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

[Apollo13]

I wasn't talking about whether you personally needed more than one set of RCS thrusters,

I didn't take it personally at all. I assumed you meant the ubiquitous "you". But, thanks for your consideration (truly, a rare thing in forums).

Similar to how MJ completely freaks out during auto-dock if the RCS thrusters are horribly unbalanced with regards to the CM, a singular set of RCS thrusters also seems to freak MJ out.

Been there. Done that. Got the t-shirt. I can't blame MJ at all if thrusters are not balanced to the load. I just wish I could use MJ' RCS balancer in the VAB.

And as I said before, if all else fails MJ will still be able to help you dock ships and station modules more easily than if you did it alone. Setting SmartASS to orient PAR- in relation to your target port will make MJ maintain the proper heading for a docking and can optionally also handle roll angle should you so desire.

I use SMART A.S.S constantly, but I didn't know about the PAR. I'll have to search through the many buttons to locate that and USE IT. Thanks for that. gave you a forum rep point.

Having said all in the above in posts, I CANNOT conclusively lay all the problems at MJ's feet. I say that, because there is something going funky with the physics. Looking at the MJ's Delta-V window (another MJ innovation in constant use), it shows the TWR for that vessel at 0.02. That's not a typo. TWR should read about 2.63. I've seen this behaviour rather recently. thus, I consider some mod (perhaps MJ) may be the culprit. I'm going to experiment with a clean, MJ-only game.

Edited December 1, 2014 by Apollo13

[lodestar]

And as I said before, if all else fails MJ will still be able to help you dock ships and station modules more easily than if you did it alone. Setting SmartASS to orient PAR- in relation to your target port will make MJ maintain the proper heading for a docking and can optionally also handle roll angle should you so desire.

Nice one. I'm always struggling with TGT for that, I never figured PAR- would do it. Thanks.

[Eleven]

Look for vessel called Skylab Repairm in the Tracking Station. Or, push the F9 key.

https://www.dropbox.com/s/cuc1n34nbtxaka6/Career.zip?dl=0

I tried, but I don't use the mods you do, so none of your vessels even loaded for me but...I gotta ask, the first pic was blurry and the second wasn't bad but I can't see any docking ports at all. What docking port are you using on that target vessel?

[Somtaaw]

came to post about spaceplanes, but I think I'll start off by mentioning my MJ never seems to have issues with auto-dock failing to work, using 1 ring of 4 thrusters, or upto 6 rings of thrusters it has always docked me, no issues. Once I get close enough to visually see and click on my targets docking port, I'll turn on AD and get up to get a drink and food. My only objection is how far away it'll move me before handling the approach. My space station is about 50m from top of bottom, and MJ will put me about 150m below/above/sides... but since it successfully gets me there in the end I live wiht that.

Now, onto my real reason for posting... I'm really getting into spaceplanes, and especially SSTO's now. I have gone to guru's and gotten some really great personalized builds that fly great, but MJ's auto-ascent feature is crazy with them. After getting to about 5km up from the runway, on occasion, MJ has decided to put my SSTO's into negative 15 degree climbs, despite checking the "limit angle of attack of 20 degrees". Luckily my jet has insane amounts of TWR so it pulled it off without a crash.

However, since SSTO's have a different launch pattern, is there any plan to make a more customized to plane takeoff routine? The previously mentioned negative climbs happens erratically, some launches it'll do it, others it won't even if I do not change the ascent path between takeoff's.

I love the autoliftoff when it comes to my rockets, it's allowing me to have more fun actually exploring Kerbol space than spending 50% of my time in liftoff, and LKO work. But even after setting the ascent path to ~15km, with a mere 10-15 degree ascension, and a 20-30 degree AoA limitation, I get very different takeoff runs, using the same jet in 10 sequential takeoff's.

[Apollo13]

I started a new game with only MechJeb plus SelectRoot (VAB-only use) plus KJR and kData (in-flight) In this image, the red-circle vessel is docking with the orange-tank vessel.

From 57 meters away, MJ Auto-Docking was flawless. It spent only 3 Monoprop; nothing wasted. There was no constant blowing of Monoprop, no constant tinkering with vehicle attitude.

This is why, in my previous post, I state that I cannot conclusively state that Auto-docking is at fault. I will continue additional testing. Perhaps, in previous examples, the RCS was not perfectly balanced; hence, the constant adjustment. Even so, I'd prefer auto-dock not constantly do that. Secondly, it still does not explain the behaviour whereby auto-docking immediately pushed the docking vessel to the left of the target, even when the two vehicles were centered on each other.

Again, I'm working with dev build #352, so I'm not expecting perfection here. Unfortunately, although I can over-ride "Starting Distance", the minimum allowable is 10. Here'as the lines that were added to MechJebModuleDockingGuidance.cs:

+ if (autopilot.overridenTargetSize < 10)

+ autopilot.overridenTargetSize = 10;

I'd like to be able to set it to whatever value I want (greater than 0), so I can close in manually then kick on auto-dock. Then, again, perhaps PAR will obviate the need at all.

EDIT: Just tried using PAR for first time to dock. OMG, I'm in love!!! LOL.

...I gotta ask, the first pic was blurry and the second wasn't bad but I can't see any docking ports at all. What docking port are you using on that target vessel?

the first picture was actually sharper, but very, very dark. I increased the brightness and contrast so that folks could better view the vehicles. There are Junior docking ports on both vessels. This is indicated because the Auto-docking window shows no yellow warning messages. Without ports, there would be warnings.

Edited December 1, 2014 by Apollo13

[Stone Blue]

This is why, in my previous post, I state that I cannot conclusively state that Auto-docking is at fault.

Again, I'm working with dev build #325, so I'm not expecting perfection here. Unfortunately, although I can over-ride "Starting Distance", the minimum allowable is 10. I'd like to be able to set it to whatever value I want (greater than 0), so I can close in manually then kick on auto-dock. Then, again, perhaps PAR will obviate the need at all.

EDIT: Just tried using PAR for first time to dock. OMG, I'm in love!!! LOL.

Yup...I always have quite a few other mods installed, so I'm also not about to say that it's strictly MechJeb, either...

Also, i just installed dev -352 yesterday, after seeing the aforementioned changes to the docking module, and I havent tried to auto dock yet...

Thanx for the heads up on PAR, everyone...Guess I better try it out...

[Starwaster]

Been there. Done that. Got the t-shirt. I can't blame MJ at all if thrusters are not balanced to the load. I just wish I could use MJ' RCS balancer in the VAB.

I hate you! I didn't get a t-shirt. All I got was one of the large solar panels floating alongside my space station in tiny sparkly bits.

I use SMART A.S.S constantly, but I didn't know about the PAR. I'll have to search through the many buttons to locate that and USE IT. Thanks for that. gave you a forum rep point.

Oops I should have remembered that in my docking dispensing advice. Yeah, using PAR is awesome for doing a manual (semi-manual?) dock

Having said all in the above in posts, I CANNOT conclusively lay all the problems at MJ's feet. I say that, because there is something going funky with the physics. Looking at the MJ's Delta-V window (another MJ innovation in constant use), it shows the TWR for that vessel at 0.02. That's not a typo. TWR should read about 2.63. I've seen this behaviour rather recently. thus, I consider some mod (perhaps MJ) may be the culprit. I'm going to experiment with a clean, MJ-only game.

Wait... is that in one of your screenshots? I'm not seeing that

Edited December 1, 2014 by Starwaster

[Apollo13]

Wait... is that in one of your screenshots? I'm not seeing that

Out of frame, but it was there.

Sidebar, having no association with MJ. I mentioned the funky physics. For your amusement, here's an image of what I'm talking about. The module at the left is actually attached at the location indicated by the red arrow. When I rotate the module, the StationScience Cyclotron rotates as well. I'm using KJR here, so this shouldn't happen. This is not an isolated case. It sometimes occurs with/without MJ.

Edited December 1, 2014 by Apollo13

[Starwaster]

Out of frame, but it was there.

Sidebar, having no association with MJ. I mentioned the funky physics. For your amusement, here's an image of what I'm talking about. The module at the left is actually attached at the location indicated by the red arrow. When I rotate the module, the StationScience Cyclotron rotates as well. I'm using KJR here, so this shouldn't happen. This is not an isolated case. It sometimes occurs with/without MJ.

http://i.imgur.com/5OO66qG.jpg

Does it 'reattach' if you do a non-phys timewarp? And then 'detach' again after you come off rails?

If so you need to check for errors (probably but not exclusively a nullref) when the ship first loads into the scene and probably before it comes off rails.

Edit:

RCS thruster power is displayed and is used for TWR if no other engines are available and activated. That's probably what you were seeing before.

Edited December 1, 2014 by Starwaster

[Apollo13]

Does it 'reattach' if you do a non-phys timewarp? And then 'detach' again after you come off rails?

If so you need to check for errors (probably but not exclusively a nullref) when the ship first loads into the scene and probably before it comes off rails.

Not on rails. At this point, I had not been on timewarp for many minutes. Never reattached. I'll check for errors.

[King Arthur]

PAR- is really nice since it lets MJ handle the heading and roll angles, which it can do with much better precision than you can, while letting you still have manual control over translation since you would in general be far more fuel-efficient and fly safer than MJ. Best of both worlds and whatnot.

Incidentally, PAR- is shorthand for "parallel negative". What PAR+/- does is it orients your ship parallel to that of your target, with the +/- dictating whether you point in the same direction as or against the direction of your target. Think of cars on a straight road for an easy analogy, PAR+ is two cars on the same side of the road traveling in the same direction, while PAR- is two cars on opposing sides of the road traveling in opposite directions.

[Starwaster]

PAR- is really nice since it lets MJ handle the heading and roll angles, which it can do with much better precision than you can, while letting you still have manual control over translation since you would in general be far more fuel-efficient and fly safer than MJ.

Actually I have seen MJ perform a docking of two really massive pieces with a minimum of RCS thrust available and I had not provided a very generous amount of propellant. MJ thrusted for about a minute and I walked away for a few and I came back and it was just sitting there seemingly inactive with the ship parts not really looking like they were going anywhere anytime soon so I shut it off and took over myself. I Quicksaved at that point just in case I fouled things up, which I did, partly because I got impatient with the small amount of thrust I'd given it and partly because I passed into shadow and nighttime dockings and I do not get along well.

When I reloaded I took the time to actually LOOK at what MJ had set up and it had the parts meeting up 15 minutes in the future. Basically it had used the tiny amount of propellant I'd given it and planned a long term burn to dock two pieces that were about 50 tons each. So it can behave impressively when it wants to.

[King Arthur]

I've have MJ auto-dock surprisingly well on a number of cases as well. Personally I have MJ fly the docking if there's plenty of open space and monoprop to spare (low risk dockings), if I'm docking something excessively heavy (in my case a 99t can of fuel...) that manually flying it would be just plain annoying, or if I'm docking something that requires absolute precision that I cannot in any way provide through manual docking. This all presuming RCS is reasonably balanced, of course.

Otherwise I dock with PAR- and manual flying since I can fly around busy/crowded stations far more safely and handle RCS-unbalanced ships better than MJ can.

Something I've noticed with MJ's auto-docking is that it does not seem to use or account for reaction wheels. I can fly RCS-unbalanced ships to a docking safely since I wait for the reaction wheels to counter-torque the RCS unbalance every-so-often, unlike MJ's auto-docker that just applies a continuous stream of RCS to attempt to correct and end up freaking out.

EDIT: Might be mistaken about the struck-out part above, just had MJ pilot one of my orbiters with just one set of RCS perfectly. Auto-docking is weird I say...

Edited December 2, 2014 by King Arthur

[johnsonwax]

I have a feature request that I think would open up some new use cases.

I like to put up properly spaced geostationary comm networks (Remotetech) that are stable over time. Ideally, that means parking a satellite directly over KSC but I realized that the easiest way to do that is a launch aiming for 2868.75 km and using the Kerbal Engineer HUD to keep horizontal surface velocity at 0. So, what I'd like is a button in the launch profile or some such suitable location to launch directly into a geosync orbit directly over the current location (keep horizontal surface velocity at 0), and a button to land at the current lat/long. MJ already has harmonic orbits to assist with satellite spacing.

Beyond the benefit of doing this for my case, it would be extremely handy for simplified station/ground station transfers - you can launch directly to rendezvous, then dock, and you can undock and land directly at your launch site. It's a bit of a haul at Kerbin and requires an extra 1000 dV compared to a 70km orbit, but there's no transfer windows, no hohmann transfer, phasing, etc. It's a straight shot up and back, reliable 24/7.

[Stone Blue]

^^ Hmmm...I just use HyperEdit for that...

[dharmdevil]

Hi guys, I just want to ask how to fix this problem with mechjeb autoland.

I'm trying to autonomously land my big, tall lander on Kerbin precisely on pad using mechjeb, completely powered--no parachutes and it has 2km/s delta V.

So far, it has 100% failed every attempt. The Landing prediction also always moves around.

It tries to retrobrake into a a steep re-entry angle everytime then does course correction for as long as it can, then it retrobrakes again to an even steeper angle until it runs out of fuel.

Any help/suggestions guys? I want my lander fleet to be completely autonomous.

[bdito]

Hi guys, I just want to ask how to fix this problem with mechjeb autoland.

I'm trying to autonomously land my big, tall lander on Kerbin precisely on pad using mechjeb, completely powered--no parachutes and it has 2km/s delta V.

So far, it has 100% failed every attempt. The Landing prediction also always moves around.

It tries to retrobrake into a a steep re-entry angle everytime then does course correction for as long as it can, then it retrobrakes again to an even steeper angle until it runs out of fuel.

Any help/suggestions guys? I want my lander fleet to be completely autonomous.

My suggestion would be to add parachutes and landing legs. It'll save you a bunch of delta v and make landings far easier.

How high is your orbit when you click the autoland button? If you're too high it will give you a very steep reentry angle which will need a lot of delta V. You should preferably be in a 100km orbit which will put you on a shallower angle and use a lot of aerobraking. But if you have parachutes and landing gear you can survive a much steeper angle.

[sarbian]

Put a save somewhere. Do you use FAR or NEAR ?

[Apollo13]

@sarbian: quick question: In the Delta-V window, MJ is simply reporting TWR and Delta-V data provided by KSP, correct? It is not setting those values. I ask, because, as I mentioned above, there are times when the Delta-V window shows a TWR of 0.0 when I have a "Skipper" engine and a ton of fuel.

Oh, and thanks for the Smart_A.S.S.TGT/PAR functionality. Never knew it was there until mentioned above. Awesome functionality there, my friend. I seldom dock with auto-dock.

Note: I was looking at the autodocking code and noted that "minimum start distance" is set to a minimum of 10. Can you change that such that value must be greater than 0? Thus, the start position becomes wherever the vessel is at that moment. This would help in situations where I've moved the vessel within a few meters of the target port and initiate auto-dock.

Sidebar: I use a mod called Virtual target. It allows me to point to any point on a planet/moon and set that as a target. It does not need to be on the vessel's flight path. Does MJ have that function somewhere? If not, it would be a nice feature, given that I appreciate MJ's one-stop-shopping system for all my KSP gameplay needs.

Edited December 2, 2014 by Apollo13

[Red Iron Crown]

KSP itself doesn't calculate delta V and TWR, that's done by MechJeb or other mods in a vessel simulation.

[Apollo13]

KSP itself doesn't calculate delta V and TWR, that's done by MechJeb or other mods in a vessel simulation.

But those MJ calculations are based upon data provided by KSP. I've been poring through the KSP class documentation for Part, PartModule, and Vessel.

[Red Iron Crown]

They are. The dV calculators pull part masses, engines specs, staging info, and fuel state from the game and calculate from there.

[sarbian]

MJ computes the TWR & Detla-V. Stock KSP does not have those info. When you have such result please share the save or the ship.

Also, make sure that you use the latest dev version, as I fixed something like that in early November.

[Felbourn]

@sarbian: quick question: In the Delta-V window, MJ is simply reporting TWR and Delta-V data provided by KSP, correct? It is not setting those values. I ask, because, as I mentioned above, there are times when the Delta-V window shows a TWR of 0.0 when I have a "Skipper" engine and a ton of fuel.

Try reducing the amount of fuel/mass above the engine. Once the TWR gets too low it shows up as 0.00 in my experience.

[Apollo13]

MJ computes the TWR & Detla-V. Stock KSP does not have those info. When you have such result please share the save or the ship.

Also, make sure that you use the latest dev version, as I fixed something like that in early November.

Using dev build #352

Try reducing the amount of fuel/mass above the engine. Once the TWR gets too low it shows up as 0.00 in my experience.

Can't. As shown in my images in previous post, I have a single tank and a single engine. Tank has lots of fuel, so there should be TWR of 2.6. this was the value reported previously on that same flight. Also mentioned, TWR shows as 0.08 and 0.02. It's random. The Delta-V window report is not an MJ problem; it'a a KSP problem. MJ is reporting/calculating on values erroneously provided by KSP to it.

As an experiment, I built that exact same vessel with same three components. It showed the correct delta-V in the MJ Delta-V window (in VAB, on the launchpad, and in flight)

Edited December 2, 2014 by Apollo13