I suck at landing on duna

[Rocketscience101]

After a long campaign, and several failed probes, I finally get the guts to launch a 3 manned interplanetary mission. It carries a lander, for 2 crew members, and a nuclear rocket engine, with enough science to bring home, it would probably get me enough to finish off the tech tree. But, as I set up for aerobraking. and then just as I enter Duna's sphere of influence, the Periaps changes. From 25 kilometers, to 300 kilometers. So I get ready for a long retrograde burn. I end up running out of fuel in the Crew/service module, and am forced to use the lander to finish. I then undock the lander, at which point I soon discovered that I had run out of monopropelant in both craft, which meant that docking was not an option again. So I went ahead with the landing. This was my first successful attempt at landing on the surface, everything went great, parachutes opened, gear down, coming straight down, then we hit the ground and the lander tipped over, and broke off the lander c4n, and docking port, only getting half the required science of the mission. So I stayed near kerbin for a while, and got 550 science in order to get the really big rocket parts. I then built a new rocket and tried again. This time still had some fuel left and plenty of monopropelant. But as I came down I tried my best to burn off as much speed as possible, but ended up coming in to step, going in a retrograde orbit. The two crew members survived, and the science from duna, was nearly useless since duna has no biomes. So in a last ditch effort to get some science, I took the little fuel and monopropellant and attempted to go to the north pole of the duna. I didn't make it and the single crew member in the capsule smashed into the surface while waiting for his parachute to fully deploy. Can anyone give me any tips on how to better complete this mission before I try again. I would like to have the crew return. Any advice would be helpful. Thank you very much. Have a nice day.

Signed,

Ben

[Awaras]

Switching SOI's under timewarp causes errors that alter your trajectory. Try to reduce warp as much as possible at the moment you switch SOI's.

Also, if your periapsis is too high, don't burn retrograde, but rather burn at a 90 degree angle in relation to your course to lower Pe...

Duna's atmosphere is very thin. If you want to aerobrake, you should aim at around 10-13 km Pe, depending on your speed, maybe even lower if you are coming in really fast.

Edited June 20, 2014 by Awaras

[KvickFlygarn87]

Get a delta V budget up, and add a very generous margin of error

[saabstory88]

Switching SOI's under warp causes errors that alter your trajectory. Try to reduce warp as much as possible at the moment you switch SOI's.

Also, if your periapsis is too high, don't burn retrograde, but rather burn at a 90 degree angle in relation to your course to lower Pe...

Firstly, this ^

Secondly, in your first attempt, what was your altitude when you slowed warp to observe the change in your Duna periapsis? It is likely that if you waited to change your periapsis until you were close, you could have wasted fuel. It is also worth noting that there are multiple ways of changing your trajectory when entering a sphere of influence. Burning to the Radial In vector will use far less fuel to change you periapsis than will a retrograde burn. Although it is worth noting, that it seems likely that if you changed your velocity by a simple retrograde burn, and you expended the fuel in your craft, you probably didn't have enough to return in that craft to begin with. EDIT: Previous poster edited before I hit send. This information is now redundant.

As far as your space navigation woes are concerned, I am assuming that you are not using any sort of Delta-V budget calculations, whether they be a mod, or manual calculations. I assume this because you have not made mention of any expected fuel expenditure at an earlier point in the mission, and felt until your unexpected trajectory, that everything was going to plan. As far as your landing is concerned, despite my best calculations, I can be pretty terrible at actually piloting landings, so I can not help you there.

As I am sure others will suggest, two mods that I have seen recommended, and use myself are Kerbal Alarm Clock, which can aid in SOI changes, among other things, and Kerbal Engineer, which will assist in planning your fuel and velocity requirements with reasonable accuracy. There is always something to be said for having a decent amount of fuel margin, especially if you have never done something before.

Cheers

Edited June 20, 2014 by saabstory88
Unintentional redundancy

[Eric S]

As for the parachute issue, Duna's atmosphere is kind of thin, so you'll want to make sure you land somewhere close to sea level. You may want to tweak the parachutes so that they fully open at a higher altitude (right click on the parachutes in the VAB to open their tweakable options).

Switching SOI's under timewarp causes errors that alter your trajectory. Try to reduce warp as much as possible at the moment you switch SOI's.

All good advice, but just to clarify, you want to cross SoIs at low or no time warp, so you want to do this just before the SoI switch, don't try to turn down your warp in reaction to crossing SoIs.

[Pecan]

Leave the science stuff at home, design and build small and have fun practicing; or go the whole hog and just practice in sandbox. With smaller and simpler vehicles your missions should be easier, you'll boost your confidence along with your experience by gaining successes, even if they are lesser ones. THEN start to build-up - landing separate modules, assembling in space/on the ground, etc. In any case the whole career mode is getting such a big redesign in 0.24 it's not worth putting much effort into mastering it in its current form.

[weezl]

Get a delta V budget up, and add a very generous margin of error

^^ what he said..

PLUS: once you have your delta V budget.. build out your manned rocket as you would normally.. but put a probe core on it and launch it UNMANNED. The purpose of the mission is to test your assumptions to make sure your delta V budget is actually true or not, with actual live hardware you will eventually launch manned. This maps to real life, where all the space missions run with humans were in some way run non-manned so as to not risk people's lives while you are figuring out if your calculations are correct.

[Claw]

I second just about everything that's been posted. Also realoze that it takes a lot more parachute than on Kerbin. So test your design and if it's barely making it on Kerbin, it is'nt going to survive Duna.

Also...

...I then undock the lander, at which point I soon discovered that I had run out of monopropelant in both craft, which meant that docking was not an option again. ...

Practice docking without monopro. You'd be surprised at how easy it can be with practice and small ships. Your docking skills get a lot better, it makes docking with RCS a breeze, and can save you in a pinch.

[Eric S]

This maps to real life, where all the space missions run with humans were in some way run non-manned so as to not risk people's lives while you are figuring out if your calculations are correct.

[Rocketscience101]

Thank you all for your tips, thanks to them I added more fuel to the Crew Service Module, and less to the lander. I was able to land at the southern pole of Duna, and gather Ike far orbit science. Sadly in my shock of the success of the mission, it wasn't until I was in Ike's Soi that I discovered I forgot all the Duna surface science on the lander. Was still able to get 577 science off the mission.

[rennsport27]

All I can say is keep at it. It's a big step at first, so it's natural you're going to struggle. There's a lot of good advice here already, so I'll try not to repeat what's already been said. It might help to do a sandbox run, and enable infinite fuel/RCS when necessary, just so you can run through the motions, and take note of how much you missed by. That helped me a bit when starting interplanetary missions.

Edit: Congrats! This is what I get I guess when I type a response, forget to hit enter, and then come back several hours later.

[TMS]

You can actually go at 50x timewarp over an SOI boundary. Anything above that is where the errors get magnified.

[Eric S]

You can actually go at 50x timewarp over an SOI boundary. Anything above that is where the errors get magnified.

I think it would be more correct to say that the errors are more noticeable at higher warp. I've had "perfect" periapsis messed by accidentally warping through SoIs at x10, requiring a slight correction after the transition. High warp crossings can be so effected that the craft doesn't have enough delta-v to make the correction. I think this is because at higher warp, you move farther into the new SoI in a single tick.

[Claw]

I think this is because at higher warp, you move farther into the new SoI in a single tick.

Yep.

I usually cross at 50x and always need a correction. If things are already tight, I will definitely slow down to 10x or even 1x to minimize the transition errors.

[Kryxal]

That's one of the great things about KAC (besides saving your nodes or your target ... you can exit time warp (physical warp too) at say 2 minutes from projected SoI change and hop to the corresponding vessel. Feel free to set your warp to 10000x, it will make it so you're slowed right down again when you have to be!

[Zylark]

I take a three step procedure to get to other planets.

- Initial burn from Kerbin, any projected encounter within a few million km of the target planet is good enough.

- Adjustment burn to bring the target planet within a few hundred km encounter when in Solar (Kerbol) SOI, preferably at a descent/ascent point to also get in the exact same plane as the target.

- When at the outer edge of the target planets SOI, another adjustment burn to either bring PE down to my wanted orbit or do aerobraking. Also, about half the time, to change from a projected retrograde orbit to a prograde orbit. Doesn't cost that much dV when far out.

Oh, and I totally over-engineer my spacecraft so that the risk of running out of fuel is pretty slim.

[James_Eh]

Not a single commenter here has mentioned that they suck at landing at Duna because Ike always gets in the way. So I will.

I am GREAT at landing on Ike. Duna? Never heard of it. (I hate that Roche-limit-ignoring jerk Ike.)

[cantab]

Sounds like you got things sussed! But some tips:

You can make a radial and/or normal burn just after entering the SOI of your destination to refine or correct your periapsis. It typically won't take much to put things right if you've suffered some orbit shift on the SOI transition.

You can dock on main engines, though it's not easy and having done it once it's not something I'd choose to do again.

For landing on Duna, parachutes alone generally aren't sufficient. The safe way is to use rocket thrust for the final touchdown. Riskier alternatives include lithobraking on cubic octagonal struts or similar, or using the Kerbin Cup footballs as airbags.