An idle question regarding the Apollo 11 checklist

[Staiduk]

Hello! Since this is a question regarding real-life space history; not the game, I chose to put it here. Anyhoo; I'm replaying the AMSO AS-506 mission and so far everything'd go approaching LM Extraction. There's a piece of dialogue that occurs earlier in the flight; just prior to S-IVB separation Capcom Bruce McCandless questions CDR Neil Armstrong about his descision to only arm Pyro Bus A; rather than both. Neil's response is "My intent is to use bottle Primary 1, as per the checklist; therefore, I just turned A on."

Question: Crew and ground staff has rehearsed this flight thousands of times. Procedure should be automatic at this stage. But Armstrong seems to be taking a shortcut here. The question is how much leeway did the astronauts have when following the checklist? Obviously as pilots; the flight crew have the final say in what they do in the cockpit but T&D would have been one of the most heavily rehearsed sections of the flight. Bruce recommends Neil arm Pyro Bus B but leaves it up to the CDR - it's obviously a minor point. So how much leeway and freedom of action did the astronauts actually have when following the checklist? Just curious.
Wups; extraction coming up in 10 mins., back to the spaceship.

 

[Quick_Nick]

This doesn't really answer your question, but IIRC Buzz Aldrin is "responsible" for the 1201 and 1202 alarms occurring on Apollo 11, because he left the computer doing more than it could handle. That might have been forgetfulness, or the radar switches might have been left on without care.
And various astronauts of course snuck stuff in or out of the missions. (And the government still isn't happy about that)
And I think you need astronauts who can act independently and respond to dynamic situations. Never, AFAIK, was a mission able to stick exactly to the checklists. And of course the astronauts are on there own on the far side of the moon for example.
Recalling another great example, I believe Al Bean took control of the Lunar Module for a while. "The only time the Lunar Module Pilot actually flew the LEM".

 

[Urwumpe]

Well, interesting to answer it would be the differences between Pyro Bus A and Pyro Bus B, in general and at the moment of flight.

http://nassp.sourceforge.net/wiki/Electrical_Power_System_(CSM)

This one could further help understand the logic:

http://history.nasa.gov/afj/pdf/seq-systems-training-course-A318-handout1-19690215.pdf

http://history.nasa.gov/afj/aoh/aoh-v1-2-09-seqsys.pdf


Note that Bruce did not recommend to arm Pyro Bus B instead of A, he recommended to arm both Pyro Buses, because Neil did only arm Pyro Bus A. One Bus is necessary for the SLA separation, but both can be used at once. The bottles refer likely to the separation thrusters.

 

[Staiduk]

Hi all. Urwumpe; sorry but the Sourceforge link was blank; I don't know if the problem is on my end. Also thanks for the manuals; very good info.
My question refers to Neil's choice of action though. To explain, as a real-life pilot; I'm aware that I hold the final responsibility for my aircraft. ATC can tell me whatever they like but ultimately I have the final say in its operation; and the same holds true in the CSM. As Nick pointed out no mission will ever perfectly follow the checklist; there are so many variables the pilots have to be able to operate on the fly and respond independantly. However; T&D would have been one of the most heavily rehearsed stages of the mission; practiced hundreds if not thousands of times. There is a set and very precise procedure for preparing the spacecraft; though changes may of course be made depending on variables - Mike's performance in the transposition is an ideal example. And yet when the astronauts perform the checklist for real; Neil diverges from the routine enough for CAPCOM to comment on it. It was clearly a change he chose to make on the spot; had he only used PYRO BUS A in the simulator it would have been discussed and hashed out there. Nor was it in response to an experienced variable; his response says he simply chose not to arm the bus. (Shrug) It's not really a technical question; more a question of how strictly the astronauts followed the checklists during routine evolutions. I simply find it odd that he would have diverged from a heavily-rehearsed checklist at that important time; however minor that divergence might have been. Probably not explaining my thought very well; it's just an idle curiosity.
Cheers! (1 hour from LOI)

 

[Quick_Nick]

Hi all. Urwumpe; sorry but the Sourceforge link was blank; I don't know if the problem is on my end.

It's sort of a forum problem. The closing parenthesis in the link gets dropped sometimes.

 

[Staiduk]

Ah - got it. If I'm reading this correctly; the difference between PYRO BUS A differs from B in that it can be tied into MAIN BUS A; while B cannot. Ground wanted both A&B on so the second could serve as a backup in case the first failed. Logical; I just don't get why Armstrong chose not to switch B on as per the checklist. (Shrug)

 

[Urwumpe]

Hi all. Urwumpe; sorry but the Sourceforge link was blank; I don't know if the problem is on my end.

Fixed it. I had forgotten to manually put URL tags around it.

And I interpret the communication that Mr. Armstrong followed the checklist, while the flight directors wanted to play safe and fire both pyrotechnical systems at once.

There is no need to fire both circuits at once, it could in theory (as Soyuz 11 reminds) also damage the spacecraft. I need to look how it was done for Apollo 10, this could bring some insights.



Also the checklists had been pretty much work in progress during the Apollo 11 training. You don't rehearse the same T&D maneuver all over again. You rehearse, practice especially for failures, debrief, and then you and the checklist can change. The feedback from the astronauts during the simulations is very important for developing the final checklists. Some astronauts in history really knew one subsystem then often better then the engineers that initially designed it, because they operated it during the hardware-in-the-loop testing to the extremes.

 

[Staiduk]

Oh; OK, that makes perfect sense then. And so saying; I remember reading in 'Lost Moon' that Jack Swigert was probably the single most knowledgeable individual regarding the CM's operations during Apollo 13 - making his portrayal by Kevin Bacon a little unfair. Thanks! It was one of those weird questions which just nags. :thumbup:

 

[Artlav]

This doesn't really answer your question, but IIRC Buzz Aldrin is "responsible" for the 1201 and 1202 alarms occurring on Apollo 11, because he left the computer doing more than it could handle. That might have been forgetfulness, or the radar switches might have been left on without care.

I think he said (AFAIR, in "In the shadow of the Moon") that he wanted the docking radar on in case they needed to abort and dock, and the landing radar was on for landing.
He then commented that the folks at MIT didn't think that way - "you want to land, you use the landing radar, you want to dock, you use the docking radar, not two at once", so the computer couldn't handle that.

 

[Tschachim]

There's a piece of dialogue that occurs earlier in the flight; just prior to S-IVB separation Capcom Bruce McCandless questions CDR Neil Armstrong about his descision to only arm Pyro Bus A; rather than both. Neil's response is "My intent is to use bottle Primary 1, as per the checklist; therefore, I just turned A on."

Just a couple of technical details: Armstrong is talking about the docking probe retraction system. There are 4 nitrogen bottles, each of them can do the retraction pneumatically and can be used once (i.e. for one retraction) as a bottle is opened by a pyro. Which bottle(s) are used is controlled by the switches shown in the attached screenshot. The pyros on the 2 primary bottles are ignited by Pyro Bus A, on the 2 secondary by Pyro Bus B. So if you want to use bottle Primary 1, you only need Pyro Bus A.

But there's no need to deactivate Pyro Bus B to use bottle Primary 1, the bottles are selected by the switches in the screenshot. You just don't need Pyro Bus B.

The problem I'd had with Armstrongs decision is that he seemingly wanted to do that before CSM/LV separation, i.e. there's only one Pyro Bus active during separation. The Pyro Busses are used not only for the docking probe, but also for a lot of pyros used during separation. These pyros are completely redundant. If one wire / relais / whatever fails for Pyro Bus A with Pyro Bus B unpowered, you loose this redundancy and the (rather complex) separation sequence isn't done correctly.

So if he really wants to unpower Pyro Bus B for whatever reasons, he should do that after separation, not before...

...and about the 1201/1202 alarms there's a good article here: http://www.doneyles.com/LM/Tales.html

Cheers
Tschachim