CO2 Light turn on and Crew dies before apollo 11 launch

[riclourenco]

Hello,

Today I was about to launch a new Apollo 11 mission. Before that I noticed that there was a new update for NASSP (1483). I upgraded before starting the mission. I started the checklist normally. However before reaching T-1h40m I noticed that the light of the CO2 press was on (yellow). Then when it was time to close the hatch at T-1h40, and I closed it, the state of the crew on the ECS was immediately "critical." I found it strange because these two situations had never happened.

https://puu.sh/F09Z3/15ce41c5ce.png

I continued with the checklist expecting the problem to be solved. But about 30 minutes later, the CO2 light went out, and the crew died.

https://puu.sh/F0a7i/b2b1f51297.png

https://puu.sh/F0a7w/42840f6f81.png

I have no idea why this happened. Could it have been a mistake I made in the checklist because there is something new in this update that I didn't notice, or I dont know how to do it, or is it a bug in the new update? I found it curious that the CO2 light came on before closing the hatch. Can you give me some help?

Thanks!

 

[Urwumpe]

You had no O2 flow, if you pay attention to the two indicators on top, left from the warning lights.

 

[riclourenco]

Hello, thanks!

I think I've figured out the problem. When I started the backup crew checklist at T-4h, I turned on project apollo MFD and selected ECS. I noticed that the number of crew members was zero. So I decided to add the three astronauts. It was the first time I did that. I just finished repeating the checklist from the start, without adding the three astronauts, at T-4h. The CO2 light didnt light up at any time. The crew is automatically added at the time of entry of the prime crew at T-3h. I did the rest of the checklist until T-1h40, closed the hatch, and it's fine. Note that I don't have O2 flow anyway.

https://puu.sh/F0deA/cf1456ea7c.png
https://puu.sh/F0deP/2b8461f766.png

I think that was the problem. For the sake of doubt, I will repeat it again from the beginning, and manually add the crew at T-4h to see if the CO2 light comes on, and they die after the hatch is closed. Be back soon!

 

[Urwumpe]

For reference, the significant part of the checklist, at T-1:40:00, for crew ingress:

C/W NORM - NORM
DIRECT O2 vlv - OPEN, adj for
O2 FLOW ind - 0.6-0.8 lb/hr
SUIT COMPR 1 - AC1
SUIT COMPR lt - out
SUIT COMPR ∆P 0.7-0.9 psi

SUIT CAB ∆P ind - > +2.0 inH2O
SUIT H2O ACCUM AUTO - 1
Verify P02

 

[riclourenco]

Thanks for the checklist, I did it well. I repeated as I said and the same thing happened. That is the problem. I added the crew at T-4h

https://puu.sh/F0ecf/05dbf3e5b8.png

Note that the CO2 partial pressure gauge is starting to rise soon. And note that is zero when we close the hatch in the previous example.

https://puu.sh/F0eky/b684444443.png

Shortly after the CO2 light comes on.

https://puu.sh/F0eqE/e2f3bc4e3d.png

Before closing the hatch at T-1h40, the CO2 light is still on and the crew is fine.

https://puu.sh/F0f5H/409bf60ec3.png
https://puu.sh/F0f5U/c464450119.png

I close the hatch and the CO2 light is still on, critical crew condition.

https://puu.sh/F0f6B/4a353f4b02.png
https://puu.sh/F0f6T/1a807ed039.png


At some point the light of the CO2 goes out, and at +- T-1h09m the crew dies.

https://puu.sh/F0fgr/1e4862128b.png

Try to do the same! I think this should not happen just by adding the crew manually. Anyway, I hope it will contribute something to the development of NASSP. Just don't add any crew!

Thanks for the help!

 

[Urwumpe]

Try to do the same! I think this should not happen just by adding the crew manually. Anyway, I hope it will contribute something to the development of NASSP. Just don't add any crew!

I can't run Orbiter (well) currently, I just use my cosmic systems engineering magic.



I notice that the suit compressor dial shows zero flow to the suit (below SUIT COMPR ΔP).



Same for the oxygen again. Did you really open the DIRECT O2 valve before closing the hatch?


Note that the crew did not die of CO2 poisoning (too low CO2 value for that), but because of asphyxiation.


The behaviour of the CO2 with open hatch looks a bit fishy to me, but the rest actually makes sense.



The question is: Is the crew, that you manually added to the capsule in suits and connected to the ECS? I think you can check the connection on one of the lower panels.

 

[indy91]

I think there are multiple things going on here. One thing is a fundamental flaw with the ECS simulation in NASSP. It doesn't allow air exchange, when the pressures on both sides (e.g. the CSM cabin and the Earth atmosphere when the hatch is open) are the same. Most notably this causes issues after splashdown with the CM shut down, where the CO2 also slowly builds up in the cabin and can kill the crew after a while, even if the hatch is open and the CO2 should go into the atmosphere by normal air exchange. I guess there should be some gas flow due to partial pressures or something.

Next, the crew is actually put automatically into the cabin at T-2h40m. So you don't have to do that manually. Doing it earlier than that T-2h40m wouldn't be realistic anyway, haha. Before that the suit loops aren't activated yet and what you are probably getting is the same effect as usual after splashdown, the CO2 isn't removed and doesn't flow out of the hatch and so builds up over time.

But from your description and this assumed behavior I would think that it all improves once the suit loops are on and CO2 is getting removed. But somehow the hatch closing is causing additional issues. I'll try adding the crew manually myself and will report back.

Oh and for general information, the crew simulation works like this with the CO2. Only when the CO2 level is above 10 mmHg should it say "critical". And if that condition persists for over 30 minutes the crew will then die.

 

[Urwumpe]

I think there are multiple things going on here. One thing is a fundamental flaw with the ECS simulation in NASSP. It doesn't allow air exchange, when the pressures on both sides (e.g. the CSM cabin and the Earth atmosphere when the hatch is open) are the same. Most notably this causes issues after splashdown with the CM shut down, where the CO2 also slowly builds up in the cabin and can kill the crew after a while, even if the hatch is open and the CO2 should go into the atmosphere by normal air exchange. I guess there should be some gas flow due to partial pressures or something.

You could cheat there by implementing reality.

There is an air hose in the white room forcing fresh air into the capsule until the hatch is closed. Otherwise, you would have an enclosed space (as in ships), where little gas exchange happens (Which is very deadly).

So you would have the following situation:

P (Air hose) > P (CM) > P (ambient)

 

[indy91]

You could cheat there by implementing reality.

My favourite kind of cheating. That actually sounds like a good idea and should work pretty well.

Ok, I tried it myself. Even more things going on! I found a bug with the CO2 gauge that I introduced when I implemented some sensors in the CSM (as opposed to the gauge directly getting the CO2 partial pressure). The gauge can't actually show more than 5 mmHg (I confused that with the 5 Volts of the sensor). Very easy fix, but it's quite deceiving as the CO2 level reaches 10 mmHg within 14 minutes of the crew being set into the suit loop. I guess it's rising so quickly because the suit loop is a small enclosed volume with no circulation at that point. So I would imagine two hours later the CO2 level is even much, much higher.

Then, the crew status in terms of atmospheric conditions isn't actually checked before hatch closure. So at that point will it start checking the CO2 level (crew is critical), and the 30 minute timer starts running. The CO2 level will be so high that the CO2 scrubber in the suit loop can't get it all out of the air before that 30 minutes and the crew dies at that point.

 

[Urwumpe]

Then, the crew status in terms of atmospheric conditions isn't actually checked before hatch closure. So at that point will it start checking the CO2 level (crew is critical), and the 30 minute timer starts running. The CO2 level will be so high that the CO2 scrubber in the suit loop can't get it all out of the air before that 30 minutes and the crew dies at that point.

Oxygen is not used for the crew health simulation? :blink:

 

[indy91]

Oxygen is not used for the crew health simulation? :blink:

We don't even simulate nitrogen yet, so it's an all oxygen atmosphere before, during and after the mission. In that sense we do simulate oxygen for crew health, as the atmosphere is assumed to be mainly oxygen for most of the time anyway.

The conditions for crew health in terms of the atmosphere are:

-Pressure in suit lower than 2.8 psi for 10 minutes
-Pressure in suit higher than 22 psi for 1 hour
-Suit temperature above about 45°C or below about 0°C for 12 hours
-Suit CO2 above 10 mmHg for 30 minutes

rcflyinghokie was experimenting with implementing the N2 in the atmosphere and the venting of it over the first few hours of the mission. But that involves implementing some more valves etc, it's a bit involved. But it will come eventually. And at that point we probably should also check on the oxygen specifically, not only total suit pressure.

 

[riclourenco]

Hello

This problem of the crew dying after the splashdow also happened to me two missions ago on Apollo 11. In the following mission (the last one I did) after splashdow, the condition of the crew at a certain point was critical again. To prevent the crew from dying, as last time, I opened the hatch earlier and saved them. Therefore I assume that in this situation, the simulation of air exchange between the CM and the atmosphere occurred. Anyway thanks again to both for the help and explanations. Glad to have helped you discover some more bugs in this wonderful simulator .