[PART, 1.0.2] Anatid Robotics / MuMech - MechJeb - Autopilot - Historical thread

[LameLefty]

You don't need a feel for it. It took me literally 5 seconds with a calculator, the math is dead simple.

Yeah, and you also need to know the diameter of every celestial body.

And I spent plenty of time with a calculator as a engineer, thanks. A user- defined offset is a much more user-friendly and functionally "realistic" way to implement a landing auto-pilot.

[sonicsst]

Post Deleted

Edited March 6, 2014 by sonicsst

[sonicsst]

Post Deleted

Edited March 6, 2014 by sonicsst

[LameLefty]

KSP is a game about engineering. Would you like MechJeb to build your ships too?

If you aren't willing to spend a minute looking up Mun's radius or the height of Eve's atmosphere or the gravity of Val I dont know how you even play the game.

Smug much? Talk to me again after you've designed real spacecraft systems for a living (here's a clue: I have, and it's hard).

If I want to go to the trouble of rescuing a stranded mission or resupplying a base I've built, I want to be able to land somewhere close without being right on top of my target. This is not a complicated or hard to understand feature request. If Sarbian or codepoet or anyone else on the MJ team thinks it's acceptable and do-able, yay for me. If not, not. But either way, I don't tell you how to play your game.

There's a lesson for you there.

[sonicsst]

Smug much? Talk to me again after you've designed real spacecraft systems for a living (here's a clue: I have, and it's hard).

...

There's a lesson for you there.

Talk about smug. You think it's a good idea, I don't.

[LameLefty]

Talk about smug.

Just giving you perspective since you seem to doubt my madd calculator skillz there, ace.

You think it's a good idea, I don't.

Then say so and why (which you did, so far so good) Just don't act like a condescending twit when someone requests a feature you wouldn't use. For that matter, I don't generally use MJ at all in a new Career save until after I've unlocked nearly all its functionality and I still do an awful lot manually because I enjoy it. But I won't criticize someone or question "how they can even play this game" if they do it differently than I choose to do it.

[sonicsst]

Post Deleted

Edited March 6, 2014 by sonicsst

[sarbian]

Behave children

[labtopia]

i also think it would be nice to have an easy 'offset to target' in the landing guidance module for the same reasons, it's so accurate it will land you ontop of your target. right now i just + or - a little in the landing coordinates.

[reschke]

OK back on topic here has anyone had any issues with a recent devbuild of MJ behaving weirdly?

[Djolox]

Please don't delete this post:i don't have github profile so i can't post issue there.

Mechjeb is Raging with RCS he is constantly burning to the node he need to align with and when he pass the node he is slowing down

So its an endless process of burning right than left than right than left. And he is using only full power thrust.

He is commonly spinning around and resetting Burn nodes.

Totally useless and uncontrollable.

[sojourner]

^Which build are you using?

[Galane]

i also think it would be nice to have an easy 'offset to target' in the landing guidance module for the same reasons, it's so accurate it will land you ontop of your target. right now i just + or - a little in the landing coordinates.

Instead of a landing ellipse you want a landing doughnut, with the target dead center in the hole. Land anywhere in the doughnut, except right in the middle.

IIRC this landing was in .21 with the then release version of MechJeb. No damage, but it flipped on it side when driving it off. Used RCS to flip it back.

Various dev builds have had varying degrees of landing accuracy, with some missing targets by up to several KM on Mun. (I'll add the Duna stuff to my ribbon, when the mission makes a safe return, in 120-ish days.)

Edited January 14, 2014 by Galane

[Djolox]

^Which build are you using?

I'm using 2.1.1

And the same is happening in dev-b 167

[labtopia]

OK back on topic here has anyone had any issues with a recent devbuild of MJ behaving weirdly?

i was having a problem with it landing large crafts on the mun, it wouldnt burn in the last 1000meters like it didnt know the correct altitude- i had hit LAND AT TARGET under 100k (i remember a post about you had to do that to get the right altitude.)

[codepoet]

Exactly! It IS a compliment. Landing has gotten really good lately!

For a lot of us, if not returning to KSC or picking a target in the middle of a crater or whatnot, we like to try to land near a prior mission for role-play purposes. Perhaps at a base or to rescue a prior mission. MJ lets us target a flag or the lander for the earlier mission but often, especially on vacuum bodies, it will land right on top of the target. As I posted this morning, the accuracy is phenomenal but dangerous to both crafts in this kind of circumstance. If the KSP Map view let us zoom in much more closely, we could use the "Pick a Target on the Map" feature in MJ's Landing Guidance to get close but not on top of the target. Since we cannot do that, on option to land short or long or even laterally offset by some distance would give us a workaround, as well as just being a great addition.

Functionally you could get the same functionality by entering lat/lon coordinates if you had a good feel for how much distance is represented by an arcsecond is on every celestial body, but since most of us don't, an offset distance would offer this ability, and more functionally for most players as well.

Well I think this is quite a good idea, and something I would probably use in my own game play. I have a few thoughts for how it could be implimented, so I plan to do this in a fork of the code. It is up to others to decide whether or not such changes are to be pulled back into the "official" dev branch though.

[Demon_82]

Those who think MechJeb is too good at landing, have your tried to do as I do? I mean, it's not that hard to instead of selecting the previously landed ship, to give it manually the landing coordinates, introducing yourself an small offset. It works wonders, and you only spend like 10 seconds more.

[Ringkeeper]

Those who think MechJeb is too good at landing, have your tried to do as I do? I mean, it's not that hard to instead of selecting the previously landed ship, to give it manually the landing coordinates, introducing yourself an small offset. It works wonders, and you only spend like 10 seconds more.

Instead of manuell coordinats you can also do the "trick" i use (found it some time ago in another thread):

-As you cant choose something specific (if you have multiple vehicles/buildings/whatever) on the surface , take what ever the game lets you target at your landing place.

-Start landing

-When your ship is closer then 2.3km you mostly can choose every target at your landing place.

- Target now the FLAG that you have planted on the landing spot before

- MJ will change now the course to the flag. In 95% of all cases so far it landed within 1-10m of the flag.

Even if MJ lands directly on the flag and the flag gets destroyed by the engines (very unlikly) , just plant a new one.

[federicoaa]

What I do is to select the objective and land, and then use RCS to offset a couple of meters after the suicidal burn

[Neutrinovore]

Hmm. I must be doing something wrong. A lot of people are talking about how freakishly accurate the landing autopilot is, that they have to deliberately create some offset, or take manual control, in order to avoid landing right on top of the flag or object that they've targeted for landing. The only thing I have to do to avoid landing on a specific spot or object is to target that spot and select 'land at target'.

MechJeb has NEVER landed me closer than 30 meters from the target, and on the few occasions when it did get that close I'm pretty sure it was an accident. When I'm in orbit and select 'land at target', MJ does the de-orbit burn, but stops trying to make corrections as soon as the predicted landing site is within 150 meters of the target, and it generally doesn't even attempt to make any corrections at all after that unless the prediction gets farther away than 500 meters or so.

This isn't really a big deal to me, I don't mind taking manual control if necessary, it's just annoying to see you guys talking about being able to have MJ land your ship right on the VAB helipad or on the launch pad without any trouble, that's all.

Anyway, my $0.02. Later.

[codepoet]

Hmm. I must be doing something wrong. A lot of people are talking about how freakishly accurate the landing autopilot is, that they have to deliberately create some offset, or take manual control, in order to avoid landing right on top of the flag or object that they've targeted for landing. The only thing I have to do to avoid landing on a specific spot or object is to target that spot and select 'land at target'.

MechJeb has NEVER landed me closer than 30 meters from the target, and on the few occasions when it did get that close I'm pretty sure it was an accident. When I'm in orbit and select 'land at target', MJ does the de-orbit burn, but stops trying to make corrections as soon as the predicted landing site is within 150 meters of the target, and it generally doesn't even attempt to make any corrections at all after that unless the prediction gets farther away than 500 meters or so.

This isn't really a big deal to me, I don't mind taking manual control if necessary, it's just annoying to see you guys talking about being able to have MJ land your ship right on the VAB helipad or on the launch pad without any trouble, that's all.

Anyway, my $0.02. Later.

You are pretty much bang on the money with most of what you say, but there is more to it that that:

After the de-orbit burn, the landing autopilot will course correct until the landing prediction is within 150m (as you observed). After this it will not course correct unless the error grows to more than 600m (almost what you observed). At this point the craft will cruise until either a deceleration burn occurs (for bodies with no atmosphere) or the parachutes are deployed (bodies with an atmosphere). The the case of a deceleration burn MJ can control the overshoot / undershoot by burning more/less than it anticipated it would have to. For parachutes it can contol the overshoot/undershoot by timing when to activate the chutes. The deceleration burn seems to be more accurate, but timing the parachutes works well on bodies with thick atmosheres in flat areas. Timing parachutes around hills is hard as the AGL triggers the full deploy.

It would be interesting to know if your landings were:

1) on a body with or without an atmosphere

2) whether or not you are using parachutes

3) if you are landing on a body with a thick atmosphere (ie not Duna)

4) if you were landing in a hilly area, or a landing site near a slope, or an approach path the pases over a slope.

5) if the landing error was an overshoot/undershoot error or if you landed to the side of the target.

[LameLefty]

Note: I had targeted the flag ("Southwest Crater" on the Mün) in order to rescue Buzz Kerman, whom I had accidentally left standing at attention when his partner took off for home. Buzz is about 1.5 meters closer than the flag; you can see his helmet there close to the target marker. I only missed him by this much because I realized I was about to crush Buzz and aborted the auto-landing and did it manually. As you can see, I also forgot to deploy the landing gear. D'oh!

[crazyewok]

I have my Mec jeb working. About 12K up as it starts it gravity turn it seems to to a complete vertical 360 before setting in on its course. Whats the issue?

[DerekL1963]

Hmm. I must be doing something wrong. A lot of people are talking about how freakishly accurate the landing autopilot is, that they have to deliberately create some offset, or take manual control, in order to avoid landing right on top of the flag or object that they've targeted for landing. The only thing I have to do to avoid landing on a specific spot or object is to target that spot and select 'land at target'.

You and me both...

And to answer Codepoets's questions;

It would be interesting to know if your landings were:

1) on a body with or without an atmosphere

2) whether or not you are using parachutes

3) if you are landing on a body with a thick atmosphere (ie not Duna)

4) if you were landing in a hilly area, or a landing site near a slope, or an approach path the pases over a slope.

5) if the landing error was an overshoot/undershoot error or if you landed to the side of the target.

The answer is "yes". I've tried a variety of scenarios, and I find it impossible to predict when MJ will land right on target, and when it will land somewhere completely unrelated.

[BARCLONE]

Sarbian or Codepoet --

I'm using dev167...

Minor technical issues to ask about. I'm experiencing a lot of nav ball target reticle jittering as a burn reaches the end, usually in the last 0.5 m/s. In the last 0.2 m/s of the burn, the reticle begins moving off-center (still shaking like a hairless dog) and the ship dutifully tries to follow it around. The other issue is when I'm closing in on a rendezvous target and switch to the docking autopilot, I cannot do a "control from here" when right-clicking the docking port, nor can I do a "set as target" on the destination's docking port. It is acting as if the ship is still in time warp, even though the warp indicator's all say I'm in normal time. I can usually clear this if I go to the Space Center, go into the Tracking Station, and select the ship to "fly".

Any ideas?