Flight Question Orbital parameters confusion

[Dennyc39]

I had entered orbit around the moon and began to adjust it to about a 100-km altitude circular. After burning retrograde to lower periapsis to some 90-odd km, I continued around towards periapsis to circularize. The Orbit MFD showed a reasonable elliptical orbit that seemed to agree with the listed parameters.

About 5 or 10 minutes out from Periapsis, the terrain whizzing by showed that something was badly wrong. PeA was still listed as about 97 km, but current altitude was 27 km and going down fast.

What kind of geometry allows me to fly below my own periapsis? This is the first time this has happened to me in several lunar landings. I felt puzzled and cheated sitting on the fresh crater rim with the DGIV parts scattered about.

 

[ADSWNJ]

Are you sure it was a PeA, not a PeD? (Ask if that doesn't make sense to you!)

 

[Cosmic Penguin]

I had entered orbit around the moon and began to adjust it to about a 100-km altitude circular. After burning retrograde to lower periapsis to some 90-odd km, I continued around towards periapsis to circularize. The Orbit MFD showed a reasonable elliptical orbit that seemed to agree with the listed parameters.

About 5 or 10 minutes out from Periapsis, the terrain whizzing by showed that something was badly wrong. PeA was still listed as about 97 km, but current altitude was 27 km and going down fast.

What kind of geometry allows me to fly below my own periapsis? This is the first time this has happened to me in several lunar landings. I felt puzzled and cheated sitting on the fresh crater rim with the DGIV parts scattered about.

Can you try to post the various scenarios after each step that you have done, or even better a video recording of your flight? Because I think you must have missed something during your burns - as you said, IF the PeA is indeed ~90 km, there's no way that your ship would plunge onto the Moon.

 

[worir1]

You may have had it set to show PeR which is periapasis radius. It is measured from the center of the moon not from the surface. You want it to say PeA

 

[Izack]

It may also be possible that OrbitMFD is using another body besides the Moon as a reference.

 

[Urwumpe]

It may also be possible that OrbitMFD is using another body besides the Moon as a reference.

PeA of 97 km and Alt of 27 km would still be a mathematical impossibility. I don't know how you feel about it.

I suspect it is really rather was, that he was using Perilune radius there.

 

[C3PO]

PeA of 97 km and Alt of 27 km would still be a mathematical impossibility. I don't know how you feel about it.

I suspect it is really rather was, that he was using Perilune radius there.

Or a PeA of -97 km. If the PeD was 97 km he would have hit the surface much earlier.

 

[Dennyc39]

I guess I should have saved the scenario, but I didn't. But I am sure that I had checked that the DST button was set for PeA, not PeR. The PeR at that point should have been around 1800 km.

I'll just have to watch for it to happen again, and save the scenario if it appears.

 

[buster]

May I suggest this:

[ame="http://www.orbithangar.com/searchid.php?ID=4690"]StateSaver Autosave[/ame]

:hello: