MechJeb - Landing Autopilot way off target

[CaptainPanda]

Hey, all, I'm having a problem with MechJeb's Landing Autopilot. I was trying to land at the Neil Armstrong memorial on the Mun. Starting from a 25km circular orbit, I opened up MechJeb, picked 'Enter Target Coordinates,' and input 0 Deg 42' 6" N, 22 Deg 44' 45" E. It did a Low Orbit Plane Change burn to bring the orbit in line with the target, which was perfect. The Deorbit burn seemed to be successful, but the Braking burn was sputtering and jittery, and the final landing site was 130 km east of the target coordinates.

Has anyone else had any issues like this, or might know how to fix it?

[MoarBoostersRUS]

Yea it doesn't work worth a damn for anyone sorry. There are mods that help with figuring out decent paths but all have their problems. I suggest learning how to set up landings yourself. Took me awhile to learn but it's actually pretty easy once you get the hang of it.

[CaptainPanda]

5 minutes ago, MoarBoostersRUS said:

Yea it doesn't work worth a damn for anyone sorry. There are mods that help with figuring out decent paths but all have their problems. I suggest learning how to set up landings yourself. Took me awhile to learn but it's actually pretty easy once you get the hang of it.

It didn't used to be this bad. Ever since I switched over to the latest release, things have started going wonky.

[MoarBoostersRUS]

I haven't use it since .9 it wasn't horrible but when trying to build surface bases you need to land on target. But if your going for basic landings get Kerbal engineer and it will display vertical and horizontal speed. Get a tight orbit as low as you can then kill all your horizontal velocity asap then you just drop down to the surface and kill what little vertical velocity you got and boom you landed.  

With landing near a target it is the same just have your orbit pass over the target.

Edited October 20, 2017 by MoarBoostersRUS

[lodestar]

The "Land at target" seems to be broken.  What I usually do is:

1. Pick the target

2. Enable the "Land at target"

3. Let it run the deorbit burn and wait until it goes into warp or goes jittery.

4. If there's no atmosphere and you have TWR>2, at this point you can just disable the "Land at target", enable the "Land at somewhere" and it should get you very close to the desired location.

5. If there's an atmosphere, or you have low TWR, disable the "Land at target" and set Smart A.S.S. to SVEL-. Every few seconds, enable the "Land at target" function again and check if it's in the braking phase, with a target speed. If it is, let it run. If not, disable, wait and try again.

 

I just landed a dozen containers on Duna within a 100m radius using this method.

[DaMaster_Architect]

As an alternative, the TCA mod has a very accurate landing mode. It allows you to select a target, or set a waypoint, and TCA will perform a pinpoint landing on that location. If there's something in the way, TCA will even perform an evasive maneuver, to avoid hitting the object! It then lands right next to the object, instead of on top of it. 

Using TCA, I usually perform landings with sub-meter accuracy. I've built some dropships that take pieces of my base to the Mun, and using TCA I can drop these pieces exactly where I want them.

Link to forum topic of TCA:

https://forum.kerbalspaceprogram.com/index.php?/topic/97154-13-throttle-controlled-avionics/

Edited October 20, 2017 by DaMaster_Architect

[Eric S]

On my last career save, I had no problems with MechJeb's "land at target."  This time?  I've had it try to land me consistently almost half a world away, even when I use "pick a spot on the map" rather than entering lat/lon.  Hmmm... I should try it again, to see if it puts the red target crosshairs in the right place or the wrong place.

 

[drlunar]

I'm finding the same kind of problems, the landing site MechJeb aims for is 180 degrees out.

I suspect a typo has introduced a + or - the wrong way round, or a π where there should be 2π (or visa versa)

If I find the time I'll have to go hunting in the source code (reaching for my old orbital track equations and notes)

:sigh:

 

[AgincourtDB]

On 10/19/2017 at 8:55 PM, MoarBoostersRUS said:

I haven't use it since .9 it wasn't horrible but when trying to build surface bases you need to land on target. But if your going for basic landings get Kerbal engineer and it will display vertical and horizontal speed. Get a tight orbit as low as you can then kill all your horizontal velocity asap then you just drop down to the surface and kill what little vertical velocity you got and boom you landed.  

With landing near a target it is the same just have your orbit pass over the target.

MJ's 'Surface Info' tab will also give you your horizontal speed, I have that tab open always while landing manually.

[taiwanluthiers]

On 10/20/2017 at 8:43 AM, MoarBoostersRUS said:

Yea it doesn't work worth a damn for anyone sorry. There are mods that help with figuring out decent paths but all have their problems. I suggest learning how to set up landings yourself. Took me awhile to learn but it's actually pretty easy once you get the hang of it.

I don't even use landing function with MechJeb anymore. If I use it, it will modify your orbit to intercept the landing site but it will then do a burn to crash (and I do mean crash) right into the landing site, without any braking burn at all! It assumes every planet you want to land on has an atmosphere.

And for planets with an atmosphere where you can aerobrake, it does not deploy the parachute either.

Basically if you use it and leave it alone, you will find your ship destroyed.

They're great for lining your ship's orbit with your landing site, and if your landing planet has a thick atmosphere, it will guide you to it, accounting for atmospheric braking. So just move the red thing over your landing site. Then arm your chute and wait.

If it's power landing in a planet with low atmosphere (like Mars), or the moon, then fly over the landing site at speed and then brake right over it, then power land slowly until you hit your site.

Edited October 11, 2020 by taiwanluthiers