IMFD EjA and InA in relation to launch windows

[Kveldulf]

Maybe I'm a little slow on the uptake, but I noticed something last night while planning a trip. As I was searching for good intercept dates for Mars, I was noticing that as I was messing with the Target Intercept date, EjA and InA were changing, and when they reached their lowest, it was in relation to when the dV values were reaching their lowest point. I believe at one point I was able to reduce EjA to 0.00, and that gave me my lowest value with dV (EjA alone, I noticed the effects with InA later).

This got me thinking, if there is a correlation between the values of EjA, InA, and the dV for the trip, would watching these values aid in finding launch windows more then just eyeballing the dV, or am I just noticing a coincidental relationship?

 

[Tommy]

Yes there is a correlation. EjA is the ejection angle, and I believe it's in reference to your current orbital plane. A lower EjA means you are performing a smaller plane adjustment during ejection. A lower InA means your ejection path is closer to due East, so more of the Earth's rotational velocity is applied to your ejection velocity.

 

[jarmonik]

Both EjA and InA are directly related to delta velocity. In this case EjA is the angle between velocity vector of the Earth and tranfer orbit velocity during Earth departure. And InA is the angle between velocity vector of the Mars and transfer orbit velocity during Mars encounter. When both of these angles are zero it will most likely give a minimum delta velocity but, of course, there are exceptions.

 

[Kveldulf]

Both EjA and InA are directly related to delta velocity. In this case EjA is the angle between velocity vector of the Earth and tranfer orbit velocity during Earth departure. And InA is the angle between velocity vector of the Mars and transfer orbit velocity during Mars encounter. When both of these angles are zero it will most likely give a minimum delta velocity but, of course, there are exceptions.

Out of curiosity, are you able to name any off the top of your head?