Question Rendezvous MFD

[sccard1]

Good evening everyone,
I have had Orbiter for a long time, but my attempts at precision long distance spaceflight/ orbital rendezvous have left me somewhat frustrated. I know that a rendezvous MFD currently exists and it uses the Hill equations if the separation is within 700 km.
Now my problems are as follows: First, I have trouble aligning the orbital planes. (the align planes MFD does fine for adjusting inclination, but does little for the Line of Nodes). Second, I have trouble making a Hohman Transfer Orbit such that I can arrive reasonably close to my target (5 or 6 km) so I can close the distance and dock.

My solution is to make MFD's to solve each problem. I have a strong enough background in orbital mechanics and math that figuring out the calculations to solve each problem is not too big of an issue. I also have experience with programming in MATLAB so I am familiar with writing code and debugging etc.

What I am not familiar with is Orbiter MFD devellopment or how its mechanics modeling engine works. I have an algorithm written down for how I would solve both the alignment and rendezvous maneuvers from a conceptual standpoint. That led me to a small issue.

Is ORBITER capable of doing a coordinate transform to work backwards to find the radius and Velocity vector pair in the Geocentric Coordinate system when the orbital elements at that time are known. Second is it possible to make the MFD orient the spacecraft using the direction vector for the burn in 3 dimensional cartesian coordinates, or am I going to have to do another coordinate tranform back to the system used by the Orbit mode on the HUD.

I am sorry for the length of the post. Any help wpuld be appreciated!

 

[tblaxland]

Now my problems are as follows: First, I have trouble aligning the orbital planes. (the align planes MFD does fine for adjusting inclination, but does little for the Line of Nodes).

I don't understand why getting the line of the nodes right is a problem. Align planes MFD includes information on when your current orbital plane intersects the target orbital plane, allowing you to burn at the right time to match both inclination and nodes.

Second, I have trouble making a Hohman Transfer Orbit such that I can arrive reasonably close to my target (5 or 6 km) so I can close the distance and dock.

IMFD is able to do this. Generally though you end up with a high interception velocity. You are better off using Sync orbit MFD and use Rendevous MFD once you are inside 700 km.

What I am not familiar with is Orbiter MFD devellopment or how its mechanics modeling engine works. I have an algorithm written down for how I would solve both the alignment and rendezvous maneuvers from a conceptual standpoint. That led me to a small issue.

Do you have the Orbiter SDK? Your best bet is to have look at the included examples and documentation to understand the Orbiter API. This article will help you get your environment right: http://www.orbiterwiki.org/wiki/Free_Compiler_Setup

Is ORBITER capable of doing a coordinate transform to work backwards to find the radius and Velocity vector pair in the Geocentric Coordinate system when the orbital elements at that time are known.

Yes, there are functions available for this in the API. Functions such as GetRelativeVel, GetRelativePos & GetSurfaceRef come to mind.

Second is it possible to make the MFD orient the spacecraft using the direction vector for the burn in 3 dimensional cartesian coordinates, or am I going to have to do another coordinate tranform back to the system used by the Orbit mode on the HUD.

Functions exist to set the vessel orientation relative to the ecliptic frame either by rotation matrix or Euler angles.

 

[Tommy]

It sounds like you are setting AlignPlanesMFD by hand using the ELS key. This will cause errors in the LAN alignment due to the time between when you set the value, and the time you get to the node.

If you click on the TGT button a dialog box will pop up. Use the cursor keys (the for arrow keys that are usually set apart) to navigate. Press the down arrow key until "Spacecraft" is highlited, then press the right arrow key to get a list of all vessels orbiting the reference. Use up and down arrow keys to highlight the one you want and then press enter. AlignPlanes will now enable you to match the target's Inc and LAN perfectly.