How to land on precisely on atmospheric planets?!

[MrPopcup]

Hi guys, so yesterday I planned on getting a storage module with big solar panels and landing legs, scientific stuff and ladders with parachutes ( load of them.. ) to laythe, all of this weighted about 6 tons, but the problem is not getting it to laythe.. the Problem is LANDING on laythe, in a previous mission I landed a rover there, using skycrane but with parachutes, then before touchdown startup the rockets and land the rover softly, It was success ( though i broke one wheel, but I sent a manned capsule there and it was solved. ) the problem is I want everything to be near other modules, because I'm making a base, and as we all know laythe is hard to land with these little islands ;(. I sent that storage module and then prepared for re-entry and you know the arch keeps shrinking cause of the atmosphere and that makes me land near the sea or very far.

so, How To Land PRECISELY on atmospheric planets? ( ~4km from target )

EDIT: Answered! thanks for everyone!

Edited August 1, 2013 by MrPopcup

[Tiron]

You need to accurately predict the effect of the atmosphere on where you'll end up. Mechjeb's landing module can do that (even for manual landings), and I think I saw a posting in addons the other day where a guy posted a calculator for aerobraking or something? Maybe it does landings too. Forget what it's called, because I've been using Mechjeb's landing and aerobraking prediction for so long I didn't look that closely at it. Sorry. :|

Edit: Okay, it's an out-of-game calculator for aerobraking only.

That leaves you with only Mechjeb that can accurately predict landing sites through atmosphere, so far as I'm aware.

Edited August 1, 2013 by Tiron

[MrPopcup]

Thanks Tiron! But I'm playing a vanilla KSP now , which makes it 10x harder ;D! ( doing it the manley way, they said.. )

but yeah, thanks for your help! I'll wait for other answers!

[Synapse]

I know that it depends on the mass of the thing landing. I was trying to land small probes on the North and South Pole of Kerbin and they kept getting blown too far away. Turned out that detaching the rocket early meant my tiny probe wasn't dragged that far off course. The rest is down to guess work.

I guess you could use an engine to exactly counteract the effects of drag by thrusting forward.

[Tiron]

Thanks Tiron! But I'm playing a vanilla KSP now , which makes it 10x harder ;D! ( doing it the manley way, they said.. )

but yeah, thanks for your help! I'll wait for other answers!

I'll try to remember to check in, I'd love to find out another mod that can do that, but I've never so much as heard of one. There's at least one other thing out there that can provide the same Information Mechjeb does for most things, except that. So far as I know it's unique in the 're-entry simulation' department.

If you want to do it manually, the thing you have to remember is that the atmospheric drag is going to make you land short of (But in line with) where the initial orbital estimate shows it at. The thing to remember there is that the atmospheric density increases exponentially as you descend. Laythe's atmosphere is aproximately 80% as thick as Kerbin's at Sea Level, and has a lower scale height, so it's going to be even more bottom-loaded than Kerbin is.

The gravity is lower too, though, by a similar factor, and I'm not sure what that's going to do to the final Descent speed. There'll be less drag, but also less gravity.

But the key thing is, you'll lose most of your speed when you hit the lower atmosphere, so for precision you want to avoid having a shallow trajectory coming in, or you'll lose so much speed to drag that you'll end up WAY short of where it originally said you'd land.

Coming in fairly steep might help. Less horizontal velocity to lose in the first place would reduce the deviation from the initial predictions. It also means a lot more G-Forces though, as you'll descend more quickly and thus the drag will ramp up faster without much change to lose speed to it.

I'm not very good at targeting an area manually myself so...take my BSing with a big grain of salt.

[Synapse]

Yeah you could cut all horizontal velocity in space and just drop down on your target...

[annallia]

One thing that always helps me with manual landings putting them on point is starting from a very high orbit (the higher the better).

This will use a lot of fuel, and I really mean a lot of fuel which isn't a problem for me since I over engineer everything anyway.

Next step is to get your orbits inclination to cross directly over your landing site. Once done select your target on the ground (assuming you have a craft/flag down there already)

Now pick the spot directly over your site and plan a maneuver, you are basically going to be flipping your ship around and doing a breaking burn until you more or less come to a dead stop letting gravity bring you down. I then use the map view to make course corrections until I enter atmo, at that point I use the gimbal to navigate with an overhead view keeping myself as close to directly above myself as I can get.

Rest is all standard landing, deploy chutes, series of small breaking burns before the suicide burn and so on.

Laythe has always been somewhat tough to do this (perhaps because of rotation speed?) but I have managed to average less than 70m from my target doing this. Longest being just shy of a km, shortest breaking the solar panels of the habitat module I had dropped earlier...

Edited August 1, 2013 by annallia

[blizzy78]

Atmospheric Landing Chart: Pinpoint landings on Duna, Eve, Kerbin, Laythe!

[GeneralDisorder]

If you play vanilla, the only option available to you is the maneuver node system. You can use it to get an initial fix on your landing site, though you have to compensate for atmospheric drag and a little for rotation of the planet. I tend to be in the map view a lot while landing and using the navball to adjust my course until I'm really close to the surface (and if all went well, the target). It takes some practice runs to accurately judge the amount you need to compensate and correct, but quicksave and quickload are your friends ;-)

[MrPopcup]

@ blizzy78 - wow! that's what I wanted! I successfully landed near my base ( 2 km further ) but hey! best than ever! thanks everyone! Much appreciated! love you guys , love this forum!

MUCH THANKS!

[Tiron]

@ blizzy78 - wow! that's what I wanted! I successfully landed near my base ( 2 km further ) but hey! best than ever! thanks everyone! Much appreciated! love you guys , love this forum!

MUCH THANKS!

Agreedo. I totally book marked that thing. That's awesome.

You should edit the first post to say 'answered, too