Mechjeb Ascent guidance failure

[Snowstorm]

Mechjeb is being a total jerk to me.  It fails to comprehend targets, it won't do anything at all for ascent guidance except autostage, and rendezvous planning also doesn't work.  It basaically just has a big catastrophic failure.  Here's a list of plugins I use:

• Mechjeb
• Hyperedit
• DynamicTextureLoader
• BetterTimeWarp

That's it.  Someone help, please!

[smjjames]

Which version or dev build are you using?

[Snowstorm]

I'm using 1.0.5.

 

EDIT: Oh you mean for Mechjeb, I'm not sure.  I got it like a month ago, about.

Edited January 28, 2016 by Snowstorm

[Guest]

Try updating to the latest version here :  https://ksp.sarbian.com/jenkins/job/MechJeb2-Dev/

Be sure to completely delete the old mechjeb2 folder before installing the new one. This will delete the old settings files for all of your ships and start over fresh.

If still having problems, be prepared to post screenshots or log files to get proper and accurate support from the mj devs.

And lastly, there have been changes to mj for ksp 1.05. Ascent guidance has new settings that coincide with the aero changes for the latest versions of KSP. In other words, if you are used to the old mj, then the new mj will require some studying and research to fully understand, something that I haven't bothered to do. All I use is the smart ass. functions, and occasionally the landing guidance for repetitive stuff, and the maneuver planners for hohman transfers and fine tuning closest approach. Everything else I am doing manually.

[Snowstorm]

Alright, I'm testing it out now, I updated it.  It seems to be working OK so far.

[se5a]

Also I've just found that it doesn't like whatever bit of your ship that's got "control from here" being the wrong way around (since it gets its frame of reference from this). fortunately I figured this out with a rover so there was no damage. 

[michelcolman]

I just installed and tried out MechJeb yesterday.

My experience:

- On a wobbly ship (4 stages, just a few struts but probably not enough), ascent autopilot wobbles a lot, I can do a much better job myself with less control inputs following the target guidance better than the autopilot does. I had to restrict dynamic pressure because otherwise the ship would blow up due to excessive wobble.

- For some strange reason, when the first stage was almost empty and apoapsis was nearing its 80 km target, it suddenly started cycling engine power between idle and full several times in rapid succession. This caused a longitudinal compression oscillation that blew up the ship spectacularly. Retried several times with the same result. The craft has 4 stages with the first stage containing 7 Mammoth engines. I don't think the real Jeb would ever cycle those engines up and down like that ;-)

- Sometimes maneuver nodes won't execute automatically, but I need to experiment a bit more to figure out what's going on. I made a maneuver, adjusted it with MechJeb, armed maneuver execution, then used warp (manually) until a couple of minutes before the 1 minute maneuver, and then waited. Nothing happened But maybe I did something wrong, Ive only tried this once.

- Autoland blew up the rocket due to aerodynamic heating. It just lowered the orbit from an 80 km circular orbit to an intersection with the surface at KSC and then used the rocket engines to accelerate during the descent. Had me frowning my eyebrows but I let it continue anyway, and then I turned out to be right.

- Sometimes parts of the blue trajectory line on the map disappear, with two "holes" in the blue line. I never saw this happen before I installed MechJeb, so I suspect MechJeb might have something to do with it, but I'm not sure.

Other than that, it certainly is a great and useful mod! Node editing is terriffic, ascent guidance is very educational (I was doing way too little gravity turning apparently), you just have to use common sense and use it only where it's appropriate. Autopilot to be used with caution.

[nobodyhasthis2]

On 2/8/2016 at 0:23 PM, michelcolman said:

I just installed and tried out MechJeb yesterday.

My experience:

- On a wobbly ship (4 stages, just a few struts but probably not enough), ascent autopilot wobbles a lot, I can do a much better job myself with less control inputs following the target guidance better than the autopilot does. I had to restrict dynamic pressure because otherwise the ship would blow up due to excessive wobble.

- For some strange reason, when the first stage was almost empty and apoapsis was nearing its 80 km target, it suddenly started cycling engine power between idle and full several times in rapid succession. This caused a longitudinal compression oscillation that blew up the ship spectacularly. Retried several times with the same result. The craft has 4 stages with the first stage containing 7 Mammoth engines. I don't think the real Jeb would ever cycle those engines up and down like that ;-)

- Sometimes maneuver nodes won't execute automatically, but I need to experiment a bit more to figure out what's going on. I made a maneuver, adjusted it with MechJeb, armed maneuver execution, then used warp (manually) until a couple of minutes before the 1 minute maneuver, and then waited. Nothing happened But maybe I did something wrong, Ive only tried this once.

- Autoland blew up the rocket due to aerodynamic heating. It just lowered the orbit from an 80 km circular orbit to an intersection with the surface at KSC and then used the rocket engines to accelerate during the descent. Had me frowning my eyebrows but I let it continue anyway, and then I turned out to be right.

- Sometimes parts of the blue trajectory line on the map disappear, with two "holes" in the blue line. I never saw this happen before I installed MechJeb, so I suspect MechJeb might have something to do with it, but I'm not sure.

Other than that, it certainly is a great and useful mod! Node editing is terriffic, ascent guidance is very educational (I was doing way too little gravity turning apparently), you just have to use common sense and use it only where it's appropriate. Autopilot to be used with caution.

1. See notes on joint reinforcement and associated fix. Highly recommended if you needed 7 mammoth engines and did not use enough struts.

2. It suddenly started cycling engine power between idle and full several times in rapid succession because you left a precision rate that was too low. It was trying to hit an exact 80 km target during coasting maneuver. Just before final orbital insertion burn. There is normally no need to have to an exact micromanaged target number.  

3. It does the the time warp if allowed to but only after getting attitude correct. Then it comes out of warp and does a final minor correction and then executes. If it can't point at the node perfectly it will not execute the maneuver. Did you switch on RCS to help it stabilize?   

4. It has a generic landing profile. It does not know how you designed your craft. The profile needs changed for every craft. Your best bet is always to manually control atmospheric insertion and use the MJ translatron for throttle control at the right time. Doing the whole automated landing is only for hitting a specific landing zone and can be heavy on fuel and does not take heating into account.

5. Never seen this. Try changing conics mode to see what happens.

Absolutely correct that it is pretty terrific. In terms of memory allocation it does save quite a bit over the list of mods it replaces. One thing to point out is the ascent profile follows a generic curve. One that needs changed depending on launch characteristics. If is applying a quicker turn that you expect you could be taking a significant steering loss to final dv. It is a tool box and a pretty clever one but only you can be the judge of what the right settings are. You design the rockets. Your instinct is correct here that the autopilot has to be used with caution.

 

Edited February 18, 2016 by nobodyhasthis2

[michelcolman]

1 hour ago, nobodyhasthis2 said:

1. See notes on joint reinforcement and associated fix. Highly recommended if you needed 7 mammoth engines and did not use enough struts.

2. It suddenly started cycling engine power between idle and full several times in rapid succession because you left a precision rate that was too low. It was trying to hit an exact 80 km target during coasting maneuver. Just before final orbital insertion burn. There is normally no need to have to an exact micromanaged target number.  

3. It does the the time warp if allowed to but only after getting attitude correct. Then it comes out of warp and does a final minor correction and then executes. If it can't point at the node perfectly it will not execute the maneuver. Did you switch on RCS to help it stabilize?   

4. It has a generic landing profile. It does not know how you designed your craft. The profile needs changed for every craft. Your best bet is always to manually control atmospheric insertion and use the MJ translatron for throttle control at the right time. Doing the whole automated landing is only for hitting a specific landing zone and can be heavy on fuel and does not take heating into account.

5. Never seen this. Try changing conics mode to see what happens.

Absolutely correct that it is pretty terrific. In terms of memory allocation it does save quite a bit over the list of mods it replaces. One thing to point out is the ascent profile follows a generic curve. One that needs changed depending on launch characteristics. If is applying a quicker turn that you expect you could be taking a significant steering loss to final dv. It is a tool box and a pretty clever one but only you can be the judge of what the right settings are. You design the rockets. Your instinct is correct here that the autopilot has to be used with caution.

 

1. Of course joint reinforcements help, but I can get a wobbly ship to orbit while MechJeb blows it up. I think it could do with some more damping, or some kind of detection of wobble. It looks like it gets into dynamic instability, overcorrecting for position deviations and making the oscillations larger. When I'm flying manually, and the ship is wobbling left-right, I actually give a right input when the ship is pointing to the right (and needs to go to the left) because I know it will go to the left by itself and I just want it to slow that motion down. MechJeb will give an input to the left and increase the amplitude of the oscillation. But I know this is not an easy thing to program, so I can't really be too harsh on MechJeb for that.

2. Where is that precision rate setting? I don't remember setting a precision rate anywhere, I've just now tried to look for it but I can't find it in any of the windows. In any case, I don't see any need to cycle between full throttle and idle. When I want to fine-tune the apoapsis, I cut the throttle just before, and then add a tiny little bit of thrust to add the last few meters. I actually get better precision than MechJeb (on a simple rocket that MechJeb doesn't blow up). Why would you ever go back to idle, back to full, back to idle, back to full again, etcetera in rapid succession? I'm not exagerrating, the large rocket blew up because of longitudinal compressions (not bending but squeezing)

3. Indeed, once I figured that out it worked correctly. Although you need to use some common sense: today I asked it to execute a maneuver to escape from Kerbin orbit with nuclear engines, it started 10 minutes before the maneuver. pointed the nose towards kerbin (since it was about 90 degrees before the node), entered the atmosphere and burned up. I kind of guessed it was going to do that and sure enough, it did.

4. I'll give that a try, thanks. Inserting to a safe speed first, then switching on the precision landing part for the last bit only, sounds like it may work rather well.

5. I see it regularly after take-off. A bit of blue orbit comes off of Kerbin, then there's a gap, then the top part of the orbit curving back down, then another gap exactly symmetrical to the first, then the last bit of orbit down to the surface. I don't think I ever saw it before installing MechJeb. Doesn't really bother me, it's just strange.

But once again, it really is an extremely useful tool as long as you remember that's what it is. It helps you a lot, but you still need to be a pilot. 

[Unlucky]

What if you didn't install Mechanical Jebediah correctly?

If this happens to me, i extract the folder again to be sure.

 

(NOTE: "MechJeb" is actually called "Mechanical Jebediah")

[Snowstorm]

I don't know why people keep responding to this....

 

It's like a month old!  (Also the problem was solved)