Dangers of high alt flying in non pressurised AC

[Herne]

I read that there were some combat engagements that took place at > 40000' which got me wondering just how the pilots were able to cope with the very low pressure ?

I've read stories of people who climb Mt Everest, having taking weeks to properly acclimatise that have problems at around 30000' One really harrowing example was where some one climbed to the top, was taking a breather, looking around, when blood vessels burst in his eyes effectively blinding him. His colleagues had to leave him behind.

 

Is it the relatively short exposure to these low pressures that make it more endurable, or was it really quite dangerous just flying at those altitudes even before the bullets started flying ? 

[Legioneod]

6 minutes ago, =FEW=Herne said:

I read that there were some combat engagements that took place at > 40000' which got me wondering just how the pilots were able to cope with the very low pressure ?

I've read stories of people who climb Mt Everest, having taking weeks to properly acclimatise that have problems at around 30000' One really harrowing example was where some one climbed to the top, was taking a breather, looking around, when blood vessels burst in his eyes effectively blinding him. His colleagues had to leave him behind.

 

Is it the relatively short exposure to these low pressures that make it more endurable, or was it really quite dangerous just flying at those altitudes even before the bullets started flying ? 

I'm no expert so I could be wrong on some accounts but it's not so much the low pressure as it is the oxygen supply and your bodies reaction to the thin atmosphere. One of the reasons they take weeks to acclimatize on Everest is because there body needs to get used to producing oxygen at higher altitudes, when you have oxygen tanks you pretty much bypass this need. If you go too high too fast and you dont acclimatize you can encounter some serious side effects and even death.

 

WW2 Pilots don't really need to worry about this because they are supplied with oxygen and they don't go high enough for the thin atmosphere/low pressure to really do any damage. 

[Finkeren]

Yeah, the problem is mainly oxygen supply and keeping warm. The human body can handle way worse differences in pressure than what you experience at a dozen km of altitude. Divers on the other hand have to be extremely careful when resurfacing, because they experience pressure changes of several atmospheres, where a pilot flying at maximum altitude experiences a difference of just a small fraction of one atmosphere.

 

For the same reason, decompression aboard a spaceship or indeed getting sucked into space without a spacesuit is nowhere near as instantly lethal as the movies make it seem (still a serious problem and likely to be catastrophic for other reasons not having to do with lack of pressure) because the pressure difference between the surface of Earth and empty space is just a single atmosphere of pressure. A leak in a submarine is a far, far more serious matter.

[ZachariasX]

1 hour ago, =FEW=Herne said:

I read that there were some combat engagements that took place at > 40000' which got me wondering just how the pilots were able to cope with the very low pressure ?

I've read stories of people who climb Mt Everest, having taking weeks to properly acclimatise that have problems at around 30000' One really harrowing example was where some one climbed to the top, was taking a breather, looking around, when blood vessels burst in his eyes effectively blinding him. His colleagues had to leave him behind.

 

Is it the relatively short exposure to these low pressures that make it more endurable, or was it really quite dangerous just flying at those altitudes even before the bullets started flying ? 

You cannot pass ~40k ft. altitude without pressurization. At roughly 10 km altitude (depending on weather) the pressure of oxygen, even at 100% concentration, is not sufficient to saturate the blood sufficiently. Below this pressure limit, you will start to suffocate. And die.

 

For mountaneering, you have roughly 7 km altitude above wich you start dying. If you venture higher, you are compelled to do so in the time that you have left when your body effectively starts to shut down until you are dead. That is you time limit. Sucks when you have 200 Chinese in front of you at the Hillary step.

 

This situation even can worsen considerably when wheather is changing. Winds are up to 500 km/h on the Everest when things go bad, just to underscore how fast weather can come in there. The upside of it is that pressure can drop so low that even 500 km/h wind will not push you over. The downside is that if a high altitude low pressure system comes in, it reduces air pressure on the summit to almost nil, basically putting you outside of what you think of as „athmosphere“. For reasons mentioned previously, this will kill everyone up on the mountain, breather or not.

 

It is of note that even in this case, blood vessels do not bust. They can do so for other reasons, but you have to be aware of the fact that up there you already reduced air pressure around you 80%. Thus, going to zero from there is only a drop of 20% air pressure, something any decent ride on a cable car can do to you. Even if you pull out a deep see fish from 6 km down, it will not explode, but be unhappy as any other fish on your boat deck.

 

21 minutes ago, Finkeren said:

For the same reason, decompression aboard a spaceship or indeed getting sucked into space without a spacesuit is nowhere near as instantly lethal as the movies make it seem

A very true statement. It is actually not even needed to make a space suit such that the whole space marine is pressurized. Doing it like a scuba gear, giving him a decent pressurized helmet and breathing system will do. The rest of him will enjoy a good heater much more than pressurization.

 

If someone just exits a space station (you have no idea how such a small quarter can smell after some years with no ventilation... or maybe you can, college dorms...), he will have a similar problem as a diver going up too fast. The low pressure makes the blood unable to keep the air and there will be bubbles in your system like when you open a soda can. This embolism will kill you. It is very painful but you will not explode. You are at only 50% or so pressure anyway to start out. Traditional space suits have the bare minimum, less than the shuttle or a space station (that for better comfort have higher pressure). This requires about an hour of aclimatization before you can take a hop into the void.

 

It is actually stupid having the whole suit pressured, as in space, it will inflate slightly, like a balloon, and you constantly have to work against the suit. This was noted by the first Kosmonaut when he tried to enter his tiny can again and found out he didn‘t fit anymore. What to do? He left out some air until he fit in again. The Americans made the same discovery a bit later. It is a good thing that both Kosmonats and Astronauts have the same kind of ingeniosness.

[Herne]

oh i found an article, that might be the same thing i was talking about :-

 

https://www.independent.co.uk/news/world/asia/everest-team-forced-to-leave-sick-british-climber-to-die-1988979.html

 

"Dangers at Altitude

* Retinal haemorrhages – bleeding from the cells at the back of the eye – are a relatively common complaint of mountain climbers. High altitude causes the blood to thicken, increasing blood pressure, which can lead to the seepage of blood from cells into surrounding tissues."

 

 

[Legioneod]

Your blood can boil but it's mostly due to the water in your blood and you'd be dead before it even happened. The main reason divers have to decompress as they resurface is because air bubbles form in the blood and can be fatal. If a diver were to experience decompression at a very fast rate their body would expand and basically explode.

I've seen photos of an offshore welder that experienced explosive decompression when his decompression chamber failed, he blew apart instantly. 

[Rjel]

Here is how the 1941 movie Dive Bomber with Errol Flynn and Fred MacMurray speculated how best to solve the issue. Imagine trying to check six with that on your head! The movie is a typical 1930/40s aviation film but it does have some great color photography of pre-war U.S. Navy aircraft.

 

[FTC_Riksen]

5 hours ago, Legioneod said:

I'm no expert so I could be wrong on some accounts but it's not so much the low pressure as it is the oxygen supply and your bodies reaction to the thin atmosphere. One of the reasons they take weeks to acclimatize on Everest is because there body needs to get used to producing oxygen at higher altitudes, when you have oxygen tanks you pretty much bypass this need. If you go too high too fast and you dont acclimatize you can encounter some serious side effects and even death.

 

WW2 Pilots don't really need to worry about this because they are supplied with oxygen and they don't go high enough for the thin atmosphere/low pressure to really do any damage. 

 

No ... thr body does not produce O2. The body produces 2,3BPG to decrease Hb's affinity for oxygen so it can better unload it in the peripgeral tissues. In addition, there is stimulation for synthesis of more red blood cells but both of these effects take longer hence the need to adapt for a few days.

[angus26]

2 hours ago, Legioneod said:

The main reason divers have to decompress as they resurface is because air bubbles form in the blood and can be fatal. If a diver were to experience decompression at a very fast rate their body would expand and basically explode.

Not really. They wouldn’t “explode”, but considering they are nitrogen bubbles in your blood it is more likely to cause a stroke / extreme blood clotting as the bubbles prohibit blood from moving through the body. Most of the bubbles form in the joints, hence the reason for a lot of people experiencing it complain of extreme joint pain. Their body wouldn’t get any bigger than it already is. 

[Legioneod]

2 minutes ago, angus26 said:

Not really. They wouldn’t “explode”, but considering they are nitrogen bubbles in your blood it is more likely to cause a stroke / extreme blood clotting as the bubbles prohibit blood from moving through the body. Most of the bubbles form in the joints, hence the reason for a lot of people experiencing it complain of extreme joint pain. Their body wouldn’t get any bigger than it already is. 

Yes they will with enough of a pressure change. I've seen the aftermath of explosive decompression, it ripped the man apart.

Also, I meant rapid pressure changes, not slower ones. If a diver gets air in the blood they wont explode of course but it can kill them and cause the bends.

Edited June 20, 2018 by Legioneod

[angus26]

1 hour ago, Legioneod said:

Yes they will with enough of a pressure change. I've seen the aftermath of explosive decompression, it ripped the man apart.

Also, I meant rapid pressure changes, not slower ones. If a diver gets air in the blood they wont explode of course but it can kill them and cause the bends.

Yes, 99% of cases it is a result from slow decompression/ going beyond no decompression limits, but it’s not common for a diver to explode. In very rare cases it happens,(extreme depths) but in recreational scuba diving most of the decompression injuries are a result of poor diving planning and limitations, poor physical health and the lack of skill in the expertise. Even going from 60ft to the surface without a safety stop is fine, (still not recommended for the sake of caution) but most recreational divers follow their no deco limits. 

You a fellow diver perhaps? 

[Legioneod]

1 minute ago, angus26 said:

Yes, 99% of cases it is a result from slow decompression/ going beyond no decompression limits, but it’s not common for a diver to explode. In very rare cases it happens,(extreme depths) but in recreational scuba diving most of the decompression injuries are a result of poor diving planning and limitations, poor physical health and the lack of skill in the expertise. Even going from 60ft to the surface without a safety stop is fine, (still not recommended for the sake of caution) but most recreational divers follow their no deco limits. 

You a fellow diver perhaps? 

 

Was going to get my cert for an offshore welding job but never did. Gonna learn one day though.

[angus26]

32 minutes ago, Legioneod said:

 

Was going to get my cert for an offshore welding job but never did. Gonna learn one day though.

Highley reccomend going for it! It’s a great deal of fun!