I suspect you haven't followed the conversation. Imagine the end of the movie Alien if Ripley had to spend ten hours prebreathing, or even 40 minutes. Thats not the future I want.
actually the Russians solved this long ago and at least one advanced space suit design is out there that does not require pre-breathing or exercises. it has a hatch in the back and can be attached on the exterior of a space RV (I mean big rover) or presumably the exteriors of colony habitats. how is that science fiction? They know they can do it. it has been done to a degree by the Russians. there are no tech or physics show stoppers for just building them.
ask the poor spouses of the Apollo crew that got incinerated in their capsule if there is no drawback to omitting nitrogen from their air. There is at least one: living without diluting gases in an oxygen environment will kill you sooner or later especially as so many things that have to be done will generate an ignition source.and i also vaguely recall that pure o2 damages biological tissue in various ways. I don't recall from where i read that but that is the feeling i get from the vast swamp of my memory.
In my opinion nitrogen's benefits ...
Quote from: Stormbringer on 09/11/2014 02:42 pmask the poor spouses of the Apollo crew that got incinerated in their capsule if there is no drawback to omitting nitrogen from their air. There is at least one: living without diluting gases in an oxygen environment will kill you sooner or later especially as so many things that have to be done will generate an ignition source.and i also vaguely recall that pure o2 damages biological tissue in various ways. I don't recall from where i read that but that is the feeling i get from the vast swamp of my memory. Yeah, that's ridiculous. The Apollo fire, the pure O2, all of those risks come from PARTIAL PRESSURE, not the nitrogen.A buffer gas can reduce risk of fire, but only by a little bit. Vast majority of effect is due to higher partial pressure of oxygen in the Apollo 1 capsule. Operating with lower-than-sea-level oxygen partial pressure also reduces the fire risk, perhaps even greater than a buffer gas, plus it increases pressure vessel safety.Appealing to "widows of the astronauts" is a just shameless emotional ploy. Pointless in this sort of discussion. There's absolutely no reason to be at 15psi oxygen partial pressure on Mars.And really, operating at higher pressures (i.e. the buffer gas adding to the pressure) means your tissue has higher concentration of nitrogen (or argon or whathaveyou) so you're at much greater risk of the bends in case of explosive decompression and being able to get into a space suit is also harder, with movement more difficult (other things being equal) if you operate at higher pressure thus increasing the risk of making more "widows". Also, for the same pressure vessel, you're at much greater risk of structural failure if you add in a whole bunch of buffer gas.There's a reason why they stayed with pure O2 on Apollo (once in orbit), just starting with standard atmospheric nitrogen mix when sitting on the pad so the partial pressure of oxygen wasn't too high.There's nothing special about nitrogen gas unless you're a nitrogen-fixing bacteria. /Might/ make sense to add a couple psi of buffer gas, but the idea that we have to have as much as sea level seems ridiculous to me.
And all of this is basically off-topic. But here's an on-topic thought:I now find it funny that in scifi, aliens are trying to steal Earth's water. How did they miss all the other icy bodies in the solar system with far greater amounts of water (liquid or otherwise, take your pick) and lower delta-v to get to them? Also, those icy bodies aren't inhabited by pesky little humans with nukes and viruses and other irritants.
What benefits (plural)? I only see one (singular): a slight reduction in fire risk.
Quote from: Robotbeat on 09/13/2014 09:55 pmWhat benefits (plural)? I only see one (singular): a slight reduction in fire risk.Read the PDF I posted. As ever in aerospace, things are more complicated than simple first order estimate might suggest.
Nice find! Going through it now.. found this one:Some investigations have reported that an inert diluent gas is helpful in preventing atelectasis, the collapse of small air sacs in the lung which may occur due to the aborbtion of all the oxygen in less ventilated sacs.but it doesn't seem conclusive and does not clarify how serious. Certainly something like this might emerge as a show stopper with more testing.
I think the atelectasis reference applies to high oxygen content under high pressure, as in increased partial oxygen pressure.
If we ever go for large scale colonization of anything, I believe aquiring nitrogen to fill living space with air is probably going to be one of the harder issues to solve. Once you make structures large enough, the mass of the air inside them tends to increase very rapidly. For O'Neill cylinders or martian air-filled domes, the air inside constitutes the majority of the total mass, and while finding the oxygen to fill them tends to be easy, making nitrogen in large enough quantities for use as a buffer gas tends to be a harder problem to solve. Even for small colonies it can be a bottleneck as it is needed to make fertilizer.
On the topic of spacesuits that don't require pre-breathe, what happened to the biosuit? is it still under development, or were there any show-stoppers?
