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

Wedge313

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Hello. Just worked through my fifth attempt at the CDH burn, again unsuccessfully.

I have read a few other threads here on the forum relating to similar issues, but my frustration continues to mount. I got through the CSI relatively well, but I've hit a wall. The main problems I'm having seem to come down to not enough time and not enough fuel. A few questions:

I'm trying to use pause and time accel of .01x to build time. It seems impossible for me to perform all the steps within the time available, mainly because I'm waiting FOREVER for the computer to make the required marks and perform required functions. Could this be connected to my very slow laptop problem?

What RR signal strength should I be looking at? I'm sitting at about 1.7 on the meter. Slewing the antenna around doesn't improve that. Would a stronger signal help the rate the marks are made?

Also, I would like to skip the Plane Change, but what required dV would I need to be below to allow that? I've blown by the CDH-30 time four times, I just can't get the info from the computer fast enough to perform the maneuver.

Also my RCS seems to be constantly chattering away, to the point where I was unable to perform the CDH burn due to lack of fuel. I've read that I can change the deadband somehow? How is that done? Any other ways I can reduce my RCS usage?

I'm going to go back to the beginning of the ascent and try it again. Any tips, advice, etc. are appreciated. Thanks
 

rcflyinghokie13

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I have read a few other threads here on the forum relating to similar issues, but my frustration continues to mount. I got through the CSI relatively well, but I've hit a wall. The main problems I'm having seem to come down to not enough time and not enough fuel.
Welcome to rendezvous! Doing the work of MCC and 3 crew in a tight timeline!

It is a tight timeline, so that is completely understandable that you are having trouble. Remember crews practiced this hundreds of times to get the timeline down. As far as RCS fuel, however, you shouldn't be running out...I am curious how much RCS you have at ascent?
I'm trying to use pause and time accel of .01x to build time. It seems impossible for me to perform all the steps within the time available, mainly because I'm waiting FOREVER for the computer to make the required marks and perform required functions. Could this be connected to my very slow laptop problem?
That is a good question, I don't think the slow laptop should cause that much of a delay on computations but I will defer to @Thymo and @indy91 on that one.

What RR signal strength should I be looking at? I'm sitting at about 1.7 on the meter. Slewing the antenna around doesn't improve that. Would a stronger signal help the rate the marks are made?
The strength will increase as you get closer to the CSM, so you need to be slewing for maximum strength. You can cheat and sanity check this by comparing the RR error needles to the CSM position to the orbiter HUD CSM position (press H 3 times, ctrl-H to exit)

Also, I would like to skip the Plane Change, but what required dV would I need to be below to allow that? I've blown by the CDH-30 time four times, I just can't get the info from the computer fast enough to perform the maneuver.
This all depends on your out of plane error which you get with the V90, your TPI should be able to make up for it but still its wise to at least check the out of plane component.

Also my RCS seems to be constantly chattering away, to the point where I was unable to perform the CDH burn due to lack of fuel. I've read that I can change the deadband somehow? How is that done? Any other ways I can reduce my RCS usage?
What deadband are you using? Are you doing any manual maneuvering with hardover (using keyboard with the ACA 4/JET Enabled)? Are you using DAP attitude hold? Auto? There are many variables here.

Any tips, advice, etc. are appreciated. Thanks
Honestly the best advice is trying to keep slightly ahead of the timeline if possible, additionally, practice practice practice! Rendezvous is one of the most challenging flows in NASSP but rest assured it is possible!
 

Wedge313

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As far as RCS fuel, however, you shouldn't be running out...I am curious how much RCS you have at ascent?

It looks like my RCS fuel gluttony started early. I went back and looked at my RCS quantities throughout the flight. I had 70% before PDI, 43% after landing.
After the insertion I had 35%, after CSI 15%. Not sure what mission abort criteria is but I have to believe I'm way behind it. I was probably doomed as soon as I started PDI.
What deadband are you using? Are you doing any manual maneuvering with hardover (using keyboard with the ACA 4/JET Enabled)? Are you using DAP attitude hold? Auto? There are many variables here.
I'm embarrassed to say I'm not sure what deadband I'm using. The STAB/CONT DEADBAND switch was in MIN, I switched to MAX before CDH but that's probably too late. DAP Attitude Hold? Again, not sure. When the checklist tells me to change the DAP, I punch in the numbers I'm told to. And the ACA 4/JET is in ENABLE, and has been there since before DOI. Why? I don't know! At some point the checklist had me position it there, and if I should have changed it I missed it.

I think I may need to go back before DOI, and start getting frugal early.

But even if I had enough fuel, I'd still have to struggle with the procedures.

Is there a gas station in lunar orbit? :unsure:
 

rcflyinghokie13

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It looks like my RCS fuel gluttony started early. I went back and looked at my RCS quantities throughout the flight. I had 70% before PDI, 43% after landing.
Yeah that's way too much consumption!
I'm embarrassed to say I'm not sure what deadband I'm using. The STAB/CONT DEADBAND switch was in MIN, I switched to MAX before CDH but that's probably too late.
So that switch is for the AGS. The PGNS deadband is set using V48. The flight plan values should be correct for proper fuel use.
And the ACA 4/JET is in ENABLE, and has been there since before DOI. Why? I don't know! At some point the checklist had me position it there, and if I should have changed it I missed it.
So if you are using a keyboard, that switch in enable makes every numpad input the same as full deflection or "hardover" on the ACA and therefore uses more fuel. Additionally, if you are using it and an attitude hold mode, the RCS will fire opposite of your input as well trying to "arrest" the movement using more RCS.
I think I may need to go back before DOI, and start getting frugal early.
Also feel free to use some of the premade Apollo 11 liftoff scenarios to get the procedures down. If you need any other help with rendezvous feel free to ask or catch me on discord :)
 

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That is a good question, I don't think the slow laptop should cause that much of a delay on computations but I will defer to @Thymo and @indy91 on that one.
Timesteps and the systems within them are synchronous. Meaning, if one part slows down, the whole simulation slows down and your FPS will drop. At very low fps (<10) there is a chance for systems to become a bit unstable but at no point will your AGC be slow compared to the rest of the simulation.
 

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OK! All sorts of stuff for me to learn. I think I've been in Attitude Hold mode a lot from the start. And the "hardover" feature explains the sporty performance of the LM.

I've had issues with my laptop's performance since I began using NASSP. I'll keep the Performance Meter displayed, and it's not uncommon for it to drop to 6 fps or lower at times. During many maneuvers the spacecraft will begin to oscillate wildly and I'll need to "step away" from the panel to improve performance (for instance reentry, LOI, Insertion etc). I usually go to an exterior view, and it'll jump up to 60 fps and the craft will stabilize.

I think I'll go back to a point just after the LM/CSM separation and give it another try.

Thanks for the help.
 

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I'm running through the ascent again. The insertion and CSI both looked good (to me), but while setting up for CDH I'm having an issue with the RR, pretty sure it's locked onto a side lobe. Is there a way to display the RR angles while I manually slew the antenna (expanding square search), or do I have to slew in the blind? Thanks
 

rcflyinghokie13

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I'm running through the ascent again. The insertion and CSI both looked good (to me), but while setting up for CDH I'm having an issue with the RR, pretty sure it's locked onto a side lobe. Is there a way to display the RR angles while I manually slew the antenna (expanding square search), or do I have to slew in the blind? Thanks
You can see the rough RR position (with respect to mode 1 or 2) on the RR error needles or you can call a V16N72 and that will display on the DSKY the RR Shaft and Trunnion angles.
 

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I'm obviously not getting this.... as I said, I THINK the CSI burn went ok (see below), I nulled everything out and proceeded into P33. The first few attempts went bad because (I think) I was locked onto a side lobe. This last time I slewed around and found what I believe is the correct signal, and following the checklists in the Flight Crew G&N Dictionary and LM 11 Handbook tried to tell the LGC "Hey, this is the correct direction to the CSM". But resuming P33 I get a repeating series of F 06 49's, which says the updates are out of tolerance. I assumed that was the LGC asking "do you really want me to use this?" and hit PROCEED, thinking that with the new (correct) lock on that's how I get the LGC to start using the new inputs. But I keep getting F 06 49's, and a PROG ALARM 00611, so I'm obviously just digging my hole deeper here.

Going back to the CSI P32, at one point the PAMFD instructs me to "Pulse Drive R1 and R2 to Zero" . My VG XYZ's at that point were -00244, +00128, and +00395. I made the assumption that I was supposed to use rotation to null out R1 and R2, and then with that orientation translated +Z to zero R3. Was that correct, or is this a source of my errors?

Just as a reference, I started this attempt at the ascent from a Apollo 11 saved scenario on the surface just before liftoff, so the Insertion burn should have gone OK (because someone knowledgeable set it up). When I first started P20 I didn't get any indications that I was looking at a side lobe. It was only after starting P33 that I start getting messages that my radar is off.

Any suggestions? Or should I just call the CSM and ask him for a pickup?

Thanks
 

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Going back to the CSI P32, at one point the PAMFD instructs me to "Pulse Drive R1 and R2 to Zero" . My VG XYZ's at that point were -00244, +00128, and +00395. I made the assumption that I was supposed to use rotation to null out R1 and R2, and then with that orientation translated +Z to zero R3. Was that correct, or is this a source of my errors?

That is exactly correct.

How about you post a scenario, maybe after CSI, and we can take a look. Either at that point something has already gone wrong or it's about to go wrong.
 

Wedge313

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Here's two saves, one after Insertion after P52, just before I started P20, and one after I completed CSI, before beginning CDH prep.
 

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  • REDO 124+55 Start P20.zip
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rcflyinghokie13

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Flying your after CSI right now, you don't have a side lobe lock but I am seeing the 06 49's but they are converging. I also noticed on the initial recycle of P33 your dH is 24.6. What values did it predict during CSI?

It looks like there was a bad SV before CSI resulting in a poor CSI burn and all these 06 49s.

Which save did you start from again?

EDIT: Following up, I just burned a CSI from your P20 scn and didnt once break RR lock or get a 06 49, not even when starting CDH.
 
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Wedge313

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I started using the NASSP saved scenario "Apollo 11-17-Before Lunar Liftoff T+124h20min".

I also noticed on the initial recycle of P33 your dH is 24.6. What values did it predict during CSI?
I ran it twice, and looking at my notes (around 125h 02min) for F 06 75 I showed a dH value of 15.0 once and 15.3 the second time.
It looks like there was a bad SV before CSI resulting in a poor CSI burn and all these 06 49s.
When should I have received a SV? There was an uplink for the CSM earlier, but I didn't see anything for the LM.
EDIT: Following up, I just burned a CSI from your P20 scn and didnt once break RR lock or get a 06 49, not even when starting CDH.
My CSIs seemed to go well. I didn't have any issues, the resulting orbits seemed correct (Orbit MFD) and the planes seemed ballpark close (MAP MFD). Using the HUD the LM seemed to be pointed straight at the CSM. It was later (about 125h 30min) after beginning P33 that I started getting the F 06 49s (codes 2, 3, and 4) I noticed the error amounts coming down, but they seemed persistent. (The radar never broke lock. I started thinking about side lobes after getting a PROG ALARM 00525 during my first try). And then I had the same issue I previously had where I had to wait forever to get the required marks, blew right through the plane change TIG, and got so far behind that I just stopped and began again.

So where do I go from here? If its not a side lobe should I just press on through the P33, despite the F 06 49s? Can I omit the Plane Change, and hope the LGC incorporates that into the CDH burn? Can I generate a SV before beginning the CDH?

Thanks for the assistance.
 

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The orbit in your scenario after CSI was definitely not good, even though the LGC thought it was. PAMFD shows 45.1 x 25.7 (adjusted for landing site altitude) while the LGC (V82) has 46.7 x 43.2. That looks like the CSI burn was done just like LGC wanted, but the state vector in the LGC prior to CSI was bad and then still is bad after CSI of course. The RR is updating the LM state vector, so the best assumption is the RR updates weren't right. Usually that means side lobe lock on. Did you not get many 525 alarms and 06 49s prior to CSI? In a way it looks more like there was some translation without the accelerometers running, because as far as your LGC is concerned everything looks fine.

In any case, I think your post CSI scenario is too far off the required trajectory for a good rendezvous. I would suggest to just try it again with your Start P20 scenario, that seems to be in decent shape.
 

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OK. I'll try picking it up after the Insertion burn. Worst case I can go back to the surface where I have a good starting point with the saved scenario.

Did you not get many 525 alarms and 06 49s prior to CSI?
Nope. Prior to CSI I thought I was looking good. It was after I started P33 that I started getting the F 06 49s, 525, and (I forgot to mention) a 611 alarm.

Thanks for looking at it.
 

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Here is something interesting, in your post CSI scenario the AGS has a perilune altitude for the LM state vector (DEDA address 403) that is a lot closer to the real trajectory than the LGC has. That supports the theory that there was some sort of thrusting event and not a side lobe lock on, because the accelerometers of the AGS are running all the time, while the ones for the LGC are only running after the display blanking in P40/41/42 at T-35 seconds.

The LGC state vector must have still been good when you sent its state vector over to the AGS with V47 at CSI T-7 minutes. In the scenario after CSI the AGS residuals (DEDA 500/501/502) are close to 0, so if there was a translation event it can't have been after the CSI burn, but before.

I made the assumption that I was supposed to use rotation to null out R1 and R2, and then with that orientation translated +Z to zero R3.

But you didn't do that translation at the same time as nulling R1 and R2, did you? In this procedure you rotate the LM so that the CSI burn will be only along one axis, but the burn itself should happen at T-0s. Any translation before T-35s will not be taken into account for the state vector in the LGC. And if there was a translation it must have been a rather large one because the perilune is off by 20NM.
 

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No, I did it the way you describe. Rotation to zero out R1 (-00244) and R2 (+00128), then waited until T-0 to translate +Z, R3 read +00395.

I'm going to restart from the surface, keep better notes. Hopefully catch my own mistakes.

Thanks
 

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Oh the total DV of your CSI burn was 39.5 ft/s? That's about 10 ft/s too little, maybe that explains the orbit difference. In that case the LGC already had a problem when it calculated the final pass of P32. The DV should be more like 50 ft/s, plus/minus a few ft/s. I actually got a very good solution and orbit when I tried your pre P20 scenario earlier.
 

Wedge313

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I've messed something up somewhere, I'll go through it again and see if anything goes differently this time.

I had one thought of something I may have done incorrectly, but I'd like to work through the scenario to make sure before I put myself on report.

Worst case? I get stuck in a decaying orbit, crash on the moon, and they name a crater after me.
 

Wedge313

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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.
 
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