... Transfer to a Polar Orbit.

[Carthaginian]

OK... so, finally installed the MapSat plugin- yeah, I know, everybody has that.

Just call me behind the curve.

The problem is, of course, the most effective orbit for a mapping mission is a polar orbit. Now, when you're trying to map Kerbin it's not that difficult to do... you just break north when you start your orbital insertion. For every other target in the sky, however, you have to transfer from your initial orbit into a polar orbit. I have had some success (+/- 30*) with getting into a polar orbit around Mun, but it is nowhere near good enough to actually get myself a complete map.

Can anyone offer some advice on how to transfer from equatorial to polar orbits... in terms that a ground-pounder used to maps and compasses can grasp?

Seriously, guys... like, Barney-style.

Thanks,

Carth

[The Destroyer]

I dont use ISA mapsat myself, but im considering it.

Also, I have no idea. all i know, is to use normal(+) and antinormal(-) while in orbit to change inclination.

[phoenix_ca]

I've never even tried this before, but here's a suggestion:

Pay very close attention to the position of the encounter with the orbital body's SoI relative to it's orbit (either "up" or "down", that is, normal or antinormal). The goal is to get your injection in a position where it intersects a polar orbit, or is as close as possible to doing so. You can make small (very, very small) adjustments to it's location relative to where the body will be about midway there (most efficient). Once there, it's a matter of adjusting the inclination to make it 90 or -90.

Note that burning normal or antinormal to the body's orbit probably won't suffice in itself. You'll also need to burn a bit "left" or "right" (That is, RAD + or RAD - ) to keep your encounter within the target body's SoI

[Atimed]

-If you want to go from a equatorial orbit on Kerbin directly to Muns Polar orbit, you need to incline your Kerbinns orbit by a few degrees (3-5°) relative to the Mun..

-Its allays 90° before your Munar Injection Point.. Then you just do a Munar Insertion.. after that when you get into Muns SOI burn until the orbital path is alighned vertically.. (passing over the poles) After that is just a fact to do a circularization and viola.. Just deploy your mapper and you're good to go..

Edited September 24, 2012 by Atimed

[Carthaginian]

OK, guys... this is getting there, but even though it's making its way to my eyes, it ain't quite getting into my thick skull yet.

I know about prograde and retrograde burns, but nothing about normal and antinormal.

Remember, your explaining this to the aerospace equivalent of a moron.

Now, if you wanna know about pharmaceutical interactions, symptoms of illness, writing your name with a belt fed machine gun, rigging a booby trap, skinning game, catching fish, growing crops suitable for temperate climates, carpentry, plumbing or creative writing... well, I can handle that.

Flying a spacecraft- that's still something I have a ways to go on.

[Nibb31]

Normal/antinormal is pointing perpendicular to prograde/retrograde, ie: "up/north" or "down/south" (in quotes, because those directions don't really mean anything in space). radial and antiradial are outward and inward from the barycenter of your orbit.

Of course, as you burn, normal or antinormal, you change your inclination, therefore the normal heading will rotate, which is why you really need to use the MechJeb SmartASS to maintain your heading normal as your orbit rotates.

Also note that it is more economical to perform an inclination change burn when you are at a higher altitude. So basically, the best time to do it is the moment you enter the Mun's SOI, before you circularize the orbit.

[PigletPG]

Start your flight FROM a polar orbit. Enter orbit in a polar orbit, it's not impossible and probably costs less fuel.

[togfox]

The KGSS journal (see my sig) has this outlined in detail.

[Jason Patterson]

For a tidally locked object, it's poles are going to be perpendicular to the orientation of its orbit. What I do to adjust the inclination of my orbit to match another is the following (it would work just as well to get perpendicular to it):

1. Get into orbit around the object - a large, relatively circular orbit (more a not highly elliptical orbit, really.) The reason for this is that the smaller your velocity is, the less delta-v you need to change the orientation. A larger orbit also gives better visual cues.

2. Go to map view and focus on the object I'm orbiting. Bring up my navball in map view (number pad . key)

3. Rotate the map until the orbit of the object (the Mun in your example) and my ship's orbit both appear to be lines. Here's a picture of what I mean. I didn't have any ships up at the time, so this is the orbits of the Mun and Minmus aligned correctly.

When you reach this point you're on something called an orbital node, a point on the line where the two orbit's planes intersect.

4. Time warp until your ship lines up with the object you're orbiting. In my picture, that would be Kerbin, in your scenario, the Mun. There are two points on your orbit where this will happen, the one closer to apoapsis is preferable, because you'll be going more slowly, but either one works in the same way.

5. Determine what compass direction you're heading. Align your ship prograde (pointing in the direction you're going) and read the direction from the navball. This is another reason that a relatively circular orbit is better, since reading the direction from the navball is quite difficult when the vertical velocity is a large component of your total velocity.

6. Adjust your ship to face normal to it. Add or subtract 90 degrees from the navball direction and turn in that direction. Adding or subtracting will depend on which way you want to tilt your orbit relative to the orbit you're trying to achieve. If your orbit starts tipping the wrong way, just turn around and burn the other way instead. In your case, you don't care whether you're starting out headed south or north on your polar orbit, so it doesn't make any difference.

7. Burn until you achieve the orbit you want. Adjust the direction of your burn as you perform it so that it stays perpendicular (+/- 90 degrees) to the direction of your travel. For example, if you started out headed at 90 degrees, and you burnt north (0 degrees) to change your orbit, the direction you're going would slowly begin to nudge northward. Your burn at 0 degrees would no longer actually be normal to the direction of travel and your orbit's properties other than inclination would start to change. Slowly changing your direction of travel further in the negative direction would fix this. Ideally, an inclination change won't change your speed at all, so that's a good indicator of how close to perpendicular you are. This will be important with a major directional change, as you're intending to do. Again supposing you started out at 90 degrees and burnt at 0 degrees to get into a polar orbit. By the time you finished you would be pointed due west (270 degrees) in order to remain perpendicular to your direction of travel.

8. Once you've got your orbital inclination the way you want it, adjust the periapsis and apoapsis as usual.

Hope this helps.

Start your flight FROM a polar orbit. Enter orbit in a polar orbit, it's not impossible and probably costs less fuel.

The downside is that your window for being captured is fairly small and your velocity is going to be wonky (the Mun is moving laterally while you're moving vertically, you still won't wind up in a polar orbit, but it will be closer than an equatorial orbit.

[PictoKong]

I recall there being a tutorial on orbital manuveurs, it might also help if you still don't quite "get it". For RAD + and RAD -, it took me a while to get the hang of it, but the only time it is really useful would be for rendez-vous and changing the periapsis of an planetary capture. RAD + and RAD - will ALWAYS be towards the planet/moon and away from it, if you are on a circular orbit. They will bring you closer or farther, depending on the direction...

This is a plane change: in the exemple they started at like 45° and got to 90° the Dot is the spacecraft. It burned when it was at the equator (that's the node, there is also one opposite to it, behind the planet). Since they want to go south, they burned 135° (assuming 45° at start) and the ship moved slowly towards 180°. The ship indeed spins with the orbit.

[elmarko]

If you wanted to make a solar polar orbit, you could do a Ulysees and have Jool gravity assist you into a higher plane. That is a lot of fun

[Jason Patterson]

It occurs to me that for a polar orbit, as long as you don't care about the other directions of the orbit, the job is much simpler.

1. Get into a relatively large, circular orbit.

2. Find the direction you're heading (not the pitch, just the compass direction), and add or subtract 90 degrees from that, doesn't matter which.

3. Turn in that direction (called normal.) and burn until your new heading is either 0 or 180. You'll need to adjust the direction of your burn as you make it so that it stays perpendicular to your heading. A constant speed means you're doing it right. You should finish up burning at 90 or 270 degrees, depending on the path you decided to take.

4. Once you're in orbit, adjust your periapsis and apoapsis as desired.

Edited September 24, 2012 by Jason Patterson

[RoboRay]

It's easy to set a polar orbit for a destination body by simply adjusting your trajectory to take you over the north or south pole rather than along the equator. You can still take off from KSC on a fuel-saving 090 heading.

Here's some pics of me setting up a polar orbit at Duna via aerobraking: http://imgur.com/a/2ZGCe#0

If you are already in an equatorial orbit and want to change to a polar orbit of the same body, it would probably actually take less fuel to intercept another body and use it's gravity to turn you around, then plot a trajectory over the poles of the first body as you return.

I believe this has actually been done for a semi-failed satellite in Earth orbit that was repurposed to perform another task; looping it around the Moon to get the proper inclination for it's orbit around Earth. I can't recall the mission name, though.

Edited September 24, 2012 by RoboRay

[GabeTeuton]

-If you want to go from a equatorial orbit on Kerbin directly to Muns Polar orbit, you need to incline your Kerbinns orbit by a few degrees (3-5°) relative to the Mun..

-Its allays 90° before your Munar Injection Point.. Then you just do a Munar Insertion.. after that when you get into Muns SOI burn until the orbital path is alighned vertically.. (passing over the poles) After that is just a fact to do a circularization and viola.. Just deploy your mapper and you're good to go..

Okay man... that was exactly what i needed, worked 100%, i ended up in what looks like a perfect polar orbit, and even better, my projected orbit in Mun's SOI is around the terminus light line or however that's called... i'm still burning, 350tons and just 8 nuclear engines so i don't know how will it look like after i'm done burning... but the proyections look awesome, i used a 5º inc in kerbin's orbit before the transfer burn!

Thank you!

[impyre]

While the inclination can be performed at low kerbin orbit, it's more fuel efficient if done in mid-course (when velocities are lower). to get a feel for where it will be the cheapest, simply establish mun encounter, drop a maneuver node somewhere around halfway between kerbin and the mun, and drag the purple normal/anti-normal adjustment just a little, maybe 10-20 m/s. Then change focus to the mun, and (while focused on the mun) grab the maneuver node and slide it around. You'll see that there's one point where the inclination change is the greatest. That's your sweet spot. Leave the node there, and further adjust the purple normal/anti-normal handles until you get the orbit you want.

[Claw]

While the subject of polar orbits itself is still relevant, this olde-but-goodie is a bit out of date with the mod references.

I'm going to go ahead and close this so it doesn't confuse anyone.

Cheers,

~Claw