Mun Landing Issue

[Steve Fink]

I have delivered 4 vehicles to Mun now, and my delivery system is in good shape. However, I have only put one Kerman boot on the surface and it wasnt pretty. The others landers succumbed to a strange anomaly (died a fiery death) as I get close to the surface. I am able to slow my craft on decent to 0 K/M s as long as I am a few hundred meters from the surface. But the closer I get, and the slower I get, the nose will tip over uncontrollably and I am unable to descend level. The behavior kicks in at less than 20 k/m s and gets worse the closer to the surface I get.

I have seen some issues with some landers on youTube that might get this behavior with an unbalanced lander (top heavy). I assure you I have brought very simple landers in that look very much like every other lander I see on the web stick their landings with no mention of this issue I am having. BTW, SAS (updated: not SAS, but Mechjeb, and that is the problem) and light RCS cant over come it either.

My newest lander has additional RCS added. I have yet to test it, but believe there is something else at play here.

Anyone?

Edited September 26, 2012 by Steve Fink

[LongHairedHuman]

By any chance, do you have MechJeb, and set it to RetroGrade? If yes, try and use ASAS and just point it up, to the middle of the blue part on your Nav-ball.

[Aphox]

By any chance, do you have MechJeb, and set it to RetroGrade? If yes, try and use ASAS and just point it up, to the middle of the blue part on your Nav-ball.

My brain was upside down until I thought of this. Locking MechJeb on retro will mess you up, because once you start to lift, the retro spins to the other side of the navball. Make sure you turn that off so it doesn't spin you about.

And a top heavy lander wouldn't have problems since the gravity on Mun is too low to affect it. Landing might tip you over, but gravity certainly won't cause you to tip.

If you aren't using MechJeb, would you mind uploading your .craft for your lander for testing?

[Steve Fink]

Yes, Mechjeb engaged in retrograde during landing. That must be it. My first and only actual landing did not have mechjeb (yet I dumped my lander on its side upon impact and survived :-) )

SO ya, I will disengage mechjeb, tonight!

Although I will add that in retro I am still in "reverse" when this issue hits and understand your point. But even though my direction is truly retro, just very slowly, do you think this is a mechjeb bug?

AND THANKS FOR REPLYING!

Edited September 26, 2012 by Steve Fink

[Tauge]

Yes, Mechjeb engaged in retrograde during landing. That must be it. My first and only actual landing did not have mechjeb (yet I dumped my lander on its side upon impact and survived :-) )

SO ya, I will disengage mechjeb, tonight!

Although I will add that in retro I am still in "reverse" when this issue hits and understand your point. But even though my direction is truly retro, just very slowly, do you think this is a mechjeb bug?

AND THANKS FOR REPLYING!

It's not really a bug per se. What happens is that as you approach 0 and beginning to move away from the surface the retrograde point on the navball will move. Mechjeb will then chase the point and your lander will go....everywhere. Using Mechjeb to keep you retrograde is fine, typically I turn it off and switch to SAS around 50-100m, especially if my horizontal speed is fairly low.

[Steve Fink]

Yep Tauge, after posting that reply I ran it through my little head and figured out that the orbital path would be changing dramatically as I slowed down and got closer to the surface with horizontal velocity etc. It all makes PERFECT sense. But I had to run off to work and could not update the post (until I got here, muuwahahaaa)

For anyone else reading this and wondering why I dont just switch to MechJeb auto land: Cause I am new and want to learn the dynamics of landing first before I let the computer take over, but eventually will, just as I have with take off and orbit.

[Kosmo-not]

For anyone else reading this and wondering why I dont just switch to MechJeb auto land: Cause I am new and want to learn the dynamics of landing first before I let the computer take over, but eventually will, just as I have with take off and orbit.

I wouldn't use mechjeb's landing autopilot even with all the experience I have. It's very inefficient and/or crashes the ship most of the time. Thus, I do all my landings manually. It's fun to do the landings manually anyway.

[RoboRay]

For anyone else reading this and wondering why I dont just switch to MechJeb auto land: Cause I am new and want to learn the dynamics of landing first before I let the computer take over, but eventually will, just as I have with take off and orbit.

Good for you. Just say "no" to MechJeb autopilots, at least until you are fully satisfied in your ability to do things yourself. Use the pointing tools and translation tools if you want, because they are really helpful and you do need to understand what you're doing to use them, but don't use MJ as a crutch.

[Steve Fink]

Right on, one step at a time is my point.

And MechJeb use is not easy to understand (unless you are already a rocket scientist) until you understand the issues involved. Also, I like to built my rockets so that they will always perform well enough to be steered manually. Then I know they will fly awesome when on autopilot.

I am in this "game" 99% for the simulation aspect. (the remaining 1% is to save the Kerbal's )

[Steve Fink]

Good for you. Just say "no" to MechJeb autopilots, at least until you are fully satisfied in your ability to do things yourself. Use the pointing tools and translation tools if you want, because they are really helpful and you do need to understand what you're doing to use them, but don't use MJ as a crutch.

I have yet to use the landing AP, but I think once I use it, I may agree with you. Landings are fun. Neil did by hand. :-)