Separation markers

[technion]

Hey guys,

I a recent eeloo trip, I found I had a 6m/s burn that made the difference between an intercept, and not even showing the separation markers. The problem with this is that it's difficult as all heck to work out what direction you want to burn in and where from, when there's no markers to adjust.

It's a problem that seems to occur regularly with meetups to inclined orbits.

What's the usual solution to this? I feel like the game really should give you a better indication of how to make correcting burns from situations like this. I must have lost over two hours just making random nodes and moving them around to see what happens.

[Scarecrow88]

If you are not seeing intercept markers, it's because your encounter is not close enough to generate them. Try putting a manoeuvre node along your flight path and adjust the handles gently to see if you can tweak the encounter sufficiently to bring the markers up. Once you do, you can fine tune the encounter to get it as close as you need, which will also give you a blue target on your nav ball for direction of required correction burn.

[technion]

it's because your encounter is not close enough to generate them. .

I really don't think it's just about distance. For example...I'm looking at an intercept. I'm using precisenode so I can make perfect increments.

Each +prograde brings the intercept closer. It started about a quarter of a orbit away, I keep clicking it until I've almost got it, then, +1 prograde and suddenly there's no intercept. Put in -1 normal, and there's that intercept. Another +1 prograde, and the pe is much better. Try bringing the pe down to <1 million meters, then remove that -1 normal. Suddenly there's no intercept markers at all, despite the orbit change barely being visible. It's very clearly a closer encounter than the quarter orbit that had a marker earlier.

[metaphor]

You should always see a closest approach marker if your relative inclination is 0, or if your ascending/descending node is touching the other orbit.

So for example if you're trying to get to Eve, you have an orbit that looks like the right Hohmann transfer, and you don't see a closest approach marker, try adding another maneuver node at the ascending/descending node and fixing the relative inclination, to see how close you actually are.

The same method works for transferring to Eeloo. You want one of the nodes of your transfer orbit to be right where it crosses Eeloo's orbit.

[EdFred]

Is your AN or DN intersecting the orbit of Eeloo? I've found that unless your orbits are co planar (or very close to it) you have a hard time getting the separation markers to show up. If your AN/DN isn't intersecting the orbit of the body you want to encounter, you will spend a lot of time trying to get an intercept/separation marker. Check your map view to make sure you are actually intersecting the orbit of Eeloo if you aren't coplanar.

Also, the further away you are the harder it is to get a precise intercept. Low dV needed = easy to over/undershoot your target. High dV needed = easier to be more precise.

Keep in mind that you said it was a 6m/s burn. Changing your dV by 1m/s is a 16% variation. Try 0.1m/s or 0.05m/s changes. Changing anything by 16% is going to probably result in a miss. If you launched towards the Mun and changed your dV by 16% you'd miss it as well.

Also keep in mind there are 6 basic spots on your orbits to get the most efficient course corrections. Apoapis, Periapsis, Ascending Node, Descending Node, and the two points that are 90º ahead/behind your periapsis and apoapsis. Most others result in having to do crazy burns to get what you want.

Kasuha should be along shortly with screen shots and a more detailed explanation.

Edited June 16, 2014 by EdFred

[blizzy78]

I'm using precisenode so I can make perfect increments.

In reality it isn't perfect. With the way current CPUs/software/... handle floating point numbers, there is no "perfect" way to just subtract "exactly 1", then add "exactly 1" again. The result may be different than what you started out with.

Also, the game tends to bug out when displaying encounters. Like, your encounter shows you clearly miss the planet. Then you modify your maneuver node, getting closer and closer, and all of a sudden, it just doesn't display any encounter at all. But of course you know that you just got ever closer, maybe even an impact with the surface. It's just a bug.

Edited June 16, 2014 by blizzy78

[Kasuha]

Is your AN or DN intersecting the orbit of Eeloo? I've found that unless your orbits are co planar (or very close to it) you have a hard time getting the separation markers to show up. If your AN/DN isn't intersecting the orbit of the body you want to encounter, you will spend a lot of time trying to get an intercept/separation marker. Check your map view to make sure you are actually intersecting the orbit of Eeloo if you aren't coplanar.

I disagree. The easiest way to get separation markers is at one of inclination nodes. Because there you can get guaranteed intersect with the target trajectory. It's irrelevant how big the inclination difference is, but if it is too small it all becomes unreliable.

To the OP: on the way to Eeloo, 6 m/s in/near Kerbin SOI translates to many thousand kilometers difference at the target. So yeah, it may need some precision setting up - after the main burn, it's very good idea to fine-tune the transfer with RCS.

Maneuvers can now be set up precisely using mouse wheel. Point the mouse at selected maneuver icon, roll the wheel up to add dv to that direction, or down to subtract dv from that direction. You can set up the maneuver in cm/s that way if you're careful.

[EdFred]

I disagree. The easiest way to get separation markers is at one of inclination nodes. Because there you can get guaranteed intersect with the target trajectory. It's irrelevant how big the inclination difference is, but if it is too small it all becomes unreliable.

I *think* we are talking about the same thing. The AN/DN are the inclination nodes.

Edited June 16, 2014 by EdFred