I'm having trouble making a Maneuver Node to get an Encounter with Jool

[FlanFan]

Hi, as the title says I suck at making Maneuver nodes to other Planets

My Encounters keep ending up like this and I have to do weird burns that lower my Periapsis below 70 km on Kerbin

My ship has TWR of 0.2 and it uses KSPIE parts 

[Streetwind]

Is it the right time to go to Jool?

In contrast to Mun and Minmus, going from Kerbin to other planets has specific times when it is much, much easier to do so than other times. Often, struggling to get an encounter and having to do weird burns is a result of not bing inside the so-called transfer window. Try using the orbit forward function to push your transfer node several days into the future and see if it has any real effect on the difficulty of obtaining an encounter.

If it is the right time to leave and you still struggle, there are two methods you can use to help. One is starting with an easier transfer burn that puts you almost at an encounter, and then later make a mid-course correction burn while you're underway to get an encounter. The other is using an external tool like Alexmoon's launch window planner which tells you exactly how to make the node you need for any given date of departure.

[jimmymcgoochie]

A few things to think about for interplanetary trips:

• Unless you have a magic torch drive with really high thrust and delta-V in the millions, you can’t just go anywhere whenever you feel like it. Planets move at different speeds around their star, often with orbits at different inclinations, so you need to pick the right time to travel between them to minimise the delta-V expended to get from A to B.
  You can get a feel for interplanetary transfers by going from the Mun to Minmus or vice versa- the fuel costs are much lower, travel times shorter and transfer windows much more frequent than going interplanetary so it’s a good way to practice.
• Long burn times are bad for three reasons: first, cosine losses, caused by burning in a direction that isn’t directly pro/retrograde, mean you expend more delta-V than you actually accelerate, so basically you’re throwing away delta-V; second, with burn times that long the burn represents a significant proportion of your total orbital period so you’ll probably be burning almost directly towards the surface to start, causing cosine losses and also pushing your periapsis down towards the atmosphere and probably into it; and third, the accuracy of your burn will be drastically worse with a longer burn time as the node tool assumes you change velocity instantaneously to reach the new trajectory- for a burn lasting one minute the accuracy is pretty good, but for one lasting 16 minutes it’ll be really bad.
• There are a couple of tricks to make those long burns more manageable: you can break it up into smaller chunks by performing a series of periapsis kicks, with each burn lasting a minute or two and boosting your apoapsis higher without getting significant cosine losses or losing accuracy too much, before the final burn to escape velocity completes the transfer- you can tweak the nodes after each burn to ensure you’re staying on target and for propulsion systems with issues around heating, charging or anything that would make a single continuous burn problematic this is a good way to go. There’s a mod called Maneuver Node Splitter that can do this automatically.
  You could also try a spiral trajectory by breaking the burn up into a series of evenly spaced chunks of e.g. 100m/s to find your starting point, then hold prograde and burn continuously and you should end up going in roughly the right direction.
• For planets which are at different inclinations, you’ll almost never get a transfer window at the relative ascending or descending node so you’ll need to change planes at some point. It’s more efficient to do this as part of your transfer burn when staying in the inner system (inside of Duna) as the cost of changing planes in solar orbit is high down there and you’ll get a bit of Oberth effect in Kerbin orbit, but for going to the outer system it can be cheaper to do your plane change in solar orbit as the velocity is lower and so the cost is reduced. A mid-course correction also allows you to fine-tune your approach to the target, giving you the chance to set up an encounter with a moon (e.g. with Tylo to help capture into Jool orbit for free) or to avoid one (e.g. with Ike which interferes with a lot of Duna missions) or to fix your periapsis to get the desired orbit of the target planet when you arrive.

There are a bunch of tools available to plot transfer burns between planets- MechJeb, Astrogator and the 1.12 stock maneuver tool can all make the nodes for you, while others like Transfer Window Planner will show you when and where to put the nodes.

[AHHans]

Hi @FlanFan welcome to the Forums!

@Streetwindand @jimmymcgoochiealready said the important parts. ("Check that you are at a transfer window" and "a mid transfer plane correction is easier") But if you have more questions (e.g. "How do I figure out if I'm at a transfer window?") then please ask.