Hi, so, I'm getting used to this tool still, and while I'm excited to see what kind of whacked out trajectories I can put together for efficient OPM transfers, I'm kind of banging my head against the wall here planning my basic self-tutorial mission that involves a Kerbin-centric Mun-Minmus transfer. The issue specifically is with the Mun ejection burn that would set my trajectory to intersect Minmus's SOI. I really hope I'm not cluttering up this thread too much by my probable PEBKAC here.
Other than importing an existing LKO satellite's orbit as a representative parking orbit, and giving it dummy dry mass/fuel values for the purposes of purely focusing on mission architecture (to be later replaced with actual values of the resultant spacecraft design) I proceeded to calculate the intercept burn from my initial orbit to the Mun, and using the optimizer and setting some constraints I arrived at a position to circularize at a good low orbit. Some more constraints were added to make the orbit more ejection-friendly, after that. I added a 24h coast around the mun to account for the lander's descent, surface ops, and ascent/rendezvous.
I then take the UT after this 24h coast (to rule out any windows opening during surface operations) as the earliest possible departure time, and then I plug in the same number for the earliest possible arrival time. I then compute the porkchop plot. The resulting graph looked reasonable, and I first tried the lowest ΔV, but then also tried a longer and shorter transit time, just in case. The maneuver looked good on the departure info window, but things fell apart when I tried to enter the departure burn into MA. My steps were as such:
Note the departure UT from the info window, under the Kerbin-Centric Transfer Orbit pane. On top of the 24h coast (using coast to delta time), I added another coast to go to this departure UT. I convert it to true anomaly after that, and already the angle is wrong. This angle is wrong both using and not using the Munar orbit's mean anomaly and epoch.
Copy the departure's burn params individually, prograde to prograde, normal to normal, radial to radial.
I then add another coast to the specified arrival UT. I find out this ejection burn has put me on an escape trajectory to heliocentric orbit at worst, and a useless elliptical orbit at best.
Even when I manually adjust the settings, setting the ejection anomaly angle manually via the coast to ejection and fiddling with the revolutions, I still end up with useless trajectories. The only way that I had any success with was to just copy the total ΔV from the porkchop plot and make a purely prograde burn at the specified true anomaly.
What am I missing here? Any help would be infinitely appreciated!
Still, I'm grateful that you'll look over it, full stop. Some more testing was done, now that I got home. I'm putting this out here now for you to look over later, or if maybe some mistake I'm making jumps out at anyone else in the mean time. I'm starting with looking at phase angles and such. At the specified time for the departure burn (UT 1748978.7063; hereafter UT α) it looks right in-game and departure planner, but in MA the angle is off considerably. (to save space, I'm only showing it in DP) Departure position/trajectory in DP, with specified orbital vector ΔV at UT α Departure position/trajectory in MA, with the same burn at UT α. I can get a better transfer with considerable manual fudge-ery, but that's aside the point. The burn doesn't pass the smell test to me, either. There's another discrepancy I found doing this, too: When I plug the orbit into DP, I tell it to use my anom/epoch info: Note how the epoch is UT α, and the departure time given to DP is UT α as well. Therefore, regardless of MA's accuracy here, DP should acknowledge that at UT α that my anomaly is 284° ; however, it still says my burn anomaly is 14.5° instead, despite still being at UT α. So at this point I'm more than a little puzzled. Once more, I cannot thank you enough for any help you give. I deeply appreciate it.