The hardest thing in KSP for me is....

[RickRastardly]

Not building SSTO's.

It's like an addiction. My Mun lander was carried into Munar orbit by an SSTO.

This!

After building a few SSTOs, going back to using normal rockets seems like a huge waste of resources but unfortunately I'm not quite good enough yet to get significant payloads into space using an SSTOs. for me getting an SSTO into orbit manned by 3 Kerbals was a huge achievement.

[Tw1]

Deciding whether to go ahead with a mission, or wait until the next patch, as it looks like might have science parts! I could bring back a sample from the bottom of the mohole! If I wait ages...

[Spartwo]

horizontal SSTOs.I just can't do it Single Stage rockets on the other hand..

[spacelemming]

Landing I can do fine, it's one of the easy things for me.

Landing within a km of a target, however, now that's difficult.

Other than that, building good SSTO spaceplanes. I have designed two that can actually get into orbit, however the second one ran out of rocket fuel and had to resort to it's RCS.

[SpaceSphereOfDeath]

My hardest thing would be a space shuttle

Damn unintended torque

[TYRT]

Rendezvous and docking

[wulf899]

Interplanetary travel - I've only successfully done so Twice.

[Galacticruler]

Docking...and launching anything above 150 parts. It just ends in a mess.

[Dangerous_Beans]

my biggest problem is remembering to keep things simple and to specialise.

for instance: i spent ages trying to design a system that could land 4-6 expansion arms for my Mun base on the Mun. every attempt failed, and i just couldn't get it.

so i sent them up one at a time, and used a light duty tug to land them. much easier, more effective, and i have realised that i don't need 6 of the expansion arms anyway.

[cesarcurado]

Landing precisely when you aim your landing from orbit.

Rendezvous turned out to be pretty easy once I did it for the first time, same for interplanetary travel.

Let's say you have a moon base near a certain crater, you want to land nearby, say, less than 50 meters or so from it, I can't do that.

[SkyRender]

Waiting for interplanetary launch windows. The X series has rather spoiled me on having tons of stuff perpetually at your disposal to do in space, in all its unrealistic "space is an ocean" glory. No wonder I was drawn to Kethane so readily...

[Kerbol Prime]

Powered landings...I usually slam into the ground at 200 m/s.

[Aragosnat]

Eve landing and returning with a 3 man capsule and 5 tons/units of dead weight for when the Science bits of 0.22 come out. I know they might be lighter. Just have a ball park figure so I know I have enough spare fuel. Still need to doa return from it with a probe. Broke down and got Engineer Redit thingy. So I can have a better feel of the DeltaVs I have.

[shoveycat]

Transfer burns, the bane of my existence

[thrashing mad]

Returning from the surface of Eve.

[NoMrBond]

Finishing a mission;

I'll frequently get a mission planned, ship/s built and have the whole thing underway then spot one tiny flaw that essentially immaterial and/or can be worked around but I'll end up scrapping the whole thing, rebuilding the ships/payloads and launch everything from scratch all over again, cycling ad infinitum

I've had one Jool moons exploration mission that's been this way for two real months now

[RSwordsman]

SSTO spaceplanes. I haven't experimented much with them, but flying one with FAR is beyond the scope of my abilities. While my space travel is usually pretty meticulously calculated, I do my atmospheric flying mostly by the seat of my pants. With the precision needed in the relationship between SSTO engineering and flight profile, I just haven't had much luck. I usually just go as high and as fast as I can until I get an engine flameout, at which my plane becomes locked in a curiously impossible to fix flatspin.

All it would take is a little documentation, but I usually just put more effort towards conventional staged rockets. With my first station in orbit though, it's time I invested in planes a bit more.

[CoriW]

Well for me I'd have to say spaceplanes, and the only reason is because I've never really tried them. Give me a decent rocket design and I can fly pretty much any mission you give me.

[Flixxbeatz]

SSTOs and Spaceplanes also.

Kinda shameful since I've been here for quite a long time now but haven't flown a Spaceplane into orbit and back successfully.

(inb4 people who will say sstos and spaceplanes are too damn easy)

[RSwordsman]

(inb4 people who will say sstos and spaceplanes are too damn easy)

IDK, I haven't seen any braggarts on here yet. All but the steeliest KSP players have some element of the game that's beyond them. Not to mention if you are putting somebody down for not being able to build something that real-life NASA hasn't figured out for earth, I don't think it's that big an insult anyway XD.

[SkyHook]

I would say that building very large cargo planes has been the bane of my existence since forever! There is something about their size and necessity to be able to carry cargo that dooms me. That, and returning from orbit and landing at KSC with my shuttles. I have been working on a foolproof deorbit procedure for weeks..

[Merinsan]

Getting space planes into orbit. I seem to constantly mess up the ascent and run out of rocket fuel before getting an orbit.

[el_coyoto]

Landing a plane on a runway!

I think I'm quite good with rockets : I can casually rendez-vous, dock, de-orbit a lander spot on KSC, use gravity assists, do interplanetary transfers and all. Not a sweat.

But, while I am still improving my plane engineering and piloting, trying to land a plane on the runway rather than on the first flat spot I can find is still an intense experience for me and my Kerbals, especially the approach and alignment with the runway.

On the other hand, I totally grokked how spaceplanes ascent profile work. So I can easily put a spaceplane in orbit, but I'm still a bit concerned when I have to get it back to KSC...

I think I should look for some kind of ILS mod or see if the MJ "Spaceplane guidance" gives good results... (I've also seen a nice PAPI lights addon somewhere)

Edited September 17, 2013 by el_coyoto

[Hixar]

Trying to land on a docking platform on the mun, really tough.

[KerbMav]

Trying to pick up a rover on Mun with a skycrane ... that said, pinpoint landing in general.