Gyroscopes

[Matte]

Hello Orbinauts,
i was wandering if it was possible to give vessels a stabilisation mechanism similar to ISS giroscopes;
if i remember well the goo Vostok 1 add-on by gekka has a strange mechanism that can keep the vessel oriented prograde or retrograde simply pointing it in that direction ( it oscillates a little bit then stabilise);
i'd like to know if possible how is it achieved, and if it is possible to reproduce for other addons like space stations...and how !
thanks
Matte

 

[Orbinaut Pete]

You want to speak to Tblaxland - he is doing the ISS CMG's for ISSU

I'm sure if he reads this he will try to explain it to you...

 

[Matte]

i'm here waiting for his words

 

[-Pv-]

Aren't the default autopilot buttons the same thing (although working with only a few preset orientations.) The idea being to point the vessel in a direction and keep it there. Related to this is the Attitude MFD which lets the user choose between Orbiter objects for references or create one on the fly.

What I would like to see is something which keeps an unmanned craft oriented so the ISS will maintain a docking attitude without tumbling while performing rendezvous or RPM.

The ISSU concept is indeed an exciting one providing the user with opportunity to actually operate a complex spacecraft, not just navigate it. What I didn't see mentioned is using ummu although I saw moving between spacecraft mentioned.
-Pv-

 

[Orbinaut Pete]

The ISSU concept is indeed an exciting one providing the user with opportunity to actually operate a complex spacecraft, not just navigate it. What I didn't see mentioned is using ummu although I saw moving between spacecraft mentioned.
-Pv-

Yes, UMMU will be included in ISSU. You will be able to EVA from Quest airlock using UMMU. Also transfer crew from Soyuz to ISS, etc.

 

[Matte]

the only difference is that the stabilization i was talking about does not need any fuel usage. try to use the Vostok 1 by gekka http://orbiter.mustard-fr.com/addons/vostok.php to see what i'm saying.

Aren't the default autopilot buttons the same thing (although working with only a few preset orientations.) The idea being to point the vessel in a direction and keep it there. Related to this is the Attitude MFD which lets the user choose between Orbiter objects for references or create one on the fly.

What I would like to see is something which keeps an unmanned craft oriented so the ISS will maintain a docking attitude without tumbling while performing rendezvous or RPM.

The ISSU concept is indeed an exciting one providing the user with opportunity to actually operate a complex spacecraft, not just navigate it. What I didn't see mentioned is using ummu although I saw moving between spacecraft mentioned.
-Pv-

 

[tblaxland]

i'm here waiting for his words

Well here I am.

I am indeed working on a control moment gyroscope (CMG) implementation for the ISS but also a more generic CMG MFD to give this capability to all vessels (once suitably configured for the vessel class).

Regarding the Vostok addon, I haven't used that before but I suspect that it works by directly setting the vessel's attitude rates via the Orbiter API. That part is not too hard and CMG MFD will do this too, but it will also have a simulation of four dual-axis control moment gyroscopes. This means that CMG saturation can be modelled and momentum will need to be unloaded occasionally using either gravity gradient torque or RCS.

Before I can do that, I need to rewrite Attitude MFD to give me the code to support CMG operations (for various reasons, but not least because the CMG controls need to know vessel know the vessel steering law). Secondly, I need to resolve how to solve the steering laws for the individual gyros given the vessel steering law - my matrix mathematics needs a little work for that.

Last point: I am modelling four dual-axis CMGs because that is what the ISS uses. I don't know how many gyros Vostok used, but I'm pretty sure it only used single-axis gyros.

All I can do at this point is beg patience. There is a reasonable amount of work required. I have a life, too

 

[Urwumpe]

Vostok did, as far as I can research, not include any gyros or reaction wheels. It had cold gas thrusters.

 

[Andy44]

That sounds great, tblaxland, good luck on that project.

BTW, if you're really ambitious, you can also model unloads using magnetic torquers, but of course those depend on how strong the primary's magnetic field is and what your altitude is.

 

[tblaxland]

BTW, if you're really ambitious, you can also model unloads using magnetic torquers, but of course those depend on how strong the primary's magnetic field is and what your altitude is.

The primary issue there is modelling the magnetic field to a reasonable degree of accuracy. I did a bit of research on that whilst working on Ananke since it is meant to use electro-magnetic propulsion (when I get round to it, currently Ananke has no propulsion).

I could probably do something but I see it as outside the scope of CMG MFD in any case. All the CMGs are really concerned about is the total torque acting on the vessel, regardless of the source (gravity gradient, RCS, magnetic torquers, green spaghetti monsters, etc). I have enough on my plate for now, I think

 

[garyw]

Well here I am.

I am indeed working on a control moment gyroscope (CMG) implementation for the ISS but also a more generic CMG MFD to give this capability to all vessels (once suitably configured for the vessel class).

Me. WANT!

There are tricks for stabalising the ISS attitude by using Attitude MFD but this uses prop rather than a CMG so it's not exactly realistic.

 

[Hielor]

All the CMGs are really concerned about is the total torque acting on the vessel, regardless of the source (gravity gradient, RCS, magnetic torquers, green spaghetti monsters, etc).

I'm glad that it will accurately model propulsion due to green spaghetti monsters, as they are the primary form of attitude control utilized by the Reptilians.

 

[AstroCam]

*facepalm*

Is there a dedicated thread for ISSU? Seems pretty cool...

 

[Orbinaut Pete]

Is there a dedicated thread for ISSU? Seems pretty cool...

http://orbiter-forum.com/showthread.php?t=6149

 

[Erupter]

Current satellites uses what i think you call GMC to hold attitude.
In some more words, using rotating mass to absorb or release momentum and thus hold attitude.
Periodically though this mass reaches saturation and it must be "zeroed".
This usually happens with the help of RCS.

Now my point is that there is a releation between the revolving mass and the attitude controlled mass. So in order to control such a thing as the ISS how heavy and big should the GMCs be?

 

[Urwumpe]

Most use actually reaction wheels, if I remember correctly, not CMGs. CMGs have some advantages over reaction wheels, but are far more complex.

 

[Erupter]

Being to lazy i forgot GIYF! (Google Is Your Friend)

http://en.wikipedia.org/wiki/Control_moment_gyroscope

explains it all...
Quite clever!
Much more efficient then the reaction wheel i was accustomed to.

 

[Urwumpe]

Being to lazy i forgot GIYF! (Google Is Your Friend)

http://en.wikipedia.org/wiki/Control_moment_gyroscope

explains it all...
Quite clever!
Much more efficient then the reaction wheel i was accustomed to.

Yes, but you still need at least 3 CMGs for attitude control. This can mean a lot of weight, but CMGs are less likely to saturate.

 

[Erupter]

Yes, but you still need at least 3 CMGs for attitude control. This can mean a lot of weight, but CMGs are less likely to saturate.

Well... from what i understand you shouldn't need 3.
Since you can well rotate the gyro, each gyro should be able to provide control over two axis. So you'd need two GMC for tri-axial control.
Am i wrong? Guess so...

 

[DaveS]

GMC

It's CMG. It's short for Control Momement Gyroscope.