TEI Question

[sw34669]

Ok TEI pad looked good, printed and uplinked it and updated my state vectors, did P52. After the burn looking at my (post TEI), orbit something seemed wrong (confirmed with MCC-5 (TEI +15h) needing a further 34 seconds of burn)

When going through P30 I noticed that the comp numbers had been updated (burn time chanaged by a few seconds, N48 ptrim/ytrim not 0, RPY 1/2 degree changed, DVC that I had set on the EMS needed increasing by 2.8 and the weight the comp had was a bit off from the pad). So, for all of these burn params, should I stick to what's on the printed pad or what had been re-calculated by the comp after the pad was uplinked) ?

Should MCC 5 be such a large burn ?

What should I see in orbit MFD directly after the TEI burn. When I did the TLI, i could see the correct pea and apa.

thx

 

[Thespacer]

Which release version are you using? Asking in light of the changes Indy has made to MCC targeting, which appears to be incompatible with pre-existing save states.

The MCC5 Dv seems high.

 

[sw34669]

yes i'm using the version from 4 weeks ago i havnt updated due to the issues it would cause with MCC
the p30 was pre-loaded from the uplink I guess and re-computed . I just went with what was in the comp rather than the original pad from a few hours before.
something is for sure not right as mcc5 is 3x what it was in reality

 

[sw34669]

just concerned about fuel usage prior to TEi I was OX/Fuel 37.3%, post was 11.7%, seems light. The trip out I only had one MCC 12.7, loi1 2927.2, loi2 136.2

 

[Thespacer]

I just checked one of my recent post-TEI scenarios, and my SPS fuel, after the burn, was 11.7%, so seems exactly the same as yours. I also had a small MCC5 burn, but it was RCS only and 2.7fps DV.

 

[sw34669]

ok thanks
Indy , as per above, going through the P30 after uplink should I default to the new P30 values or use the printed PAD from 90 mins before (trim/dv/rpy etc)
nacht !

 

[MrFickles]

I wouldn't be surprised that your SPS fuel gets to around 10% by TEI. After all, you're lugging over 35000 lbs of dead weight at LOI 1 and 2.

Even though it looks critically low, there was enough reserve that the J missions (15, 16, 17) could use the SPS to perform the DOI maneuver before undocking and circularizing at 60nm.

 

[indy91]

Did you maybe confuse two TEI PADs? The one you want to do is TEI-30 (TEI on your 30th orbit around the moon). There is a preliminary Maneuver PAD for that coming from the MCC at about 132:10h. Then there is the final TEI-30 PAD that comes together with the target load and state vector uplinks at around 134:20h. That PAD should be nearly identical to the preliminary one. But just after that the crew is given a TEI-31 Maneuver PAD to perform TEI one orbit later than nominal, if something goes wrong during TEI-30 and/or they loose communication with the ground. And I guess it is that PAD that will be shown to you by the MCC as the current PAD from that time on through TEI. It will have quite similar DV etc but definitely not identical. So which maneuver did you burn? TEI-30 at around 135:30h, using the uplinked P30 load? That should have worked fine then, unless you modified that when going through P30.

I'm not really understanding your point about V48 data having been changed. That doesn't get uplinked, always has to be changed manually. Pitch and yaw trim will have still been non-zero from LOI-2 and have to be set to 0 for TEI, as per the TEI Maneuver PAD. Setting the deadband needs some work for Apollo 11 in the Checklist MFD, they did some last minute and inflight changes to that and rarely or never actually used the 5° deadband. Or did the Maneuver PAD have trim gimbal angles for the SPS that aren't zero? That wouldn't be right, for the CSM alone they are currently always 0.

 

[sw34669]

yup understand about t30 and t31 pads, not confused about what those are and how to use them. it was the initial tei-30 pad i printed out, for example, it had a burn time of 135:34:3460 but by the time this has been uplinked it was already in the P30 data.

It was the P30/P40 data I was meaning. For example, I didnt enter any of the P30 pad for the TEI burn, but, when going through the P30 setup all the params were already there from the uplink. When the first P30 / TEI=30 pad came in I didnt enter that data ..... it already was there in terms of defaults winthin the P30 prog (time / dv / attitude and trim).

Just to be clear the sequence of events is as you mentioed above, I got an initial SV uplink, then the first TEI30 pad, which I printed, then the TEI-31 pad , printed. Going through P30, it had the TEI30 pad params already there time dv etc. How did the MCC pad get into the memory of P30 if it's not uplinked ?

I've just run through the sequence again. Here's my tei-30 pad and the first P30 external dv checklist, it's already got the time in (I didnt enter that time).

it's also got the DV's pre-loaded, again, i didnt enter these

so the confusion I have is :-
1) How does the P30 external DV prog get the data from the TEI-30 PAD when I havn't enter it?
2) If any of this info already loaded into either P30 or P40, and, is different, from the original, printed TEI-30, which one should I use?

my SPS gimbal angles are ...... so in the burn setup, should I zero these out or use what was on the pad
also other slight differences around dv and attitude are alreaady defaulted in P30/P40 should I reset these back to the printed pad or have they been re-calculated ?

thanks

 

[sw34669]

here's my scenario just before the pre TEI30 ... P52
the weight is also different between the TEI 30 pad i printed and what's in the comp, which one is the single source of truth?

 

[indy91]

The data that is being uplinked is TIG and DV for P30, so that should of course appear in P30 and you can simply PRO on those values after checking them against the Maneuver PAD. These values, the "target load", were uplinked together with the state vector.

The data you need to manually enter from the PAD and which is not uplinked is everything in V48. So the DAP configuration, CSM and LM weights, the SPS trim gimbal angles. LM weight can be zeroed out, although it doesn't matter if the first digit in the DAP configuration is a 1. So weight should be entered from the Maneuver PAD, also the trim gimbal angles. They are always zero for a CSM only burn. The computer does store the trim gimbal angles from the previous SPS burn (LOI-2) and usually they are good, but you of course had a major configuration change, you don't have a LM anymore. So it's always better to enter the trim angles from the PAD.

So if there was a single source of truth it would be the final TEI-30 Maneuver PAD. The TIG and DV that was uplinked should agree with it exactly (except for maybe a rounding error in the AGC of 1 centisecond) and the rest should be entered from the PAD into the computer.

I think you did nearly everything correct. You probably got a nice attitude rate excursion when the SPS ignited, if you used those non-zero trim gimbal angles. But it should easily have recovered and it should have lead to a good TEI. I'll check your scenario, if I notice anything being off. And by good TEI I mean, you would get a MCC-5 of maybe up to 5 ft/s. On my last mission I got a 1.5 ft/s MCC-5 and MCC-6 and 7 were scrubbed, but that is about the best case you can ever expect.

EDIT: I verified everything in your scenario with RTCC MFD etc. Did everything except for actually burning TEI. And I am still convinced that the P30 data you have in the computer should lead to a good burn. I would use a DAP load that differs from the Checklist MFD, 10101 instead of 10111. That was a handwritten change in the flown flight plan which we haven't implemented in the Checklist MFD yet. There are several places in the original flight plan where it wants 5° deadband but it was changed to 0.5°. And 0.5° is definitely the much better choice. But still, I don't think that should cause any bigger issues. Did you have any residuals after TEI that you didn't null? I really have no clue why you would get a large MCC-5. Just try it again with the better DAP settings, maybe it works out this time. The data loaded in P30 also seems slightly different than the PAD you are showing. Also not sure where that comes from.

 

[sw34669]

Indy, superb as always "I think you did nearly everything correct. You probably got a nice attitude rate excursion when the SPS ignited" made me laugh.

Your questions
In my first test, i nulled out a +x res of 12 i think it was small, as was x and z i nulled those to zero just for OCD sake. I then got the mcc-5 burn of 30 seconds which was why i thought mmmm something smells here. I had used 20x between the TEI-30 burn ending and mcc-5, this may have skewed things.

After running through this again a couple of times, going back through the P30 it seems the comp slighly tweaks the DV and attitude, not by much, but it then differs from the printed pad and I had to increase mt DVC on the EMS by 5.1 i think.

sorry for being thick it took me a bit of time to see that the latter half is the DAP setup not P30, it's in addition to P30.

off to change my DAP load.

 

[sw34669]

ran through with my 35 min to go TEI, fixed dap deadband as you suggested and the trim to +0 and -0, mmmmm the star check now is in the crosshairs not slightly to the left. i am an idiot.

btw small story about + and - zero . Many years ago I was running a lab of positron unix workstations and a prime mainframe. Being a unix person, I am no fan of mf's but the workstations ran well. Every so often, the mainframe would crash badly and dump its core out on some sort of weaving loom . We had months of this and it was a critical system for us so the beardie crew from prime HQ were in and out a lot. It was a maths student that spoke to me about something strange he'd found with integers and signing . if (0 != -0) { printf("This mahine is mad"); } . After a quick compile, It was indeed mad, and a small error in the systems microcode was quickly fixed, by prime. The same issue was cauing the horrific weekly crashing, when the c-lab was on. Ah, tell the Java coders of today that, they wouldn't believe you

 

[sw34669]

after going back into P40, the burn attitude has been changed by the comp a little

 

[indy91]

Yeah +0 and -0 is quite relevant for the AGC, it's a one's complement machine. 77777 in octal being -0. Definitely have encountered that many times when working with the AGC software.

By going back to P40 you mean that you left P40 and then went back into it? What for and what did you do in between? If you call the sequence P30 -> P40 -> P30 for example that causes problems, as the DV vector gets changed. Usually by a lot more than what you saw in P30 with the slightly different DV. But that's not a good thing to do. If you exit P40 without doing the burn it's better to re-enter P30 and type in the burn parameters again.

 

[sw34669]

in the end i just repeated both so should be good (p30 and p40) should be good !

 

[sw34669]

just had my new mcc5 all looking ....... nominal
gravity is a mervellous thing