouble with a Tylo assist because I was encountering it at the wrong point in its orbit, but now I see where I was going wrong.

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