P22

[Sverige]

Hello guys,
I'm working through the Apollo 7 mission and love it and have reached the Auto Optics P22. I have absolutely no idea how to use P22 . First, where do I find "previously computed landmark coordinates"? After typing V37E 22E, F 06 89 is requested. Where do I find landmark and their coordinates? What landmarks are I expected to use and where do I find them? Is there any available comprehensive instruction that I can use? Please help me! Thank you for this amazing but really complicated simulator

Mikael

 

[thewonderidiot]

Hey Mikael, welcome to the Orbiter forum! Sorry we didn't get back to you quickly here; since this was your first post it was awaiting moderator approval where the people that know what they're talking about couldn't see it. :lol:

For anybody reading this in the future, Mikael popped into our IRC channel earlier today, and I think got this question answered. If you want to know the resolution, you can find it in our chat log (search for the timestamp 17:25:32).

 

[Sverige]

Thanks for your reply! a really cool simulator! I spend a lot of time with it and always learning something new. I look forward to the day I land on the moon with Apollo 11 but I still have a lot left with Apollo 7. :hello:

Mikael

 

[AliDarwesh]

Hey Mikael, welcome to the Orbiter forum! Sorry we didn't get back to you quickly here; since this was your first post it was awaiting moderator approval where the people that know what they're talking about couldn't see it. :lol:

For anybody reading this in the future, Mikael popped into our IRC channel earlier today, and I think got this question answered. If you want to know the resolution, you can find it in our chat log (search for the timestamp 17:25:32).

I am reading this having exactly the same question but the link you attached returns a 404 error

 

[indy91]

We have a list of Apollo 7 landmarks in the "Apollo 7 Update Forms.doc" document under Doc\Project Apollo - NASSP\Flightplans\Apollo 7. A great document that helps with Earth landmarks is this one from Apollo 8: https://www.ibiblio.org/apollo/Documents/A8-Landmark maps+photos-1004.pdf It's helpful to prepare for landmark tracking by familiarizing with the area around the landmark, works quite good with the high res textures in Orbiter 2016.

 

[AliDarwesh]

thanks!

 

[AliDarwesh]

Update: When doing the p22 with the coordinates and landmarks from the update forms, the sextant seems to be pointing in a totally wrong direction. when doing the 5 marks, 06 49 will show difference of about 35nm and no speed difference. when I update the sv by pressing PRO, then after completing the next landmark (point chimanche) will show an increased difference both position and speed. the third landmark (augusto severo airport) will yield a W-matrix overflow error (V05N09 421) when doing the marks, and even greater 06 49 differences also the 06 45 'max mga' is very low (less than a degree) before the first landmark, and was significantly greater but still below 60 before the second and third.

have tried alternative landmarks like key west (from the obsolete docs flightplan apollo 7 vagc) yielding the same results. (about 35 nm difference and no speed difference)

I start marking the target as soon as it is in sight but a bit below the horizon. with about 15 seconds between marks. what am I doing wrong? I suppose all 06 49 readings should be zero or close to zero. Perhaps I'm missing something obvious? I'm following the project apollo checklist MFD.

I'll add the scenario just before the first landmark just in case it is helpful.

 

[AliDarwesh]

We have a list of Apollo 7 landmarks in the "Apollo 7 Update Forms.doc" document under Doc\Project Apollo - NASSP\Flightplans\Apollo 7. A great document that helps with Earth landmarks is this one from Apollo 8: https://www.ibiblio.org/apollo/Documents/A8-Landmark maps+photos-1004.pdf It's helpful to prepare for landmark tracking by familiarizing with the area around the landmark, works quite good with the high res textures in Orbiter 2016.

I've read this thread and basically have the same issue as this guy. I even tried key west just to be sure and had exactly the same problem.

Apollo 7 vAGC P22 orbital navigation questions

makes me wonder if the coordinates need to be converted to orbiter2016's earth model? I've tried the landmarks.xls in the GNC tools folder, one time even trying wgs84 coordinates from a map application, but no real improvement in results.

Edit: I have kept trying using the coordinates from the update forms, and sometimes managed to get less than 10nm error, but I can't reproduce these results reliably. my error is usually anywhere between 40 and 10 nm. I'm at a loss here!

Update: After days of trial and error I have seen that even if I get 10nm or less position error on the firtst landmark, the results of the second landmark will always have great errors in them, sometimes more than 500fps velocity error. I have never had anything close to 0 error, with the lowest value ever achieved being about 6.5nm. I decided to disregard any P22 for now until I know what the cause is for the inaccuracy. I have semi-good results with my P23's, though.

 

[indy91]

Hmm, there is something strange in the scenario you posted above. Specifically in two values in the erasable memory that are quite important for finding a landmark on the Earth. First, the liftoff time in the CMC is wrong by about three minutes. In the checklist it says at T-3min: "V75 (NO ENTR)". The NO ENTR might be missing from the Checklist MFD file, if that is the case I will add it. But in any case it says V75 and not V75E. Did you maybe press enter there? That would account for the 3 minutes error in stored liftoff time and that amounts to 3 minutes of Earth rotation that the CMC doesn't know about.

But I think the main issue is another erasable memory location (AZO, azimuth of 0° longitude), which is not something that anything in the CMC should ever write to, so I am quite confused why it would be different than the launch scenario. Some people had bugs, which I could never replicate, that random memory locations are overwritten. Or not really random, but ones that are often accessed. Maybe you got that!? Did you have any restarts or weird program alarms during the mission?

In any case, here is how you can fix the scenario. Search for EMEM1706 in the scenario. Find this section:

EMEM1706 3
EMEM1707 11546
EMEM1710 13213
EMEM1711 36033
EMEM1712 33240

and change that to

EMEM1706 3
EMEM1707 11547
EMEM1710 25066
EMEM1711 30636
EMEM1712 33240

EMEM 1706 to 1710 is TEPHEM, the triple precision liftoff time in octal. The changed value here is the planned liftoff time, the number that is used in the T-4 hour launch scenario. Should be close enough. EMEM 1711 to 1712 is AZO, double precision prime meridian azimuth. Only EMEM1711 is different from the preloaded number, really weird. Nothing should change that value.

With these fixes P21 finds the correct latitude and longitude again. I will try a P22 with the fixed scenario later today.

 

[AliDarwesh]

Thanks. I had many restarts and program alarms during the mission, all of them during time compression. I found out by trial and error that the only 'safe' time compression in my case 10x.

I might indeed have pressed enter during the prelaunch checklist where I shouldn't. I will change the EMEM values and try again. Will let you know the results!

Update: Fixed! 6 49 showing single digit values now.

 

[n72.75]

10x time compression is kind of a rule-of-thumb max for NASSP. In some cases fast computers can do a bit more, especially if there's no load on the AGC. But 10x is a safe place to stay.

 

[thermocalc]

Hi, common to this tread is the fact that during time acceleration (max x30 on my PC) many times I also got RESTART and PROG alarms, few times I also got the NO ATT light ON losing the alignment, and things get screwed up, so I also started using only x10 most of the time without having similar alarm problems; now I am using x30 only when the AGC is in standby during the sleeping periods.
In my case I am only using Apollo 9 so far so don't know if the same problems will happen to me as well on other missions.
glad to see I am not the only one.
bye Paolo

 

[indy91]

In the Orbiter Launchpad under Extra, Vessel Configuration, Project Apollo Configuration, Miscellaneous you should have "Multi-Threading in time acceleration" enabled. Is that enabled by default? Not quite sure, we can make it default. That probably helps in time acceleration.

And as a general tip for time acceleration, for more stability I like to do longer periods on a panel that is not that resource intensive. Probably anything but the CSM main panel is fine. With that my usual time acceleration settings are 10x in low Earth/Moon orbit and 50x in translunar coast. I think I can get 50x with no problem for longer periods.

 

[AliDarwesh]

In the Orbiter Launchpad under Extra, Vessel Configuration, Project Apollo Configuration, Miscellaneous you should have "Multi-Threading in time acceleration" enabled. Is that enabled by default? Not quite sure, we can make it default. That probably helps in time acceleration.

And as a general tip for time acceleration, for more stability I like to do longer periods on a panel that is not that resource intensive. Probably anything but the CSM main panel is fine. With that my usual time acceleration settings are 10x in low Earth/Moon orbit and 50x in translunar coast. I think I can get 50x with no problem for longer periods.

If I recall correctly it was enabled by default when I opened those settings first time.

 

[thermocalc]

yes, I also enabled it since the beginning so the alarms I got were surely due to time acceleration issues...and as I said if I stick to x10 they never repeat themselves ... surely each computer make the difference but so far I feel comfortable with x10 and x30 when the AGC is down; I tried also to run x30 in external view, or on the CSM/LM forward hatch, or on the audio panel 10 .... but still when I get out of time skip and go to the main panel many times I still got the PROG/RESTART alarms...but know I keep saving very often....