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Originally posted by jra
Well I skimmed through all the surface pics from Apollo 17. I didn't see it in there (all though I could have missed it). But I think that pic is croped out from some video footage and not from a still photo.
Originally posted by pepsi78
If this images are from the moon
The LEVA was an elegant design, consisting in one assembly of a thermal cover, 2 visors, and 3 eyeshades.
The 2 visors were layered over each other. The inner "protective visor" was made of ultraviolet-stabilized polycarbonate plastic and filtered ultraviolet rays, rejected infrared and, in combination with the sun visor and pressure helmet, formed an effective thermal barrier. The outer "sun visor" was made of high-temperature polysulfone plastic and filtered visible light and most ultraviolet and infrared rays.
The protective visor is an ultraviolet-stabilized polycarbonate shield which affords impact, micrometeoroid, and ultraviolet ray protection. It can be positioned anywhere between the full-Up and full-Down positions and requires a force of 2 to 4 pounds for movement. A coating is added to the inner surface of this assembly. The elastomer seal on the upper surface of the stiffener prevents light passage between the two visors. The protective visor can be lowered independently of the sun visor, but cannot be raised independently with the sun visor in the Down position.
The inner surface of the polysulfone sun visor has a gold coating which provides protection against light and reduces heat gain within the helmet. The visor can be positioned anywhere between the full-Up and full-Down positions by exerting a force of 2 to 4 pounds on the pull tabs. The sun visor cannot be independently lowered unless the protective visor is in the Down position, but it can be raised or lowered independently when the center eyeshade is in the full-Up position and the protective visor is in the Down position.
One of the major considerations in flight was the amount of harmful ultraviolet (UV) radiation to which the crewmen would be subjected during extravehicular activity. Prior to Apollo missions, the UV threshold of the eye was unknown. Over a three-year period, NASA-sponsored research determined these levels. The problem was, however, subsequently resolved with the development and use of Lexan in the extravehicular visor assembly, since Lexan was opaque to UV radiation. A minimum of 2000 hours of exposure would be required to produce a corneal "burn" through this plastic.
The astronaut wore two helmets. The transparent "fishbowl" helmet was worn underneath, and the LEVA "hardhat" with the visors attached was placed over this helmet for lunar EVA activities. The LEVA had the gold visor, which could be rotated upward if necessary.
Both the "fishbowl" and the visor were made of Lexan, a polycarbonate which is almost perfectly opaque to ultraviolet. Even with the gold visor up, the astronaut would be subject to very little ultraviolet.
I'm not sure what other forms of radiation people believe are out there. The visor will not stop cosmic rays, but they aren't that plentiful. The Lexan will stop a good portion of ambient x-rays, but they aren't that plentiful either. The particle flux isn't much to worry about either.
The gold on the visor was simply to dim the glare to improve the astronaut's vision. If he worked for prolonged time in the shade, he raised the visor to get a better view of details.
Home Depot sells plastic sheets of Lexan (poly-carbonate) which are printed with claims of blocking UV. Try this stuff. You might find it blocks only 90%, depending on your UV meter. I do not think it depends on thickness, though. I think they take a
clear plastic that transmits most UV, then they soak into one face a "UV dye" that absorbs only UV, just like the PABA or other active chemical in sun-screen lotions. Even says on the cover sheet: "this side towards the sun". This is the side with the
UV-blocking dye, less than 0.1mm deep.
These children suffer from a rare genetic disorder (called Xeroderma Pigmentosum) that puts their lives at risk when they are exposed to the Sun. Their bodies are extremely sensitive to the Sun's ultraviolet (UV) rays. This means they cannot go outside in daylight, except with special protection. Unless all UV is blocked, their skin and eyes may be severely damaged, eventually leading to cancer.......
There are two parts to the suit. The headgear, designed to look 'cool' for children, covers the head and face. It includes a large see-through, polycarbonate visor, an adjustable plastic headband and a fabric hood.
Any shooting glasses lens rating less than 99% or 400nm probably won't provide adequate UV protection. It should be noted that even clear Polycarbonate lens will block or absorb UV rays, so don't become focused on the tint as playing a role in the level of protection.
Better quality coated lenses, most "high index" (thinner and lighter-weight materials) and all polycarbonate lenses block virtually 100% of the UV.
LMP Nice day for an EVA, Ron. Go out and have a good time.
CMP Yes, it ought to be pretty good out there. I ... - -
CDR Okay, we're coming off the ...
CMP I just need that one visor down, don't I?
CDR No, you need your Sun visor down, too. Bring it - one is protective, and the other is the Sun.
CMP It is? Well, it looks dark out there. Can't even see.
CDR Well, use your own judgment. If - if you're in the shade, you won't need it. But if you're in the Sun, you ought to have it down.
CMP Man, that Sun is bright. Whoooo!
CDR Pull down that visor, Ron. You're going to need it.
CDR Not the metal one, unless you really need it.
CMP No, I don't want the metal one.
CDR No, just get the gold one. That's all you need.