Apollo CM Crew Hatch

[Algebraist]

I think this is a fantastic project zrowny. The detailed explanations are great. When finished do you think you will release your model? I for one would love to have a go at building it.

Regards and take care

Kevin

[zrowny]

After this is the Vent Valve, or Pressure Equalization Valve. This is used to equalize pressure between the cabin and outside, and can entirely vent cabin pressure in less than a minute.



From inside the cabin, the handle is raised (see the tab that locks the handle into one of the 36 slots) and rotated to open the valve. Externally, a tool can be inserted to rotate the same shaft to open the valve.



I'm not entirely sure when this valve was used. On the ground, the CM was kept at a slightly higher pressure than outside, so opening this valve shouldn't have made it easier to open the hatch in an emergency (there's also a pressurized cylinder that helps act as a counterbalance to make the hatch easy to open). After launch, the CM's pressure was lowered to 5 psi (about 1/3 normal atmospheric pressure), so after splashdown the CM would have to have it's pressurization equalized before the hatch could be opened. If this valve was the one used for equalization, rescue crew would have to be able operate it from the outside if the crew was unable to for any reason, but I found a Recovery Procedures Manual and this isn't mentioned anywhere.

Outside of an that, I'm not sure when this valve would have a reason to be used. Spacewalks were performed on Apollo 9, as well on the last three Apollo missions to retrieve film from cameras in the Service Module. There are other computer-controlled valves in the CM that vent air into space (specifically lowering the cabin pressure after launch), and I'm not sure why those wouldn't be used to depressurize before these EVAs. I think I'm going to look and see if I can find more details in a mission log or operations guide or something, but if anyone knows more, please speak up!



Anyways, here's the paper version of the frame the will the assembly sits in. I don't think it's possible to make a paper version of the screw that the valve plug rides on, so I think it will just be fixed and the shaft inside will just rotate.

Originally Posted by Algebraist

I think this is a fantastic project zrowny. The detailed explanations are great. When finished do you think you will release your model? I for one would love to have a go at building it.

Regards and take care

Kevin

Thanks Kevin, and thank you to everyone else who has offered praise!

I'm definitely going to release this for free when I'm finished. I can't guarantee great instructions or a lot of polish on this, so you'll definitely need some paper modelling experience for this.

[SAustin16]

WOW....At a loss for words.

For years the Block 2 Hatch has fascinated me, and is in itself a functioning and life-saving work of art.

Fabricating these assemblies "in real life" at 1:1 scale by artisan machinists is challenging. Designing and building these in paper is astounding...beyond impressive.

This is a great thread. Thank you Zrowny and other Commenters.

One comment on NASA documentation...The American space program was a SPRINT from Kennedy's speech in 1961 until 1969, and then resulted in massive layoffs beyond that until the end in 1972. I think that everyone thought they'd update erroneous documentation when "things slowed down"....but they sadly never got the chance.

Bravo from Texas.