Flight Question Docking with arrow - RCS behavior inside the docking bay

[Iberville]

I have a simple question of users of the UCGO Arrow and the DGIV (or any ships that fit in the bay of the Arrow):

-I can dock any ship to any station in Orbiter, thanks to hours of reading tutorials and playing with the simulator. I realized that on the final approach whil trying to dock to the Arrow (when the DGIV or XR2 is in the bay), the RCS linear thrusters, when fired on the X or Y axis, also have influence on the RCS rotation thruster (yawn and bank). It's subtile but enough to turn a simple docking procedure to a annoying game of cat and mouse with the docking door. Usually, to dock with the ISS or anything else, the last meters can be really smooth (ship perfectly centered and closing vel to 0,02m ) I was wondering if it's due to the fact that we are almost docking IN a ship?

Did anyone even see that or am I the only weird here? :hello:
I can still dock easily, but it's more difficult than with an exterior docking port. I have done research on this forum and on Dan Steph forum and I can't find answers related to this specific topic.


Thanks!

 

[PhantomCruiser]

While I'm fairly certain that you are not the only weird one here, I'm not able to reproduce your gripe... It may be the way I approach the docking bay, I dunno.

I'll approach the arrow from the stern, drop down underneath and approach the docking bay. When I'm underneath it I kill forward monentume and translate up into the bay, center up and move forward to dock. I'm afraid I haven't noticed any funny business with rcs/rotation crossover.

Do you have gravity gradient torque selected by any chance? (grasping at straws...)

 

[Iberville]

I have "complex flight model" on but all the Perturbations settings off (no gravity gradient torque, no nonspherical gravity source and no radioation pressure).

-Let's say I am about 2 or 3 meters from any of ISS docking ports. I always start by fixing the rotational alignment first. I then move with linear thurster only to dock. I never have to use again rotation thrusters unless something bad happened (forgot to closed hover or whatever). But inside the arrow, I try to do the same thing : coming under the bay, stopping, aligning right under it, moving up with linear thrusters to be in front of the docking port. I then fix the rotation alignment and finish by the same thing than with the ISS: linear forward, a often a little bit on the X and Y axis. But inside the Arrow, it influences somehow the rotation alignement.

Maybe something I did before outside the ship inflenced it after. I'll give it a shot a few times and try to figure it out.

 

[Kveldulf]

What's probably happening is the Arrow is still rotating. Make sure that you hit killrot in the Arrow before you start approaching. If needed, use the scenario editor to completely kill your rotation. Stock Orbiter will still leave you with a little rotational velocity.

 

[Iberville]

What's probably happening is the Arrow is still rotating. Make sure that you hit killrot in the Arrow before you start approaching. If needed, use the scenario editor to completely kill your rotation. Stock Orbiter will still leave you with a little rotational velocity.

Did not tought of that. I'll give it a try.

 

[insanity]

Kveldulf is right on here. What's happening is that the Arrow is subtly rotating to maintain heading and pitch (for example, prograde mode) Killrot still won't get rid of all of it. What I try to do is use the CTRL + rcs direction to sync my rotation to the arrow's. Then do as phantom cruiser said and translate along the stern (watch out for that gravity wheel!) up in to the bay and over to docking port.

 

[Iberville]

Thanks for all the ideas. Problem is solved!

 

[garyw]

I've had that with the ISS so part of my checklist is to "Set the ISS to free drift (hit 5)". Makes docking a lot easier.

 

[Tommy]

This may also come in handy:

[ame="http://www.orbithangar.com/searchid.php?ID=2899"]AbsoluteKillrot v.1.2[/ame]

 

[LuckyHendrix]

Another solution is to put both ship in prograde mode , docking ports will stay aligned.