posted 05-06-2018 10:42 AM               

The visor guard was like a protruding shell that sat on top of the helmet and it had unusual thick "L" shaped grooves on it as well. Does anyone know what the grooves on the visor guard were for?

posted 05-06-2018 02:29 PM               

I don't know the helmet's dimensions, so I can't say if it was larger than Gemini or not.

posted 05-06-2018 09:21 PM               

quote:

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Originally posted by Jim_Voce:
an especially unusual feature

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By design, if the Apollo 1 helmet is a Gemini design with the addition of a cover over the top, then yes it will be wider final dimension.

The Apollo bubble helmet design came about for many reasons, including removing the complex visor seal and lock (somewhere else a leak could occur) removing the bearing requirement from the neck ring, and ease of maintaining the helmet over mission lengths without a suit tech. I believe that one of the most important reasons for the change was in the case of rapid cabin pressure loss.

If you watch Apollo training films taken during altitude chamber training, rapid pressure loss caused the suit to expand rapidly, if the suit neck ring straps were not snug, the helmet and neck ring rapidly move upwards, making the astronaut look like they are shrinking down in the suit.

A serious problem with this when wearing the Gemini style fitted helmet is the risk of breaking the astronauts neck during pressure loss. The problem was dramatically reduced with the bubble design. So the visor and cover assembly became an attachment to the new helmet design.

posted 05-07-2018 09:52 PM               

Although the actual pressure shell was the same size for the two helmets, as pointed out the addition of the unique Apollo visor guard and the Gemini parachute riser guard added width to the helmets.

Measuring the overall widths of the helmets indicates the widths only differ by 0.14 inches with the Apollo 1 (A1C helmets) being wider. So they are very close.

As mentioned above, the ridges provided reinforcement since the vacuformed visor guard was very thin. The top ridge provided clearance for the visor latch when the visor was in the open position.

The Apollo 1 style visor guard was developed to provide bump protection for the visor when in the open position. During weightless conditions in the Apollo capsule, the astronauts could float freely whereas the Gemini crews could not move freely enough to develop sufficient speed to cause substantial impact damage to the open visor.

The Apollo 1 style visor guard served a different function than the over-shells on the later used bubble helmets. The over-shells on the bubble helmets were developed to provide attachment points for the EVA visors and also later to provide a surface for TMG attachment.

The over-shell EEVA that was developed for the Apollo A5L development suit (that later evolved into the LEVA an SEVA) was already in existence when the Apollo 1 helmets were developed so the Apollo 1 visor shell did not evolve into the extra vehicular visor assembly but was a separate development to solve a different problem.

The bubble helmets also had their own protective shell that was used for pre-launch entry to the spacecraft, and possibly for in-flight tunnel transition to the LEM to protect the helmet from damage.

Single piece bubble helmets are preferred over helmets with opening visors due to the possibility for leaks during EVA. A large visor opening has a greater potential for leaks due to the length of the sealing surface around the opening of the visor, and is more susceptible to impact damage than a single piece dome.

Any penetration through the suit pressure layer is a point for potential leaks, so there is a strong desire to keep the size and number of openings to a minimum. However launch/entry requirements are different than EVA requirements.

Bubble helmets were not used for the shuttle launch/entry suits primarily since a bubble helmet requires gas flow to the suit anytime the helmet is on.

The shuttle ECS was not designed to handle a closed loop suit circuit nor an open loop suit circuit that exhausted for long periods of time into the cabin.

Thus a bubble helmet could not be used for the shuttle unless it was not donned until needed. If the bubble helmet was off it takes a lot more time to get the helmet and put it on and then start gas flow.

The open visor helmet provided a rapid emergency response alternative. It can be worn with visor open which allows the crew to be fully suited but not using suit oxygen, but ready to go in the event of an emergency.

An open visor helmet is also preferred for comfort when using purely as a backup system (ie launch/entry) as it is more desirable to have the face area open until actually needed.

(However, as it turned out, the desire to minimize oxygen enrichment of the shuttle cabin affected when the visors were closed, which impacted the effectiveness of the suit.)

The down side, as was pointed out, was that since the Shuttle open visor helmet was a large non-conformal helmet, it did not move with the head so that to look sideways the crew had to grab the neckring of the helmet and turn the helmet.

Normal conformal helmets with opening visors fit tightly to the head so that he helmet turns with the head.

The larger non-conformal open visor helmets were chosen for comfort over a tight fitting conformal helmet.

posted 05-08-2018 10:22 AM               

quote:

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Originally posted by oly:
This raises a question I have regarding why the bubble helmet was not used by shuttle crews on the launch and entry suits for both the early suits and the later suits.

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1. The Shuttle LES was a modification of an existing suit design.
   
2. The Shuttle LES was for bailout protection more than anything (the same as original suit design U-2 and SR-71 crews).

posted 06-21-2018 09:32 AM               

Also was a communications cap worn with the Apollo 1 helmet?

Included below is a photo of Roger Chaffee trying on a communications cap. Now typically, a communications cap was worn underneath an astronaut's helmet (as was done on Apollo 7 through Apollo 17, Skylab, ASTP and the shuttle missions) because the helmet did not have earphones or a microphone. But the Apollo 1 helmet was an all-in-one unit. To my knowledge, it did have earphones and a microphone. And if this is correct, then there was no need for a communications cap for the Apollo 1 astronauts.

I have considered that this Apollo 1 communications cap was suppose to be worn by the crew in orbit after they removed their helmets. But there are indications that the Apollo 1 crew, once in orbit, would have worn a simple headset with an earpiece and microphone as was done by the Gemini astronauts and the Apollo astronauts starting with Apollo 7.

Conversely, it is also true that on later Apollo flights (Apollos 7 through 17), a communications cap was indeed worn in orbit. But it appears the crews preferred most of the time to wear the simple headset with an earpiece and microphone instead of their communications caps. So this makes me wonder if the Apollo communications cap was worn in flight just for a short time until the astronauts had a chance to transition over to their simple headsets.

So based on these details, what purpose would the communications cap had for the Apollo 1 mission?

posted 06-22-2018 08:37 AM               

quote:

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Originally posted by Jim_Voce:
...what purpose would the communications cap had for the Apollo 1 mission?

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posted 06-22-2018 12:24 PM               

The Apollo A1C helmet did not have a separate or removable communication headset assembly aka Snoppy cap. The earphones and microphones were built into the helmet the same design as the Gemini helmets.

Regarding the photo of the headset with the black hard-shell earphone covers being evaluated by the Apollo 1 crew, I am not sure of the genesis of that particular headset.

However I can say it was not part of the Apollo A1C helmet pictured at he start of this discussion thread.

Clearly for Apollo 1 the crew needed some type of communication headset for use after the A1C helmets were removed. The caption on the photo implies some sort of crew evaluation.

I have seen that particular headset being used under the clear bubble helmet dome on an ILC A5L suit, however I am not sure if the headset was developed for use with the ILC suit or whether it was developed as a light-weight headset for use after the A1C helmets and/or suits were removed to provide a shirtsleeve operating environment.

I used to think that headset was a early development version of the Snoopy cap but after seeing the photo of the Apollo 1 crew evaluating it, I am rethinking its origin. More research is needed.

Thanks for sharing that photo.

posted 10-08-2018 07:45 AM               

quote:

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Originally posted by Philip:
The Apollo 7 crew also used those helmets during CM checkout training in September 1967.

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posted 10-08-2018 12:07 PM               

quote:

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Originally posted by DG27:
The bubble helmets also had their own protective shell...

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