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Author Topic: parking orbit inclination  (Read 1378 times)
henryhallam
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« on: April 14, 2005, 07:40:43 PM »

I've noticed that with my installationg of Project Apollo 6.4, when flying an Apollo 12 mission the parking orbit inclination always ends up around 0.2 degrees greater than it should be (should be 32.540 degrees according to historical data).  I think this is why I'm having such difficulty getting my lunar orbit inclination greater than about 167 (should be 175 or higher) without an enormous mid-course correction.

The AGC launch heading, 72.029, matches the scenario file and the historical takeoff heading.  I'm not sure how to calculate which inclination that -should- give.

Could this have anything to do with the recent change to use a "heads down" launch configuration?

I spent the last hour or so rerunning the launch and the behaviour is consistent. (didn't use time acceleration, stayed in panel view the whole time).  I haven't yet checked the other missions, though I recall flying an Apollo 11 mission with a lunar inclination of close to 180 without much difficulty.

I realise you can change your inclination by burning while in lunar orbit - was this actually done on the Apollo missions though? You need quite a large burn to do so and it cuts the margin pretty thin for TEI.


Thanks so much to all the developers for working on this wonderful project!  I've got some limited experience with C and C++ programming, how would you guys rate the difficulty of working with the NASSP code and the orbiter API in general?  I haven't tried making any addons yet but I might try putting together a simple MFD which sums up the delta-V provided by engines during a flight.  When I've done that and got a bit more experience I'd love to help out in some way.
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movieman
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« Reply #1 on: April 14, 2005, 07:47:39 PM »

Apollo 12 has always been a tricky mission to fly: I'm not sure that the current guidance is accurate enough to get close enough to the correct inclination. Also, I think the TLI burn on a real Apollo could be set up so that it wasn't flown prograde and could do some plane change as well... at some point we should investigate that and implement it if we have to.

Quote
how would you guys rate the difficulty of working with the NASSP code and the orbiter API in general?


Hopefully most of it is fairly self-explanatory, and there's the sticky thread about how the C++ code was designed...
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chode
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« Reply #2 on: April 14, 2005, 09:50:53 PM »

Quote from: henryhallam
I've noticed that with my installationg of Project Apollo 6.4, when flying an Apollo 12 mission the parking orbit inclination always ends up around 0.2 degrees greater than it should be (should be 32.540 degrees according to historical data).  


The current launch autopilot isn't accurate enough to deliver you exactly into the desired inclination.

One solution is to edit your scenario and tweak the "TOHDG" parameter.
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