Why landing on Moho is damn difficult

[Pawelk198604]

I made several mission to Moho, all crashed. I have problem with orbital insertions?

Landing on Eve and Duna is easy i can use their atmospheres to break, but Moho has not atmosphere.

Now I know why there are so few unmanned mission to Mercury:D

[GamerMitch]

I haven't tried it yet,so i don't know.But You made a point with the little to no missions part.

[The Jedi Master]

Moho is evil. It is the I Want To Be The Guy of KSP. If you can so much as land there, you will offically be awesome. And if you can return...

It has mostly to do with high inclination and huge Delta V requirements.

[regex]

Braking at Moho is murderous because you're so close to the Sun; a complete transfer will cost you enormous amounts of fuel but if you catch the right window it can be as little as 4km/s (IIRC).

[sporkafife]

This may sound a little crazy, and I haven't tried it so it might be a complete bust, but maybe an ion engine would be good to put a probe into Moho orbit. With the sun so close, you could probably get enough power to run it with the smallest solar panel, so the t/w ratio wouldn't be too terrible. In fact, I wanna go try it now

[Pawelk198604]

Braking at Moho is murderous because you're so close to the Sun; a complete transfer will cost you enormous amounts of fuel but if you catch the right window it can be as little as 4km/s (IIRC).

And it's like you're lucky, I recently had a 6000 m / s

I have tried several times and always I ended fuel just before landing.

Moho is a demanding planet.

Fortunately, the launch window is once a month.

[RocketPilot573]

Landing on Moho is difficult? Try Tylo... It's getting there thats hard.

[Giggleplex777]

I found landing on Moho was as easy as landing on Vall. I landed first try with this weird flat landing pad with a rover on top.

Here's a better view of the landing platform on the Mun:

The entire rocket looked like this:

In orbit around Moho:

The rover system was also used for Eeloo:

Edited January 1, 2014 by Giggleplex777

[RuBisCO]

I've landed there easy, manually even, what the deal? The problem is Delta V needed just to get to Moho. I done it by using KSPX ion engines or huge nuclear engine powered mother ship assembled in Kerbin orbit with fuel tanks and nuclear engines sheded on the way to moho, and a small lander and orbital docking. Also a Kethane refueling station on Gilly helps because getting to Gilly by way of Eve is like 1000 m/s less then getting directly back to Kerbin.

[Scarecrow88]

Landing on Moho isn't difficult, but slowing down enough to get captured in orbit prior to landing is a tad tricky.

[Aragosnat]

This may sound a little crazy, and I haven't tried it so it might be a complete bust, but maybe an ion engine would be good to put a probe into Moho orbit. With the sun so close, you could probably get enough power to run it with the smallest solar panel, so the t/w ratio wouldn't be too terrible. In fact, I wanna go try it now

Nah. Those things don't even have enough power to slow down. You would need to use something with greater push. Unless you slow down an increadable amount before hand. One thing to consider would be to get an obit within Eve and refuel there. That way one can have more fuel as well as less need less to stop with.

[Sof]

You can reduce the delta-v needed with a slingshot off Eve.

All of my "successful" Moho missions have ended with a suicide burn and no chance of returning.

Also, in response to OP, I don't think that NASA or any other space agency has used aero-braking to get to Mars or any other planet. Mercury's lack of atmosphere isn't the obstacle.

[MalfunctionM1Ke]

Yeah, I know exactly what you mean.

I just made a Moho-Atempt to complete my Easter Egg Collection with the Moholes.

Moho is in fact not much bigger than the Mun bit it has 2,7m/s² Ground Acceleration that is pulling on you, what makes Moho like Duna without an atmosphere

It is not so hard to figure out the correct Burnwindow if you are already in Orbit and you want to land but it is quite hairraising when you are pummeling to the ground with 700m/s

Edited January 1, 2014 by MalfunctionM1Ke

[goldenpeach]

I have sent a rover to Moho some day in the past.

However, it had used almost entirely the fuel of the transfer stage and could only land near the equator(IIRC, I don,t want to try and discover that it can't after spending more than 20 minutes just for the circularization burn(not counting the transfer burn))!

[Spatzimaus]

Landing on Moho isn't too difficult. Its gravity is only 0.275g, less than twice that of Mun. The challenge is matching its orbit in the first place, given the small intercept window; if your ship doesn't have much thrust, such as an ion-powered ship, then you simply might not have enough time to do a full deceleration before leaving the sphere of influence.

Here's the thing that most people don't get, though. The amount of delta-V you spend to enter a circular orbit just inside a body's sphere of influence is just how much you'd have to spend matching its orbit outside that window. So you don't actually have to wait until the intercept to do your burns; if you were to put yourself into a circular orbit somewhere between Moho and Eve, and then set up the intercept from there, you won't have to do nearly as much thrusting inside the Moho sphere of influence and the delta-V cost difference will be negligible. Likewise, matching Moho's orbital inclination is best done out at your solar apoapsis, instead of waiting until you're inside Moho's intercept window (which'd be at your solar periapsis), and that can save you quite a bit of thrust.

Alternately, burn just before the window. If you see Moho is moving at X meters per second, and your speed is approaching Y as you near your solar periapsis, it's not too hard to figure out how long your burn will have to be and you know it'll be almost purely a periapsis burn. So, do as much of the thrusting as necessary just before entering Moho's sphere of influence, and just do the fine-tuning once you see the actual intercept.

[liweih]

Just landing is easy, no more difficult than landing on mun. It was the landing into Mohole that really killing me.

[MalfunctionM1Ke]

Just landing is easy, no more difficult than landing on mun. It was the landing into Mohole that really killing me.

I really would like to see a Picture of it

[Redshift OTF]

Here's the thing that most people don't get, though. The amount of delta-V you spend to enter a circular orbit just inside a body's sphere of influence is just how much you'd have to spend matching its orbit outside that window. So you don't actually have to wait until the intercept to do your burns; if you were to put yourself into a circular orbit somewhere between Moho and Eve, and then set up the intercept from there, you won't have to do nearly as much thrusting inside the Moho sphere of influence and the delta-V cost difference will be negligible.

Wow, I never thought of that. Thanks!

[A Fat Pokemon]

Heh, Moho was even harder to land on after its initial release, with that atmosphere that would overheat your engines if you had your thrust too high. Oh I miss that atmosphere

[flightmaster]

I managed to land a manned science mission on Moho but I had to send a refueler down to be able to get it back to Kerbin, that was an absolute nightmare given that my docking node was on the top of the ship. Without sounding too up-myself I managed to create quite a clever system to refuel, however it was only thanks to Mechjeb that I could fine tune my docking.

[LameLefty]

I've managed a crewed orbital mission but had to send a tanker to refuel and get home. Had that mission had a lander, I wouldn't have a had a problem. I've also sent a robotic probe lander but of course that wasn't intended to get home.

[viktorserecros]

I know it sounds weird, but I found landing on Moho easier than Duna. Now, of course, Duna is an easier intercept, but Duna was a harder landing because I kept wanting parachutes to do more work than possible. Moho's lack of atmosphere forced me to plan for every single m/s. What surprised me about my trip to Moho was pulling it off in career mode without mods (no mod parts, mechjeb, anything useful beyond mainsails and nukes...)

I haven't returned in .23 because I'm going through a "why is everything blowing up?" phase with rocket design.

[ComradeGoat]

Here's the thing that most people don't get, though. The amount of delta-V you spend to enter a circular orbit just inside a body's sphere of influence is just how much you'd have to spend matching its orbit outside that window. .

But if you want to enter low Moho orbit, you'll want to time your burn to happen at Moho periapsis to take advantage of the Oberth Effect. Entering orbit at the SOI is much more expensive.

[Kasuha]

But if you want to enter low Moho orbit, you'll want to time your burn to happen at Moho periapsis to take advantage of the Oberth Effect. Entering orbit at the SOI is much more expensive.

That's of course true, but Moho's Oberth effect is rather weak, much less than on Kerbin.

Also in all my Moho missions, I had to start the decelerating burn some three Moho diameters before the periapsis or I'd overshoot. If the Oberth effect is weak near the surface, it's almost negligible at that distance.

True, my ship did not have too much TWR.

[Felsmak]

Nah. Those things don't even have enough power to slow down. You would need to use something with greater push. Unless you slow down an increadable amount before hand. One thing to consider would be to get an obit within Eve and refuel there. That way one can have more fuel as well as less need less to stop with.

Actually, I did that once! It's certainly possible, but it should be noted that I first had to use most of my fuel for getting Moho to fling the probe into an orbit that would give it a cheaper, second encounter later.

Edited January 2, 2014 by Felsmak