Question ISS v3.0 by Thorton Station attitude

[BenSisko]

What key commands do you use to get the ISS in STS-92 docking scenario to maintain an attitude on the R-Bar for rendezvous, TORRA, and docking?

Ben

 

[Turbinator]

I don't know the key commands myself, but I know that for docking the ISS disables all attitude control.
The awesome thing is that both in real life, and in Orbiter, you have to do it for exactly the same reason.

 

[Orbinaut Pete]

I know that for docking the ISS disables all attitude control.

The ISS doesn't disable attitude control during Shuttle docking itself, it disables it immediately after the docking.

 

[Turbinator]

Are you 100% sure about that, because it's disabled in order to prevent any accidental movements during the critical phase of docking, if it where to move the results could be catastrophic.

 

[DaveS]

Are you 100% sure about that, because it's disabled in order to prevent any accidental movements during the critical phase of docking, if it where to move the results could be catastrophic.

Incorrect. ISS remains in attitude control during the docking approach. It's only after contact and capture that both ISS and shuttle goes into free drift. It's only after the orbiter docking ring has been retracted for hard docking that attitude control is resumed.

 

[BenSisko]

Here's my issue: Opening the STS-92 Docking scenario from Donamy's SSU STS-92 add-on has the shuttle ahead of the R-Bar below the ISS. In the time it takes me to set up the DAP, the station has pitched ~ 15 degrees off the R-Bar (the Progress end of the station is pitching toward the +V-Bar). Is there a command that holds the ISS on the R-Bar? Thorton's documentation suggests disableing the CMG for docking but I'm stumped?

 

[Donamy]

Yes, it is difficult. I've had some success with AttitudeMFD, but make sure you disable it, before returning focus to the Shuttle.

 

[BenSisko]

Thanks, I'll give it a try

---------- Post added at 02:12 PM ---------- Previous post was at 01:49 PM ----------

Donamy,
I see what you mean about disabling Attitude MFD before changing focus.

Thorton,
Any thoughts about adding an attitude hold function to the CMG of your ISS model? It would be most helpful for ISS models; 1A, 2A, and 3A where the shuttle flew an R-Bar approach.

Ben

 

[Thorton]

Thorton,
Any thoughts about adding an attitude hold function to the CMG of your ISS model? It would be most helpful for ISS models; 1A, 2A, and 3A where the shuttle flew an R-Bar approach.

Ben

Maybe, but 1A, 2A, and 3A doest have CMG.

 

[BenSisko]

Ok, I'm curious. How did they maintain those iterations of the station on the R-Bar then, IMU's & thrusters?

 

[Donamy]

They used the thrusters of the Zarya, and then also Zvezda.

 

[BenSisko]

Thorton,
What about an attitude hold function then? You could use the Surface MFD and HUD with the Zvezda thrusters to establish a LV attitude then the attitude hold to maintain it for an R-bar approach.

Ben

 

[Shadow Addict]

Why do they keep the station rotating throughout the docking? Wouldn't it be easier to just kill the rotation throughout the whole docking?

 

[Donamy]

It is that way, for docking with Hubble.

 

[tblaxland]

Why do they keep the station rotating throughout the docking? Wouldn't it be easier to just kill the rotation throughout the whole docking?

Not necessarily. Gravity gradient torque makes it difficult (ie, propulsively expensive) to maintain an inertial attitude. In addition, rotating at a synchronous rate means that you can keep a constant visual attitude reference to the horizon.