Apollo 1

[ka9q]

My father underwent two, and yes I also remember carefully monitoring his hematocrit.  I also remember the size of the needle, and I'm pleased you didn't feel much pain.

I don't think I had a single needle during the whole procedure because I had a special 3-lumen catheter installed that emptied in the superior vena cava, the heart's "return port". Drawing blood and administering IVs was then a simple matter of connecting to the external ports. When I first had blood drawn through them I suddenly felt like a cow being milked, so after that I referred to them as my "udders".

Catheters are not only easier for the nurses and less painful for the patient, but whatever you put into them is quickly diluted in a large volume of blood. This is good for some of the more toxic chemo agents.

[ka9q]

I've hung my work pass around my neck and then 2 minutes later gone on a 20 minute hunt for it - several times may I add. 

Or looking for my glasses when they're already on my head.

I've found that one of the best ways to find something is to stop looking for it. I'm serious; it'll invariably turn up shortly afterwards.

[Luke Pemberton]

Or looking for my glasses when they're already on my head.

I once looked for my car keys when they were in my hand. 5 minutes. I've done the glasses one too.

[ka9q]

I once looked for my car keys when they were in my hand. 5 minutes. I've done the glasses one too.

My current car (2011 Nissan Leaf) is my first with keyless entry, and I love it. It also has Bluetooth connectivity. So I just leave both my keys and my phone in my pants pocket and everything just works. Until I change pants and have to go looking for them in the clothes hamper before they get dumped in the washing machine...

[Dalhousie]

O2 at one bar (atmospheric pressure) is toxic, therefore in a pure O2 environment the pressure is reduced to 1/5th atmospheric normal. There would be advantages in decompressing and recompressing a craft. Using an air mix does introduce the problems of narcosis, but reduces the problems of fire in a pure O2 system.

Actually O2 is considered potentially toxic above 2 atmospheres partial pressures, which is why oxygen rebreathers were not used below 10 m.

[Dalhousie]

O2 at one bar (atmospheric pressure) is toxic, therefore in a pure O2 environment the pressure is reduced to 1/5th atmospheric normal. There would be advantages in decompressing and recompressing a craft. Using an air mix does introduce the problems of narcosis, but reduces the problems of fire in a pure O2 system.

Ps this is what limits compressed air diving to 40meters, after that depth other gas mixes have to be used, at 40 meters the pressure of O2 reaches one bar

Again no.  Compressed air is generally avoided below 40 m because of nitrogen narcosis.  One bar partial pressure is not reached until 50 m, and the two bar limit is thus not reached until 100 m.

[ka9q]

I read through those test results, and it was rather striking how many fires still occurred in the 100% O₂ 6.2 psi and 60% O₂ 40% N₂ 16.2 psi cases. Though they were certainly much less severe than the 100% O₂ 16.2 psi case, it shows that the Apollo CM was never made fireproof, only fire resistant.

I wonder if helium might be a good diluent gas in a spacecraft. Its heat conductivity is significantly higher than air, so it ought to suppress fire better than an equal percentage of nitrogen. Helium speech used to be a real problem in diving, but I believe it's now possible to use special vocoders to correct it.

I saw a documentary on Sealab showing some guys trying to light matches. It was impossible.

[ka9q]

I also wonder why Apollo used such a high cabin pressure. Maintaining the same ppO₂ as sea level air requires only about 3 psi of 100% O₂.

[JayUtah]

I also wonder why Apollo used such a high cabin pressure. Maintaining the same ppO₂ as sea level air requires only about 3 psi of 100% O₂.

Two reasons:  reserve pressure in case of a puncture, and the general precision of pressure regulators for that volume of gas at that pressure.  For the latter, putting the pressure at or above 5 psia makes the gas-handling equipment more reliable.

[Luke Pemberton]

I wonder if helium might be a good diluent gas in a spacecraft.

That would stuff up the 'film was slowed down' claims

[JayUtah]

Thanks, guys.  Now all I'm hearing in my head is a Porky Pig voice saying, "The Ea-ga-ba-eag-- The Eag-aga-ba-- The Eagle has landed!"

[Al Johnston]

"That's one small squeak for a man..."

[Sus_pilot]

Thanks, guys.  Now all I'm hearing in my head is a Porky Pig voice saying, "The Ea-ga-ba-eag-- The Eag-aga-ba-- The Eagle has landed!"

More like Donald Duck in my mind.

[VQ]

I wonder if helium might be a good diluent gas in a spacecraft. Its heat conductivity is significantly higher than air, so it ought to suppress fire better than an equal percentage of nitrogen. Helium speech used to be a real problem in diving, but I believe it's now possible to use special vocoders to correct it.

My guess is that the heat capacity of the gas is much more significant than the conductivity - lowering the flame temperature would be a function of concentration and heat capacity of the mixed smoke/gas. Helium also has storability problems because it is so difficult to keep liquid.

What about SF6? It is inert, its high molecular weight should give it good heat capacity, it is easy to store as a liquid, it is a stellar dielectric thus reducing the likelihood of electrical fires in the first place, and it would give the astronauts a resounding bass register so Jay can imagine James Earl Jones instead of Porky Pig.

[Luke Pemberton]

...and it would give the astronauts a resounding bass register so Jay can imagine James Earl Jones instead of Porky Pig.

So now we have Darth Armstrong exclaiming 'micrometeorites do not concern me Aldrin' as he steps down from the LM.