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Clamp-O-Tron Sr. Not Working

NewsDude
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NewsDude

NewsDude

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I am trying to dock a ship to a station that is in Kerbin orbit, using the Clamp-O-Tron Sr. docking port. 

Station

C2RvjKi.png

 

ship

p2T5fCw.png

 

 

During Attempt (wide)

fqbyBkO.png

 

 

During attempt (close-up)

ybmYqv7.png

 

 

The mods in play are: OPT Spaceplane Systems (legacy, core, reconfig), Bluedog Design Bureau, B9 Part Switch, Spacedocks Redeployed, Station Parts Expansion Redux, and various IVA mods

 

The mods I have listed are the ones that I believe were in use while I was attempting this docking maneuver. I do have more mods downloaded and installed with KSP.

I've also included my log as well as a part of a GitHub repository: https://github.com/NewsDude49/KSP-Logs

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AHHans

AHHans

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A general tip when asking for help: don't crop the screenshots! In the GUI elements that often get cropped away there is a lot of information that gets cut away, some of which might be useful. [End of rant]

Well, the one thing that I can tell you is that you didn't make the mistake of mounting one of the seniors the wrong way around. But to tell you more it would be really useful to see the navball during your docking attempt, preferably from both vessels - i.e. two screenshots, one from each vessel.

Edited by AHHans
fixed typo
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steuben

steuben

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There used to a bug in which the docking ports would get "stuck" and wouldn't dock. You had to back right off wait a bit and try again. Don't know if it was fixed. But it might be what you're seeing here.

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AHHans

AHHans

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13 hours ago, NewsDude said:

How's this?

Better! What I can say is that you are not really aligned well and not moving towards the docking port. (If I interpret the MechJeb output correctly then you are moving mostly perpendicular to the docking axis.) Is that after you "bounced off" from the docking port? Do you feel any force from the magnetic attraction of the docking ports?

The "distance to dock axis"  in the MechJeb output is that for the docking port of your ship, or for the CoM of the ship?

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NewsDude

NewsDude

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"distance to dock axis" is for the docking port. What I can't figure out is what the 39.1m is measuring in the display. Is it possible that the fact that my command pod and the docking port are on opposite sides of my ship might be contributing?

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Gargamel

Gargamel

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5 hours ago, NewsDude said:

"distance to dock axis" is for the docking port. What I can't figure out is what the 39.1m is measuring in the display. Is it possible that the fact that my command pod and the docking port are on opposite sides of my ship might be contributing?

It shouldn't  But it should read a very small number.   The design of your two crafts might also be confusing MJ's bounding box, causing it to go too slow.  

Here's my recommendation, and up until I recently got a new machine, I was a hardcore MJ user just due to the framerates.   Get one of the Docking Port Alignment Indicator Mods, and fly some practice missions to get familiar with it's in's and outs.    I would keep it on standby for the times when MJ would bug out and either overshoot repeatedly, or would fail to dock like you have here.   Especially with the seniors.   

I believe MJ relies a bit on the magnetic force of the docking ports to finish off the docking manuever, but both your crafts are so massive, I would suspect the seniors don't have enough omph to get it done.  I don't know when your last screen shot was taken, but that speed is too slow to dock.  So use MJ lined up to start the approach, let it get the craft in the correct position and orientation.  Then take over and manually guide it in.  Keep your forward speed at 1 m/s, and fly gently to keep it oriented correctly.  With a little bit of mashing your head against the wall, you should get it to work.

My rule of thumb was before I used MJ, I learned to do it manually.  Didn't have to be good, just had to do it.  But after spending years using MJ on my potato computer, I watched how it did it, and would just mimic it's actions if I had to take over.   I'm assuming you'll be in the same boat, having used it enough to know what to expect and when. 

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AHHans

AHHans

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Posted
7 hours ago, NewsDude said:

"distance to dock axis" is for the docking port.

So the docking port is right in front of the the other docking port but at quite some angle. Now in order to dock your ship has to rotate to get the ship docking port pointed at the station docking port while keeping the ship docking port mostly where it is. So it needs to swing the whole ship around, while not gathering enough speed to fling the ship completely away. In large and heavy ships that takes ages if you rely on the magnetic forces of the docking ports.

It may work to just switch off SAS and MechJeb to just let the magnetic forces get your craft oriented. But that will only work if you don't already have too much speed to get away from the magnetic forces again.

7 hours ago, NewsDude said:

What I can't figure out is what the 39.1m is measuring in the display.

AFAIK that's the distance from your CoM to the target docking port. So it will never get smaller than the length of your ship from the docking port to the CoM.

7 hours ago, NewsDude said:

Is it possible that the fact that my command pod and the docking port are on opposite sides of my ship might be contributing?

No. The fact that your ship is  long and heavy is part of the problem because it means that it has a high moment of inertia and you need a large torque to get it turned. In addition turning it around the docking port (= re-orienting the ship while keeping the docking port in place) means moving the CoM quite a bit.

If you have solely been relying on MechJeb for docking then I also recommend to learn to dock manually. Just enough to learn what is needed for docking and to see when MechJeb is failing and needs help with docking. A good guide is @Snark's Illustrated guide to docking

1 hour ago, Gargamel said:

but that speed is too slow to dock.

Why do you say that? Docking means coming to a stop when the two docking ports are touching, so there is no minimum speed for docking. It's quite the opposite: if you are too fast when touching the docking port then you just bounce off, even if everything else is aligned perfectly. My recommended speed for docking is 0.1 m/s, maybe a bit less. (I typically slow down so that the display just switches from 0.1 m/s to 0.0 m/s just before I get close enough to feel the magnetic forces.)

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Gargamel

Gargamel

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9 hours ago, AHHans said:

Why do you say that? Docking means coming to a stop when the two docking ports are touching, so there is no minimum speed for docking. It's quite the opposite: if you are too fast when touching the docking port then you just bounce off, even if everything else is aligned perfectly. My recommended speed for docking is 0.1 m/s, maybe a bit less. (I typically slow down so that the display just switches from 0.1 m/s to 0.0 m/s just before I get close enough to feel the magnetic forces.)

With regular ports and "normal" mass ships, I agree 100%.  But the with the seniors and huge ships, I have never been able to dock at low speeds.  There just isn't enough magnetic force in the ports to have any effect on the ships. 

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AHHans

AHHans

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31 minutes ago, Gargamel said:

But the with the seniors and huge ships, I have never been able to dock at low speeds.  There just isn't enough magnetic force in the ports to have any effect on the ships.

And how does increased speed help there? When I'm docking large craft then I'm going extra slow (during the approach) so that I have more time to get well aligned.

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Gargamel

Gargamel

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1 minute ago, AHHans said:

And how does increased speed help there? When I'm docking large craft then I'm going extra slow (during the approach) so that I have more time to get well aligned.

I think my main point to the OP here, which seems to have gotten buried in this discussion, is that MJ accounts for the magnetic pull.   So it slows way down so you don't slam into the other ship.  So slow that it never actually docks.  So when you get close to docking, turn off the autopilot and coast in.   Be it .1 m/s or .3 m/s or 1 m/s, fast enough to have some momentum, but not so fast you're going to crash. 

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NewsDude

NewsDude

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Posted (edited)

I have been at it for an hour, and I can't get it to work. Should I do a screen record, and upload it?

 

Edit: I have been doing what @Gargamel recommended, and trying to manually with a Docking Port Alignment Indicator mod. 

Edited by NewsDude
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Gargamel

Gargamel

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Posted
4 minutes ago, NewsDude said:

I have been at it for an hour, and I can't get it to work. Should I do a screen record, and upload it?

 

Edit: I have been doing what @Gargamel recommended, and trying to manually with a Docking Port Alignment Indicator mod. 

That might help.  

Also, as a last resort, did you check this?:

c59QvPn.png

It looks like it in the pics, but it never hurts to triple check.... again.... :D

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AHHans

AHHans

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37 minutes ago, NewsDude said:

sorry, I'm still new to actually uploading to youtube.

No problem, it worked this time.

If I see that correctly then you don't feel any magnetic force from the two docking ports coming close together, right?

Is there anything connected to the front of the docking port on the station? Does it work if you leave away this girder structure from the station (the one that surrounds the ship)? Does it make a difference if you also set the ship as a target for the station?

Edited by AHHans
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