Question Apollo 10 LEM activation questions

[riclourenco]

I have three main questions regarding the preparation of LEM in apollo10, which also had them when I was trying to make Apollo 9.
The first one is regarding to the gimbal angles that we have to load AGC of the LEM. In apollo 9 the checklist said to put the PAMFD with the alignment in “LVLH”:

https://puu.sh/C7tcE/e2ec4cd7bd.png

but in Apollo 10 the check list says to put the alignment in ”Identical”:

https://puu.sh/C7tct/68e1850045.png

Is this because apollo 10 is on the moon, or can it be a checklist error?

The second question is regarding the LEM LGC/CMC clock sync /TEPHEN update. The CSM time that I have to load in the LEM AGC is the current GET in the CSM/LEM?

https://puu.sh/C7t0a/8c3f4ec9db.png

Or do I have to first start the CSM AGC to give me the time I have to load in the LEM AGC?

https://puu.sh/C7t0W/ebe84f6320.png

What I did in Apollo9 and now in Apollo 10 was to load the current GET, pressing enter after I load the line R3 when the GET I chose arrives (chosen for the next minute to be synchronized). This way:

https://puu.sh/C7uAM/62db68c50e.png

Then I execute the command V06N65 and the GET in the AGC of the LEM changes to these values:

https://puu.sh/C7uCz/17726d6914.png

I change to the CSM and I also execute the command V06N65 and it gives me this time:

https://puu.sh/C7uED/0e3d6b3580.png

I go back to the LEM and open the PAMFD in the LGC and press the “ENT” button, and the time in the both AGC of the LEM and CSM changes to:

https://puu.sh/C7uIO/cabe4cb55d.png

https://puu.sh/C7uHn/84b43e499a.png

After that, I copy the new time from the CSM and LEM which are:

CSM
R1= +00095
R2= +00029
R3= +03168
LEM
R1= +00095
R2= +00029
R3= +03103

Then I subtract these time values (CSM-LEM), namely the seconds, and then I load the difference in the AGC of the LEM for the dT:

R1 =+ 00000
R2 = +00000
R3 = +00065

https://puu.sh/C7uKy/83aabda698.png

Is this correct?

The third question is in regarding to the IMU Fine Align and the Gyro Torquing Angles, in which according to the checklist you have to enter them in the GET 96h20, but the PAD with these values only appears in the GET+- 97h00. What I did was wrote down the values and then went back to GET 96h20 to insert these angles which are:

Gyro Torquing Angles
- 00149
+00072
+00141

https://puu.sh/C7eT4/7ac61b865b.png

However I found that I could get exactly the same angles in the PAMFD by pressing “LGC” and then pressing “V42”, in which it shows exactly the same values as the PAD in the GET+ -97h00. I have entered these values in the LEM AGC:

https://puu.sh/C7vIi/ddacaff12c.png

After entering the command V16 N93E to monitor the Torquing, all values appear as zero:

https://puu.sh/C7vKy/cf489b33c8.png

This does not seem right, because in addition to the values being zero, they also do not show any variation to monitor. After that I have to check the GIMBAL angles of the LEM with the command V06 N20E and they seem to be +- correct comparing with the PAMFD:

https://puu.sh/C7wOZ/4f167b4399.png

Later in the checklist when the Torquing angles PAD time appears again (at GET +- 97h00 again), the PAD and also the PAMFD displays the values of zero, just as in the LEM AGC after I enter the command to monitor the Torquing angles:

https://puu.sh/C7wVN/cbc8dbd305.png

This is going well, is it my mistake, or is it some bug?
I also have the AGC "TEMP" light red! I think it's because the temperature in the space Suits and the cabin are marking 100º F. It must be due to some mistake I made in the checklist previously. Anyway I am going to restart the LEM.

https://puu.sh/C7xoo/8e1c0a8253.png

At this point also the Uplinks for LEM and CSM appear out of time with the checklist, between GET 97h00 and 97H20, in which it takes us a while to do the checklist because we have to wait for them.

I think these are maybe the main causes of not having been able to finish Apollo9!
I apologize for making so many questions, which are very likely to be basic, as for the long text. Can you give me some help with this?

Thank you in advance for your attention.
Best Regards

 

[indy91]

I have three main questions regarding the preparation of LEM in apollo10, which also had them when I was trying to make Apollo 9.
The first one is regarding to the gimbal angles that we have to load AGC of the LEM. In apollo 9 the checklist said to put the PAMFD with the alignment in “LVLH”:

but in Apollo 10 the check list says to put the alignment in ”Identical”:

Is this because apollo 10 is on the moon, or can it be a checklist error?

Using identical is correct. Apollo 9 is a special case and only that mission needs to use the LVLH option. The reason is that normally the CSM and LM use the identical alignment and REFSMMAT. In lunar orbit it's an alignment relative to the landing site. Having the same attitude reference helps with docking. For Apollo 9 there is no landing site, so the decision was made to use local vertical, local horizontal (LVLH) alignments in both vehicles. This is the same as an P52 option 2 using the TPI time as the reference time.

However, a LVLH REFSMMAT is defined differently in CSM and LM. The IMU is oriented the same way relative to the main engine in CSM and LM. The LVLH alignment always means looking forward at the given time gives a pitch angle of 0°. Looking forward means the SPS is pointing backwards in the CSM, but it means the engine pointing downwards in the LM. That's how you end up with different REFSMMATs, alignments and aligment procedures for Apollo 9 only.

The second question is regarding the LEM LGC/CMC clock sync /TEPHEN update. The CSM time that I have to load in the LEM AGC is the current GET in the CSM/LEM?

Or do I have to first start the CSM AGC to give me the time I have to load in the LEM AGC?

Same thing really. This part of the procedure just gives the LGC a roughly correct clock time. Looking at the procedure in the LM Activation Checklist it seems that the CMP would be looking at his clock time on the CMC, the CDR would enter the time but wait for the actual enter press and then presses enter when the CMP says so. So basically like the V55 Delta T procedure that then follows.

What I did in Apollo9 and now in Apollo 10 was to load the current GET, pressing enter after I load the line R3 when the GET I chose arrives (chosen for the next minute to be synchronized). This way:

Then I execute the command V06N65 and the GET in the AGC of the LEM changes to these values:

I change to the CSM and I also execute the command V06N65 and it gives me this time:

I go back to the LEM and open the PAMFD in the LGC and press the “ENT” button, and the time in the both AGC of the LEM and CSM changes to:

After that, I copy the new time from the CSM and LEM which are:

CSM
R1= +00095
R2= +00029
R3= +03168
LEM
R1= +00095
R2= +00029
R3= +03103

Then I subtract these time values (CSM-LEM), namely the seconds, and then I load the difference in the AGC of the LEM for the dT:

R1 =+ 00000
R2 = +00000
R3 = +00065

Is this correct?

Exactly right. Just, when you initially type V06 N65 in both vehicles you don't even need to press enter. When you have the V06 N65 up, then any enter press shows the current time. But you are of course only really interested in the times at the simultaneous enter press you are commanding with the PAMFD.

So typing V06 N65 (no enter) on both DSKYs would be sufficient. The goal is to get the CMC and LGC clocks exactly in sync. That should then be achieved (and can be checked by repeating the V06 N65 procedure with the PAMFD enter press).

The third question is in regarding to the IMU Fine Align and the Gyro Torquing Angles, in which according to the checklist you have to enter them in the GET 96h20, but the PAD with these values only appears in the GET+- 97h00.

The flight plan has the gyro torquing angles at 96:45h GET, so maybe a checklist error. Every event in lunar orbit will be delayed by 15-25 minutes for Apollo 10 as compared to the flight plan. That is expected. So the timing seems right.

What I did was wrote down the values and then went back to GET 96h20 to insert these angles which are:

Gyro Torquing Angles
- 00149
+00072
+00141

However I found that I could get exactly the same angles in the PAMFD by pressing “LGC” and then pressing “V42”, in which it shows exactly the same values as the PAD in the GET+ -97h00. I have entered these values in the LEM AGC:

After entering the command V16 N93E to monitor the Torquing, all values appear as zero:

This does not seem right, because in addition to the values being zero, they also do not show any variation to monitor. After that I have to check the GIMBAL angles of the LEM with the command V06 N20E and they seem to be +- correct comparing with the PAMFD:

Later in the checklist when the Torquing angles PAD time appears again (at GET +- 97h00 again), the PAD and also the PAMFD displays the values of zero, just as in the LEM AGC after I enter the command to monitor the Torquing angles:

This is going well, is it my mistake, or is it some bug?

The actual missions got a PAD with the gyro torquing angles. This is also done by the MCC in NASSP. The PAMFD just has the same functionality so that you can do this in the non-MCC scenarios.

Noun 93 displays the "remaining" angles to gyro torque. With small angles used in V42, N93 will display 0 before you can even type V16N93 because the IMU is already done torquing. That's quite normal.

When the PAD appears and you have already done the gyro torquing procedure with the PAMFD before that, then the two IMUs are of course already perfectly aligned with each other. So three zeros on that PAD are then expected.

I also have the AGC "TEMP" light red! I think it's because the temperature in the space Suits and the cabin are marking 100º F. It must be due to some mistake I made in the checklist previously. Anyway I am going to restart the LEM.

Usually the explanation is that time acceleration during translunar coast will drive the temperatures up in the LM. It should settle down during LM activation when the ECS is activated.

Is the glycol temperature also offscale high? If yes then you might have gotten a separate bug, which is caused by instabile suit and glycol loops. I'd like to have a look at your scenario if that is the case, it might be in need of being edited to be repaired. The LM ECS still needs a lot of work, easily the system in the LM that needs the most tweaks at this point.

At this point also the Uplinks for LEM and CSM appear out of time with the checklist, between GET 97h00 and 97H20, in which it takes us a while to do the checklist because we have to wait for them.

I'll check if the MCC has any wrong timing here for Apollo 10. Could very well be.

 

[macieksoft]

Usually the explanation is that time acceleration during translunar coast will drive the temperatures up in the LM. It should settle down during LM activation when the ECS is activated.

IIRC temps go crazy especially when tunnel is open or dump valves are.
When i was testing this i noticed that closing dump valves and both tunnel hatches makes ECS much more stable.

 

[riclourenco]

Thanks for your quick reply and for your great explanations! Regarding the Glycol is exactly at the maximum temperature (80 ° F), but is not off the scale i think.

https://puu.sh/C7FnU/ee4d80b8bc.png

Briefly: Cabin and space suits = 100 ° F; Glycol = 80 ° F. You think it's a bug? I can send you my save files . Just tell me where to send it!

Thanks again

 

[indy91]

Yeah, I think your scenario might have been broken thanks to the LM ECS. If it's the same issue as I had then it might already be fixed in newer NASSP 8 Alpha releases, although that doesn't help your scenario anymore.

Just upload your scenario to Dropbox or so, unfortunately the scenario files with CSM+LM have gotten too large to be attached to a forum post here. That's what saving the state of 3 computers does to the file size :lol: I can easily fix the broken part of the scenario if it is the same issue. Then all your temperatures will settle down after a bit of time.