NASSP Apollo 8 TLI Scenario Questions

[Wedge313]

I have a number of questions about the NASSP Apollo 8 TLI scenario. I've run the scenario five times, each time with different results. Only once have I ended up with a course that looked like I'd get to the moon. So I'd like to find out what I'm doing wrong. I'm trying to follow the checklist, but would like to understand what I'm doing, not just flipping switches or entering numbers. So some questions:

1. When the scenario begins, there's a message from CAPCOM on the screen, P30 Maneuver. What am I supposed to do with that?

2. The checklist step "Set EMS dV to TLI dV": Where do you get that dV? I've been digging up a TLI PAD from the Apollo RTCC MFD, is that correct? And what does the EMS do during the burn, are we just setting this to watch the required dV run down?

3.The step "ATT set tw (3)- set to FDAI att", again I've used the TLI PAD from the RTCC MFD, R179 P047 Y001. Later it says "ATT set tw (3)- null FDAI errors". I assume I'm supposed to center the yellow error bars? The roll and yaw yellow error bars only require one or two degrees correction, but the pitch requires a LOT of correction. I've ended up going from 047 to 135, 149, or even 154 to center the pitch bar. Is that normal?

4.At TB6+0, I'm supposed to see a SII SEP lt. All five times I've run this the light never comes on. Later just prior to ignition the SII SEP lt is supposed to come on again, but mine doesn't. What's happening here?

5. A few minutes before ignition, I get a CAPCOM message with a new TLI PAD. Should I update the dV I set earlier in the EMS (it was slightly different)? Does putting the new RPY numbers into the thumb wheels do anything at this point?

6. Finally, where can I find information on what I'm actually typing into the AGC DSKY? When do we actually tell tell the computer when to start and stop the burn?

I've searched (mostly unsuccessfully) for information trying to understand this better.Thanks in advance for any guidance or direction you can give me.

 

[indy91]

I have a number of questions about the NASSP Apollo 8 TLI scenario. I've run the scenario five times, each time with different results. Only once have I ended up with a course that looked like I'd get to the moon. So I'd like to find out what I'm doing wrong. I'm trying to follow the checklist, but would like to understand what I'm doing, not just flipping switches or entering numbers.

The Apollo 8 TLI scenario that comes with NASSP is quite old by now, it hasn't been updated since the NASSP 7 release. Most of the issues can be explained by that, although none of them should really cause trouble for TLI. I'll explain with each point. I want to fly Apollo 8 again soon though and work on some stuff, I will update the scenarios then.

Also, if you haven't yet, I would really recommend trying to get the DX9 Client to work. That is probably an issue that doesn't have to do with NASSP, so maybe ask in the DX9 Client thread or so. If you get bad performance due to the default graphics client then that can make some of these issues worse.

1. When the scenario begins, there's a message from CAPCOM on the screen, P30 Maneuver. What am I supposed to do with that?

That's a Maneuver PAD (Pre-Advisory Data) coming from our mission control feature (the CAPCOM menu). Before TLI the Apollo crews got some data to write down to perform abort maneuvers after TLI. These are called TLI + 90 (minutes) and TLI + 4 (hours). They were of course not normally executed, so you don't really have to write them down.

2. The checklist step "Set EMS dV to TLI dV": Where do you get that dV? I've been digging up a TLI PAD from the Apollo RTCC MFD, is that correct? And what does the EMS do during the burn, are we just setting this to watch the required dV run down?

Due to the scenario being outdated, the MCC functionality is a bit behind the timeline. It wants to uplink a state vector to the AGC, which actually happened about 50 minutes earlier. What you have to do there is press TAB (to open the CAPCOM menu) and then allow the uplink of the state vector to happen. For that you have to switch the UP TLM CM switch to accept for that. When the uplink has gone through then it gives you some more time to write down the TLI+90 PAD. After a few minutes the TLI+4 Maneuver PAD will appear. And then a few minutes later the TLI PAD and the MCC has then caught up in the timeline.

The TLI PAD is the one that has the number for the "Set EMS dV to TLI dV" step of the checklist, as "DVC". About 10500 ft/s. You can also use the RTCC MFD to generate a TLI PAD, but with the MCC feature using the MFD is not required at all. And yeah, the EMS DV counter is just one way for the astronauts to monitor the progress of the TLI burn, nothing more.

3.The step "ATT set tw (3)- set to FDAI att", again I've used the TLI PAD from the RTCC MFD, R179 P047 Y001. Later it says "ATT set tw (3)- null FDAI errors". I assume I'm supposed to center the yellow error bars? The roll and yaw yellow error bars only require one or two degrees correction, but the pitch requires a LOT of correction. I've ended up going from 047 to 135, 149, or even 154 to center the pitch bar. Is that normal?

This is part of the GDC alignment, the backup to the IMU. What you want to align it to is your actual current IMU attitude, not the attitude planned at TLI. Basically you want both FDAIs to look the same at the end of this procedure, GDC and IMU having the same alignment. So for "set to FDAI att" you need to look at the attitude currently shown on the FDAI. See here for more info: http://nassp.sourceforge.net/wiki/Attitude_Set_Control_Panel

4.At TB6+0, I'm supposed to see a SII SEP lt. All five times I've run this the light never comes on. Later just prior to ignition the SII SEP lt is supposed to come on again, but mine doesn't. What's happening here?

Outdated scenario again. And some control electronics being implemented too realistically. :lol:

Basically there are some latching relays that haven't been set, as they weren't implemented yet when the scenario got created. There is a realistic way to set the relays via a ground uplink, using the Project Apollo MFD, if you really want to try. First set the UP TLM IU switch to accept. On the IU page of the PAMFD, press the SRC button and enter "AS-503". That's the name of your current vehicle. Then press the CHA button and enter 48 and press UPL. It should now say uplink successful or something like that. Do the same with channel 28. That is a method that would have worked on the real Saturn vehicles.

5. A few minutes before ignition, I get a CAPCOM message with a new TLI PAD. Should I update the dV I set earlier in the EMS (it was slightly different)? Does putting the new RPY numbers into the thumb wheels do anything at this point?

Oh, so you do get a TLI PAD. Is that even for the first TLI opportunity or does it have a TB6 time much later? And again, the RPY angles there are for reference, not to be used in the GDC alignment.

6. Finally, where can I find information on what I'm actually typing into the AGC DSKY? When do we actually tell tell the computer when to start and stop the burn?

The AGC is not in control of the TLI burn, it is only monitoring it. Program 47 is just a navigation program (uses accelerometers to updated your state vector), it doesn't do any guidance. The Launch Vehicle Digital Computer in the IU is in control of TLI and there are only a few switches that can affect TLI (XLunar injection/safe for example).

A good reference for the AGC is the actual checklists: https://www.ibiblio.org/apollo/links.html#Checklists

The Apollo 8 CMP checklist has the best descriptions of all the programs, verbs and nouns.

 

[Wedge313]

Great info, thanks. This is such an incredible simulation. I spent over 40 years as a professional pilot (both military and airlines), and I have the utmost appreciation for the effort that must have gone into the programming. I've been fascinated by the Mercury, Gemini, and especially the Apollo program since I was little (I followed Alan Shepard's Mercury flight listening to a transistor radio), so it's a blast to get some "hands-on" stick time. Thanks again for your help. (I'll ask about my D3D9Client issue in another thread)

---------- Post added at 04:43 PM ---------- Previous post was at 10:28 AM ----------

Also your link https://www.ibiblio.org/apollo/links.html#Checklists is a great collection of information sources, thanks. That should give me an afternoon or two of reading to keep me busy!

 

[Wedge313]

Also....I tried to do your solution for the SII SEP lt issue, When I open the Project Apollo MFD and select IU, the SRC button and enter AS-503, but the the CHA button doesn't do anything, no place to enter 48.

 

[indy91]

The uplink type (TYP button) has to be set to "Switch Selector". I didn't mention that because it is set to that by default. And equally the stage (STA button) should be set to IU, which is also set by default. But the only restriction for the CHA button to work is that the uplink type is set to switch selector. Then it really should work.

Of course all of this is just a fix for an old scenario, in general I would suggest to use the "Apollo 8 MCC - Launch" scenario, which is always kept up-to-date, and get to TLI from there.

 

[Wedge313]

That seems to do the trick, CHA now opens a window to enter 48. Thanks

 

[indy91]

No problem. I have to document those codes properly some time, there is a lot of fun things you can do by uplinking commands like that. Here it is in code (at least those for the IU): https://github.com/orbiternassp/NAS...samples/ProjectApollo/src_saturn/iu.cpp#L1569 So e.g. with switch selector channel 80 you can switch on the S-II sep light yourself, and with 81 turn it off (after you have enabled them with 28 and 48 of course). Done in this details so that if we ever get a LVDC emulator in NASSP that the actual LVDC software can send those commands to the Saturn stages.