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

[cicatrix]

Before I let linuxgurugamer take over the replies for the ascent AP let me explain

I understand your frustration but this is a MAJOR CHANGE in the mod. People used MJ for a long time and expect some behavior that was changed. A changelog with a brief description on the first page might help a lot.

[ikehaiku]

Actually, it is a major change in the game, not in the mod.

MechJeb, along with any player, simply have to comply with what the new atmosphere is.

[slaintemaith]

Might have the node bug reproduced. I doubt this will help you, since it's essentially the same one I wrote up yesterday, but here we go:

MJ Version: 2.5.1.0-462

Kerbal Version: 1.0.2.842

Clean Install, Mechjeb is the only mod installed.

Steps to reproduce:

1) Extract "To Save Folder.zip" in your save game folder.

2) Open KSP

3) Select "Start Game"

4) Select "Resume Saved"

5) Select "To Save Folder" and Continue

6) Press "Esc" at the KSC screen

7) Select "Load Save..."

8) Select "quicksave" and Select.

9) From the open Manuever Planner, select "Fine Tune Closest Approach With Target

10) Select "Remove All Nodes"

11) Select "Create and Execute"

(Further Steps, although the fault is here)

12) Warp until "Node in T-" reaches a period you're comfortable waiting out.

13) Wait that time.

Noted Result:

Although the burn node is created, time is not accelerated to the node time, and if the node time is waited out, the burn still does not occur. Est. Burn shows N/A even though delta-V information is displayed in the nav ball.

Expected Result:

Time should automatically accelerate to the node time, Est. Burn should display properly, and the burn should occur automatically.

Notes:

***Important*** (maybe): This only seems to happen with -unkerballed- craft. When you have kerbals flying, everything seems to work just fine.

There only appears to be one MJ2.AR202 unit on the current craft.

Output_Log: https://www.dropbox.com/s/ewoioshmtjemkqi/output_log.txt?dl=0

Save Folder: https://www.dropbox.com/s/vildk2c14q6irgz/To%20Save%20Folder.zip?dl=0

Screenshot1: https://www.dropbox.com/s/bb1yxbl7hopiyhs/screenshot1.png?dl=0

Screenshot2: https://www.dropbox.com/s/5pamc9bwcl2t7vo/screenshot2.png?dl=0

Thanks for your time!

Edited May 19, 2015 by slaintemaith

[cicatrix]

Actually, it is a major change in the game, not in the mod.

MechJeb, along with any player, simply have to comply with what the new atmosphere is.

Nevertheless, I judge my own experience. I've been using MJ for months with FAR and editing ascent path was sort of necessary. Now I downloaded a new version an not only I didn't look at the settings (thinking they are the same as always have been) but could not understand why my rocket starts the turn at 100 m. It's been only after I read three whole pages of posts here until I found relevant information.

If there was a change log I could expect different behavior right from the beginning.

[Red Iron Crown]

*snip*

Now *that* is how to report a bug!

[smjjames]

I understand your frustration but this is a MAJOR CHANGE in the mod. People used MJ for a long time and expect some behavior that was changed. A changelog with a brief description on the first page might help a lot.

Yeah, I was actually using my normal FAR ascent profile and while I did have some problems initially, it just took some tweaking to the ascent profile and small changes to the way that I built rockets. I don't even USE the AoA limiter anymore, I don't need to.

@ those having ascent problems: Use this ascent profile as your starting point and tweak from there. The only problems that I've had with Ascent AP since the initial days were due to rocket design, so tweak around with the ships as well, get a feel for the new aero. I'll restate that I haven't even NEEDED to use the AoA limiter.

And yes, that rocket doesn't have fins, doesn't need em.

[Ninjahgoblin]

Understandably. But I have no idea how to set it up. No videos are posted for 2.5.1 Mechjeb nor a written guide for 2.5.1 on how to setup ascent guidance with the new atmosphere mechanics.

So I sit here for hours trying to figure out the correct ascent variables. While I could be manually flying, but the point of me installing mechjeb is to automate this.

Please ignore this post as it is mostly a rant. Am by no means upset as I love KSP and this Mod. Just trying to figure out the new system.

Trial and error. Or until some one figures out the "sweet spot" setup and posts an across the board configuration. *fingers crossed*

Actually, it is a major change in the game, not in the mod.

MechJeb, along with any player, simply have to comply with what the new atmosphere is.

[terahurts]

Actually, it is a major change in the game, not in the mod.

MechJeb, along with any player, simply have to comply with what the new atmosphere is.

I totally agree with you. Might be better to have a short sentence mentioning that the accent AP may require some manual tweaking as it's not a 'one size fits all' solution due to 1.x introducing changes to the aero model along with a paragraph about current known bugs and issues along with a request to try the dev build before posting a bug report that bug reports are provided with .craft/rar'd saves etc. That might remove some of the noise in the thread and allow Sarbian to focus on the fixes rather than having to repeat himself here ever other day.

[slaintemaith]

Now *that* is how to report a bug!

I used to work QA for Microprose 1000 years ago. =)

[smjjames]

Trial and error. Or until some one figures out the "sweet spot" setup and posts an across the board configuration. *fingers crossed*

Use the one I posted up then.

I actually didn't have to do a whole lot of tweaking, most of the tweaking was actually in the way that I build rockets.

[slaintemaith]

Fins near the tail of any rocket help immensely. I've also found that disabling roll/pitch/yaw on the fins (when an option) is also helpful with stability. Make sure to add fins to -all- stages that will have to ascend through a thick atmosphere. (Duna probably won't need fins so much) Believe it or don't, this is something very "real world" about launching anything. The fins help "windcock" the rocket and offset the weight of the nose and help maintain AoA.

Edited May 19, 2015 by slaintemaith

[IntoSpaceAgain]

@Sarbian

My issue with the below in bold. Is that yes, the turn starts early and I don't mind. But my apoapsis never gets above 20km. Ever. The turn starts early, I reach an exceptionally low apoapsis (when successful), I burn up in atmosphere while trying to complete Gturn.

If you're burning up during the gravity turn, it suggests that your TWR is too high. Try limiting your acceleration to around 15-16 m/s/s until 25km, or thrust limiting the rockets to give a TWR of around 1.5 on the pad.

With these numbers, the ascent profile I use is as follows:

Turn Start: 100m/s

Turn End: 50km

Turn Shape: 66%

This gets me to an 80km orbit with the majority of the rockets I build.

[smjjames]

Fins near the tail of any rocket help immensely. I've also found that disabling roll/pitch/yaw on the fins (when an option) is also helpful with stability. Make sure to add fins to -all- stages. Believe it or don't, this is something very "real world" about launching anything. The fins help "wind ...." the rocket and offset the weight of the nose and help maintain AoA.

Not ALL stages, just the ones that are powering you through atmosphere. Fins on upper stages (unless you're using them as radiators) are just dead weight.

I've also noticed that large rockets (like in the example I posted) with strong engines and strong SAS don't need fins. It may be in part that they accelerate slowly.

[Ninjahgoblin]

Thank you for this. I have seen a few ascent profiles I am going to try and match once I get home. *fingers crossed*

I'll post back after I test them with a few builds. And perhaps we can get a community standard posted in regards to this.

If you're burning up during the gravity turn, it suggests that your TWR is too high. Try limiting your acceleration to around 15-16 m/s/s until 25km, or thrust limiting the rockets to give a TWR of around 1.5 on the pad.

With these numbers, the ascent profile I use is as follows:

This gets me to an 80km orbit with the majority of the rockets I build.

[slaintemaith]

Sorry to be keeping this off-topic (this has turned into ascent help, and not Mechjeb, really) but I've also found the most -efficient- use of fuel 'on the way up' is to make sure that little or no wake turbulence happens around the ship at all during the ascent, and especially no "reentry" heat. Those things mean your ship is wasting energy (precious fuel!) by nudging air molecules out of the way instead of letting you go up. You can really open the throttle higher up when the air is thin, but you really -do- want a nice, slow elevator ride up to that point.

Thanks for the correction, smjjames, you're absolutely right.

[smjjames]

Sorry to be keeping this off-topic (this has turned into ascent help, and not Mechjeb, really) but I've also found the most -efficient- use of fuel 'on the way up' is to make sure that little or no wake turbulence happens around the ship at all during the ascent, and especially no "reentry" heat. Those things mean your ship is wasting energy (precious fuel!) by nudging air molecules out of the way instead of letting you go up. You can really open the throttle higher up when the air is thin, but you really -do- want a nice, slow elevator ride up to that point.

Thanks for the correction, smjjames, you're absolutely right.

So, basically no mach effects? I have no idea how to make sure there is little or no wake turbulence.

[slaintemaith]

So, basically no mach effects? I have no idea how to make sure there is little or no wake turbulence.

Typically, with a high TWR (over 2) craft, I'll limit accel to 20-25 m/s/s. I could be wrong and those effects might just be there to look cool. =)

[Jim DiGriz]

Noted Result:

Although the burn node is created, time is not accelerated to the node time, and if the node time is waited out, the burn still does not occur. Est. Burn shows N/A even though delta-V information is displayed in the nav ball.

Expected Result:

Time should automatically accelerate to the node time, Est. Burn should display properly, and the burn should occur automatically.

I had this problem yesterday and then after fighting with it for a bit I noticed that 'auto-warp' wasn't ticked.

[smjjames]

Typically, with a high TWR (over 2) craft, I'll limit accel to 20-25 m/s/s. I could be wrong and those effects might just be there to look cool. =)

I just use limit acceleration to 18m/s until 20-25km.

[slaintemaith]

I just use limit acceleration to 18m/s until 20-25km.

Also works. Depending on the spacecraft, you might want to up that a bit. Pushing the edge of speed/drag is where you want to be.

I had this problem yesterday and then after fighting with it for a bit I noticed that 'auto-warp' wasn't ticked.

Wasn't my issue, as the screenshot clearly shows Autowarp ticked. Furthermore, I manually warped to about 2 minutes before burn time, waited, and the burn still didn't happen.

[linuxgurugamer]

I made an account to post feedback. 1st- Thank you for this outstanding mod. Has helped me enjoy the game worlds over.

ISSUE:

-KSP 1.0.2

-Mechjeb 2.5.1

Every single time I use ascent guidance, no matter how I fidget with the turn start or shape. It starts the Gturn at around 1000, and proceeds to start doing flips after10000ish. Never getting an Apoapsis above 20k.

I am not sure what to do, I have tried the "more fin method" I have tested using designs I know fly into orbit. Still no ascent.

Do you need any more details? Rig info etc.?

You are probably hitting the speed at which the turn should start.

How fast are you going when it starts to turn?

Take a look at the Ascent Profile edit page, you should see a line which says at which speed it should start. Try increasing that from 100m/s to 350 or 400 m/s

LGG

[linuxgurugamer]

@Sarbian

My issue with the below in bold. Is that yes, the turn starts early and I don't mind. But my apoapsis never gets above 20km. Ever. The turn starts early, I reach an exceptionally low apoapsis (when successful), I burn up in atmosphere while trying to complete Gturn.

Also with the Limit AOA default setting of 5', it always goes past this and does a hard 90' turn from about 20sec after take off

I have done reinstalls, fresh isntalls, just Mechjeb and KSP, the default settings and playing with the Edit Ascent path variables.

Maybe I am not understanding things completely.

Ninjahgoblin,

it sounds like a couple of things here:

1. Your rocket is somewhat unstable, and when it tilts to 5 degrees, it just can't maintain that.

2. Try limiting your acceleration to 10-20 m/sec as mentioned in other posts. Also, try increasing the speed at which it starts the turn.

LGG

- - - Updated - - -

Not ALL stages, just the ones that are powering you through atmosphere. Fins on upper stages (unless you're using them as radiators) are just dead weight.

I've also noticed that large rockets (like in the example I posted) with strong engines and strong SAS don't need fins. It may be in part that they accelerate slowly.

The large rockets may have enough gimboling to compensate for the lack of fins

LGG

- - - Updated - - -

Also works. Depending on the spacecraft, you might want to up that a bit. Pushing the edge of speed/drag is where you want to be.

Wasn't my issue, as the screenshot clearly shows Autowarp ticked. Furthermore, I manually warped to about 2 minutes before burn time, waited, and the burn still didn't happen.

Are you running Remote Tech?

LGG

[slaintemaith]

Are you running Remote Tech?

LGG

As stated in the bug report, I'm running Kerbal with Mechjeb only.

Edited May 19, 2015 by slaintemaith

[linuxgurugamer]

As stated in the bug report, I'm running Kerbal with Mechjeb only.

Ok, sorry about the question. I had missed that original report of yours.

[skips]

I do not see this problem with craft that have two MechJeb parts on the same stage (for symmetry reasons) and a MechJeb module in a probe part.

skips