Author Topic: Earth to Mars in 1.0.8?  (Read 109 times)

pclaurent

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Earth to Mars in 1.0.8?
« on: December 31, 2017, 04:27:29 PM »
Using 1.0.8 for Android, several problems appear in the Orbit planner when trying to plan a trip from earth to mars using a custom mission. In that situation it seems that Orbit planner is not really usable for Hohmann transfer to external planets.

Let's try a custom mission using Shuttle Orion; with a date around Feb. 2016 (a launch window to mars). We start from a LEO (200 km circular). Using earth reference, we apply an escape velocity in the terrestrial orbit direction. Using sun ref, we increase DeltaV until reaching mars orbit, in a Hohmann transfer trajectory. Till then, everything seems OK. Then...

1.    Frequently (at each new orbit simulation?), a new "ghost" Shuttle Orion appears in the middle of nowhere. After a while, the screen is literally filled with "Shuttle Orion" labels. They even reappear if the game was previously saved.

2.    During time acceleration, the predictive @APO position of mars constantly shifts during the ongoing travel. If it first appeared at our trajectory apoaxis (which sounded good), then it moves further, as if mars were speeding up! So, the initial @APO seems to have no meaning at all… Or at least it doesn’t have to me presently..

3.    When touching again the DeltaV or DeltaT after an initial setup, the predictive orbit often skips in one direction or another (not so much, but enough to modify values again and again).
« Last Edit: January 01, 2018, 04:49:42 PM by pclaurent »

jcarrion

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Re: Earth to Mars in 1.0.8?
« Reply #1 on: January 11, 2018, 02:33:41 PM »
hi. Thanks for your comments. 

well , the predictive APO changes, as it is analitically computed. That means where would the apogee  if it werent other elements affecting the orbit.

in reality , Mars, and the rest of the planets are also affecting the spacecraft's orbit ,hence the orbit -while theorically inmutable -  will change over time.

that said , there was  a bug that corrupts a bit the orbit solver when time compression is set to a very high value. This has been fixed , will be in the next beta version. 

Thanks

pclaurent

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Re: Earth to Mars in 1.0.8?
« Reply #2 on: January 16, 2018, 06:12:57 PM »
@jcarrion, thanks for your input.
About target position at our apoaxis and its "shift" during the trip: I'm not talking about 0.5 or 1° deviation (which would be normal as you say, and I agree), but 10, 20° or more... Easy to reproduce if you try a Hohmann transfer from earth to mars: the predicted mars position (@apo) progressively shifts during travel, making mars impossible to reach (v1.0.8 Android).
« Last Edit: January 16, 2018, 06:15:52 PM by pclaurent »