SyncMFD Manual axis moves in Sync Orbit MFD during burning

[misha.physics]

Hi,

I would like to understand why it happens. So, I set the Manual axis to be, for example:
[math]\operatorname{RAnm}=28.00^\circ[/math]


Then I give thrust in "Prograde" orientation and during this the Manual axis moves in Sync Orbit MFD:



I'm wondering, why it happens?

 

[Krishnan]

Hmm interesting. Does it move automatically because it detects an intersection with the best closest times of arrivals?

 

[misha.physics]

Honestly I don't know how it works. I've made some similar tests right now in OpenOrbiter and it remains. Maybe it works smarter than I can understand yet.

 

[Eddie C.]

Hi, I've just seen this interesting post looking for some other stuff. I am in office on work laptop and I just imagine it....so I may be saying BS
In order to best understand this phenomenon, we should look also (simultaneously) at Orbit MFD.
RAnm (in degrees) is defined as True anomaly of Ref. Axis = the angle between direction of the Ref. Axis and direction of your ship's Periapsis.
This can be best visualized if you choose in SyncOrbit MFD as intersection point (MOD button) your ship's Periapsis (Sh Periapsis) - in this case RAnm = 0 deg. If you, similarly choose intersection Sh Apoapsis then RAnm becomes 180 deg.

IF your prograde burn happened anywhere else than Periapsis, in your current orbit, then your periapsis might move around and the 28 degrees setting is keeping your Ref. Axis "following" the Periapsis.
If you do this burn exactly at your current orbit's Periapsis then I believe that the Ref. Axis will stay put.....or maybe I am wrong. When I arrive home I will give it a try.

 

[GLS]

Hi, I've just seen this interesting post looking for some other stuff. I am in office on work laptop and I just imagine it....so I may be saying BS
In order to best understand this phenomenon, we should look also (simultaneously) at Orbit MFD.
RAnm (in degrees) is defined as True anomaly of Ref. Axis = the angle between direction of the Ref. Axis and direction of your ship's Periapsis.
This can be best visualized if you choose in SyncOrbit MFD as intersection point (MOD button) your ship's Periapsis (Sh Periapsis) - in this case RAnm = 0 deg. If you, similarly choose intersection Sh Apoapsis then RAnm becomes 180 deg.

IF your prograde burn happened anywhere else than Periapsis, in your current orbit, then your periapsis might move around and the 28 degrees setting is keeping your Ref. Axis "following" the Periapsis.
If you do this burn exactly at your current orbit's Periapsis then I believe that the Ref. Axis will stay put.....or maybe I am wrong. When I arrive home I will give it a try.

The documentation agrees:

(from Orbiter.pdf, page 88)

 

[misha.physics]

@Eddie C., @GLS, thanks! I'm sure it's definitely so. My mistake was not paying attention to this in the documentation.

IF your prograde burn happened anywhere else than Periapsis, in your current orbit, then your periapsis might move around and the 28 degrees setting is keeping your Ref.

And it could also be apoapsis until he become periapsis (during "long" burning).

 

[misha.physics]

I just thought that the reference axis direction is setting in relation to some fixed axis which isn't changing (and can't be changed) during burning

 

[Eddie C.]

And it could also be apoapsis until he become periapsis (during "long" burning).

Yes, correct and valid remark. An Apoapsis prograde burn will also keep Periapsis at same angular deviation from Ref. Axis.

 

[misha.physics]

I would even say that we will just watch that Reference Axis is moving on Sync Orbit MFD during this burning (it won't be move if we do the burning at Periapsis (and Apoapsis for a while)). But the angular derivation between Periapsis and Reference Axis will always keep at any burning point, because they move in sync since RAnm is always keeping, namely not only at Periapsis and Apoapsis burning.