Does orbital rendezvous require six degrees of freedom

kerbal-space-program

I'm trying to accomplish my first orbital rendezvous by following the Gemini 6A and 7 mission tutorial on the KSP Wiki.

I've gotten the orbiters on about the same orbital plane, and orbiting at about the same speed. They're down to thrusters only and there's less than 50m between them. However, I still can't seem to get them perfectly lined up for mating. The problem is that, no matter how hard I try to keep them pointed at each other, the target orbiter is always aimed just a bit off from the one I'm controlling as I get close. Sometimes, the alignment is close enough that they'll bump into each other but the docking ports won't connect – other times they completely miss each other by a few meters.

What is most complicated about the whole thing is that there seems to be no way for me to "strafe" the orbiters.

The movement options (considering the orbiter's nose "forward") are:

  • Thrust forward/backward
  • Roll clockwise/counter-clockwise
  • Yaw left/right
  • Pitch up/down

The critical pieces I'm missing here are:

  • Thrust up/down
  • Thrust left/right

To compensate for these missing controls, I have to point the orbiter in the left/right or up/down positions and use the forward/backward thrusters to effect the desired adjustments. However, by the time I get pointed back at the target and start closing in again, I quickly find that tiny discrepancies in my adjustments are putting me off on the wrong trajectory again. Without having a full six degrees of freedom, which would allow me to more quickly correct for these errors, I'm having a hard time seeing how orbital rendezvous is possible.

Are there controls I'm missing that would facilitate the sort of movements I need? Or, are there other techniques I need to learn to compensate for the lack of those controls?

No mod suggestions please.

Best Answer

What you're looking for is called translation, and it is possible in KSP. But you'll need Reaction Control System enabled on your vessel to be able to do it.

You can use H, N, I, J, K, L (default keybindings) to perform short RCS thrusts in every direction. Or you could switch to docking mode (it's the small blue button in the bottom-left corner of the screen) and press the space bar to switch A, D, W, S between rotating the craft and translating it.