Ibra wrote:
I think past FL500 pressure altitude blood boils at 37C deg with or without oxygen? the pax & crew are not planning on wearing Virgin Galactic suits?
That’s a myth. Our body is actually able to withstand even a complete vacuum, i.e. deep space without a suit on, because the skin is that tight and the blood will still be under its normal blood pressure.
The main reason astronauts wear space suits is the lack of oxygen and to protect themselves from radiation.
See also Wikipedia
In the atmospheric pressure present at sea level, water boils at 100 °C (212 °F). At an altitude of 63,000 feet (19,000 m), it boils at only 37 °C (99 °F), the normal body temperature of humans. This altitude is known as Armstrong’s Line. In practice bodily fluids do not boil off at this altitude. This is because the skin and outer organs have enough strength to withstand this pressure, thus pressure inside the body would be significantly higher—however, bubbles starting to form is still an issue.
MedEwok wrote:
That’s a myth. Our body is actually able to withstand even a complete vacuum, i.e. deep space without a suit on, because the skin is that tight and the blood will still be under its normal blood pressure.
Got it, but will not test it, I think normal blood pressure is already a problem at 0ft amsl 
But there is high altitude flying flatulence and abdominal bloating, my biggest worry !
Also “time useful consciousness”, I tested this with another EuroGA pilot, we went to FL230, I removed oxygen for 30 seconds then I made rapid decent to FL80, I don’t think I was in good shape to cover his round as safety pilot, so I still owe him one (his other alternative is to get rapid decompression chamber experience in Oklahoma), we talked about this during a lunch with friends and now my wife put 9000ft ceiling on my flying
Peter wrote:
If pressurisation fails, a descent is obviously the immediate action – to FL160 I think
A year or two ago there was an interesting article in one of the German aviation magazines on how emergency oxygen supplies have been limiting the direct route from Europe to East coast China over the Himalaya as there are extensive stretches of the route where an emergency descent would not be possible due to terrain.
@medewok: then what about decompression / caisson disease ?
As a diver I have to ascend slowly so that the CO2 dissolved in my blood doesn’t act like in a bottle of mineral water.
Wouldn’t a rapid decompression in an almost total vacuum do the same ? Assume I am in a pressure cabin at i.e. 8000ft. The weight of air at that altitude is still is about 0.8 kPa. In a rapid decompression this amounts to an emergency ascent from 8 meters. Not good. If divers have to do that – with an open mouth – they need a compression chamber afterwards. Every .1 kPa makes things worse.
Survivable, but not good.
Right ?
Sea level to vacuum is worth just 10m of water.
Peter wrote:
Sea level to vacuum is worth just 10m of water.
It’s logarithmic scale when comparing 0 to 1 and 1 to 2?
It’s also 100kft of air and 30cm of sand !
Just 10m can be just too many to live. A safe CESA from that depth takes about a minute, and if you don’t have the air to do that you blow your BCD and up you go, which will form bubbles in your blood, and damage your lung if you don’t think of blowing air out. Not that it really matters, because the fantastomatic Celera won’t ever be in that situation :)
We will follow this story through certification. The Eclipse saga told us FAA can be pretty flexible with new airplane concepts
According to this, they project a bigger version.
I don’t quite guess the market they aim for:
Its long climb would make for a much slower ride wouldn’t it ?
It would make a good airframe for a large UAV. Could it be a defence project, hidden in plain view ?
EuroFlyer wrote:
@medewok: then what about decompression / caisson disease ?
As a diver I have to ascend slowly so that the CO2 dissolved in my blood doesn’t act like in a bottle of mineral water.
Wouldn’t a rapid decompression in an almost total vacuum do the same ? Assume I am in a pressure cabin at i.e. 8000ft. The weight of air at that altitude is still is about 0.8 kPa. In a rapid decompression this amounts to an emergency ascent from 8 meters. Not good. If divers have to do that – with an open mouth – they need a compression chamber afterwards. Every .1 kPa makes things worse.
Survivable, but not good.
Right ?
Yes in fact at these altitudes (>FL600) you don’t even need rapid decompression: Just being exposed to the environmental pressure at that altitude is enough to lead to gas bubbles forming in your bloodstream. This can lead to swelling of tissue, gas embolism and other problems. From the Wikipedia article I linked in the previous post:
Ebullism is the formation of gas bubbles in bodily fluids due to reduced environmental pressure, for example at high altitude. It occurs because a system of liquid and gas at equilibrium will see a net conversion of liquid to gas as pressure lowers, for example, liquids reach their boiling point at lower temperatures when the pressure on them is lowered.
So yeah, being exposed to low pressure or vacuum is pretty bad, but people get the wrong idea when you say their blood is “boiling”
A human can exist in vacuum (the skin contains the pressure), though obviously not for long.
But such an experience must turn someone into a walking hickey.
