Moho Landing

[xXRandomUserXx]

How much ÃŽâ€V do you need to transfer, get captured, and land on Moho? I just wasted about 3 hours building a ship that couldn't even get captured...

[Spartwo]

17000m/s to orbit kerbin and all.

[Jason Patterson]

You should be able to do it if you launch with ~10km/s delta-v. 4.5km/s to get to LKO, ~2 km/s ejection burn, ~2 km/s for capture, ~1.5km/s for landing. Realistically speaking your launch window won't be perfect, so you should add in another couple of km/s for all of the maneuvering you'll wind up doing in order to hit your mark. The good thing about all of this is that Moho's surface gravity is low and the bulk of the delta-v is spent in space, so you can get away with LV-N's for everything except your launch to LKO.

The vehicle in the image below has more than enough delta-v and a good enough TWR to land on Moho, once it has gotten to LKO. (26 tons) The parts shown have ~10km/s of delta-v to play with, so you can even do big inclination adjustments and the like without running out of fuel.

Moho is tough, plain and simple. Best of luck.

ETA: Forgot to put a ladder on there. I can't recall if Moho's surface gravity is low enough for a kerbal to fly with his rocket pack or not. They definitely could make a pretty impressively high jump to get up to a single ladder though.

Edited May 29, 2013 by Jason Patterson

[Francesco]

17000m/s to orbit kerbin and all.

that sounds excessive.

[DMagic]

that sounds excessive.

Yeah, 10k is probably enough, but you have to really get the timing right. Maybe 12k is better to give you some leeway.

[ThePyrateCaptain]

Moho is a pain. Weird orbit, hard to catch.

[xXRandomUserXx]

Thanks For the advice. It clearly is way to hard to get a 3 man pod to orbit moho and land with a single pod lander attached to it

[Specialist290]

I was actually trying this myself right before 0.20 launched. Got my lander in orbit around the planet, but had no way to get back with what little fuel I had left. Even sending a refueling vessel didn't quite give me enough fuel to get back, as it burned too much fuel getting into a properly-inclined orbit itself.

Moho is hard.

[Scottiths]

I am actually getting quite good at landing on Moho. You can do it with 9,000 starting D-v with some margin for error. I have not been to any other plaents besides moho yet because moho had the first transfer window, and I kinda got obsessed with going there after I tried and failed to make it my first exokerbin landing. Now I have a full base on Moho. Final plan is to have a base on every planet with a refueling station and mining so I can use my space plane to ferry tourists to every single planet!

[stupid_chris]

Once in LKO, for the transfer burn, the orbit adjustment burn, the capture burn, then the orbital adjustments (inclination, etc.) you need about 7000 delta V. To land, its around 1000 delta V (not 100% sure, would need a double check). Then you add the Launcher to LKO, which is roughly 4500m/s of Delta V. And if you want to get back from Moho, an additional 2500/3000m/s would be necessary. Overall, for a trip to Moho with return, you'd need pretty much 15500m/s of delta V on the launchpad.

What's hard with Moho is that it's eccentricity and inclination makes it extremely expansive on the transfer and correction burn. Then the capture burn is expansive because it's gravity is so weak the escape velocity is pretty low and you gain so much speed from the Sun's gravity you have to cancel it out once you enter Moho's SOI. It's really expansive. At least you can aerobreak on your way back. It's really easy to undershoot your delta V for Moho. Good luck on your mission! ^^

[Spartwo]

that sounds excessive.

sounds like his first time I like to have room for error(plane changes,low peri`s ect).17000 also includes landing.

[TheDarkStar]

The only good thing about Moho is that landing is easy. The dV to get there (along with reaching a stable orbit) tends to be more than to get to Eeloo. Return takes about 2500 m/s, which is as much as most people bring to come back from Jool.

[AndreyATGB]

Over 10k easily. My ship had 13000 delta-v and I even used phase angles and still barely landed. The capture burn especially is what will get you stuck. I suppose it's even possible to miss your encounter if you don't have enough thrust and have a high periapsis.

[tomf]

Another problem with Moho is that the eccentricity of its orbit means that the phase angle calculations done by protractor, mechjeb etc can be significantly wrong. At different points of its orbit moho can be traveling at very different speeds so it won't be where those tools based on circular orbits predict.

I ended up setting an alarm for 3 days before the simple phase angle and then using a maneuver node to attempt to create a transfer. It was miles out so I waited for 12 hours and tried again, and again, and again. In the end the true windows was 6 days after the theoretical one.

You want a transfer that just kisses the orbit of moho, and you want to do it at a time when moho will actually be at that point. If you come in to moho with any angle other than perfectly parallel to it's motion you end up with a massively more expensive capture burn.

[El wonso]

Flying to Moho is quite easy actually.

1. You just need to aim for orbit (around the Sun) like this (2000m/s dV):

Apoapsis as high as Kerbin's orbit.

Periapsis as high as Moho's orbit (closer to Moho's Periapsis).

Ascending node at Apoapsis (if I remember correctly, just go for Pe close to Moho's Pe).

Don't bother with phase angles.

2. Then fix planes with Moho at Ap (750m/s dV).

3. Orbit a few times until you get the closest approach distance you can have without burning any fuel and play with maneuver nodes at Pe to get an encounter (<100m/s dV). Try lowering your expected Moho Pe to 60km or lower.

4. Burn to circularize orbit around Moho (1900m/s dV).

5. Landing and taking off is another ~1900m/s dV.

6. Going home is ~3100m/s dV (wow, didn't expect that).

In total -> ~14500m/s of dV is needed (including getting to LKO).

Edited May 30, 2013 by El wonso
updated values

[Francesco]

I'd be interested in knowing why you suggest a Moho periapsis higher than 60 km.

[El wonso]

I meant 60km or lower, sry.

edited

[Thefallenhun]

The point about theoretical vs actual windows is an interesting one, does anyone know a good way to calculate truee transfer windows taking into account eccentricity? It seems like it would be easier to correct for that THEN burn, rather than go from a planar orbit around kerbin to a planar sun orbit, THEN correct.

[joppiesaus]

Moho is a pain. Weird orbit, hard to catch.

Landing his hardest, not very hard to catch thought.

[tomf]

Working out the perfect launch window is pretty hard, I looked into it and it seemed to come down to equations that weren't solvable algebraically. I think what people IRL do is draw up lambert pork chop diagrams and visually look for a minimum.

[cxg2827]

my moho capture was on the high side (4,800m/s).

[Francesco]

Landing his hardest, not very hard to catch thought.

the opposite is true: Moho has a very small sphere of influence, while landing on it is not much harder than landing on the Mun.

[alexmun]

Yeah, getting to Moho is hard. You can get there and achieve orbit with about 5000m/s of delta-v, but the launch window is small and very different from what the Hohmann transfer calculators would suggest since Moho's orbit is eccentric and inclined. In fact, my troubles getting to Moho are what got me to put together a tool to calculate proper launch windows for inclined/eccentric orbits. You can try it out here: http://alexmoon.github.io/ksp.

[mpk10]

The vehicle in the image below has more than enough delta-v and a good enough TWR to land on Moho, once it has gotten to LKO. (26 tons) The parts shown have ~10km/s of delta-v to play with, so you can even do big inclination adjustments and the like without running out of fuel.

How did you get the structural elements for your landing feet to go at angles other than 90 degrees?? That would have saved me so much time if I knew I could do that!

[James_Eh]

How did you get the structural elements for your landing feet to go at angles other than 90 degrees?? That would have saved me so much time if I knew I could do that!

In the VAB, if you hold SHIFT while using WASD the parts rotate in 5 degree increments.