Apollo 13 Launch Scenario: What should I expect?

[Wedge313]

Good Morning,

I'm running the Apollo 13 scenario. I started using the Apollo 13 Launch option (vs the Apollo 13 Launch and Landing choice), which I believe will simulate the O2 Tank 2 problem? I'd like to get a better understanding of what I should expect to happen as I approach the 55:55 point of the simulation. What (if anything) has this scenario been programed to do?

Thanks.

 

[n72.75]

The one person I know for a fact has flown the whole thing is @rcflyinghokie.

There is a lot of really good information that you can get out of the Apollo-in-realtime recordings for Apollo 13.

The scenerios itself has been programmed to add a rather large hole to the O2 tank, which will cause some asymmetric thrusting and some sounds to be played.

The fuel cell voltage won't actually drop at the moment; I'm still working on some improvements there so, eventually this will be the case. But for now you'll have to manually disconnect them at the right time (mission audio is helpful here).

 

[rcflyinghokie]

I have indeed flown this, it's not for the faint of heart! I used the procedures from the actual flight, the mission ops report for read up procedures, and the real time audio/transcripts for procedural changes. It took a lot of work!
You will also be using RTCC a lot as you can imagine, but computing things like getting back on a free return and your PC+2. Then learning how to fly the LM with a CSM attached.

 

[Wedge313]

I have indeed flown this, it's not for the faint of heart!

Yeah, I expect this will be an adventure, but I enjoy digging through the documentation and finding the appropriate procedures etc. And I know some very knowledgeable people I can reach out to if I hit a roadblock.

Speaking of which.... I have a possible self-induced glitch in the scenario that I may have caused when I inadvertently yanked the laptop power cord out of the receptacle. The power disruption occurred while I was in the PTC roll sometime after 31:43. (I was in 6x time accel).

When I re-started the scenario the first time, the simulation crashed. External view showed that the LM was missing, no longer docked to the CSM. I closed the program, then re-started again, and this time the simulation loaded OK, the LM was back. I continued running the scenario, in PTC at 6x, thinking all was well. But around 53:30 i noticed the O2 Tank 2 quantity gauge was reading 20 percent. I worked my way back through quicksaves I made prior to the power interruption, and each time I started the program it would crash, followed by a successful re-start the second time. Finally I found a save point where the O2 Tank 2 quantity was normal (about 84 percent). Then I ran the simulation forward until I found the point where the O2 quantity dropped, which was exactly at 46:45.

Having not run this scenario before I wasn't sure what to expect, but the quantity decrease at 46:45 doesn't seem right to me. So I'm attaching two saves, one at 46:44 just before the drop, and one just after the drop, and hoping you might be able to tell me what I've messed up with the power disruption.

FWIW I ran the sim up to 55:54 and I still get the explosion (didn't need to turn on the fans, no sound but O2 Tank 2 pressure drops to zero rapidly, along with a really nice visual of the panel blowing off and gas venting). O2 Tank 2 quantity stayed at 20 percent. You can see O2 Tank 1 pressure and quantity dropping. The fuel cells continue to run and all the power seems ok, so I guess at some point I'm going to have to self-induce the power issues?

Thanks for the help.

 

[rcflyinghokie]

When I re-started the scenario the first time, the simulation crashed. External view showed that the LM was missing, no longer docked to the CSM. I closed the program, then re-started again, and this time the simulation loaded OK, the LM was back. I continued running the scenario, in PTC at 6x, thinking all was well. But around 53:30 i noticed the O2 Tank 2 quantity gauge was reading 20 percent. I worked my way back through quicksaves I made prior to the power interruption, and each time I started the program it would crash, followed by a successful re-start the second time. Finally I found a save point where the O2 Tank 2 quantity was normal (about 84 percent). Then I ran the simulation forward until I found the point where the O2 quantity dropped, which was exactly at 46:45.

Hmm not sure what would be causing the crashes unless you had some sort of corrupt save state there.

Having not run this scenario before I wasn't sure what to expect, but the quantity decrease at 46:45 doesn't seem right to me. So I'm attaching two saves, one at 46:44 just before the drop, and one just after the drop, and hoping you might be able to tell me what I've messed up with the power disruption.

That was actually a sensor failure:

047:41:00 Kerwin: We verify that. At 46:45 we had 82 percent and apparently when he stirred the, the cryos, the sensor broke.
https://history.nasa.gov/afj/ap13fj/pics/quantitygauge.png

FWIW I ran the sim up to 55:54 and I still get the explosion (didn't need to turn on the fans, no sound but O2 Tank 2 pressure drops to zero rapidly, along with a really nice visual of the panel blowing off and gas venting). O2 Tank 2 quantity stayed at 20 percent. You can see O2 Tank 1 pressure and quantity dropping. The fuel cells continue to run and all the power seems ok, so I guess at some point I'm going to have to self-induce the power issues?

The pressures will slowly drop and also 2 of your reactant valves closed but you cant tell due to an oversight of how the talkbacks were designed. The REACT VLV tbs only barberpole if both the H2 and O2 vales for a cell shut, however if only the O2 or H2 valve closes, it still shows gray (open) so this is why the fuel cells started dying early.

You will eventually get power issues with the FCs but I believe you will close the valves before that and the FCs will run for a bit longer on the residual reactants in the lines

 

[Wedge313]

That was actually a sensor failure:

Well, that's what I get for not reading the voice transcripts closely. I skipped right over that, in a big hurry to get to the LM entry/activation part around 54:00. Haste makes waste.

So, I think I'm squared away, a few more questions. When I checked the supercritical He pressure I got 848. That's much higher than I expected. Anything I should do here?

Also, I've got a CRYO PRESS light which I think is "normal" because I turned off the H2 Tank 1 heater at 50:58.

Finally, I grabbed an Apollo 13 LM Activation Checklist from the Apollo Flight Journal. After checking the He press I'm supposed to return the c/b's to the configuration on pages ACT 3 and 4. Page ACT-4 shows the RCS system QUAD 1 breaker in/closed. I don't think that's correct? I left it open.

Otherwise I think I'm ready for the fun to begin.

Thanks.

 

[rcflyinghokie]

So, I think I'm squared away, a few more questions. When I checked the supercritical He pressure I got 848. That's much higher than I expected. Anything I should do here?

SHe isnt modeled well yet, but it was higher than normal on 13, I wouldn't worry about this.

Also, I've got a CRYO PRESS light which I think is "normal" because I turned off the H2 Tank 1 heater at 50:58.

Yep normal because of the sensor failure as well.

Finally, I grabbed an Apollo 13 LM Activation Checklist from the Apollo Flight Journal. After checking the He press I'm supposed to return the c/b's to the configuration on pages ACT 3 and 4. Page ACT-4 shows the RCS system QUAD 1 breaker in/closed. I don't think that's correct? I left it open.

Interesting I see that, I think that is indeed an error in whoever scanned and digitized this checklist. I will do some homework to verify but yeah I think that quad heater should be open based on other LM activation procedures.

 

[Wedge313]

Continuing on through the Apollo 13 scenario, up to 57:00, following the edited flight plan, reading along with the Apollo Flight Journal and trying to configure accordingly. A few questions that probably will cause me great embarrassment:

At 56:35 "Turn BAT A off". What do they do here? MN BUS TIE A/C to OFF? I'm not clear on how to turn off a battery.

At 56:37 "Isolate the O2 SURGE TANK". How do you do that, just turn the SURGE TANK to OFF?

And back at 56:25 I got the CO2 PRESS light, the CO2 PP was climbing quickly, until at 56:59 I got the "Crew Dead" on the PAMFD ECS display. I guess I missed something?

 

[rcflyinghokie]

At 56:35 "Turn BAT A off". What do they do here? MN BUS TIE A/C to OFF? I'm not clear on how to turn off a battery.

Correct, the battery ties were put on previously.

At 56:37 "Isolate the O2 SURGE TANK". How do you do that, just turn the SURGE TANK to OFF?

Yep, this isolates it from the system.

And back at 56:25 I got the CO2 PRESS light, the CO2 PP was climbing quickly, until at 56:59 I got the "Crew Dead" on the PAMFD ECS display. I guess I missed something?

Did you have your suit compressor off at this point? One issue with our CM is the CO2 climbs very fast with it off as it doesn't diffuse well.

 

[Wedge313]

Did you have your suit compressor off at this point?

Yes, it was on the Emergency Powerdown Checklist page EMER 1-5 that was on the Apollo Flight Journal. Following the audio transcript I took it down to BMAG 2 Warmup. I wasn't exactly sure what to look at to determine when I got my 10 amp decrease (another learning opportunity), but figured the goal here was to configure as closely to what they had anyway.

Rather than turning the SUIT COMP on, I'd guess I should press on as-is and ignore the "dead" issue?

 

[rcflyinghokie]

Yes, it was on the Emergency Powerdown Checklist page EMER 1-5 that was on the Apollo Flight Journal. Following the audio transcript I took it down to BMAG 2 Warmup. I wasn't exactly sure what to look at to determine when I got my 10 amp decrease (another learning opportunity), but figured the goal here was to configure as closely to what they had anyway.

Rather than turning the SUIT COMP on, I'd guess I should press on as-is and ignore the "dead" issue?

I mean I personally wouldn't want the "DEAD" to remain...also every time you load you get the alarm sound.
Work around is cycle the compressor when you get the CW light until LM ECS is up. You will have to do this for entry as well as they flew entry with it off.

 

[Wedge313]

Well OK, if you want to eat up all that power over a little thing like killing the crew I guess I can turn the SUIT COMP back on.

"....You're telling me what you need, I'm telling you what we have to work with at this point. I'm not making this stuff up."-John Aaron in the Apollo 13 movie.

 

[rcflyinghokie]

Well OK, if you want to eat up all that power over a little thing like killing the crew I guess I can turn the SUIT COMP back on.

"....You're telling me what you need, I'm telling you what we have to work with at this point. I'm not making this stuff up."-John Aaron in the Apollo 13 movie.

Haha dont worry, cycling it will only eat a little more power.
Also, we cannot charge the CM bats from the LM yet, still trying to find a solution for 2 way power flow, so when you get to that point you will be manually "filling" them with scenario edits...

 

[Wedge313]

Getting ready to pressurize the LM RCS. I don't see where they apply power to the Temp/Press gauges. I'm guessing they relied on their system knowledge to close the required c/b's? How do I configure for this step? Or were they just going through the steps without looking at the readings?

Thanks.

 

[rcflyinghokie]

Getting ready to pressurize the LM RCS. I don't see where they apply power to the Temp/Press gauges. I'm guessing they relied on their system knowledge to close the required c/b's? How do I configure for this step? Or were they just going through the steps without looking at the readings?

Thanks.

Considering the expedited nature, I don't think they bothered bringing up the displays/flags. They could hear the squibs fire when they pressurized and that was probably enough since they had to use LM RCS regardless. They had all necessary breakers closed at that point to pressurize it.

 

[Wedge313]

A question about the coarse alignment. I followed the procedure converting the CSM O/I/M to LM O/I/G. Conveniently the PAMFD LGC page does this for us. I used the LM O/I/M gimbal angles displayed on the PAMFD LGC page and entered them with V41N20E. Then I followed along to the point where they finally get the FDAI powered up. Here's what I'm looking at: my V06N20 O/I/M reads 235/270/006. My FDAI shows 169/100/055. I understand that the CSM roll is yaw in the LM, and CSM yaw is LM roll. But I'm not seeing any correlation between the V06N20 and the FDAI. What have I done wrong here? Thanks.

 

[rcflyinghokie]

A question about the coarse alignment. I followed the procedure converting the CSM O/I/M to LM O/I/G. Conveniently the PAMFD LGC page does this for us. I used the LM O/I/M gimbal angles displayed on the PAMFD LGC page and entered them with V41N20E. Then I followed along to the point where they finally get the FDAI powered up. Here's what I'm looking at: my V06N20 O/I/M reads 235/270/006. My FDAI shows 169/100/055. I understand that the CSM roll is yaw in the LM, and CSM yaw is LM roll. But I'm not seeing any correlation between the V06N20 and the FDAI. What have I done wrong here? Thanks.

If you are using PAMFD you need to make sure the REFSMMAT selection is correct. It needs to be on "identical." Did you verify those numbers coorospont with the gimbal conversion in the LM activatiopn checklist to ensure you used the correct conversion in PAMFD?

Also, in the LM, FDAI and N20 angles are different (this caused lot of crew and ground controller confusion as well) its not as simple as "yaw is roll and roll is yaw" there is actually a mathematical conversion in the background that converts those IMU angles to FDAI angles.

So first thing to check is make sure you have done the conversion correctly on paper and they match the PAMFD, then you should be set (and yes you will see FDAI and N20 be different.)

 

[Wedge313]

If you are using PAMFD you need to make sure the REFSMMAT selection is correct. It needs to be on "identical." Did you verify those numbers coorospont with the gimbal conversion in the LM activatiopn checklist to ensure you used the correct conversion in PAMFD?

"Identical" was selected. And I did crunch the numbers manually following the checklist (assumed docking angle zero), and they matched the PAMFD values. (Hey! I can still add and subtract!)

(and yes you will see FDAI and N20 be different.)

OK. I'll have to continue on through the scenario, I assume at some point they were able to try some sort of alignment check? But for now I'll press on.

Thanks.

 

[rcflyinghokie]

"Identical" was selected. And I did crunch the numbers manually following the checklist (assumed docking angle zero), and they matched the PAMFD values. (Hey! I can still add and subtract!)


OK. I'll have to continue on through the scenario, I assume at some point they were able to try some sort of alignment check? But for now I'll press on.

Thanks.

Yeah they managed to do an AOT check before the first DPS burn.

 

[Frilock]

Problems?
(I'll see myself out)