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


r4m0n

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Thanks for the detailed feedback Starwaster. I'll what I can do for those

Thanks for the work.

I pretty much stress tested it by throwing things at it that I probably wouldnt do in actual practice but I figured it was best to give it some harsh conditions. Though the thrusting away thing happened to me under fairly normal conditions. Just happened again though the second time was with docking parts I'm working on that might not have the right transforms... when force rolling what axis is the port trying to align?

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Orbit is the main issue, MJ tends to do things mathematically perfectly and game then can't decide which point of orbit is highest or lowest. Same thing goes for inclination when you intercept a target. BTW, it may generally help to increase tolerance a bit in maneuver planner, I usually put 0.3-0.5 m/s. This way MJ won't make sudden moves at the end of the burn trying to catch "escaping" node to make such a precise corrections and it won't make thing THAT perfect.

This has a downside too... "The last 10% does 90% of the work" - a 0.3m/s error isn't much in Kerbin orbit, but in an interplanetary burn it's a heck of a lot.

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Just pushed a fix for the "MJ can't control vessel that just undocked".

DerekL1963 : it is, but most of the time it's better to wait to be nearer the target. It may cost a bit more dV but it's easier.

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Maybe your TWR was pretty low and planner had to split burn time in 10 minutes before and 10 minutes after node. That may result in such a situation, especially if starting orbit was low enough to be unable to compensate such a burn.
Yeah it's not a bug, it's mis-use of MJ, it can't compensate for really low TWR + low orbit, if you want to leave kerbin with TWR that low you need to manually burn multiple times, you can't complete the burn in one orbit, either increase your TWR or raise your orbit if you want to use MJ to do your escape burn.

it had a TWR of at least 2:1 (it still had the 1st stage Titan on), and the orbit was ~4,000 km (for reference, that ring of probe orbits is kerbisync, and the farthest out is the mun). the image is the end result of the burn.

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What would be nice is to add a low TWR spiral-escape mode in the Manoeuver planner... not efficient, but with very low TWR (ion engine comes to mind), it's a pain to manually calculate the spiral duration to arrive precisely at an escape point, but since KSP doesn't handle such non-impulsive manoeuvers, you have to guess where the escape point should be...

Here's a little reading on the matter Low thrust rocket trajectories

Edited by Cairan
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Commissar : It's quite hard to see how that went wrong without the a picture of before the node execution.

And is this with the official release or the dev one ?

pretty sure it's dev 168.

pretty sure this image is from just after it started the burn, might be a different craft that had the same issue. removing the node, and creating a new one fixes it. doesn't happen every time either...

E9w5o0N.png

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Okay- is there a way to see what is conflicting with what? For some reason I booted KSP today- without changing any mods since yesterday- and this is my new HUD. But only when I slap a Mechjeb core on there. I also can't stage, throttle up outside of the IVA mode, or pretty much do -anything.-

2u956lN.png

Edited by Tassyr
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Okay- is there a way to see what is conflicting with what? For some reason I booted KSP today- without changing any mods since yesterday- and this is my new HUD. But only when I slap a Mechjeb core on there. I also can't stage, throttle up outside of the IVA mode, or pretty much do -anything.-

http://i.imgur.com/2u956lN.png

output_log.txt is a good place to start. Look for keyword 'exception', 'mechjeb' 'nullreference'

That's output_log.txt, NOT ksp.log

You'll find it in the folder named ksp_data

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Is there a roll program in mj that make the rocket(or the KSO) alwasys pitch towards the launch heading??

Thank you.

The Smart A.S.S. module Surface mode allows you to specify a heading, pitch, and roll, so you can use that to gradually lower the pitch from 90, while keeping the wings level. Once you get high enough and over enough, you can switch to orbital mode and use prograde, but be aware at launch that there is a big difference between surface prograde and orbital prograde.

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The Smart A.S.S. module Surface mode allows you to specify a heading, pitch, and roll, so you can use that to gradually lower the pitch from 90, while keeping the wings level. Once you get high enough and over enough, you can switch to orbital mode and use prograde, but be aware at launch that there is a big difference between surface prograde and orbital prograde.

I guees he meant surface prograde. Sometimes I miss such and option too, especially when I found out that with FAR I make much more efficient launches manually rather then using MJ ascent guidance (or maybe I just can't predict correct trajectory for each rocket), though in stock I always used MJ for ascent.

This has a downside too... "The last 10% does 90% of the work" - a 0.3m/s error isn't much in Kerbin orbit, but in an interplanetary burn it's a heck of a lot.

Yet if it's 20 min burn, it already has such an error that those 0.3 m/s won't change anything and you'll have to make corrections anyway ;)

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Okay- is there a way to see what is conflicting with what? For some reason I booted KSP today- without changing any mods since yesterday- and this is my new HUD. But only when I slap a Mechjeb core on there. I also can't stage, throttle up outside of the IVA mode, or pretty much do -anything.-

http://i.imgur.com/2u956lN.png

Duplicate files. Corruption of files. Antivirus flagged some dll as dangerous. /shrug

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Testing docking with #180...

Initial impressions, it doesn't seem to me to be much of an improvement. In some ways, it seems a step backwards. It doesn't handle unbalanced payloads nearly as well, and still has the annoying tendency to sometimes try and dock while still moving laterally and/or with significant lateral misalignment (the "lets just get it in range and let the magnetics handle it" school of docking). Turning "smart translation" on and off doesn't seem to have any effect.

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i dunno waht it is about my mechjeb... it seems to be easily confused.... now the landing guidance is maneuvering away from my target, to an inclination that has periapsis on the other side of the planet...

it's worked perfecly before, maybe it just doesn't like the target being on the side of the planet?

i'll upload a screenshot when i'm done working around the confusion of the guidance

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Testing docking with #180...

Initial impressions, it doesn't seem to me to be much of an improvement. In some ways, it seems a step backwards. It doesn't handle unbalanced payloads nearly as well, and still has the annoying tendency to sometimes try and dock while still moving laterally and/or with significant lateral misalignment (the "lets just get it in range and let the magnetics handle it" school of docking). Turning "smart translation" on and off doesn't seem to have any effect.

I'm afraid I have to give a similar observation. The Docking Autopilot tonight told me it was "Backing up" at some m/s, but watching the screen said it was trying to pass the target. Starting positions when I engaged the DAP had the target behind the ship, with both vessels in retrograde attitude (target catching up to me).

I am also using dev180...

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The Smart A.S.S. module Surface mode allows you to specify a heading, pitch, and roll, so you can use that to gradually lower the pitch from 90, while keeping the wings level. Once you get high enough and over enough, you can switch to orbital mode and use prograde, but be aware at launch that there is a big difference between surface prograde and orbital prograde.

Hmmm, that could be a work around for my purpose~~

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hi guys, just updated mechjeb to the latest version but have a little problem when i right click on command pod i no longer have the crew report options same with goo cannister and spacebar for staging. did not have that problem with the older version i had

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Great tool which help (I see it as one or more engineer(s) on the space center, helping us with physics and math stuffes ;) ).

One suggestion (if not already set): in Hohmann calculation, add either multiple dV choice (minimum required/any delay, minimum delay/any dV, or max dV/max delay I want=try to find a solution with this parameter)

One question: is there any module which can help me to make a chopper/VTOL (built with FireSpitter) completely steady, I mean killing totally any horizontal speed ?

(I know, I'm a terrible pilot :confused: I'm just learning how to land a plane in a way it can takeoff again after :D)

thanks.

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