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Author Topic: Apollo 8 Testing using Apollo 8 Flightplan  (Read 12254 times)
Admiral
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« on: February 04, 2008, 07:49:45 AM »

Hi all

I am new to the forums and have been working through the Apollo 8 FlightPlan over the last couple of weeks of the new year since the latest beta release on 15 Jan.

I am now at the 100 hour mark about to prepare for my final course correction before Earth reentry.

Well done to all for the very good work over a long period of time.  It is just sensational and you should be all very proud for the work you have achieved.  Well done.

Here is my feedback.
The checklists are of a very high quality and very easy to follow and very accurate.

Prelaunch, launch and separation worked fine

At my first state vector update at MET 08:00:00, I forgot to put in the launch mission time in the CMC update.xls.  (I recommend that this gets added to the excel Apollo 8 Flightplan, AGC worksheet as an instruction).  I was able to correct my mistake.

While on trans lunar coast my screen saver kicked in while on 10x warp.  I had a CTD when trying to regain the focus again.  I am running orbiter in a 1280 sized  window.

Between 052:30:00 MET (after 3rd P23 of the mission ) and 060:00:00 MET I noticed I had a constant Comp Activity light come on.

The 2nd mid course correction had prog error 1520 or error 1202 alarms occur at execute.  P00 would not set and the comp Activity light stayed on.

To fix, I did a V36 CMC restart procedure.  This cleared the comp activity light error and I performed an IMU recovery.  Interestingly I was out of both Earth and Moon SOI according to IMFD so did not do a state vector update until I was in th Moon SOI well after the burn.

No problems encountered with the Lunar insertion burn.  The only thing I found annoying was using the increment/decrement EMS wheel.  I couldn't refine it to exactly match the burn time.  I did get it close though.  I don't know if it can be programmed to be set using the mouse scroll wheel to adjust.

The circularisation burn ended up quite a bit shorter than it should have been.  Not sure why.

For the man set Roll, Pitch, Yaw scroll wheels.  I noticed if you decrease the butons from 001 to 000 (or 360 depending on you poinrt of view), 350 is displayed, then 359  is the next dowm, so just a minor display issue.


At 88:00:00, I left lunar orbit and had a constant Comp Activity light after that burn.  Another CMC reset fixed it

I am now at the 100 hour mark, and I've had another constant Comp Activity light and 1520 alarms at the next p23 program start.  I am testing to see if V96 is possible to use.  I seems it might temporarily delay the light enough to execute a procedure.  I am likely to do a cmc reset though.

The state vector updates after the first one were ok.  I key in the full 5 digits in the cmc (eg 00021) for each vextor.  It is a bit clunky to work with the copy and paste.  Is it possible to push the values to excel. Or if easier pushed to a text file on  v71 execution that can then be read and  imported via an excel macro as a simple alternative. 

The IMFD takes a bit of getting used to, but the more I use it, the more I see its power

I am performing all tasks listed in the flight plan and plenty of quicksaves along the way. 

With plenty of consumables left, I have just 45 hours to go until splashdown  I love this program. Very Happy
The alarms along the way add to the realism and force good troubleshooting!



From The Admiral

« Last Edit: April 08, 2008, 05:21:21 PM by Tschachim » Logged
Tschachim
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« Reply #1 on: February 04, 2008, 10:23:35 AM »

Thanks for your kind words and sharing your experiences!  Happy

...The only thing I found annoying was using the increment/decrement EMS wheel.  I couldn't refine it to exactly match the burn time.  I did get it close though.

Use the right mouse button for fine tuning, also you need to set the delta velocity in ft/s, not the burn time: http://nassp.sf.net/wiki/EMS

Cheers
Tschachim
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irnenginer
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« Reply #2 on: February 04, 2008, 11:32:17 AM »

The 2nd mid course correction had prog error 1520 or error 1202 alarms occur at execute.  P00 would not set and the comp Activity light stayed on.

The state vector updates after the first one were ok.  I key in the full 5 digits in the cmc (eg 00021) for each vextor.  It is a bit clunky to work with the copy and paste.  Is it possible to push the values to excel. Or if easier pushed to a text file on  v71 execution that can then be read and  imported via an excel macro as a simple alternative. 

Welcome to the party.  Thumbs Up

You win the prize. you found one of the current issues with the vAGC. The explination takes too long to go into right now (at work) There will be a big post soon that explains this and the other problem which you will find at LOI. I would suggest you DO NOT use the vAGC for the LOI burn, if you do you will see why Wink.

I have no suggestion for making state vector updates go better other then you do not need leading zeros when entering the numbers.
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lassombra
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« Reply #3 on: February 04, 2008, 01:33:27 PM »

As I mentioned in another thread in development, we are going to be working soon on integrating the CMC update sheet with the MFD, this will provide a much cleaner system I think.
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My current Project Apollo work:

Quickstart to the Moon initiative (Quickstart_to_the_Moon): Done through earth orbit.  Working on new method of calculating TLI.

Checklist Controller: 
  • MFD Interface 99%(Minor cleanup and future features remain)
  • Panel Interface 99%
  • Excel interface and logic 99%
  • LEM Event code.0%
  • DSKY Interface code. Framework complete, creating "buttons"
  Approximately 80% done. (Checklist Controller
Admiral
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« Reply #4 on: February 04, 2008, 04:04:26 PM »

Thanks for the quick replies. Thanks for the EMS tip - very helpful.

I can also add that the minor display problem for the Attitude Set scroll wheel is on the Pitch wheel only when rolling to 000, it displays 350.

Cheers

The Admiral
« Last Edit: February 04, 2008, 04:12:25 PM by Admiral » Logged
Tschachim
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« Reply #5 on: February 05, 2008, 01:40:36 PM »

I can also add that the minor display problem for the Attitude Set scroll wheel is on the Pitch wheel only when rolling to 000, it displays 350.

Yes, that's really a display problem: Only the last digit is rolled partially, the first 2 digits only show whole numbers/degrees. So if your pitch setting is 359 and you increase that number by clicking up with the right mouse button, which add 0.1 each click, the 9 begins to disappear and the 0 (of 000) begins to appear, but the first 2 digits show 35.. until you actually reach 0, so 359.9 looks almost like 350 and not almost like 000. This problem exists at every 10 step of every wheel and since it's some work to fix this rather minor problem, I don't expect a fix soon...

Cheers
Tschachim
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Admiral
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« Reply #6 on: February 05, 2008, 02:42:51 PM »

For those following the thread, here is some more relevant information from irnenginer that relates to the issues I encountered mid flight using the vAGC

http://www.ibiblio.org/mscorbit/mscforum/index.php?topic=1566.0


Thanks Tschachim for your explanation on the scroll wheels.  It makes perfect sense and simple workaround.


The Admiral
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Admiral
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« Reply #7 on: February 10, 2008, 02:44:49 AM »

Here's how I went on from the T+100hour mark.

The Comp Activity light was stuck on.   I found that V96, would terminate the activity.  I found that I could not load P00 without the light occurring though.  The reasons for the constant Comp Activity light are suggested in this thread.

I tried a CMC reset and tried a complete CMC shutdown and restart, but the light wouldn't clear.

I decided to postpone P23 and my final mid course correction until I was in Earth SOI.  IMFD showed me outside Earth SOI and outside Moon SOI.

Once I was in Earth SOI, I was able to enter P00 and the light problem cleared and able to do a state vector update.

I set up IMFD for the mid course correction.  I couldn't get the map IMFD to show a prograde intercept with the Earth for reentry.  It showed only as low as 158k.  On my current course, I was going to overshoot by a couple of thousand miles but at least land in the Pacific Ocean and reenter with a 6.2 degree entry angle. I decided that this would be okay on this first test run.  Better than missing the Earth entirely!  The only issue was that I would be entering 2 hours early.

All procedures up to reentry were nominal.

On reentry, all looked good by the AGC.  I was surprised by how much RCS activity there was orientating the spacecraft very quickly to entry orientation.   I was clearly going to overshoot as well.  I also realised my early arrival meant that I was going to splashdown in the dark.  Not quite ideal.


During the initial descent, the CM rotated 180 degrees a few times around its axis and there was a lot of RCS activity.  The heatshield remained pointing the right way so all seemed okay. I suspect the RCS activity was due to the overshoot.  I had programmed in the mission desired landing lat and long in the agc as the splashdown point.  I now realise imfd reentry displays entry interface lat and long.  How do i find out my new landing predicted splashdown point?

The G's maxed out and the crew died.  I thought my 6.2 degree angle would be too shallow if anything.

The rest of the descent was nominal (if I really didn't burn up).  On landing, the AGC displayed my lat on long, way off.

According to the AGC, my Lat and Lon on landing was 9.2 degrees north and 8 degrees west and 9800 miles away from the landing zone.
I knew i wasn't there.  The scenario editor pinpoints me at 8.96 degrees north, 145.99 degrees west which is in the zone of where I had been targeting.

It was hugely fun (except I killed the crew  Crying or Very sad) and will try reentry again.  It is very satisfying to have got to moon orbit and back under a full checklist.  The Apollo 8 Flightplan is very well done

The Admiral




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Christophe
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« Reply #8 on: February 10, 2008, 06:18:11 AM »

Hi Admiral!
Congratulation for your flight, and thanks for sharing.

About your entry: I think you probably missed your TEI.

The TEI is usually considered as the most critical and tricky maneuver, but I remember that a procedure using IMFD 4.6 gave some good results.
Since I'm no longer familar with IMFD especially with the last IMFD 5 version, I guess it has to be updated, but anyway, here it is:



1/
On one MFD, (called further as MFD 2) open ORBIT MFD.
2/
On an other MFD (further called MFD 1) open IMFD, module BASE APPROACH
3/
on MFD 1 , IMFD:
- Set the Moon as the source (SRC button)
- Set TEJ equal to the Perigee time (PeT) displayed on orbit MFD (MFD 2)
- Set Longitude and Latitude equal to the coordinate of your landing site. You can use the historical one at first.
- Set ALT to 121.95 km. (caution! don't forget to set km and not meters!)
- Set REA to 6.50
- Set ANT to 21
- Set HINT to the historical value (from flight plan, mission report or any other doc you want) or adjust and search so as to get the mini Ov displayed on the IMFD.
4/
On MFD 2, bring up IMFD too and shared with the IMFD already displayed in MFD 1
From that step, we use "IMFD 2" to designate this IMFD and "IMFD 1" those where the Base Approach mode is running.
On IMFD 2, open the Orbit Eject program and choose the submode Base approach (don't mistake with the Base Approach prog)
5/
On IMFD 2, set and adjust TEJ to get the mini delta V
6/
On IMFD 1 (Base Approach running), Set the TEJ so as to be syncronysed with TEJ on IMFD 2
7/
IMPORTANT!
Check the EIN parameter. For the burn to be smooth and in order to avoid erratic and premature shutdown while in autoburn, this value should be less than 1.
If not, you can adjust some parameters to decrease it within 1. For example you can change the latitude of your landing site or maybe slightly change the TEJ. But don't change the other parameters and above all, don't change the following entry values: ALT, ANT, REA !
8/
That's all!
Perform your burn and welcome back home!


Note:
If you're not following the historical timeline and trajectory during lunar orbit, you may encounter some trouble with the historical landing site: wrong EIN and/or inappropriate heavy delta V (above your fuel capacity)
In this case, 2 solution:
1/
Wait for the historical TEI time and/or a proper time when the landing site is reachable again.
2/
Change the landing site.
NASA had a method for that:
It consisted in the definition of several longitude lines called as "recovery lines" where an adequate landing site could be located.
The latitude was updated in real time depending on time and lunar orbit inclination.
All the official recovery lines for a specific mission can be found on the presskit from that mission.
Presskit are available on numbers of web site. For example:
http://www.hq.nasa.gov/alsj/frame.html


If you would like to test wether that works in a way or an other with IMFD 5 I would be very pleased and I think it would be very helpfull for other people.

Regards,
Christophe
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rwitham
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« Reply #9 on: April 07, 2008, 03:06:10 PM »

I'm also in the middle of running the Apollo 8 mission.  I agree with Admiral.  Everything is very well done.   Thumbs Up

I have not encountered any CMC problems however, but I'm only at MET 037:xx:xx.

One question I have is regarding two different worksheets with similar names: "G&N maneuver" and "SCS Maneuver".  They both have similar procedures in them (TLI, MCC's, etc.)

1.  What is the difference between these two "sets" of procedures?

2.  It appears the G&N maneuver worksheet is not finished.  Or, at least, does not cover as many maneuvers as the "SCS Maneuver" sheet.  There is no LOI, LOC, TEI, or 3rd MCC.  Is this an error/oversite or intentional?  Perhanps the answer to question 1 will provide an answer to this question also.

Thanks

Reuben
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pattersoncr
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« Reply #10 on: April 07, 2008, 06:16:47 PM »

Reuben,
As I understand it, there are significant issues with the way thrust vector control (TVC) or engine gimballing works.  As a result, attitude control becomes unstable during long burns controlled by the vAGC.  See the thread Admiral linked in reply #6.


- Chuck
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lassombra
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« Reply #11 on: April 07, 2008, 06:43:40 PM »

The answer to the question is simple.  G&N procedures use the CMC to fly the ship through the procedure.  SCS procedures use the standby system, which is not as susceptible to the problems we currently have with the AGC due to our modeling of the TVC being incorrect.  Since the SCS is also modeled by us (and possibly also incorrectly) we are able to make sure that it works correctly.  Right now, some of the higher-duration burns are much harder to do using the CMC because of the poor TVC.  We are working on the problem, but in the meantime, if the maneuver you need to perform isn't on the G&N page, go to the SCS page.
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My current Project Apollo work:

Quickstart to the Moon initiative (Quickstart_to_the_Moon): Done through earth orbit.  Working on new method of calculating TLI.

Checklist Controller: 
  • MFD Interface 99%(Minor cleanup and future features remain)
  • Panel Interface 99%
  • Excel interface and logic 99%
  • LEM Event code.0%
  • DSKY Interface code. Framework complete, creating "buttons"
  Approximately 80% done. (Checklist Controller
rwitham
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« Reply #12 on: April 07, 2008, 07:52:07 PM »

Thank you Chuck and Lassobra.

I would assume that the G&N maneuvers was how it was actually done.  Are you using a PID loop to control the TVC?  I've worked with those quite a bit.  I'd be happy to lend a hand if anyone needs one. Two Cents


Reuben
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irnenginer
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« Reply #13 on: April 07, 2008, 11:53:53 PM »

Currently the TVC is controlled directly by the AGC. There is some filtering in AGC software but the direct connection to the TVC angle creates an unstable condition that causes it to go out of control. Basically there is a big piece of the control loop is missing. There is a lot more to this piece and it really needs some work. If you like I will put together what I have figured out.
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lassombra
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« Reply #14 on: April 08, 2008, 02:43:54 AM »

Reuben, I think it'd be great to have you on the team.  I'm sure between you and irnenginer you guys can solve the problem with CMC navigation.
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My current Project Apollo work:

Quickstart to the Moon initiative (Quickstart_to_the_Moon): Done through earth orbit.  Working on new method of calculating TLI.

Checklist Controller: 
  • MFD Interface 99%(Minor cleanup and future features remain)
  • Panel Interface 99%
  • Excel interface and logic 99%
  • LEM Event code.0%
  • DSKY Interface code. Framework complete, creating "buttons"
  Approximately 80% done. (Checklist Controller
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