Aiming for high inclination orbit?

[Kip336]

Hi Guys 'n Gals,

I'm in the stages of setting up my first ever interplanetary campaign in KSP to Duna. Currently underway is a science probe which will map and scan the planet. I designed the probe to take a lot of extra fuel in order to get into a high inclination orbit.

Now I'm designing stage two of my mission, which will include a rover, a small communications satellite that will orbit in a very low orbit to provide a link with Kerbin (RemoteTech), and a larger communications satellite that will be in a highly inclined, elliptical orbit around Duna to form the backbone of my Duna communications relay for later exploration and colonization missions.

While designing the probe, I wondered, isn't there a way to aim for an inclined orbit when transferring to Duna? This would save a lot of fuel, as I know that the further away from a body you do a maneuver, the less dV you need, as opposed to aiming for Duna in an equatorial orbit.

Many thanks!

Edited February 26, 2015 by Kip336
Question Answered.

[WhiteKnuckle]

Sure. After you've left kerbin and have an encounter with Duna set, make a correction burn (I usually do this at roughly the halfway point of the trip, or at the ascending or descending node if the inclination is off).

Click on Duna and select Focus View, now you'll be focused on Duna and you'll be able to see your orbital path once you reach Duna's SoI. From here I usually just make tiny burns in each of the main directions to see how they'll adjust the encounter (you may be able to do this with a maneuver node as well, but I don't normally bother since we're talking about only a few m/s of delta-v) You should be able to get an encounter that comes right over one of the poles or at whatever inclination you want.

The key to interplanetary missions is make burns as far out as possible. Tiny course corrections on the other side of the system have huge impacts months later when you finally get where you're going.

Also: Beware Ike... it's huge, it's close, and it likes to take things on highly elliptical orbits and throw them out of the Duna system.

[Kip336]

Ike....yea....his name comes up a few times too many. I sometimes wonder if I shouldn't have gone with Eve

So in this case, I'd just burn my inclination up a bit to get captured by Duna in a higher inclination orbit?

[WhiteKnuckle]

Ike....yea....his name comes up a few times too many. I sometimes wonder if I shouldn't have gone with Eve

So in this case, I'd just burn my inclination up a bit to get captured by Duna in a higher inclination orbit?

Probably. But not necessarily, for example you may already be coming in high or low and you might want to burn radial to move yourself over the center of the Duna system, or it might take a little bit of prograde or retrograde thrust... who knows. Just play around a bit until you like what you see. If you're doing the maneuver far away it takes so little DV you can afford to play around. Heck, on ships with an RCS system I usually just do little bursts of translation to see which direction will move me where I want to end up.

Again, you can use a maneuver node, but since you're talking about at most 5-20m/s it can be more trouble then it's worth to try to set one up.

And no... Eve is a cruel mistress... save her for last unless you want to be caught in her purplely clutches forever. And Gilly is a boring space potato. Duna is where you want to go... just watch out for Ike.

Edited February 26, 2015 by WhiteKnuckle

[Kip336]

Alright, thanks for the input then!

As for Eve/Duna, I was basing myself of the travel to Duna tutorial on the wiki:

'Duna is Kerbin's second closest neighbor. After a successful landing on Eve, it is likely your next logical step. It perhaps the ideal planet for interplanetary voyages for several reasons:"

[WhiteKnuckle]

http://forum.kerbalspaceprogram.com/threads/111211-Eve-or-Duna

This thread from a few days ago goes over the Eve vs Duna argument. But to boil it down:

Landing on Eve is easy, just bring parachutes. Taking off is the single hardest mission in the game.

Landing on Duna can be a little tricky. But getting back isn't that much harder than a Mun mission.

I also like Duna cause it's purdy...

[Laie]

Landing on Eve is easy, just bring parachutes. Taking off is the single hardest mission in the game.

I'd call it the hardest single mission; single hardest probably still is Jool-5 (although it has become much easier to overprovision on fuel and just do it with very little planning at all)

isn't there a way to aim for an inclined orbit when transferring to Duna?

I almost don't get the question: you don't aim for an inclined orbit, you get one -- unless you carefully aim for equatorial.

Try a mid-course correction, at AN/DN, to get an equatorial orbit -- if it is cheaper than 200m/s, just do it and don't worry. Otherwise, just try to make it so that your periapsis will sit close to the equator, and the apoapsis as far out as possible (which isn't as far as one would like, not near Duna; and there's always the Ike problem). The high-apo plane change will probably still cost on the order of 100m/s; not having to worry about Ike is worth another 100m/s, I'd say.

[eddiew]

I find that the point of SOI entry is a really good time to make a choice about polar or equatorial orbits. Transfer burns rarely drop you into the perfect plane when you arrive, and most adjustments here seem to cost about 50 delta-v to set the orbit either way

It's true that you can do them earlier while still in solar orbit, but getting it fine tuned can be challenging, as 0.1m/s can fling you round the other side of the planet entirely. Being the the edge of the body's SOI is still vastly cheaper than when you're already in an orbit around it while not requiring inhumanly precise throttle control.