Mechjeb worked and now it doesn't (2.0.7)

[marktye]

Hey so I know this probably isn't totally mechjeb's fault because it worked at first but I installed a few other mods and now it doesn't. Specifically, the ascent autopilot has no concept of what terminal velocity means and runs at full throttle until my vessel goes too fast to be controlled and does flips of death. I've tried everything I can think of at this point besides a fresh install of KSP but I would really like to avoid that. E: On a side note: I was having some weird UI issues but clearing the mechjeb plugin data fixed that. E2: I also found a plugin in my plugins called MuMechLib. I'm going to try playing without it. E3: So the MuMechLib appears to have done nothing whatsoever. Its named the same as the one from 1.9.8 but its nearly twice the size. I'm hoping its not from a mod i've had for a while so I'm going to put it back since it did no good to remove it. E4: Sorry to spam, I created a custom window with the terminal velocity in it. Sitting at the launch pad, its fluctuating extremely rapidly between ~2.1-2.4km/s. I used solid rocket boosters on a tiny pod to check that it does indeed slow down at this speed. Do you know how I can fix the calculations for terminal velocity to be correct again?

[marktye]

Gaaahh I'm so dumb. K so the issue was I have the FAR mod installed. I guess I hadn't done a launch since I installed it. Reading through the forum post basically says that because I didn't back up my parts folder, I screwed myself and have to reinstall KSP. Having said this, it would be wonderful if you could get these to work together. It is also possible that romfarer's GUI is causing issues as that was suggested in the FAR forum thread but I don't know for sure. Again, I'm willing to provide any useful logs or whatever you need. Only reason i've hesitated so far is that they are so large I don't know if sifting through them would be possible, let alone useful.

[Tallinu]

Terminal velocity is calculated from the drag of the craft and the atmospheric properties at current altitude. FAR alters the game's aerodynamics, including drag, I believe. From what I understand of it (I haven't used FAR), to make a rocket not flip over with FAR you have to keep its angle of attack very low (the nose must be aimed fairly close to the prograde marker). This would be done by altering your ascent path settings and performing test flights until you get a gradual turn that works.

As for UI issues, alt-tabbing while KSP loads is known to cause problems. Not sure if that applies if it's in a window, though.

[gmcnew]

@lotzofgibberish, what exactly is the bug you want solved? What parts of MechJeb2 fail to work properly with FAR?

Whatever failures you're still observing, can you please provide a clear list of steps to follow (perhaps including mod installation notes) to get those failures to occur?

[marktye]

I can't provide a complete mod list as I did a fresh install and so far haven't had the issue (I avoided installing FAR or Damned Robotics along with any other mods that weren't extremely popular). Basically what would happen is no matter what rocket/space-plane I made or flew, Mechjeb couldn't calculate my terminal velocity correctly. It would rapidly fluctuate between 2.1-2.4km/s at the ground and increase steadily towards infinity as I gained altitude. It could get my gravity, height in atmosphere, speed, atmosphere density, and temperature right. This made me suspect the drag changes induced by FAR. Basically when I launched a rocket/space-plane, it would follow the correct ascent profile except that it would never throttle back because it incorrectly thought the terminal velocity was over 20x too large. If I weren't manually flying it, it would inevitably end with doing flips of death because it would get to speeds of 400+m/s well under 10km. If it didn't outright crash or explode, it would try to correct its path and ultimately end up doing it all over again. Its possible it would've gotten to space with enough fuel and some luck but the fuel always ran out first.

On Mon, May 13, 2013 at 9:50 AM, gmcnew notifications@github.com wrote:

@lotzofgibberish https://github.com/lotzofgibberish, what exactly is the bug you want solved? What parts of MechJeb2 fail to work properly with FAR?

Whatever failures you're still observing, can you please provide a clear list of steps to follow (perhaps including mod installation notes) to get those failures to occur?

— Reply to this email directly or view it on GitHubhttps://github.com/MuMech/MechJeb2/issues/91#issuecomment-17824567 .

[Tallinu]

"increase steadily towards infinity as I gained altitude" - That is normal, it's what terminal velocity does.

At lower altitudes: Terminal velocity is an effect of drag, and FAR modifies the way drag works. It's possible that what MechJeb is reporting as terminal velocity is, in fact, correct under FAR's aerodynamic model. If your ships are capable of accelerating to more than 400 meters per second near sea level, that seems to indicate (unless your ships have very high TWR, in the 2.0 to 3.0+ range for example) that terminal velocity is, indeed, faster than it would be without FAR.

Regarding the loss of control: If you think MechJeb is doing something wrong when autopiloting a ship while FAR is installed, then in order for anyone to help, we need to be able to see the problem ourselves. To that end, what you need to do is the following.

1. Set up a second, completely fresh copy of KSP, in a different folder, so you can still play with the working copy you have now and the mods and other things in your normal copy won't potentially mess anything up.
2. Install only MechJeb and FAR in the new KSP folder.

3. Using that copy, launch a ship with MechJeb, and write down exactly what Ascent Autopilot settings you are using. All of them. Every checkbox, every number, including the "edit ascent path" values. You can't assume that any of them are unimportant, even if you think they're still at default settings. Also write down the configurable settings in the attitude adjustment window, just in case.

   Other very useful information would include the time and altitude at which MechJeb begins to lose control of the ship, maybe even the time and altitude each stage of your test vehicle gets decoupled (you can hit ESC to pause the game so you have time to glance at the clock and altimeter and record the values in a text file; pressing F3 will also show the exact mission time at which stages separated).

4. Provide a copy of the craft file used as well as all of the above details, so that other people can reproduce exactly what you are seeing and figure out what's going on. You can open the craft file in a text editor and copy/paste the contents to pastebin.com and then post a link to that paste here along with the details.

[marktye]

Okay, I'm not going to be able to do that until tomorrow but ill do that and send you the text file along with the craft file.

On May 14, 2013, at 4:45 AM, Tallinu notifications@github.com wrote:

"increase steadily towards infinity as I gained altitude" - That is normal, it's what terminal velocity does.

At lower altitudes: Terminal velocity is an effect of drag, and FAR modifies the way drag works. It's possible that what MechJeb is reporting as terminal velocity is, in fact, correct under FAR's aerodynamic model. If your ships are capable of accelerating to more than 400 meters per second near sea level, that seems to indicate (unless your ships have very high TWR, in the 2.0 to 3.0+ range for example) that terminal velocity is, indeed, faster than it would be without FAR.

Regarding the loss of control: If you think MechJeb is doing something wrong when autopiloting a ship while FAR is installed, then in order for anyone to be able to look at the problem, what you need to do is the following.

Set up a second, completely fresh copy of KSP, in a different folder, so you can still play with the working copy you have now and the mods and other things in your normal copy won't potentially mess anything up.

Install only MechJeb and FAR in the new KSP folder.

Using that copy, launch a ship with MechJeb, and write down exactly what Ascent Autopilot settings you are using. All of them. Every checkbox, every number, including the "edit ascent path" values. You can't assume that any of them are unimportant, even if you think they're still at default settings. Also write down the configurable settings in the attitude adjustment window, just in case.

Other very useful information would include the time and altitude at which MechJeb begins to lose control of the ship, maybe even the time and altitude each stage of your test vehicle gets decoupled (you can hit ESC to pause the game so you have time to glance at the clock and altimeter and record the values in a text file).

Provide a copy of the craft file used as well as all of the above details, so that other people can reproduce exactly what you are seeing and figure out what's going on. You can open the craft file in a text editor and copy/paste the contents to pastebin.com and then post a link to that paste here along with the details. — Reply to this email directly or view it on GitHub.