Tips for getting to Moho

[wahchewie]

Haha, Well this is well and truly frustrating - I think I'm at a bad phase angle, but regardless I Definately have enough Delta V if i use the correct technique for getting there,

Please understand friends, that i am familiar with the Hohman transfer already... Duna, and the outer planets - No problem.

I'm just finding Moho is an absolute pain in the backside to get to without using an extraordinary amount of delta v, So I'd just like some tips on the most efficient way to get there... Generally I try to aim for 2-3 burns to get there, which is easy with Duna for example, not sure if it's feasible with the inner most planet. Of course i could just run a similar orbit for years until I got a close encounter, but this isn't very realistic.

*Should I leave Kerbins influence/orbit before burning doing my first pereapsis?

*Should I aim for my first burn to put my pereapsis exactly on mohos orbit line? Or slightly further out to allow that catch up time?

*When do you initiate the vertical burn to get into the elipse with Moho? At the ascending node?

* In General, do you find it takes many orbits (so hundreds of days) to get a reasonable encounter with Moho?

Any tips - greatly appreciated. How did you get there, & How much Delta V?

Cheers!

[Brun]

Haven't been to Moho yet myself (either it or Dres will be my next target), but I know some people try to grab an aerobrake/gravity assist off of Eve to help slow down during Moho approach.

[Pecan]

First make sure you leave when there is a transfer window. Easiest way is to make 4 burns; leave Kerbin's SOI, match planes at AN/DN, rendezvous, orbit. Mind you, I always seem to come in way too fast and burn a hell of a lot of fuel slowing down to orbital velocity.

[maccollo]

I did an elaborate explanation a while back so I will just direct you to that post.

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

Unfortunately my dropbox is temporarily disabled due to exceeding bandwidth limitations, so you wont get any pretty pictures =P

[cantab]

Warning: I've not actually been to Moho yet, so take my advice with a pinch of salt.

*Should I leave Kerbins influence/orbit before burning doing my first pereapsis?

NO! Make your full ejection burn from Low Kerbin orbit, getting your periapsis down to the level of Moho's orbit. If you try and do that while in direct Kerbol orbit it'll take insane amounts of fuel.

*Should I aim for my first burn to put my pereapsis exactly on mohos orbit line? Or slightly further out to allow that catch up time?

You want your orbit to be tangent to or intersect Moho's.

*When do you initiate the vertical burn to get into the elipse with Moho? At the ascending node?

Probably not. Sometimes the best option is to sort your inclination out to start with from the ejection burn, getting directly on course for a Moho intercept. Maccollo mentions this is the case in the best Moho windows. In a good Moho window you can get from equatorial LKO to low Moho orbit for a bit over 4000 m/s delta-V, while in a bad window it might take over 5000. (Still much less than if it's completely out of window, in that case you're looking at ten, twenty, even thirty thousand m/s.)

Other times you'll want to make a mid-course correction, but that may not always be cheapest at the AN, so experiment with manouevre nodes.

* In General, do you find it takes many orbits (so hundreds of days) to get a reasonable encounter with Moho?

If you wait for a good window, go directly to Moho, and sort things out properly, you'll only need to make one half-orbit transfer. Of course if you're gravity assisting you're liable to have waits.

[700NitroXpress]

You can get to Moho in one burn from outside of the Kerbin SOI. You don't need to do that horrible inclination burn at all if you don't want to. You just have to get an intercept at the exact point Moho passes the inclination marker on the orbit. So you do one burn to get that intercept and once you get to Moho, it's just one burn to obtain orbit. As long as you pack plenty of fuel and have enough TWR you should be able to slow down fast enough before you leave the Moho SOI. To get this kind of intercept, you have to wait for the planets to align and be lucky. Moho will orbit much faster so you won't need to wait long to get an intercept like this, it just takes some tweaking to get it right.

[Redshift OTF]

I'm finding getting an encounter with Moho quite easy now after having tried it quite a few times. I don't wait for a transfer window, I just leave Kerbin's sphere of influence, set up an manoeuvre node so I reach Moho when it is near it's ascending or descending node, (Moho travels quite quickly so getting an encounter timing is fairly simple), then I don't have to do one of those nasty inclination burns. It usually takes about 3000 DeltaV from KLO. The only problem with doing it the lazy way like this is the slowing down. I'm usually coming in pretty fast and need lots of DeltaV to slow down so it may be easy but it is definitely not efficient.

[bsalis]

You can avoid a plane change if you leave Kerbin at the ascending or descending node.

Then get the rendezvous timing right by adjusting the Ap when at Pe the first time.

Would elaborate more but ipad posts are tedious. Mebe someone else could illustrate.

[elmarko]

Use Eve to help ;-)

[TheExplosionist]

Use lot's of 8x symmetry asparagus nukes.

[MarvinKitFox]

Moho is a bit of a special case.

The orbit is quite inclined, so plane change can be very expensive if not done right.

and, the orbit is *very* eccentric.

Getting down to MoHo's apogee around the sun will need something like 4000m/s more juice than meeting it at the high point in its orbit.

Not the most efficient way, but the easiest for me without bankrupting my rocket fuel account, is to launch from Kerbin while Kerbin is at an ascending/decending node with MoHo.

I launch *out* from the sun.(prograde from Kerbin)

Half an orbit later, I'm at my own ascending/descending node with Moho, and loitering out near Duna orbital distance. At this range the plane change is almost trivial, and the delta-v needed to drop my periapsis down to MoHo's level is not so bad.

The final braking run at MoHo is one monster of a burn, but it can be done at high speed and close to MoHo, so Oberth helps to forgive some of my earlier inefficiency.

[technion]

Pack nonsensical amounts of dv and just go for it

[wahchewie]

Thank you so much for the advice all. I'm going to take it on board & try tonight. Hopefully this helps others with similar issues