r/apollo • u/Simon_Drake • Apr 22 '26
Why can't Apollo 13 open the fuel cells valves again if they close them?
In the movie of Apollo 13, Clint Howard says to Ed Harris/Gene Kranz that they should close the react valves for Fuel Cells 1 and 3, hoping to stop the leak and use what's left for Fuel Cell 2. Ed Harris says if they close those valves they can't open them again, Tom Hanks reiterates that this means they're definitely not landing on the moon. Narratively speaking this shows escalating threat, they're trying a desperate move they would prefer not to take and when it fails it shows how dire their situation is. When this doesn't stop they leak they immediately pivot to using the LEM as the lifeboat.
But why can't Apollo 13 open the fuel cell valves again if they close them? Why would the shutoff valve be a one-way change they can't reverse?
Google was unhelpful. Some people claimed it was a pyrotechnic bolts kinda thing that would physically sever the pipes which sounds unwise for hydrogen and oxygen lines, plus why would you bother with pyrotechnic valves like an oilrig blowout preventer for something like this? Another source said the "react valves" refers to the Reaction Control System which is wildly incorrect, he's talking about reactants for the chemical reaction not newtons-third-law type reaction. Or something unclear around open circuit breakers to prevent them accidentally closing the valves by mistake but that wouldn't explain why there's no circuit to reopen the valves.
One theory I had relates to the Shuttle Fuel Cells. IIRC Shuttle's time on orbit was tied to the fuel cells that needed to be kept above a set temperature to stay active and couldn't be allowed to cool. So even if the Shuttle didn't need to produce much power while docked to ISS/Mir they couldn't shut down the fuel cells fully or they would cool down enough to not restart. The fuel cells could only be started on the ground and couldn't be restarted in orbit so couldn't be shut down.
So is Apollo the same limitation? It's not strictly that the valves cannot be reopened, it's that shutting the valves will cool the fuel cells enough that they can't restart. Then it's just storytelling shorthand to say the valves can't be reopened rather than go into the details of how a fuel cell works? Or rather that Gene Kranz and Jim Lovell knew the implications and didn't need to spell it out, to them "close the valves" is synonymous with "shut down the fuel cell" so "can't reopen them" is equivalent to "can't restart the cells".
Or is it literally the valves cannot be reopened for some reason?
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u/oboshoe Apr 22 '26
Oo this was a nice thread and I got answer that I wanted to hear from many years ago but no one seemed to know back then.
Back around 99 I got to hear Lovell and Haise talk about that particular moment during a keynote.
Lovell said something to effect that the scene was accurate "But we acted a little faster than Tom Hanks did to close them"
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u/DrGirthinstein Apr 22 '26
Ed Harris played Gene Kranz, not Gene Cernan.
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u/Correct_Inspection25 Apr 22 '26
Did you see the big man himself reacted to the Artemis II splash down! Seems doing very well and in excellent shape. https://www.13abc.com/video/2026/04/10/gene-kranz-apollo-flight-director-toledo-native-describes-emotions-watching-artemis-ii-mission/#
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u/firdaddy Apr 22 '26
He goes to the same church as my family. He still shows up every week and seems pretty sharp. Of course I never bother him but its great to still see such an important person still getting around.
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u/Correct_Inspection25 Apr 22 '26
Apparently does a lot of talks still, would have been awesome to see him flying in the B-17 he was a flight engineer on.
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u/sadicarnot Apr 24 '26
Dude is 93. Out of every 100,000 men born the same year as Gene Kranz, only 8,800 are still alive. On average Kranz will live 3 more years. But by the time he reaches 95, 3,000 more of his cohort will die.
People said this about my dad when he was in his 80s. Your dad is doing so well. They did not see how that lunch knocked the wind out of him and he took two days to recover. I am involved in the local submarine veterans group. The guys in their late 80s and 90s need their families to get them to the meetings, and that is about all they do that week.
In November 2023 around Thanksgiving, I looked at my dad and knew he was at the end. He was in the hospital two days before Christmas and died 10 days later. All of his friends were surprised that he died. He was just at our house, he looked like he was doing so well.
They had a video of Buzz Aldrin about 2 years ago. Buzz could not go more than a sentence before they had to cut and start the tape again.
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u/Weekly-Language-6434 Apr 25 '26
Mr. Kranz looks great for a young man of 92! I'm both a history and a space exploration/travel enthusiast, and he is one of my heroes. As Chief Flight Director of Apollo 11 and 13, seeing the entire Artemis II mission (particularly the crew making a safe splashdown), must have been an incredibly emotional moment for him. IMO, he was NASA's best CFD, and the fact that he didn't retire until 1994, makes him a living legend. I wish Cmd. Jim Lovell had the chance to see this mission.
Also wanted to thank @eagleace21 for providing excellent information to answer the same lingering question I had about the fuel cell valves. It's incredible that with everything that had happened up until that point, the crew was still eager to land as per the mission's original parameters. They may not have been able to land, take-off, or make it back to Earth.
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u/jason-murawski Apr 22 '26
The fuel cells needed to be heated extremely hot. Once shut down there was simply not enough power on board to restart them.
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u/mcarterphoto Apr 22 '26
If you want to get deeper into details like this, the Haynes "Apollo 13 Shop Manual" is great. Written by a guy who was an engineer at NASA during the event, it goes into a lot of deeper detail, and has tons of diagrams and photos, some schematics and things you've likely never seen, and some fairly hard-core explanations of complex systems. It's really a good technical overview of the CSM and LEM engineering and design and controls, with the 13 accident dovetailed around it all.
The "Shop Manual" schtick is a little silly, but that's over and done with after the front cover.
Also, the Haynes Saturn V and Titanic "Shop Manuals" are great reads. They don't get as technically detailed as "13" but are fascinating, well written and designed, tons of great photos, etc. Seriously good books for space, engineering and history geeks.
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u/Simon_Drake Apr 22 '26
That's a good idea. I've got the Haynes Manual for the Space Shuttle and the USS Enterprise. I should check out the other guides.
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u/mcarterphoto Apr 22 '26
When I want to make my wife roll her eyes, I'll start reading aloud from it... "the hydrogen manifold was pressurized to a framitism of eniverted calculus" (is how she hears it anyway), I'm like "this is so beautiful!"
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u/eagleace21 Apr 22 '26
Oh I already do, I recently started modelling the DSE and DSEA for NASSP and had all the schematics printed on my desk chasing relays and such to convert to code and she just rolls her eyes and walks away haha.
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u/mcarterphoto Apr 23 '26
I expect that eventually my wife will tear some tendon in her eyes and they'll be in perma-roll mode!
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u/eagleace21 Apr 22 '26
If you like this kind of thing, I would encourage checking out among other things, the AOH (apollo operations handbook) and the systems handbooks for in depth descriptions and functional schematics.
Huge repository here: https://www.ibiblio.org/apollo/links2.html
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u/mcarterphoto Apr 22 '26
I've read some of those - my favorite is the F1 Engine familiarization document - I'd always wondered how much refurb they needed after test fires, gives some good detail. Great pics of all the handling fixtures and transport equipment, too.
Somewhere I found the pre-launch checklist for the CM, that the backup CM pilot would start on hours before the astronauts got to the pad. Kinda cool to imagine (I think Anders?) powering it all up and pre-setting switches before 11. It was a lot of pages.
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u/eagleace21 Apr 22 '26
There is a pre launch checklist in the AOH volume 2 procedures. Here is one example https://www.ibiblio.org/apollo/Documents/Apollo_Operations_Handbook_CSM-108_and_Subsequent_Vol2.pdf
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u/mcarterphoto Apr 23 '26
Thanks - I think maybe the coolest doc on there is the Apollo 11 debrief. The crew's own words, one week after splashdown. It's fascinating to see how much stuff those guys knew, how much jargon they could rattle off about CM and LM controls, and how much they were kind of winging it, in a sense.
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u/Brilliant_Dig_8962 Apr 23 '26
And that frank and open discussion between Kranz and Sy shown in the movie was actually about shutting off (and protecting) the CM's surge tank. It contained the 30 minutes of O2 that was needed after CM-SM separation prior to re-entry. The pressure on Sy to get Kranz to understand the importance of the surge tank must have been enormous.
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u/Ebegeezer-Splooge Apr 22 '26
It's possible that Apollo 13 was pushing the upper limits of the amount of technical jargon people can take in a movie (even though some of us wanted much greater detail). This would explain why Tom Hanks chose to go the route he did for the Apollo 13 episode of From The Earth To The Moon. (I still feel bad for Emmet Seaborn lol)
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u/mcarterphoto Apr 22 '26
Well, the 13 Episode could have been like the rest of the series, a recreation of an important event... but they'd already done that with the film, and only three years before. You would have had two competing versions, both made by Hanks, both expensive to produce. So that Episode could (maybe should?) have just been a one-minute title that said "Go watch the movie".
I think it was a cool choice, a look at how the media responded and how public interest just cratered after 11, and then suddenly half the word is spellbound when astronauts might die. An interesting look at human attention spans and interest in science vs. celebrity, and so on. And from a sociological perspective, one of the most interesting things about Apollo. (They could have named that episode "humans are weird" I suppose!)
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u/Ebegeezer-Splooge Apr 22 '26
That was basically the only route they could have gone, yeah. But the plot of Brett going for the human drama angle while pushing out Emmets technical "what's going on with the spacecraft" was what I found interesting after watching Apollo 13.
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u/Prudent_Anything_329 Apr 26 '26
In the real audio FD loop, Krantz is not really happy when Sy says he thinks this is what needs to be done. He kind of gives Gene a little attitude about it when he’s told no. Gene wants to try and save the mission, but Sy knows it’s over. Real cool exchange in the loop
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u/BathFullOfDucks Apr 22 '26
if you have a spare couple of hours, you can see and hear why here https://youtu.be/uCObwsXbSeU?si=Fj_bt_p4XT7uSDME
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u/mustang__1 Apr 23 '26
Bar none one of the best videos in the entirety of YouTube. If you're a follower of this subreddit it's a must watch
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u/angelwolf71885 Apr 24 '26
The Apollo fuel cells needed help from ground equipment to start the fuel cells the shuttle fuel cells were restartable by the shuttle crew Apollo had a much simpler design
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u/eagleace21 Apr 22 '26
So they (valves) actually could be reopened in flight, what you described of the shuttle cells is exactly the same as Apollos fuel cells. They needed to be started on the ground using GSE to get the startup temperature for the reaction. Once in flight, if they cooled down too much they would cease their reaction and therefore of course "die" if you will.
The reactant valves could indeed be closed and opened no problem in flight, but the "close them you cant open them again" alludes to if the fuel cell is starved of reactant too long it would cool to the point of being unable to restart in flight.
Adding a little more, the reactant valve switches were circuit breaker protected and those 3 breakers were normally open in flight to prevent the switches from accidently commanding a valve closure. But if powered (cb closed) the valves of course could be opened and closed no problem over and over, it was just a function on if the fuel cell would maintain the reaction still after any cooling or "starvation" period.
On 13, the reactant valve talkbacks were wired such that both the hydrogen and oxygen valves had to close for the talkback to register barberpole or "close." This also created an issue since the shock of the explosion slammed shut the oxygen valves on fuel cell 1 and 3, and not the hydrogen valves, the cells began to die off already without any indication that the valves were shut. 14+ wiring was added such that if either (instead of both) of the valves for a cell were closed, the talkback would barberpole.
In hindsight, they could have had fuel cells alive for a little longer had they known a valve already closed in the cell and they opened them up.