[Improvement] Landing guidance / Inspired by a kOS program

[Sakata-MC]

Hey. Just saw this on youtube, and think this would be really darn cool to have in MechJeb. Not sure if this is a direction that you all would want to take MechJeb, but it does seem really darn neat. I'm not too sure about the whole skycrane bit, but the slope detection would be mighty handy. http://kos.wikia.com/wiki/File:Kerbal_Space_Program_w_KOS_mod_Descend_with_skycrane.

EDIT: I think the youtube video for this is still around: https://www.youtube.com/watch?v=Ww0WAFG_hYU

[sarbian]

For those trying this link they need to add a '.' at the end of the URL since github removed it from the link.

Yep, this is a nice idea. The landing AP would need an additional step where it hoover and choose a new site. BloodyRain2k also gave me an idea to change the landing site visually that would need that. Later, but on my list.

[Sakata-MC]

On the subject of landing... Since I actually needed something similar to this program, but don't have it, I tried what I figured would make sense -- the translatron. I'm not sure if this is only for spaceplanes, but it seems to want to pitch the rocket sideways as if for aerodynamic flight.

Steps I used -- landing autopilot with Mun-base target, which it wanted to land on top of, so I quickly switch to translatron, hit "Kill H/S" and "Keep Vert") Seems to work for a moment, but then pitches the ship to the side.

Is there something I'm doing incorrectly, or is there a tool for rockets that functions similarly to the translatron?

Github needs (or I haven't found) a discussion page so I'm not putting this into an issue page and cluttering up the issues list.

[sarbian]

No the translatron is made exactly for that. You re sure you did not run out of electric charge for the reaction wheel ? Or maybe you need to add a reaction wheel. Hard to tell without seeing the lander.

[Sakata-MC]

Let me get you an image... Built with the uber powerful Ion-Hybrid generator (overgrown RTG), Capsule, RC-L01, Fuel tank, Nuke, on "wings" are ASAS (that might be problem), small tank, the useless thing to mount engines on, 3 small nukes.

[BloodyRain2k]

If Kill H/S with Keep Vert tips over your craft is mostlikely broken in a way, either thrust imbalance or weight inbalance.

Did MJ try to counter it meaning was the yaw or pitch opposite of the direction it's tipping to maxed out?

[Sakata-MC]

Nope. It actually pitched the vehicle over horizontally after it killed the speed. Does that for almost any vehicle I've tried (regardless of having SAS vs ASAS) Here is another vehicle it likes to do that with (and this one is a miner so its a highly desired feature for me) The white 'rings' on the kethane tank below the kethane converter are reaction wheels (added extras because I figured the same thing you said (not enough torque):

[Sakata-MC]

Just a note, but it does initially work fine, but once the translatron kets the h/s killed, and meets the 'hover', then it kills the engine and pitches to the side.

I also tend to run this with SASS set to aim (what's it called?) straight up from ground.

[Sakata-MC]

Just tried it from KSP. Staged, punched Keep Vert, Kill h/s, speed .5, execute. Expected behavior is to hover with .5 m/s acceleration upwards. As soon as the landing legs clear the ground, it pitches to side and engines cut, ship goes boom:

(Tested a few times, seems to work half of the time, other times it actually tries to hover (though it does seem to have issues with wanting to "rock" back and forth instead of keeping pointed straight up (since h/s was almost non-existant from a launch)

[sarbian]

I'll do some test tonight.

[BloodyRain2k]

Yeah there's really something wrong with the hover mode, even a totally simple craft, just a medium 1m tank with 909 can't hover properly. It seems as if Kill H/S lags behind or rather doesn't do head calculations and also it only seems to use 5% of the steering power at most.

[sarbian]

:( I don't remember changing anything in that part of the code so it must be some side effect from a change to the attitude controller...

[Sakata-MC]

Hrmm, I've never been much for recording, but I'll see if I can find some decent free software.

[Brians200]

MSI Afterburner is free http://www.youtube.com/watch?v=CSbJlfJtbsE

[sarbian]

http://obsproject.com/ can record and is open. Never tried it but an other mod dev use it

[Sakata-MC]

Here ya go. BTW -- OS ftw. http://youtu.be/F_M4d387g4U Has a funny end... lol the MJ module survived the initial explosion...

[sarbian]

After a quick read of the code : does those engine have gimbals ? This code is OLD (like 8 month old :p ) and predate the improved torque handling. It should be a quick fix

[BloodyRain2k]

My test had thrust vectoring and what the Kill H/S used was at most 5%. And as he said when you're mostly upright and hovering it tips over for no reason.

[Sakata-MC]

Yep, the engines do have gimbals. Still one thing that really bugged me was that the whole thing just gives up at a certain point and plummets to the ground (and doesn't allow thrust changes until you turn off the translatron which is a bad thing since that click is time you need to be correcting the vessel's free-fall)

[sarbian]

My test with the current dev version of MJ : http://www.youtube.com/watch?v=8i8MgfniyoY&feature=youtu.be

Looks fine on my end

[Sakata-MC]

hrmm. Any known reaction with any of these mods? Might have to remove something if so.

Actions on the Fly 1.1.1 BioMass (Latest dev) Kethane 0.8.1 KSP Interstellar 0.8.2.1 MechJeb2 2.1.0.0.129 (Think I'm on latest dev (from jenkins)) Procedural Dynamics 0.5 Texture Compressor 1 Quantum Struts 2.0.3 IonHybrid 30.08 B9 Aerospace 4.0c KAS 0.4.4 KSPX 0.2.4 NovaPunch 2_03a Procedural Fairings 2.4.2 Kerbal Joint Reinforcement 1.4.21 KW Rocketry 2.5.52 Tac Fuel Balancer 2.1.13322.15

[sarbian]

I use all of them except Biomass, Quantum Struts and Actions on the Fly (it's getting old and throw some exception)

I don't see how Biomass could mess up the flight.

[Sakata-MC]

hrmm... when I download from jenkins I usually just grab the ZIP, and ignore the DLL (seems to be in the zip) Is this correct?

[sarbian]

There is no difference between the two.

Can you put your ship file somewhere ?

[Sakata-MC]

Sure. https://drive.google.com/file/d/0B93bqeFAXRZwb3o5LTRMTFdiVDg/edit?usp=sharing

[BloodyRain2k]

I can probably rule out Q-Struts, I use them myself and got no problems.

[sarbian]

Ok I had the bug with your ship. I just need to find out why now ....

[Sakata-MC]

Hrmm... Could it be the tri-engine setup? I have no idea.

I probably would make an F- in rocket-building

[Sakata-MC]

Hey Sarbian, did you find the bug? Or is it being elusive? Curious, I know you've been busy with .23 so was just wondering if ya found it before the update got thrown into the mix.

[sarbian]

I managed to duplicate it with a 1 engine craft, like BloodyRain2k, but did not find what was wrong. It just give up at one point even if it was working fine before. I am too busy with .23 for now, but need to work on it later

[Sakata-MC]

No problem mate. Take your time, know your plate is full, just don't burn out.

This message was sent via phone. Please excuse any typos, as my phone loves to 'autocorrect' to the wrong words. On Dec 20, 2013 1:15 PM, "sarbian" notifications@github.com wrote:

I managed to duplicate it with a 1 engine craft, like BloodyRain2k, but did not find what was wrong. It just give up at one point even if it was working fine before. I am too busy with .23 for now, but need to work on it later

— Reply to this email directly or view it on GitHubhttps://github.com/MuMech/MechJeb2/issues/254#issuecomment-31029767 .

[lamont-granquist]

Related to #1052

Leaving this open for historical reference and 'cuz very cool.