Visual Surveys of Non-Kerbin bodies.

[qoonpooka]

So I picked up a contract to do some flyovers with crew reports on the Mun, figuring: "Hey, I'm sending a lander and have to do a rescue over there anyway, surely one of these boats can pack some extra fuel and make the flyovers!"

So I drop into an equatorial orbit and, lo and behold, the points aren't anywhere near my orbit. No biggie, I figure, I should just do some normal burns to change my orbital angle, it's the Mun, how much could I.... HOLY WHOAZERS - 500+ dV needed?!

So I've built a flying gas can that can handle the needed maneuvers but yikes. There's got to be a more efficient way to do this. I'm still using 1.25m diameter gear because I haven't upgraded my R&D yet, but this looks like you basically need orange tanks to do it.

Is there a guide for optimizing completion of these contracts or some pointers folks can give me?

Edited October 30, 2015 by qoonpooka

[Superfluous J]

I don't know of any guides, but what I do is set up a polar orbit around Mun and do a combination of just waiting, and doing small (<100m/s) burns to tweak as I get close.

And whatever you do, don't get into an equatorial Mun orbit and then burn into that polar orbit. Set up your maneuver node in LKO to hit the Mun's SOI in such a way that you pass over the North or South pole, and then when you burn to slow down there you'll just naturally be in a polar orbit. And it won't have cost you any more dV.

The next thing I suggest is to do these contracts on Minmus instead. Minmus is so dV friendly it won't matter much how you get from one reading to the other.

[Snark]

The easy way is to set up a steeply inclined orbit that goes far enough north and south to encompass all the target zones. That's pretty cheap to do if you set it up before you get to the Mun (that is, don't go to equatorial orbit first and the. Try to muscle it around).

Once you've. Done that, you're set. Just let the Mun rotate underneath you, it will eventually bring all of the zones under your orbit and.you should need to make only minor inclination changes.

[qoonpooka]

I don't know of any guides, but what I do is set up a polar orbit around Mun and do a combination of just waiting, and doing small (<100m/s) burns to tweak as I get close.

And whatever you do, don't get into an equatorial Mun orbit and then burn into that polar orbit. Set up your maneuver node in LKO to hit the Mun's SOI in such a way that you pass over the North or South pole, and then when you burn to slow down there you'll just naturally be in a polar orbit. And it won't have cost you any more dV.

The next thing I suggest is to do these contracts on Minmus instead. Minmus is so dV friendly it won't matter much how you get from one reading to the other.

Is there something about being in a polar orbit that's just easier to change? Or should I aim for least difference? These aren't polar coords, they're below the 45-degree mark, in fact (though only just).

[Phil deCube]

It wasn't written for this purpose, but my tutorial called "KSP Career Mode for Absolute Beginners - Part 3" starting at this slide http://imgur.com/a/LHoNm#81 shows how to get into a polar orbit of Mun and do EVA reports for loads of science.

[Superfluous J]

Is there something about being in a polar orbit that's just easier to change? Or should I aim for least difference? These aren't polar coords, they're below the 45-degree mark, in fact (though only just).

You can aim for the least difference, sure. It may even save some time. One nice thing about a polar orbit though is that as you orbit and Mun turns under you, you can more easily predict visually what spot will be under your ship on the next pass. It gets a bit muddier (though still predictable, and maybe even not any more difficult for others but my brain won't do it) when your ship is also going prograde relative to Mun's rotation.

[DeMatt]

Is there something about being in a polar orbit that's just easier to change? Or should I aim for least difference? These aren't polar coords, they're below the 45-degree mark, in fact (though only just).

Polar orbit or equatorial orbit, if you need to change the orbit's inclination, it'll cost the same amount of dV for the same change in angle.

What a polar orbit does do, however, is position your craft's orbit at a right angle to the planet's rotation. So, your craft goes around the planet, the planet rotates a new bit of land underneath the craft when it comes back around. With enough patience (and an orbital period that isn't a simple multiple or fraction of the planet's rotation), every bit of the planet will eventually pass under your craft.

[Alshain]

Is there something about being in a polar orbit that's just easier to change? Or should I aim for least difference? These aren't polar coords, they're below the 45-degree mark, in fact (though only just).

A polar orbit will eventually cross every part of the body. Your craft orbits on a direct tangent to the rotation of the Mun. So eventually the target points will rotate underneath your orbit at two locations.

An easy way to get a polar orbit from Kerbin to the Mun is to burn prograde till the trajectory is inside the moon and looks polar even though it would collide with it. Once you cross into the Mun's sphere of influence, burn Normal or AntiNormal to push it out into a close fly-by.

Edited October 30, 2015 by Alshain

[flipmcf]

HOLY WHOAZERS - 500+ dV needed?!

To quote Neil Stephenson - all the times he has said it in all of his books:

"Plane change maneuvers are expensive"

So I've built a flying gas can that can handle the needed maneuvers but yikes. There's got to be a more efficient way to do this.

The answers here are the most efficient - change your inclination so it can reach the latitude that your landing point is at, then wait for the landing point to rotate below and intersect your orbit.

However, you have another trick to reduce deltaV: the biecliptic transfer:

In a nutshell, burn to bring your apoapsis very high, so you're doing only a few tens or hundreds of m/s when you reach it. At that point, do your plane change, and at the periapsis, re-circularize your orbit. All three burns combined will save you about %10 DeltaV - but only if your ellipse has an extremely high eccentricity.

http://i.imgur.com/8x7GFJU.png

Here's some more links:

https://www.reddit.com/r/KerbalSpaceProgram/comments/23ri7a/how_to_do_a_bielliptic_inclination_change/

http://forum.kerbalspaceprogram.com/threads/56983-What-is-the-most-efficient-way-to-make-large-orbital-plane-changes/page2

[qoonpooka]

That biecliptic transfer is super counterintuitive, but yay for Oberth Effect. Is there a point (other than SOI boundary) beyond which you don't get much fuel savings anymore? Is there a minimum eccentricity I should look for?

[flipmcf]

. Is there a point (other than SOI boundary) beyond which you don't get much fuel savings anymore? Is there a minimum eccentricity I should look for?

Short answer: Yes.

But at that point, you have to do the math. Finding these max/mins are beyond my patience really. But they do exist.

I had to calculate this stuff when I took Astromechanics in college, and I don't get the enjoyment out of it that others might.

There is a minimum eccentricity to gain efficiency, but since KSP gives us periapsis and apoapsis altitudes, not semi-major and semi-minor axis, there is a bit of a math hoop to jump through before you can even measure eccentricity.

(math people? help?)

However, if you just play with the idea, you'll get a feel for it.