Apollo 13 Launch Scenario: What should I expect?

[rcflyinghokie]

Yes that's the one, when I got to the Flt Bus MN B closed the meter sprang to life.

Sounds good, I actually have improvements for the injector temps in an update coming up, so you might notice them a little cold compared to how they were in the mission

 

[Wedge313]

I still don't understand where I got off the proper configuration. Something that sends the voltages to the meter isn't powered. The FLT BUS breakers should be out at this point, and I should be able to see readings on the meter without them. I missed something somewhere, there were so many changes to the changes along the way that I probably missed one. I'll keep playing with it. Hey, it got me into the Systems Description manual looking at circuit diagrams, so instead of looking at it as a major procedural error I'll consider it a valuable learning opportunity!

It's all in the packaging. One man's explosion is another man's rapid unscheduled disassembly.

 

[rcflyinghokie]

Are you sure you should be able to see the injector temps at that point? If you can give me a mission time that you are currently following along with I can backtrack.

 

[Wedge313]

I'm at about 136+10, about 6+30 before EI, and I went through these steps:

You can see where it refers you to the CM RCS Preheat on the entry checklist:

Later they had this exchange:

137:06:57 Haise: And, Joe, Jack just handed me some injector temperatures, if you want to read these on [garble] so I can plug them in.
137:07:05 Kerwin: Roger. Go ahead with those.
137:07:07 Haise: Okay. 5 Charlie, 4.0; 5 Dogs, 3.7; 6 Able, 3.5; 6 Bravo, 4.1; 6 Charlie, 4.2; 6 Delta, 3.8.

Swigert started the preheat around 136:23, reached 20 minutes at 136:43, and these were read up about 20 minutes later. But that is still well before the point where they would close the FLT BUS breakers, which isn't until EI -2+30.

That's why I think I missed something.

 

[rcflyinghokie]

I could be way off here, but it seems injector temperature data is only powered through the instrumentation bus (V1 and V2 busses) not the SCE/FLT BUS. I need to do some digging but our modeling could be wrong here haha!

 

[Wedge313]

I've been enjoying NASSP for around two years (my first question on this forum was January 2021). Based on historical data, the odds are 99.98 percent the issue is on my end.

 

[Wedge313]

I think something is way off in the CM. I'm at about 138+00, just completed MCC-7 and maneuvered to the SM SEP attitude. I did the PYRO BAT check, and went through the CM RCS Activation.

I don't think the electrical system is configured correctly, not sure I'm getting power to anything. Running through the CM RCS hot fire I get nothing, so I don't think the system ever pressurized. I can see voltage on the DC main A and B busses, and on the BAT Bus A an B, and on Bat C. But there are no amps showing, so I wonder if anything is getting powered?

Earlier in the scenario, after the explosion, there was some mention about getting the Main Bus Ties open before losing power, I thought I did that but could that be my issue?

Anyway, I'm at a loss trying to figure out where I went wrong, and don't see how I can continue until I get this fixed. So once again I'm asking for your help. Here's my save at 138+06, I'm down to the point where I check the Ring 2 thrusters.

And, just to keep things interesting, at 137+11 I got a DC BUS light in the LM, BAT #3 is dead. I took it offline, and so far the other batts seem to be holding up. I guess I could edit the scenario and get the volts back up but I'm curious how this will work out. I still have power left and haven't really touched the ascent batteries yet. I just need the LM to hang in there for about 3 more hours.

Thanks.

 

[rcflyinghokie]

I think something is way off in the CM. I'm at about 138+00, just completed MCC-7 and maneuvered to the SM SEP attitude. I did the PYRO BAT check, and went through the CM RCS Activation.

I don't think the electrical system is configured correctly, not sure I'm getting power to anything. Running through the CM RCS hot fire I get nothing, so I don't think the system ever pressurized. I can see voltage on the DC main A and B busses, and on the BAT Bus A an B, and on Bat C. But there are no amps showing, so I wonder if anything is getting powered?

Earlier in the scenario, after the explosion, there was some mention about getting the Main Bus Ties open before losing power, I thought I did that but could that be my issue?

Anyway, I'm at a loss trying to figure out where I went wrong, and don't see how I can continue until I get this fixed. So once again I'm asking for your help. Here's my save at 138+06, I'm down to the point where I check the Ring 2 thrusters.


View attachment 33245

And, just to keep things interesting, at 137+11 I got a DC BUS light in the LM, BAT #3 is dead. I took it offline, and so far the other batts seem to be holding up. I guess I could edit the scenario and get the volts back up but I'm curious how this will work out. I still have power left and haven't really touched the ascent batteries yet. I just need the LM to hang in there for about 3 more hours.

Thanks.

I will check out the save and see.

Actual LM lost Bat 2 due to a short as it is

 

[rcflyinghokie]

Something is screwy with this save it seems, I need to dig a bit more, but you should have power in MNA and MNB. I will report back.
Also I see in the save there are a few NaN's which is a computation error (not your fault.)

 

[rcflyinghokie]

Yeah looks like something got screwed up way back when, your main bus tie is still "tied" to fuel cell 2 and it has generated NaN values, so nothing can power up properly through the main busses.

Could you humor me and dig back through your save files and find where your fuel cell 2 went to NaN? It looks like this:

<FCELL>  FUELCELL2 0 -nan(ind) -nan(ind) 0.0000 -nan(ind)

In the mean time, you can fix your save or an earlier one by replacing those values with good ones and also the main must tie to FC2. The values below should work, just find those lines (2676 and 2697 in the save you sent me):

<DCBUSCONTROLLER> MainBusBController 0 0 0 2 0 0 0 0 0

<FCELL> FUELCELL2 2 0.0519672311 300.0000 0.0000 0.0047187134

 

[Wedge313]

I have a save at 59:10 where FC2 looks OK. Then one at 59:28 where FC2 shows NaN.

Reading the transcript it looks like I had finished the CM power down by that point, and wasn't doing anything with the switches or c/bs in the CM.

I'm guessing I may have mis-configured something during the shutdown, and then somewhere between 59:10 and 59:28 FC2 completely died, or something like that?

Anyway thanks for finding that. I'm going to go back to 136:10, edit the scenario, and see if that fixes the issue I had with the test meter readings.

 

[rcflyinghokie]

I have a save at 59:10 where FC2 looks OK. Then one at 59:28 where FC2 shows NaN.

Reading the transcript it looks like I had finished the CM power down by that point, and wasn't doing anything with the switches or c/bs in the CM.

I'm guessing I may have mis-configured something during the shutdown, and then somewhere between 59:10 and 59:28 FC2 completely died, or something like that?

Anyway thanks for finding that. I'm going to go back to 136:10, edit the scenario, and see if that fixes the issue I had with the test meter readings.

Would you mind sharing the save before the NaN? I can see if it was procedural (ie not getting the FC off the bus) or if there is something else going on.

Also the test meter is wired incorrectly, those injector temps only need the INST power to generate a signal, so thats on our end

 

[Wedge313]

I might know what happened. Looking over my notes there was a period from about 58:04 and 58:51 where I was going back and forth to earlier saves and re-doing certain steps (like the LM alignment). I'm guessing at some point I resumed the scenario from a "bad" save that put me out of the proper sequence, and switches or c/bs were missed.

With that in mind it looks like once I pressed on the last save I have where FC2 looks OK is at 61:15, and the next save at 61:50 shows NaN.

And so I'm pretty certain this issue was self-induced.

 

[rcflyinghokie]

I might know what happened. Looking over my notes there was a period from about 58:04 and 58:51 where I was going back and forth to earlier saves and re-doing certain steps (like the LM alignment). I'm guessing at some point I resumed the scenario from a "bad" save that put me out of the proper sequence, and switches or c/bs were missed.

With that in mind it looks like once I pressed on the last save I have where FC2 looks OK is at 61:15, and the next save at 61:50 shows NaN.

And so I'm pretty certain this issue was self-induced.

In any case, the fuel cell shouldnt have thrown a NaN (kind of a divide by zero state) so anything helps us look into it.

 

[Wedge313]

To further confuse things...

I dug through my saves and tried to figure out what I did. It looks like originally I was OK through a save at 57:48, and then at 58:26 FC2 went NaN (unbeknownst to me). I went as far as 60:17 (with FC2 NaN) with this scenario, then for some reason stopped and went back to 57:48 (where FC2 was OK) and started to re-do the process. This time FC2 looked good through 59:10, when for some reason I stopped and went back to a save at 58:51. FC2 looks good at the save at 58:51, and since then I haven't looped back. The last good FC2 was at 61:15, which is the save I sent you. Then at 61:50 FC2 is NaN.

 

[n72.75]

@Wedge313 I looked through the code, and I am fairly confident that the fix for the NaNs is just to guard against the potential of divide by zero cases (basically, we calculate the resistance of all the load attached to the cell and use that to calculate voltage drop and heat and a bunch of stuff, the input of that calculation is power draw...which can be zero...).

This is a bug I introduced a few years ago with my fuel cell update, but people don't fly 13 that often so we're just finding it now. It's an easy fix and I'll have an update out soon.

 

[Wedge313]

I edited my scenario with the values you posted:

<DCBUSCONTROLLER> MainBusBController 0 0 0 2 0 0 0 0 0

<FCELL> FUELCELL2 2 0.0519672311 300.0000 0.0000 0.0047187134

What about the Main Bus A controller values? Should they look like Main B?

I ask because I'm still not seeing things work the way I expect (such as: after the initial power up steps I show volts and amps on Main A bus, but nothing on Main B. Shouldn't Main B be powered here? And later on the CM RCS hot fire, the procedure has the Rot Contr Pwr Normal to AC/DC, but I can't get the RCS to fire unless I put the Direct to MNA/MNB. )

So I wanted to check and make sure what I need to edit.

Thanks

 

[rcflyinghokie]

I edited my scenario with the values you posted:



What about the Main Bus A controller values? Should they look like Main B?

I ask because I'm still not seeing things work the way I expect (such as: after the initial power up steps I show volts and amps on Main A bus, but nothing on Main B. Shouldn't Main B be powered here? And later on the CM RCS hot fire, the procedure has the Rot Contr Pwr Normal to AC/DC, but I can't get the RCS to fire unless I put the Direct to MNA/MNB. )

So I wanted to check and make sure what I need to edit.

Thanks

When I looked at your save, the MNA values are what I copied to generate those MNB values.

 

[rcflyinghokie]

I can check into that hot fire later today

 

[rcflyinghokie]

I ask because I'm still not seeing things work the way I expect (such as: after the initial power up steps I show volts and amps on Main A bus, but nothing on Main B. Shouldn't Main B be powered here? And later on the CM RCS hot fire, the procedure has the Rot Contr Pwr Normal to AC/DC, but I can't get the RCS to fire unless I put the Direct to MNA/MNB. )

Looks like another case of incorrect NASSP code! They should fire in RHC normal and man att accel command without any AC power, but there are checks in the code incorrectly preventing it.