Orbital inclination changes; also, Moho scares me.

[godefroi]

So, for my second manned mission to another planet, I picked Moho. Mostly because the transfer window was the next available. I sent two rockets, one with a lander/ascender, and one with a return transfer vehicle. Due to some piloting errors on my part, or maybe just the luck of the IEEE floating point math, the return vehicle ended up in an orbit with an inclination somewhere in the neighborhood of 150 degrees. I didn't look that close, but I believe that it's something like a BACKWARDS equatorial orbit?

Anyway, two more ships have been dispatched, and are on their way, but because, you know, Moho, you can never really have enough dV, so I'd like to salvage what is essentially a mostly-full big orange tank. The inclination change is extreme, though, so I'm wondering what the most efficient way to do it is.

I can do it the "normal" way, burning normal/antinormal at the AN or DN, or I could raise my orbit, and then do it at the Ap. Which would be more efficient? Does it matter?

[KvickFlygarn87]

Doing it at apoapsis is more efficient, but not easier.

Also, Moho is a horrid choice for a second planet to go to. If you haven't yet, do a mission to Eve. If you have done Eve, go for Duna or Dres.

[capi3101]

For Moho - try maccollo. http://forum.kerbalspaceprogram.com/threads/61478-Oh-bugger-Injection-burn-at-Moho?p=835667&viewfull=1#post835667

I'm not 100 percent sure I understand the issue. Where exactly is the return vehicle, in orbit of Kerbin, Moho, the Sun, where exactly?

If it's in orbit of Kerbin, you could just launch to the west. The extra delta-V you'd need is not that much all told. You'd only be about thirty degrees or so off the inclination of the return vehicle but that's doable; far better than doing the 150.

EDIT: I agree. If you've done Duna, I might suggest either Gilly or Dres as a second manned interplanetary destination. Hell, you might even consider Ike. I've had a single success in regards to Moho...the satellite you see down in my salad bar.

[MartGonzo]

One thing I don't get about Moho, according to the Wiki it takes about 1600 Dv to get an encounter, I've tried going to Moho a few times and never spent less that 2600 getting there, what am I doing wrong?

[godefroi]

Both vehicles are in orbit around Moho. The lander/ascender is in a ~60 degree inclination (easily solved by landing at the equator and launching to equatorial orbit) and the return transfer vehicle is in the ~150 degree orbit.

I got to Moho using Alex Moon's transfer window calculator tool. The problem was mainly that I was sending two ships, and after doing one of the burns (using a low TWR transfer stage) it was past time to do the burn for the second ship, and I ended up a little off.

Also... it's not the ejection burn for Moho that kills you, it's the insertion burn. Also, you don't have much time to do it. A giant ship with a single LV-N might not be able to make the insertion burn successfully. That's my experience, anyway.

Maccollo's method might be much better, if you're not in a hurry. Unfortunately, I'm in a hurry. Bill only has so many snacks...

[KvickFlygarn87]

Mart: If you get an encounter at a descending/ascending node, you could probably do it in less than that. Injection burn is a different tale though.

[godefroi]

Doing it at apoapsis is more efficient, but not easier.

But, the question is, is it more efficient to do it in the orbit I'm in (~30km Ap), or more efficient to raise my Ap to something really high, do the inclination change at the new, high Ap, then circularize again at a low altitude?

[godefroi]

Mart: If you get an encounter at a descending/ascending node, you could probably do it in less than that. Injection burn is a different tale though.

Alex Moon's calculator gets me encounters at AN/DN, but like you said, it's the injection burn that kills you. Take more dV than you think you need, then double that.

[capi3101]

Okay, both over Moho. Yeah - what you need to do is kick out the Apoapsis of one of the two craft very high (close to escaping Moho's SOI). At the apoapsis, make your plane change burn, then circularize again. That's the most efficient way to do it, but as has been pointed out, it's not exactly easy.

[SRV Ron]

Attempt to catch an intercept of Moho as it crosses your orbital plane. That way, you don't have to adjust your orbital plane to match Moho's, a maneuver that will take tons of fuel to do. It make take several Kerbal years to find that ideal intercept window.

The same is true for orbiting Eeloo. Do the intercept as it crosses Jool's orbital plane.

[Xavven]

Honestly, I just brute force it and pack 9000 m/s2 of dV for my transfer stage

[cantab]

Yes, an inclination greater than 90 degrees is a retrograde orbit.

IMHO, in the situation you are now, just land the lander, then launch it to match the returner's orbit as best you can. You'll need a touch more delta-v and a lot more finesse, especially if you don't want a long wait for Moho to rotate you into position for the ascent, but it's probably far preferable to trying to make big orbital changes now.

[Taki117]

So, you want to get to Moho? Look here!

[KvickFlygarn87]

So, you want to get to Moho? Look here!

Hey, a link that has been posted before! Super helpful. It's less than one and a half page, at least check the links that were posted.