Mod to simplify maneuver nodes?

[visivante]

Hey, I'm curious if anyone knows of a mod that would simplify the use of Maneuver nodes. For instance if I'm in an equatorial orbit and I want to change to a polar orbit I would try and create a maneuver node to a polar orbit first. But I've found that its not as simple as dragging the radial nodes; you end up having to fiddle back and fourth with different node directions for quite a while to get the right balance.

Is there any chance a mod exists which would simplify this process and reduce the amount of fiddling necessary?

I'm aware of MechJeb and PreciseNode and as far as I know neither of these (besides automatically doing it for you) mods make the process of manually adjusting maneuver nodes like I've described any easier.

Thanks in advance! Safe flying!

-Visi

[WuphonsReach]

PreciseNode really is the best.

Use the "7" or "9" keys on the numpad a few times, then use the "5" key to increase the angle and decrease the Ap.

What you have to do is balance out how much +/- Normal DV you are using vs +/- Prograde. The optimal burn to switch from equatorial (0 inclination) to polar (90 degree inclination) orbits uses a combination of both vectors.

(Use MechJeb's change inclination feature to see what the optimal burn looks like - then recreate it using PreciseNode.)

[Taki117]

When going from an equatorial orbit to a polar orbit it is best to increase your AP as high as possible, then perform the plane change and circularize at Pe.

[Laie]

Hey, I'm curious if anyone knows of a mod that would simplify the use of Maneuver nodes. For instance if I'm in an equatorial orbit and I want to change to a polar orbit I would try and create a maneuver node to a polar orbit first. But I've found that its not as simple as dragging the radial nodes; you end up having to fiddle back and fourth with different node directions for quite a while to get the right balance.

The problem is that even if you thrust nor/rad, this still adds to your orbital velocity. If you have a circular orbit before and want a circular orbit after, you have to offset it with adding a retrograde component to your maneuver. How much retrograde will you need? That depends not only on the maneuver, but also on the velocity you have as you enter into the maneuver.

TL;DR: it's diffcult.

The only mod I know that does anything like that is Mechjeb; but (as you said) it just sets up the right maneuver and you won't really know how it happened. But then again, an auto-magic node editor would be similar.

[vexx32]

In all honesty, changing from an equatorial to a polar orbit is tricky no matter how you go about it. If possible, it's best to launch into one to start with. :/

[Vanamonde]

Moved to Add-on Affairs.

[regex]

When I was still maintaining PreciseNode I wrote a little routine that would combine two nodes into one, exactly for this sort of situation. Create your plane change node, whack another on immediately after it to circularize, combine. While not perfect, it did the job well enough to reduce the fiddling to a minimum. Not sure if that's still in the mod, it's changed a lot since my time.

[strongest_2hu]

You can figure out exactly how much dV you need in each direction with some very simple math, then precisenode makes it very easy to add and subtract the exact amounts. Take (speed at plane change)*sin(desired angle change) and add that in the normal, take (speed at plane change)*(1-cos(desired angle change)) and subtract it from prograde. This will result in a node set up for precisely the correct amount of dV in the correct direction, the only source of error is your vessel's acceleration and you at the controls.

[Axelord FTW]

If MJ (and PN, which I never used) don't fulfill your need here, there's not much else you can do.

Switching from an equatorial to a polar orbit is quite the heavy procedure. If you find the fiddling complicated, it's because the maneuver is not simple.

I'm not sure anyone could make a stiff maneuver node mode so that the original position and orientation of the node doesn't change as you put some order into it. If someone actually do something like that, you might find it more troublesome than what it's worth.

[*Aqua*]

Changing an equatorial to a polar orbit is never a simple maneuver if you are in an equatorial near-circular orbit.

Why? In the end it means you'll have to change your current prograde velocity to 0 m/s and your (anti) normal velocity to orbital speed. You'll usually can't do that when orbiting in a low orbit around a heavy planet/moon because you most likely don't have enough thrust to do that fast enough. In orbits around light planets or moons it is possible (i. e. Gilly).

I don't see a way for a mod to help you with that. In my experience you'll always need at least two maneuvers (first: inclination change; second: inclination fine tuning & circularize again). In my opinion it is best to either launch directly into a polar orbit on Kerbin (if you need that kind of orbit there) or plan your transfer orbit so, that you'll end up in a polar orbit.

[Streetwind]

I don't find the given example (changing from equatorial to polar) to be a particularly big issue. If you need a very specific longitude of ascending node, then yeah, things are going to be tricky... but creating the maneuver node is going to be the least of your problems. Far more important will be your precision in executing it, and the amount of thrust you can put to the task. If you need so much precision that you cannot simply eyeball it, you'll likely end up having to make an extra longitudinal plane correction burn over the poles anyway.

And if you don't need a very specific longitude... why are you making a maneuver node at all?

The thing with maneuver nodes is that they're always relative to your current orientation and position. Because of this, you constantly need to fiddle with the prograde and retrograde markers to compensate for the fact that applying normal/antinormal dV would actually move the normal/antinormal markers - which is something the maneuver node only improperly reflects. This is precisely the problem you experience.

The simplest way around this: do not use a maneuver node. Instead, point your ship towards normal/antinormal and start your engines until your orbit is polar. Boom, done! If you follow the marker on your navball as it moves while you burn, you never need to correct for anything. And in .90, it's even easier: you can just ask your pilot Kerbal to keep the ship pointed towards the marker for you.

[cicatrix]

MJ allows you to tweak the maneuver node via Maneuver node editor. Also there is precise node. You don't have to do it automatically. You can put a new node on your trajectory then edit it manually. MJ can do it all by itself though, but if you feel strongly against it just stick to the maneuver node editor.

[Renegrade]

The simplest way around this: do not use a maneuver node. Instead, point your ship towards normal/antinormal and start your engines until your orbit is polar. Boom, done! If you follow the marker on your navball as it moves while you burn, you never need to correct for anything. And in .90, it's even easier: you can just ask your pilot Kerbal to keep the ship pointed towards the marker for you.

Actually, I suspect that's a rather non-optimal burn - if you want to go to a course that's ninety degrees inclined from the current course (example: equatorial to polar), just roll 135 degrees from your current heading along the horizon and burn there.

(note that I've rolled a bit in frame 2 to show where the retrograde marker is better as the speed indicator was covering it halfway before)

[hab136]

See http://bugs.kerbalspaceprogram.com/issues/3953 and pick up the IntuitiveManeuvers.zip mod attached.

[Streetwind]

It's quite possible that it's not optimal, yes. But it's the simplest, because of the autopilot feature

Got a rough estimation on how large the difference between the two approaches is? Not exactly on topic, perhaps, but I'm curious.

[Navy4422]

Merged threads together, no need for two.

[Renegrade]

It's quite possible that it's not optimal, yes. But it's the simplest, because of the autopilot feature

Got a rough estimation on how large the difference between the two approaches is? Not exactly on topic, perhaps, but I'm curious.

Well, an inclination change for a 90 degree turn like that is something like 2*v * sin( di / 2), or about 224.86 in this situation. I'm not sure of the extra overhead from following the normal marker around, but I suspect it might be something like 1.0-cos(45) extra? My off the cuff guess would be then 290.72..ish

Basically..it's like taking a curved path between two points that are in a plane. If you fight with the maneuver node, it will eventually settle down to being on that '135 point' (90-135 = -45, 360-45 = 315 in this case), which implies to me that it is in fact the shortest route to that direction (well, unless you wanted to go south, but that would just be 90+135 )

I did some empirical testing around Minmus, thanks to VOID and autosave:

135 test: 5,135 - 4,911 = 224

normal test: 5,135 - 4,891 = 244 (+20)

Well, it looks like my off the cuff overhead guess isn't right. Maybe it's more like 1.0-cos(22.5) as you're only on average about 22.5 degrees off the correct vector? (that woudl imply 17.05 which is close to the observed 20)

Anyhow, it's about 9.2% or so cheaper to do it the 135 way. Not much at Minmus (this is why I love Minmus-sized planets so much) but at Kerbin it would save you nearly 300 dv. Also, this is a simple method too once you know it - you just roll around about 45 degrees past the heading you want to be at, and let 'er rip until the orbit is correct. You don't need to upgrade your SAS or anything, just basic SAS will do (and basic SAS is a lot less wasteful of monoprop and such than the new fancy SAS for some reason)

[Streetwind]

Thanks for the analysis!

[Renegrade]

Thanks for the analysis!

No problem, it's fun, and navball-only maneuvers are a bit of a specialty of mine (like the OP, I find that there are certain limitations of maneuver nodes, the large-inclination change being one of 'em. Another big one is that you can't reverse an orbital direction on approach within the SOI)

[visivante]

See http://bugs.kerbalspaceprogram.com/issues/3953 and pick up the IntuitiveManeuvers.zip mod attached.

All of the suggestions and tips presented in this thread are awesome! Thank you so much for taking the time to make these beautiful explanations, I actually learned a lot just by reading through.

And this the exact mod I was looking for, thank you so much!

-Visi