Frustrated I can't get a simple Duna encounter

[zanie420]

Trying to get a probe to Duna. I am using the Olex transfer calculator.  It's day 189. My phase and ejection angles seem right but I can't seem to actually get the SOI icon to pop up like I see in other's videos. 

[regex]

I see the first best transfer from the start of the game at day 286. You can definitely get there on day 189 with a reasonable delta-V bump though. Maybe try moving the maneuver node around in the orbit to change your ejection angle.

Edited January 9 by regex

[Pthigrivi]

10 minutes ago, zanie420 said:

Trying to get a probe to Duna. I am using the Olex transfer calculator.  It's day 189. My phase and ejection angles seem right but I can't seem to actually get the SOI icon to pop up like I see in other's videos. 

I find this tool also to be very helpful for finding the best windows, though it doesn't have those nice phase angle diagrams: https://alexmoon.github.io/ksp/

[hatterson]

Post a screenshot of your orbit and we can help troubleshoot.

Also I've occasionally seen a bug where the close pass (and sometimes even actual encounter) markers on the map don't actually show up on your normal orbit, but if you add a maneuver plan a couple days forward in your orbit it suddenly shows up on the "planned" version.

[MechBFP]

9 hours ago, regex said:

I see the first best transfer from the start of the game at day 286. You can definitely get there on day 189 with a reasonable delta-V bump though. Maybe try moving the maneuver node around in the orbit to change your ejection angle.

I am not sure if I am misremembering or not, but I am almost positive that in KSP1 the node either had to be on the sunny side, or the dark side, directly parallel to Kerbin's orbit depending on if you were going to inner or outer planets. In KSP 2 I find my nodes have to be on the sides (between the light and dark sides, perpendicular to Kerbin's orbit)) to get the best ejection angle... which is weird.

I know the changes to the maneuver node burning will change the positon of the node a bit, but this seems like ALOT different.

[Superfluous J]

34 minutes ago, MechBFP said:

I am not sure if I am misremembering or not, but I am almost positive that in KSP1 the node either had to be on the sunny side, or the dark side, directly parallel to Kerbin's orbit depending on if you were going to inner or outer planets. In KSP 2 I find my nodes have to be on the sides (between the light and dark sides, perpendicular to Kerbin's orbit)) to get the best ejection angle... which is weird.

You don't want the NODE on the dark/light side, you want the EJECTION POINT from the planet's SOI to be directly in front or in back of the planet you are ejecting from.

Generally this means the NODE will be between sunset and midnight for outward planets, and between sunrise and noon for inward planets.

Doesn't matter though were the NODE ends up. if the EJECTION POINT is correct that's correct.

Edited January 10 by Superfluous J

[MechBFP]

11 minutes ago, Superfluous J said:

You don't want the NODE on the dark/light side, you want the EJECTION POINT from the planet's SOI to be directly in front or in back of the planet you are ejecting from.

Generally this means the NODE will be between sunset and midnight for outward planets, and between sunrise and noon for inward planets.

Doesn't matter though were the NODE ends up. if the EJECTION POINT is correct that's correct.

Yup that is right, that is what I was misremembering.

[Superfluous J]

I should add, from the few ejections I've done so far in KSP2 (Duna, Jool, and Eve, a couple each) I've found that I'm burning at about the time I did back in KSP1.

[Pthigrivi]

43 minutes ago, Superfluous J said:

You don't want the NODE on the dark/light side, you want the EJECTION POINT from the planet's SOI to be directly in front or in back of the planet you are ejecting from.

Generally this means the NODE will be between sunset and midnight for outward planets, and between sunrise and noon for inward planets.

Doesn't matter though were the NODE ends up. if the EJECTION POINT is correct that's correct.

Yo I been manually tweezing this in the dark for years and never knew that. If Im headed outer I generally guess a point between midnight and sunrise and midnight and drag out till the Kerbol Ap intersects the orbit line, then I move the node forward and backward till I find the intercept, then refine, refine, refine reducing the target Pe and dV cost until I get bored. I’ll definitely check out ejection opposite Kerbol as a starting point. 

Edited January 10 by Pthigrivi

[Superfluous J]

1 minute ago, Pthigrivi said:

I’ll definitely check out midnight ejection as a starting point. 

No! Not midnight!

Eject forward or backward. Basically what you did. Node location doesn't matter except it needs to be wherever your ejection point is most forward or backward.

[Pthigrivi]

7 minutes ago, Superfluous J said:

No! Not midnight!

Eject forward or backward. Basically what you did. Node location doesn't matter except it needs to be wherever your ejection point is most forward or backward.

Haha okay that makes more sense. Line up the escape either directly behind (to inner planets) or in front (to outer planets) of the body you’re leaving (the orbit line) Ive always been more focused on the resulting kerbolar transit orbit to notice. And nobody make fun of me for saying ‘midnight ejection’. 

Edited January 10 by Pthigrivi

[The Aziz]

I mean.. what you all saying is kinda correct simply because of how the maneuvers worked in KSP1. With the nodes representing instant change in speed, they could be placed a lot further.

Now though, to get the same result you have to place the node earlier as it takes into account the burn time. The lower TWR, the earlier the node has to land. Sometimes, a lot earlier

Same goes of course for ejection, not only insertion.

[hatterson]

The key regarding burns/nodes is that actual burn locations (and thus ejection angles) should be basically identical to KSP1 because we're working in essentially the same system with essentially the same parts (very minor differences, but nothing significant). However, node locations for burn might be significantly different, especially for craft with low TWR because of the differences in the way nodes are calculated (actual burns with duration versus instantaneous acceleration)

[Superfluous J]

16 minutes ago, hatterson said:

The key regarding burns/nodes is that actual burn locations (and thus ejection angles) should be basically identical to KSP1 because we're working in essentially the same system with essentially the same parts (very minor differences, but nothing significant). However, node locations for burn might be significantly different, especially for craft with low TWR because of the differences in the way nodes are calculated (actual burns with duration versus instantaneous acceleration)

That's because the node now is where you start, and the node before was midway between start and end. We guessed it was roughly in the middle and were generally not so far off as to cause problems. But if you tried to eject to Duna with a low TWR in KSP1 you'd have had similar issues.

You'd have just not noticed them while making the node. You'd have discoverd them somewhere in the second half of your 10-minute burn.

[cocoscacao]

I'd just like to add that you don't need to get an encounter right away. I couldn't do it so far in KSP 2. Just get the markers as close as possible and then you can do a correction burn later to get an encounter. They are usually cheap. Usually...

EDIT:

It would be a nice QOL feature, if there was a separate popup window, still focused on a body of MN, when you zoom out. Dragging MN even for a millimeter results in throwing it to the opposite side.

Edited January 10 by cocoscacao

[regex]

14 hours ago, MechBFP said:

directly parallel to Kerbin's orbit depending on if you were going to inner or outer planets

No, in certain cases and for certain encounters (probably much more commonly than "in certain cases" tbh), depending on where both planets are in their orbits, you would want different ejection angles (as @Superfluous J points out, that's the final ejection angle, not the node's). You might want an orbit with a higher eccentricity in order to encounter the target earlier in its orbit, for instance. This is why the ability to move the node around on the orbit and KSP2's burn indicator (which isn't single impulse) are so powerful, it's much easier to fine-tune encounters and reliably get the exact burn you want.

Edited January 10 by regex