IMFD Display behavior question

[PaulG]

Here is the scenario.

Planning a minimal energy transfer to Mars. Intercept MJD is 55385.601 which intercepts Mars at the transfer Apd.

Given that date, if the ejection date is set for 55139.2 (246 day trip) and I manually rotate the display (shift-z) so that I'm almost looking across Mars' orbital plane (orange) the anticipated trip plane (blue) is nearly parallel to Mars's orbital plane. See image below.

Now, if I do the same, but set the ejection date 22 days earlier, at MJD 55117, for a total trip time of 268 days, the trip plane rotates to nearly 90° of mars' orbital plane (see image below).

Why? What is happening with earth that causes this plane to change. As I increase the days, it reaches a nearly parallel plane again.

Thanks,
Paul

 

[jarmonik]

It's very simple. In the Off-plane transfer mode transfer orbit normal vector is a crossproduct of source position and target position. When these vectors are pointing in opposite directions, the transfer plane is not well defined. Use any other mode instead of Off-plane.

 

[PaulG]

Thanks, That's what I thought. I was thinking about this last night after I wrote it. What you are saying is that this would occur when the source position and the target position are nearly 180° apart?