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The question and answer are both quite fascinating. But I think they hint at something potentially even more interesting: To figure out that they needed to coat visors with gold, without doing it by trial-and-error and frying a few retinas in the process, the level of planning and attention to detail in the early days of NASA must have been phenomenal. I'd love to know more about how they knew they had asked all the right questions.
If you can dig up a copy of the 1962 book "Space Medicine" by U. Slager, it's really interesting. It makes you realize how many questions they needed to answer experimentally before going into space. For example, how much acceleration can someone withstand. How much vibration and tumbling. Minimum and maximum survivable temperatures. How long can you be exposed to a vacuum. This was the era of putting people on rocket sleds to see what happens ( http://en.wikipedia.org/wiki/John_Stapp ). My favorite factoid from that book is that guppies can tolerate 10000G for 30 sec. It also describes a guy who survived 482 degrees F for 4 minutes.
guy who survived 482 degrees F for 4 minutes

Can you give some more details about this?

Behold the Bioastronautics Data Book [1], featuring sections like "Generation and Composition of Flatus" [2] and "Buttock Areas and Thigh Dimensions" [3] and captions that start "Data obtained on two subjects in ejection seat attached to arm of underwater centrifuge..." [4]

[1] http://articles.adsabs.harvard.edu/full/1973NASSP3006.....P

[2] https://secure.flickr.com/photos/40605738@N03/3737695623/in/...

[3] https://secure.flickr.com/photos/40605738@N03/3737695681/in/...

[4] http://articles.adsabs.harvard.edu//full/1973NASSP3006.....P...

Why do you believe they didn't fry a few retinas? They could've used animals for experimentation - I'm sure a lot of rats and monkeys gave their lives for the goal...
They knew the blackbody radiation spectrum back then and had lux meters. I'm pretty sure this wasn't unexpected but still a nice engineering tale.
This just reminds me how horribly stifling it is to the entirety of science that so many people love hoarding bricks of gold in underground vaults rather than use it for productive purposes. Besides the maliability and corrosion resistance mentioned in the article, it is also a strong conductor, and very good at heat transfer.

It has so many practical useful purposes besides rotting in a bank vault. But a lot of that potential is wasted on those that value it so highly for its scarcity rather than its utility. Why can't we just hoard iron oxide?

Another interesting story about precious metals in bank vaults:

During the Manhattan project they needed to build something with a ridiculous amount of copper coils, and copper was scarce due to the war. So they used silver instead. Who cares if it's more expensive, if that machine is going to be more heavily guarded than any bank anyway and you can always melt it back into ingots when you're done?

Since you bring up the Manhattan Project... Feynman described during the Manhattan Project they were testing different metals to find one with the right neutron properties. At one point they wanted to test gold, so they ordered a 6 inch gold sphere. The powers-that-be pointed out that the sphere would be 80 pounds of gold and would cost a fortune, but they ended up delivering it from Fort Knox. Gold didn't have the required properties, so the scientists ended up using the sphere as a doorstop for a while. The other interesting part of the story is the librarian who received the gold amused herself by asking people to move the small package for her - they failed, not expecting a small package to weigh 80 pounds; gold is much heavier than you'd expect.

http://articles.latimes.com/1985-08-05/news/mn-3468_1_manhat...

They didn't take it out of the treasury, on a technicality: The room the machine was in was declared a bank vault, and 99.9% of the silver was recoverable, so it never really left!
What are silver and gold, when you're making enriched uranium?
Col. Nichols from the Manhattan Project went to the director of the Treasury and said that they needed to borrow 6000 tons of silver. Who replied frostily: "We measure silver in troy ounces here."
I think you need to show a connection between storing gold in a bank vault and how somehow, that affects it being used in scientific purposes.

I would have to guess that perhaps at most, 1 gram of gold would be needed for a space visor? The process involved in deposition must be considerably more expensive than the actual material involved (a gram of gold is about $44 at today's prices).

(Actually about 300 square feet can be covered by 1 ounce of gold (31.1 grams per troy ounce) I believe; so the amount would be less than 1 gram, but maybe they would waste some, etc. )

> I think you need to show a connection between storing gold in a bank vault and how somehow, that affects it being used in scientific purposes.

? This is supply and demand: the use as a currency/store-of-value is extra demand, hence the price is higher, and other users (like science) will demand less gold.

> The process involved in deposition must be considerably more expensive than the actual material involved (a gram of gold is about $44 at today's prices).

Which is ~$44 you wouldn't have to pay for another metal, and the penalties only get worse from there. (Want to manufacture a billion smartphones for Africa using efficient gold circuits? Sorry, not going to work out well.)

> rotting in a bank vault

I thought this turn of phrase was rather amusing, considering that gold is often favored because it doesn't deteriorate at all.

But wouldn't the resulting iron shortage just cause bigger problems? I mean, gold is great, but steel is really useful. Not to mention all that oxygen we'd be locking up, too. People might start suffocating! </sarc>
> Why can't we just hoard iron oxide?

Because it isn't scarce.

A more elaborate answer:

http://www.npr.org/blogs/money/2011/02/15/131430755/a-chemis...

You can buy gold on the open market and use it as you wish. I think the important uses for gold can use small amounts, like gold plating electrical connections. There's no use for bulk gold that justifies the cost.
Is there not a way to synthesize gold, like how diamonds can be synthesized (obviously a different process.) I searched around, and I guess there isn't a good process for this, yet.

Also, how much could NASA really be spending on gold, anyway? They're already spending billions on the rest of their space program.

I concur, it would be much better put to use coating DeLoreans... for science!
Gold would be silver-colored if it weren't for special relativity. http://www.fourmilab.ch/documents/golden_glow/
It's not actually gold foil, it's typically a mettalised polymer film, Kapton. This becomes part of a multi-layer insulation material where each layer is composed of a different material that has certain advantageous properties, with all of the layers separated by a small shim between them to avoid thermal conduction.

I really gotta stop playing so much Kerbal Space Program.

Most of the shiny 'gold' things seen in aerospace and motorsports is just vapor deposited Kapton/polymide.

But there are applications where gold is indeed used - but it's unclear (in the literature I've read) when/where it's appropriate to use gold. The helmet use case I can believe. I also imagine large swathes of gold would be problematic - structural surfaces being unnecessarily conductive or introducing inductive noise.

Visors are metallic gold. The foil surrounding other equipment are most likely not metallic gold though.

Source: http://www.nasa.gov/pdf/188963main_Extravehicular_Mobility_U...

Good point. Here's some more background on multi-layer insulation:

http://en.wikipedia.org/wiki/Multi-layer_insulation

Of course, gold foil per se would end up being too heavy for a spacecraft thermal blanket.

Not for spacesuit visors though, right?
You can buy your own space age gold foil from many places as "rescue blanket". Quite cheap, around $3 for an adult sized sheet.

I've used it to insulate south-facing windows in summer. It's phenomenally effective.

The gold color in this case comes from the compound kapton, versus the elemental gold deposited on space helmet visors.

https://en.wikipedia.org/wiki/Space_blanket#Manufacturing

http://spinoff.nasa.gov/spinoff1997/hm2.html

I dunno how it is in the US, but here in Brazil, firemen also use gold-plated helmets.

I once in a first aid training asked one fireman that was present to borrow me his helmet, because I was doubting you could see through it (I was 12).

The nice man put the helmet correctly on my head, and to my surprise, I really could see! Everything was blue, but I could see everything, it was really cool.

This article explained to me WHY I could see... I was still puzzled (I thought gold reflected 100% of visible light)

> I thought gold reflected 100% of visible light

It depends on how thin it is. There is no 100%, the thinner the more is transmitted (weighted by the curve shown in the linked article). A solid block of steel would be transparent if you illuminated it with enough light.

Note that in the 1960s gold was valued at a fraction of the cost of launching its weight into orbit.
so you're saying we should go on an orbital prospecting trip.
Good point ...
I have known for a while (since I read Quicksilver) that gold becomes visibly transparent if you hammer it thin enough, and transmits greenish light, but I have never been able to find a picture of this or a video of someone demonstrating it. How is this possible?
You've seen it before... Stained glass. Stained glass was one of the first use of nanoparticles and plasmonics to become commonplace. The wide range of colors that you can get in stained glass is due to the nano properties of the materials you add to the glass. The effect is due to surface plasmons - electric field waves that travel on the surface of conductors. Much like ocean waves, plasmons are created from light's electric field. They bounce back and forth, and since they are only permitted on the surface of a material, there are limits on what waves can exist. This is what gives them the weird properties - the size and shape determine the optical properties.

On another tangent (this one's pretty cool) - since you can tune the properties of these nanoparticles, you can make them respond in a specific way. Let's say we have a cancer cell that we want to kill, and only that cancer cell should die. We can create nanoparticles that bond with that cancer cell, and only that cancer cell. But how do we kill it? We can tune the absorption spectrum of the nanoparticle to absorb infrared light - light that is transparent to the human body. We create a small heater that absorbs tons of the input energy, while keeping the rest of the area cool. Localized heating destroys the nearby cancer cell.

Plasmonics are really cool - http://en.wikipedia.org/wiki/Plasmon

http://en.wikipedia.org/wiki/Plasmonic_Nanoparticles

You can buy a gold coated filter plate from a welder's supply for less than ten bucks.
Gold reflects reddish light. That means only greenish light gets through. You don't need a solid piece of gold to see this; anything tinted with gold dust will work as well.
I am surprised that I can't find evidence of consumer gold foil sunglasses. Are the optical properties really terrible for day-to-day use? I'd think they'd be pretty sharp looking, and the cost of the gold shouldn't be prohibitive.
Most sunglasses are intended to reflect or absorb UV. As you can see in the OP, gold is only good at absorbing IR, which the atmosphere (and clouds and trees) do a decent job of absorbing when we are at ground-level. The gold would be more style than function for non-astronautical activities.
As I noted elsewhere, gold visor make you really see everything blue. I think few people would tolerate it.
This reminds me of uchuu kyodai or the space brothers anime where hibito wraps his comadre's body with a gold like foil to keep his body warm but also to reflect sunlight when it gets too hot. This anime is pretty realistic and I recommend you watch it if you'd like to know what it takes to be an astronaut.
Reminds me of the movie Sunshine, with their striking gold space suits. I thought it was just for theatrical effect until I read it was actually based on this theory.

The gold-leaf shielding in Sunshine was influenced by NASA satellite designs for deflecting heat and other forms of radiant energy. Boyle designed the gold-coloured space suits along these lines despite persistent encouragement to model them after the NASA template.

http://en.wikipedia.org/wiki/Sunshine_(2007_film)

I am not qualified to understand the chemistry, but I got the idea from somewhere that the ionization of the atmosphere filled near earth space a highly corrosive environment because a large number of liberated hydrogen atoms were present. Gold is inert and therefore not subject to the corrosion that would otherwise take place, and also would not catalyse other material.
Maclaren also lined the engine bay of the 90's F1 road going car with gold. Additionally many of my friends who highly modify their turbo charged cars line the interiors with gold foil (although I can't help but think this is mostly for aesthetics :).
I misread this headline as "NSA".

Time to take a break from HN, I guess.

Because NASA is all about the bling.
Doesn't it look cooler if we use gold? Short of practical purposes, if you have something that you need to convince a politician to support, wouldn't gold be better than silver for no reason other than it looks good?
I suspect painting it red white and blue would have been even better for political support.