On 3/24/2016 at 6:01 PM, Unknown Venom said:
So I've been trying to find a way to get to moho. Do I use Jool or just drop down near Kerbol?
Welcome aboard.
The hard part about Moho isn't so much in getting there from Kerbin, it's STOPPING there once you arrive. If you're not extremely careful with the transfer, you will often find that capturing into a Moho orbit takes ungodly amounts of dV, like 4000-6000m/s. This has been the ruin of many 1st-time Moho expeditions and is what has given Moho its evil reputation 
Because the cost of the transfer burn is essentially fixed due to orbital altitudes of Kerbin and Moho, the objective is to reduce the captureburn down to something reasonable, say 1000-1500m/s, without simply shifting this cost to the transfer burn.
At any planet, the cost of the capture burn is proportional to the angle between the ship's trajectory and the planet's orbital path. The closer these lines are to being parallel, the lower the relative velocity between the ship and the planet, so the lower the capture burn cost. The closer these lines are to being perpendicular, the greater the capture burn cost. Therefore, the objective is to approach Moho at as small an angle as possible. This is achieved by making the ship's orbit as similar to Moho's as possible. Because a direct transfer from Kerbin to Moho makes a rather elliptical orbit not at all similar to Moho's reasonably circular orbit, it's apparent that you must somehow lower the ship's solar Ap from the altitude of Kerbin's orbit down closer to Moho's altitude. The various tricksexperienced players use to get to Moho on the cheap perform this lowering of the solar Ap in different ways.
There is also the matter of Moho's inclination. The further Moho is above or below Kerbin's orbital plane by the time you get there, the more dV the transfer burn itself costs, either up front on a ballistic transfer or en route with a plane change. This can be a significant amount so experienced players avoid it as much as possible by arrivingat Moho only when it's at or near its AN or DN with Kerbin. This has NOTHING to do with conventional transfer windows based on the phase angle between Moho and Kerbin, which don't take this into account. Therefore, experienced Moho explorers totally ignore transfer windows between Kerbin and Moho and leave only when they need little or no inclination change (more on this in a while).
So, what do you do? Well, as a general rule in KSP (and probably real life as well), you can trade fuel for travel time. If you don't care how long the trip takes, you can usually get there for very little fuel by taking an indirect route. Conversely, the shorter the travel time, the more fuel it requires. Elapsed mission time in KSP doesn't matter in stock games. If you're using a life support mod, however, you need to pack enough supplies for the trip or use DeepFreeze. Indirect transfers to Moho typically take about 1-2 years of gametime because they usually require you to do 1 or more solar orbits.
Anyway, probably the most efficient way to get from Moho to Kerbin is to leave Kerbin when it's at an AN or DN with Moho's orbit. Pay no attention to where Moho itself is at the time, only where Kerbin is. Do a transfer burn from Kerbin so that your trajectory hits Moho's orbit at the AN or DN with Kerbin that's on the other side of the sun. Thus, once you leave Kerbin's SOI, your solar Pe is at Moho's orbital altitude and your solar Ap is at Kerbin's altitude. Once you get to Pe (which is on or near Moho's AN/DN with Kerbin's orbital plane), burn retrograde to lower your solar Ap down to somewhere between Eve and Moho so your orbit is fairly circular, minimizing the angle at which you'll meet Moho. Then you wait, tweaking your Ap as needed, until you meet Moho at your ship's Pe, which might require making several solar orbits. This pretty much eliminates all the inclination change you'd otherwise have to do and also minimizes the capture burn, although you effectively need more on the transfer due to lowering your solar Ap with thrust. The name for this method is the bi-elliptic transfer.
Not quite as efficient but still pretty good is to use a gravity brake at Eve. In this scenario, again you totally ignore Moho's position when you do the transfer burn. Instead, you leave Kerbin on a regular transfer window to Eve. You tweak your departure burn from Kerbin (and maybe tweak your trajectory en route or once in Eve's SOI) so that your ship will pass Eve on the sunny side and somewhat above or below its orbital plane. Adjust your Eve Pe altitude so that once you leave Eve's SOI, your solar Pe will be at or near Moho's orbit. Also adjust your Eve Pevertically to get as much inclination change as possible towards matching planes with Moho. Once you leave Eve's SOI, your solar Pe will be at Moho's altitude and your solar Ap will be at Eve's altitude, and you'll have done some (but never all) of the plane change. From here, it's a matter of burning to match planes with Moho and then tweaking your solar Ap and/or Pe as needed to intercept Moho. Because you're matching planes with Moho, you can intercept it at any point around its orbit instead of having to hit it at an AN or DN with Kerbin. This means you can usually hit Moho within 1 solar orbit instead of maybe having to wait several solar orbits, so travel time this way is usually rather shorter than with a bi-elliptic transfer. And the actual transfer burn is minimized because you only burn to go to Eve and its gravity does the work of lowering your solar Ap. However, you make up for that in usually having to do a fairly significant plane change burn to match planes with Moho, and this usually makes this method require somewhat more fuel than a bi-elliptic transfer.
With both methods, the capture burn can be further reduced by gravity braking off Moho itself. The 1st time you meet Moho, pass it on the sunny side to further lower your solar Ap so that now your orbit is very similar to Moho's. Then do another solar orbit and finish capturing the next time around. However, this will add even more travel time.
So there you are, 2 indirect methods for getting to Moho that cost significantly less in total (including the capture burn)than trying to do a conventional direct Hohmann or ballistic transfer based on phase angles. Both take considerably longer than direct transfers however. The opportunities to do bi-elliptic transfers happen regularly twice per year as Kerbin passes the AN and DN with Moho's orbit. The opportunities for Eve gravity assists happen with the regular Eve transfer windows rather less frequently. So take your pick.
Have fun
