Why does my rocket go back into the Mun's SoI? (Story/rant included)

[turbine495]

Greetings fellow Kerbonauts!

I was playing 0.24.2 Career Mode, and I, to complete a contract and get science, decided to go to the Mun. My landing stage had too small of a fuel tank (an FL-T200, with an LV-909), considering that I had tons of science gear aboard. The landing used up about 1/3 of my fuel, and I considered myself screwed. After giving the ship the name "Mun Base A", I started using it to complete contracts (flag and Science). As I did not want to transmit all my science, I eventually quicksaved, and took off in the general direction of Kerbin. (I landed in the Farside Crater). I reverted to quicksave several times to get an optimally fuel-efficient ascent profile.

Here is where I goofed.

After a not-so-optimal launch, I wanted to revert to quicksave to try again. But no! My brain decides that pressing Quicksave right now was a good idea. I realize my error and attempt to revert to quicksave ASAP. After loading up my botched launch mid-flight, I settled for "attempting to escape the Mun and getting into a Kerbin orbit" . I burned for escape, and when the map showed my Kerbin orbit, I set up a maneuver node to lower my periapsis into the atmosphere. From here on I timewarped, happily watching the node coundown tick.

The first indication of trouble came when I slowed down timewarp to grab some "high above Kerbin" science. When I tried to resume my previous rate of warp, the game told me I cannot warp faster than 'x' while below 'x' meters. (I didn't remember the exact values). Woah, so I am THIS close to Kerbin already? I looked at Kerbin in the distance. Nope. I went into Map View, and was shocked. My ship was in a high parabolic tragectory over the Mun and about to crash. I went into "Emergency Landing Mode" in an attempt to save Bill and some science. But alas, the ship crashed, and ~300 science was lost. Poor Bill.

Can anyone tell me why my ship goes back into the Mun's SoI, when Map View showed it was escaping?

Thanks!

Edited August 18, 2014 by turbine495

[Belphegor]

maybe you burned in a direction that allowed the moon to 'catch up' with you or cross your path again, puling you back into it's SoI?

or you did an adjustment burn in the wrong direction somewhere during your escape.. so many times i confused the front of my ship for the engine.. so many kerbals lost..

[Master Tao]

Two possibilities: high timewarp across SOI boundaries breaks the patched conics system and can drastically alter your final orbit. Alternatively, you may have found a parabolic arc that went higher than the Mun's orbit, but fell back toward Kerbin, intersecting the Mun's SOI. Possibly a combination of the two.

That said, even with an optimal escape burn from the Mun's SOI, your AP will still be at an altitude that intersects with the Mun's SOI. You'll need to aerobrake around Kerbin or make a retrograde burn at PE to lower your orbit away from the Mun.

Shame about Bill and the science.

[cantab]

Didn't use Shift+Tab and accidentally throttle up the engines did you?

If you can (and will) revert back to before your Mun ejection burn, do that burn to put you right back on course for Kerbin, no need for a second manouevre.

[Geschosskopf]

Can anyone tell me why my ship goes back into the Mun's SoI, when Map View showed it was escaping?

This is a known bug in the game. If you're in orbit around the central body and your orbit does not cross the orbit of a moon or planet also orbiting the central body, then the map will not show you any encounters, even though you might have some. So like both you an Mun are orbiting Kerbin. When you burn to leave Mun, you must have done so in such a way that once you escaped, the Ap for your orbit around Kerbin must have been inside Mun's orbit. Thus, your orbit and Mun's didn't cross, so the game won't show you any Mun encounters ahead of time, but will give them to you if they happen.