Multi-Flyby Maneuver Sequencer output
Hello, Arrowstar! When doing some research on gravity assists in KSP I came across your tool, and I must say it looks absolutely amazing. The two included PDF tutorials are great for describing the functions of the tools, especially Mission Architect, and their intended uses. At this point I have worked my way through the two PDF tutorials plus the one in this thread linked in the first post, and I have read through the first 23 pages of this thread. As an idea of how familiar I am with orbital mechanics, I find myself having to look up how to spell Hohmann, ie very little to speak of. I apologize if I've overlooked the solutions to the problem I describe below, and would be grateful for a nudge towards more information. I have some feedback to offer from the eyes of a new user who is familiar with computer science but not much with orbital mechanics, if that would be welcome.
However, before I can provide that, I'd like to make sure I actually understand what it is I'm supposed to be doing, and I'll admit that my ignorance of the math involved here appears to be seriously hampering my ability to meet with success while using KSPTOT. After an initial 2 hours of getting familiar with the tool's components and trying to get information into and out of KSP, I started working through the Kerbin to Lathe tutorial. It took my 4 hours to complete. The Solar System Edge tutorial, while admittedly more complex, took me 10 frustrating hours of trial and error and rerunning identical optimization steps to get through (final optimization attempt to reach Plock SoI took over 2 hours, not counted in the 10, during which I had dinner). I decided from there to attempt my own similar mission, doing a Jool assist to reach Sarnus and Urlum. I'm 8 hours into this one and I haven't left Jool yet in MA. I haven't tried any of this mission in KSP yet.
My problems seem to center around the optimizer not being able to find the solutions I am expecting it to. This is undoubtedly due to my lack of understanding, so I am hoping you can find the flaw in my process. I first open the Mutli-Flyby Maneuver Sequencer and choose the appropriate bodies. It runs through its calculations. I have gotten anywhere from 1500 to 5500m/s solutions. While I understand that there's some randomness involved and that these burns are just a starting point for MA, I still find that to be a very large variance, and I'm afraid this may be the beginnings of my problem.
From there, I set my initial state in MA to be identical to the parking orbit I used in MFMS (I tried the tutorial's suggestion of an optimized parking orbit that only requires prograde as well, same problems encountered). I orbit to true anomaly with -180 to 360 optimization and an initial guess provided by MFMS. I add the ejection burn MFMS provides with some variance in optimization on all three components. I add an SoI coast followed by a coast to Jool periapsis. The final state sometimes shows me in Mun SoI, sometimes in Sun, but never at Jool where I would have hoped to be given the identical parameters to MFMS. But fine, MFMS is just an approximation, I forge ahead. Next comes optimization.
At this point I hopefully haven't screwed anything up too badly. I run the initial pass to land within Jool's SoI successfully. Then I add the Central Body and UT constraints, which take some effort to satisfy by eventually they work out. Then I add Inclination, RAAN and Arg of Peri constraints, giving each of them a wider range than the tutorial suggests is appropriate. This is typically where things start to go wrong in earnest. The optimizer chugs away, and as it goes along the constraint violations go up up up and the radius of periapsis goes up up up. Eventually it gives up much worse off than it started. Sometimes it will show the initial state, think for a while, and then declare that it has finished with no iterations completed. Sometimes it will find a solution better than the one it started with, then wander off again, and clicking Accept ends up applying the last result found instead of the best (both in terms of the objective function and the constraint violations), which I find extremely non-intuitive. The tutorials don't really cover what to do if the constraints aren't satisfied or if the radius can't be brought under control; changing the optimization function around and possibly ignoring some of the constraint problems doesn't seem to help in this case.
Because I can't get the constraints satisfied with anything resembling a low radius of periapsis at Jool, my attempts to flounder around making a burn at Jool to correct the problem and still get to Sarnus all fail miserabily as the dV required continues to skyrocket.
I hope the descriptions of my difficulties are sufficient to send some guidance my way. I've included a link to some screenshots plus the MA file I saved and whatever logs I could find. Please let me know if there's anything additional I can provide.
Please do not take any of the above as criticism of your work. From what I can tell the tool itself is fantastic and working as intended; I simply do not know how to wield it yet. I very much appreciate your continued work on this project and I look forward to planning some awesome missions with it.
Hyperbolic Departure Orbit from Kerbin
---------------------------------------------
Semi-major Axis = -402.721 km
Eccentricity = 2.9865
Inclination = 9.483 deg
Right Ascension of AN = 11.387 deg
Argument of Periapse = 0.000 deg
---------------------------------------------
Inbound Hyperbolic Flyby Orbit to Jool
---------------------------------------------
Semi-major Axis = -43396.252 km
Eccentricity = 4.3488
Inclination = 8.153 deg
Right Ascension of AN = 145.196 deg
Argument of Periapse = 285.871 deg
Periapse Radius = 145323.266 km
---------------------------------------------
Outbound Hyperbolic Flyby Orbit from Jool
---------------------------------------------
Semi-major Axis = -43396.251 km
Eccentricity = 4.3488
Inclination = 8.153 deg
Right Ascension of AN = 145.196 deg
Argument of Periapse = 285.871 deg
Periapse Radius = 145323.266 km
---------------------------------------------
Inbound Hyperbolic Flyby Orbit to Sarnus
---------------------------------------------
Semi-major Axis = -42810.337 km
Eccentricity = 1.1374
Inclination = 176.825 deg
Right Ascension of AN = 31.048 deg
Argument of Periapse = 189.532 deg
Periapse Radius = 5880.000 km
---------------------------------------------
Outbound Hyperbolic Flyby Orbit from Sarnus
---------------------------------------------
Semi-major Axis = -8077.142 km
Eccentricity = 1.728
Inclination = 176.825 deg
Right Ascension of AN = 31.048 deg
Argument of Periapse = 189.532 deg
Periapse Radius = 5880.000 km
---------------------------------------------
Inbound Hyperbolic Orbit to Urlum
---------------------------------------------
Hyperbolic Excess Vel. = 1.257 km/s
Phase 1 Transfer Orbit (Kerbin -> Jool)
---------------------------------------------
Semi-major Axis = 50677193.878 km
Eccentricity = 0.73165
Inclination = 2.157 deg
Right Ascension of AN = 32.865 deg
Argument of Periapse = 359.056 deg
Period = 66202326.1753 sec
Departure True Anomaly = 0.944 deg
Arrival True Anomaly = 156.133 deg
---------------------------------------------
Phase 2 Transfer Orbit (Jool -> Sarnus)
---------------------------------------------
Semi-major Axis = 79552504.572 km
Eccentricity = 0.6187
Inclination = 1.522 deg
Right Ascension of AN = 151.597 deg
Argument of Periapse = 276.410 deg
Period = 130207259.1409 sec
Departure True Anomaly = 120.073 deg
Arrival True Anomaly = 163.948 deg
---------------------------------------------
Phase 3 Transfer Orbit (Sarnus -> Urlum)
---------------------------------------------
Semi-major Axis = 144352923.016 km
Eccentricity = 0.83643
Inclination = 1.697 deg
Right Ascension of AN = 169.851 deg
Argument of Periapse = 202.241 deg
Period = 318267860.6428 sec
Departure True Anomaly = 219.869 deg
Arrival True Anomaly = 175.406 deg
---------------------------------------------
Kerbin Departure Date =
Year 4, Day 353 19:19:56.539
(125090396.539 sec UT)
Jool Arrival Date =
Year 5, Day 177 04:06:22.748
(141365182.748 sec UT)
Sarnus Arrival Date =
Year 6, Day 161 02:03:20.564
(171511400.564 sec UT)
Urlum Arrival Date =
Year 11, Day 217 22:00:31.725
(334101631.725 sec UT)
Burn Information to Depart Kerbin
---------------------------------------------
Total Delta-V = 2.151 km/s
Prograde Delta-V = 2036.635 m/s
Orbit Normal Delta-V = 691.183 m/s
Radial Delta-V = -0.000 m/s
---------------------
Burn True Anomaly = 11.387 deg
---------------------------------------------
Burn Information to Depart Jool
---------------------------------------------
Total Delta-V = 0.000 km/s
Prograde Delta-V = 0.000 m/s
Orbit Normal Delta-V = 0.000 m/s
Radial Delta-V = -0.000 m/s
---------------------
Burn True Anomaly = 0.000 deg
---------------------------------------------
Burn Information to Depart Sarnus
---------------------------------------------
Total Delta-V = 0.709 km/s
Prograde Delta-V = 708.890 m/s
Orbit Normal Delta-V = -0.000 m/s
Radial Delta-V = -0.000 m/s
---------------------
Burn True Anomaly = 0.000 deg
---------------------------------------------
Multi-Flyby Maneuver Sequencer output
Mission Architect initial setup, pre-optimization.
Optimizer can't figure out how to get closer.
Working on UT constraint, made some periapsis progress.
Adding inbound hyperbolic parameter constraints.
Constraints get worse instead of better.
Even ignoring radius of periapsis, constraints continue to get worse. Selecting Yes will result in last result being applied, rather than 5th point where constraint violation was minimized.
Re-enabling minimize distance objective function results in radius of periapsis climbing along with constraint violations.