Apollo 11 CSI, CDH, Plane Change, TPI: So many questions, so little time.

[indy91]

Ah no problem, there is always something to learn or some bug or unclear documentation. If you want to prevent the issue from happening again you could switch the left TTCA/TRANS switch on panel 4 to disable. Of course then you can have the situation that translation isn't working when you want to use it. I have definitely done both in the past, accidentical translation and forgetting to enable translations again.

 

[Miriam]

If you want to prevent the issue from happening again you could switch the left TTCA/TRANS switch on panel 4 to disable.

That has become standard procedure for me after I had my share of those acts of idiocity: verify that TTCA/TRANS -disable (resp. TRANS CONT PWR -off in the CSM) before I key 00E on the F V37 once any thrusting program is finished. On the other hand, once the DSKY blanks and average G starts: verify that it's back to enable/on -and that orbiters control mode is in translation (!).

 

[rcflyinghokie]

Indy, you were spot-on with your assumption that there was an unscheduled thrusting event. And I was the cause of it.

After the Insertion, I'm embarrassed to say that when I did my P52, I was inadvertently using Translation instead of Rotation to get my marks.

After correcting my error, my new dV XYZs for CSI were +00482, -00000, and -00000.

I'll press on with the CSI, and I expect it will go better this time.

Thanks for your help. Sorry to send you on a wild goose hunt.

Hey its great that you found the error! Now you should be able to press on with little to no difficulty

As a sanity check, be sure to check your CDH dH value as well it should be close to 15.

 

[Wedge313]

RE: Sanity Check...after the CSI burn I'm not getting a warm fuzzy feeling.

I thought I had found the problem, but after my CSI burn I checked the orbit on the Orbit MFD and I'm at 51 x 48. I think I'm supposed to be around 45? And shortly after I started P33 I got a (now becoming familiar) 525 alarm. My radar signal was just below 1.6. I slewed around until the signal got to 1.8 and then gave it back to the LGC. Got a series of about seven F 06 49s, and I PRO'd through them as they converged.

Then after V32 recycling I got my F06 75. My CDH dH is 13.6, not what I hoped, but is it acceptable? The dT CDH/TPI was 49m 58s, and the dT TPI/TPI was 06m 57s. (not sure exactly what dt TPI/TPI is, but I probably want more than 7 min between them?) Something tells me these numbers aren't what I should see. But this is new ground for me. Should I press on, or do I need to redo the CSI?

And in the event I press on, can I skip the plane change maneuver?

Thanks.

 

[Miriam]

Then after V32 recycling I got my F06 75. My CDH dH is 13.6, not what I hoped, but is it acceptable?

Should be. I never get exactly 15 nm, I guess you could achieve that by playing around with the TPI time, but as that is restricted due to lighting conditions...don't bother.

The dT CDH/TPI was 49m 58s

That's about 10 mins longer than the flightplan. Hard to say. I had deviations of +/- 5 mins or so, but 10...I'd press on and see what happens.

TPI/TPI was 06m 57s. (not sure exactly what dt TPI/TPI is, but I probably want more than 7 min between them?)

No, you want that value to be 0.? Thats the difference between the planned TPI TIG and the actual predicted TPI TIG. Again, 7 mins aren't good or bad.

And in the event I press on, can I skip the plane change maneuver?

Depends. That's what V90 is good for. V90E (you can do that while P33 is running), enter the PC TIG (which is calculated CDH time -30 mins) and it will come up with Y, Ydot and psi. Only Y dot is interesting here, it's the required PC dV. I don't know the exact threshold, but I haven't had more then 5 fps or so ever. Never burned them and came out okay.

 

[indy91]

I agree with everything that Miriam has said. You must have some source of error that is making the state vector bad during thrusting or at least some minutes of not taking RR marks. What angle difference did you get in your P52? You are good to continue, I think, but you will probably get a few more 06 49s. If everything is going really well it would be one or even no 06 49 at the start at each marking sequence.

Orbit MFD and I'm at 51 x 48

How did you calculate that? Apollo program uses nautical miles and it calculates altitude relative to the landing site. PAMFD shows apoapsis and periapsis in nautical miles, but relative to the mean lunar radius. For Apollo 11 add about 1.6NM to the HA and HP in the PAMFD and you get your actual numbers, that ideally the LGC also shows in V82 if its state vector for the LM would be perfect.

 

[Wedge313]

What angle difference did you get in your P52?

After P52 the difference was .00002. BUT I did manually select the stars, the star the program wanted to auto select (35) was not visible (below the horizon). I used stars 37 and 45. The star check was good.

How did you calculate that?

The 51 x 48 came straight off the Orbit MFD, I just converted km to miles. But I just ran V82 and got Ha 46.2 and Hp 44.7. PAMFD shows 44.4 x 42.6.

Only Y dot is interesting here, it's the required PC dV. I don't know the exact threshold, but I haven't had more then 5 fps or so ever.

Ouch. My Y dot is 13.8. V90 F 06 90 shows -00217, -00138, +00131. Before I did the CSI burn I ran V90 and got a Y dot of -00000 (F 06 90 +00009, -00000, +35996). So if I had to guess (and it is a guess since I'm still learning how this all fits together) I'd say I'm in-plane before CSI but out of plane after? Which means I'm oriented incorrectly when I do my +Z RCS burn, right? I'm going to revisit that point of the sequence and see if I can find what I did wrong.

Thanks for the help.

 

[Miriam]

Hm. Again: not good, not bad. I'd burn the PC. That'd be a P30 maneuver, TIG is CDH time -30 mins, dVx and dVz are 0, dVy is Y dot with inverted sign.

 

[rcflyinghokie]

After P52 the difference was .00002. BUT I did manually select the stars, the star the program wanted to auto select (35) was not visible (below the horizon). I used stars 37 and 45. The star check was good.

The 51 x 48 came straight off the Orbit MFD, I just converted km to miles. But I just ran V82 and got Ha 46.2 and Hp 44.7. PAMFD shows 44.4 x 42.6.

Ouch. My Y dot is 13.8. V90 F 06 90 shows -00217, -00138, +00131. Before I did the CSI burn I ran V90 and got a Y dot of -00000 (F 06 90 +00009, -00000, +35996). So if I had to guess (and it is a guess since I'm still learning how this all fits together) I'd say I'm in-plane before CSI but out of plane after? Which means I'm oriented incorrectly when I do my +Z RCS burn, right? I'm going to revisit that point of the sequence and see if I can find what I did wrong.

Thanks for the help.

Just throwing this out there, if you want to pop into the spaceflight discord, https://discord.gg/wevRzNuU, I would be happy to watch your rendezvous and see if I can identify any issues in real time.

 

[Wedge313]

That'd be a P30 maneuver, TIG is CDH time -30 mins, dVx and dVz are 0, dVy is Y dot with inverted sign.

So with my Y dot MINUS 00138, I'd enter PLUS 00138?

And while we're on the subject (another learning opportunity ), does the Plane Change have to be done at CDH - 30m, or can it be done at some other time, like CDH -20? I'm asking because I've got about 10 minutes before CDH -30, and in previous attempts I've blown by the TIG long before I got all the procedure done.

I would be happy to watch your rendezvous and see if I can identify any issues in real time.

Thanks for the offer. I'm unable to run these maneuvers in "real time", at time accel 1x the LM quickly develops a wild gyration, due I think to the fact that my extremely limited laptop CPU can't keep up with everything. I'm running it at 0.3x, which seems to be it's happy spot. But if I'm still struggling after re-re-doing the CSI burn (third time's the charm?) I may take you up on it, Thanks!

 

[rcflyinghokie]

So with my Y dot MINUS 00138, I'd enter PLUS 00138?

Yes the Ydot value you obtain with V90 and entering ther CDH-30m TIG you invert when you enter it in P30. So this is correct (though very high)

And while we're on the subject (another learning opportunity ), does the Plane Change have to be done at CDH - 30m, or can it be done at some other time, like CDH -20? I'm asking because I've got about 10 minutes before CDH -30, and in previous attempts I've blown by the TIG long before I got all the procedure done.

Technically it can be done at a different time, the CDH-30 allows ample time to keep computing CDH after the burn. If you wish to use a different time, however, you need to use that as the TIG for V90.

Thanks for the offer. I'm unable to run these maneuvers in "real time", at time accel 1x the LM quickly develops a wild gyration, due I think to the fact that my extremely limited laptop CPU can't keep up with everything. I'm running it at 0.3x, which seems to be it's happy spot. But if I'm still struggling after re-re-doing the CSI burn (third time's the charm?) I may take you up on it, Thanks!

Hmm I wonder if running at 0.3x is causing any issues? What kind of gyrations and issues are you seeing at 1x? What framerates are you getting? @indy91 @Thymo could running entirely at less than 1x cause problems with any maneuvers, AVG G, etc?

Also, you can still stream at 0.3x I just meant we can actually watch what you are doing to identify issues in real time.

 

[Wedge313]

I think I found my (latest) error. After re-running the CSI, it appears I was messing up the "Pulse To Drive R1 And R2 To Zero" step. I'd been doing this in 0.3x time while watching the DSKY. So I was mashing the appropriate NUM keys for a significant period while waiting for the R1 and R2 values to change, and not looking at the FDAI (or out the window) to see that I was building up some big rates. I think this caused the radar to loose lock (which I missed), and threw off everything from that point on. (I now have a better understanding of how the RCS works in ATT HOLD)

I re-ran the Pulse step, paying attention to the FDAI (and yes I cheated a little and used the HUD). After carefully and patiently orienting the LM and conducting the CSI burn I ended up with a Y dot of -00001 (a little better than -00138!). F 06 75 dH is +00150, dT CDH/TPI +35m 13s, and dT TPI/TPI is -02m 49s. (V82 gave me Ha 45.6 Hp 43.7). So, not perfect but much better than I was.

Proving that my default reasoning is correct: In NASSP if something isn't going right, it's usually because I messed up somewhere. "We have met the enemy, and he is us".

Pressing on, I'm going to make a command decision and try to skip the Plane Change. I only have 4m 38s to the CDH -30 time, and there's no way I can squeeze it in. I've seen this discussed in another thread so I THINK I can skip it. I'll find out soon.

Thanks again for the help.

 

[rcflyinghokie]

Excellent news! Those values look good. And with a Ydot of 0.1 fps you can certainly opt to skip. I believe they would be skipped if less than 0.2fps but I need to re review that to be certain.

 

[Wedge313]

Systems question:

Shortly before the CDH burn I got a HEATER light, RR temp was 148. I followed the checklist, pulled the two RR heater cb's on P11. I just finished the burn, and the RR temp has climbed to 180 (30 deg. rise in 22m). The LM orientation has the RR in direct sunlight, and nighttime is still a ways off (10 minutes?). At the current rate the RR temp could reach approx. 194 before then.

1. With the heater cb's pulled, can I assume the sun is the culprit? Do I need to roll the LM and get the RR into the shade?
2. If I do nothing and wait to pass into dark, will the RR fail at some (unknown) temp, or can I trust it will bravely soldier on for 10 minutes?

Thanks

 

[rcflyinghokie]

Systems question:

Shortly before the CDH burn I got a HEATER light, RR temp was 148. I followed the checklist, pulled the two RR heater cb's on P11. I just finished the burn, and the RR temp has climbed to 180 (30 deg. rise in 22m). The LM orientation has the RR in direct sunlight, and nighttime is still a ways off (10 minutes?). At the current rate the RR temp could reach approx. 194 before then.

1. With the heater cb's pulled, can I assume the sun is the culprit? Do I need to roll the LM and get the RR into the shade?
2. If I do nothing and wait to pass into dark, will the RR fail at some (unknown) temp, or can I trust it will bravely soldier on for 10 minutes?

Thanks

Hmm I havent seen the RR overheat but this is worth investigating of course. So the RR will heat up if in sunlight, if the STBY and/or OPR heater breaker are in, and if it is powered (RR cb (2)). Over a normal rendezvous I havent seen the RR heat up to that point before.

Which build are you on? And would you mind posting a scn so I can go take a look at some of the nuts and bolts?

 

[Thymo]

Hmm I wonder if running at 0.3x is causing any issues? What kind of gyrations and issues are you seeing at 1x? What framerates are you getting? @indy91 @Thymo could running entirely at less than 1x cause problems with any maneuvers, AVG G, etc?

I can't think of any. In fact the simulation should be more stable due to the shorter timestep length.

 

[Wedge313]

OK, here's where I'm at. And I'm using NASSP v1702 that I installed in August.

 

[rcflyinghokie]

OK, here's where I'm at. And I'm using NASSP v1702 that I installed in August.

When I load this scn the temps are normal.

 

[Wedge313]

Sorry my bad, I clicked on the wrong save. THIS one should be where I'm at, just coming out of the CDH burn and beginning TPI P34.

 

[rcflyinghokie]

So during rendezvous you typically have your "back" to the sun forward facing the CSM. This is the only reason I can think of for your RR heating up that much.

The heaters have thermostats so they stop heating at a certain temperature, so the only sources of heat are the electronics (powering and moving the RR) and the sun.

I have never seen it heat up, but your orientation also has more sun impact than normal rendezvous positioning I think. I still will investigate and see if I can replicate this