Partial Vacuum Exposure?

[SilentP]

We know that vacuum is pretty deadly, not instantly *pop* fatal, but a completely exposed person doesn't last particularly long. My question is pretty much is it possible to last longer if equipped with partial life support system?

To be specific, here's a hypothetical scenario:

"Our unlucky soul's spacecraft/station suffers a large breach in the section he's in, and loses atmosphere. He pulls out his breathing mask (linked to a small pressurised air tank on his back), and puts it on, activating the air supply. It seals the astronaut's face and ears inside a small bubble of atmosphere. The straps are tight enough to hold it on and keep the seal of atmosphere intact. While this won't keep him healthy for long (since vacuum exposure will harm the rest of his body), but it keeps him breathing and concious hopefully long enough to be able to be retrieved, and taken to a safe part of the ship/station."

Now how realistic is this? Could something portable enough to not be a hinderance for onboard operations be carried to increase life expectancy in such a scenario? Or would the vacuum effects to the rest of the body happen quickly enough for such a device to merely just lengthen the time the astronaut is tortured by vacuum exposure and die, while not giving enough time for a rescue to be mounted? Or not even work at all?

 

[Alpha_Geek]

The minimum breathable gas mix is about 3psi pure O2. Rapid decompression to this level of amoshpere would result in decompression sickness (the bends) if the normal environment is Earth sea level standard. Nitrogen would start outgassing from blood and tissue immediately, and if it's rapid, bubbles will form and unfortunate results are likely.

If your device delivers anything that's more than about 5 psi over ambient pressure, you'll need to address the ptential issue of overpressure blowing out the lungs. Some type of pressure suit or mechanical compression device (garment) will be needed.

 

[SilentP]

Just for clarification, ambient pressure refers to the pressure that the body is being subjected to in any particular instance, so in the case of the astronaut using the device, the pressure is 0psi?

 

[Alpha_Geek]

Ambient being the pressure of the environment the body finds itself in. At sea level, that's 14.7 psi. Standing on the hull of an orbiting spacecraft or in deep space? Pretty much 0 psi.

If you're thinking about that whole lung blowout thing, then you need to consider the pressure differential between what's in the lungs, sinuses, etc, and the environment the body finds itself in. The body is much more forgiving of rapid ambient pressure increases than decreases.


So yeah... in theory 3 psi pure O2 will work in a 0 psi environment, but if you get to that level quickly with no protection or decompression by going on pure 02 prior to the event to get all the nitroge out of the tissues, your guy is gonna have debilitating pain in the joints, possible blindness, strokes due to embolism, anuerisms and other fun stuff.

Open a coke bottle. Put your thumb over the top. Shake bottle. Slip thumb off slightly. Imagine that happening to your blood as the nitrogen on your blood and tissues tries to outgas.

There may be some other psysiological issues also. I'm not sure how well the diaphragm would work under these conditions, and it's gotta work to get air in and out of the lungs.

Devices that regulate the gas supply to match ambient pressure are commonplace in SCUBA gear, firefighting gear, etc, so mechanically your escape pack would be a sound concept.

 

[Saturn0660]

The minimum breathable gas mix is about 3psi pure O2. Rapid decompression to this level of amoshpere would result in decompression sickness (the bends) if the normal environment is Earth sea level standard. Nitrogen would start outgassing from blood and tissue immediately, and if it's rapid, bubbles will form and unfortunate results are likely.

If your device delivers anything that's more than about 5 psi over ambient pressure, you'll need to address the ptential issue of overpressure blowing out the lungs. Some type of pressure suit or mechanical compression device (garment) will be needed.

What if you were only breathing O2 first. No nitrogen to bubble out.

 

[SilentP]

The minimum breathable gas mix is about 3psi pure O2. Rapid decompression to this level of amoshpere would result in decompression sickness (the bends) if the normal environment is Earth sea level standard. Nitrogen would start outgassing from blood and tissue immediately, and if it's rapid, bubbles will form and unfortunate results are likely.

If your device delivers anything that's more than about 5 psi over ambient pressure, you'll need to address the ptential issue of overpressure blowing out the lungs. Some type of pressure suit or mechanical compression device (garment) will be needed.

What if you were only breathing O2 first. No nitrogen to bubble out.

I'm guessing it could be nitrogen already present within the blood stream that would bubble, not the nitrogen in the oxygen supply. I'm also guessing that the air in spacecraft isn't pure O2, for safety reasons presumably.

 

[Alpha_Geek]

Both correct. Astronauts currently pre-breathe pure O2 for at least an hour before suiting up. This allows the accumilated nitrogen to outgas from their body.

...and we haven't had a pure O2 spacecraft environment since the Apollo 1 disaster.

 

[Saturn0660]

Both correct. Astronauts currently pre-breathe pure O2 for at least an hour before suiting up. This allows the accumilated nitrogen to outgas from their body.

...and we haven't had a pure O2 spacecraft environment since the Apollo 1 disaster.

I don't think thats right... If i remember right Apollo did a Ox/Nit mix on the pad. And after lift off it was slowly brought down to a lower O2 only mix. Am i remembering wrong?

 

[Alpha_Geek]

I know the shuttle and Soyuz don't. I'll double check the Apollo stuff... gotta go earn my paycheck right now. Will report findings later.

 

[Alpha_Geek]

Wow, I thought they redesigned more than they did after they lost Grissom, WHite, and Chaffee...

At launch the cabin atmosphere would be at sea-level pressure and consist of 60% oxygen and 40% nitrogen, lowering to 5 psi during ascent and gradually changing over to 100% oxygen at about 2 psi during the first 24 hours of the trans-lunar coast.

 

[SilentP]

Hmmm, so the general problem in any case, in terms of respiration, is that sudden depressurisation of the one's surroundings for the whole body is what would cause a major problem, even with a breathing apparatus close at hand.

In cases of wearing something for sudden emergencies, I'm guessing you'd need at least some kind of 'constrictor' suit that can be worn for general IVA activity to mitigate the pressure changes for the rest of the body?

Are there any materials that can constrict on command, like say a mild electrical current (a similar fictional example being the electro-polymer that is shown in Batman Begins, that allows the cape to go from flexible cape, to rigid wini-wing)? Something like this could, in theory, be used to help reduce the pressure differential between the body and vacuum, and while not 'activated', would allow comfort for general wearing.

 

[sojourner]

^ there has been work on negative pressure space suits that used the suit to provide pressure on the human body instead of an atmosphere in the suit. Sort of like space spandex.

You could use those space "beachballs" that NASA developed for vacuum emergencies. They were fairly compact when not in use if I recall. Let me find a link.

Found it: http://www.astronautix.com/craft/reseball.htm

You could have an advanced version of this that is worn in a pouch on the belt of your crew.

Also, that counter pressure suit: http://www.astronautix.com/craft/biosuit.htm

very sci-fi looking!

 

[Alpha_Geek]

There's also stuff about skinsuits in the link referring to "pressure suits or mechanical compression device (garment)" I cited earlier. The're a link there for a "space activity suit" that has a picture of what looks like a prototype Buck Rogers rig... except Buck Rogers never stole Thomas Magnums' mustache!

I think the pat answer for storytelling purposes would be to have the standard uniform for shipboard ops be a skinsuit, or something similar to a "G-Suit" currently used by fighter pilots. Make the footgear spaceworthy and add gloves to the emergency stations that have the breathing apparatus.

G-suits rely on pneumatic bladders within to restrict bloodglow to lower extremeties during high G manuvers. The bladders inflate automatically. Note that these current models don't do much more than keep blood flowing to the brain though.

There is some precidence for this. In US military one of the states of rediness for nuclear, biological, or chemical attack is to have the suit on, save for gloves and mask. This affords the wearer to do most normal duty functions unemcumbered, yet save presious time in the event bad stuff happens.

As for other materials... dunnno. I know some folks have made muscle-like movement from nichrome wire that moved when current was applied, but I don't know if enough of this could be woven into a garment and still afford good mobility.

 

[Alpha_Geek]

Oh, and someone already mentioned rescue balls, yes? If mobility isn't a factor for your hero, this is the best option for safety.

 

[STR]

Both correct. Astronauts currently pre-breathe pure O2 for at least an hour before suiting up. This allows the accumilated nitrogen to outgas from their body.

...and we haven't had a pure O2 spacecraft environment since the Apollo 1 disaster.

I don't think thats right... If i remember right Apollo did a Ox/Nit mix on the pad. And after lift off it was slowly brought down to a lower O2 only mix. Am i remembering wrong?

Mergury, Gemini and Apollo were oxygen only. Soyuz is oxygen-nitrogen, which complicated Apollo-Soyuz. Shuttle is oxygen-nitrogen and I don't know what Vostok/Voskhod was. I assume Shenzhou is o-n, but have never researched it.http://en.wikipedia.org/wiki/Shenzhou_program

 

[Shaw]

As I recall the astronauts on the Challenger blacked out within a few seconds after the crew compartment was compromised... and that was even with individual oxygen tanks. One of the changes after that accident was that the crews had to ware pressure suits during launch and reentry.

 

[Alpha_Geek]

As I recall the astronauts on the Challenger blacked out within a few seconds after the crew compartment was compromised... and that was even with individual oxygen tanks. One of the changes after that accident was that the crews had to ware pressure suits during launch and reentry.

Approximately half of the Personal Egress Air Packs on Challenger were found to have been activated. Michael Smiths' (the pilot) was positioned in such a way that he could not activate it himself, Judith Resnik or Ellison Onizuka did it for him.

The Rogers commission report does not indicate if or when cabin integrity was lost.

More salient to this conversation is that these were designed to provide safe egress from the shuttle on the ground. Essentially, they dumped air into a helmet that was not much more than something you'd wear on a motorcycle.

 

[Saturn0660]

Both correct. Astronauts currently pre-breathe pure O2 for at least an hour before suiting up. This allows the accumilated nitrogen to outgas from their body.

...and we haven't had a pure O2 spacecraft environment since the Apollo 1 disaster.

I don't think thats right... If i remember right Apollo did a Ox/Nit mix on the pad. And after lift off it was slowly brought down to a lower O2 only mix. Am i remembering wrong?

Mergury, Gemini and Apollo were oxygen only. Soyuz is oxygen-nitrogen, which complicated Apollo-Soyuz. Shuttle is oxygen-nitrogen and I don't know what Vostok/Voskhod was. I assume Shenzhou is o-n, but have never researched it.http://en.wikipedia.org/wiki/Shenzhou_program

The Shuttle of course is shirtsleeves. So is ISS. I knew Soyuz was/is. But i thought i was right about Apollo..

 

[Shaw]

As I recall the astronauts on the Challenger blacked out within a few seconds after the crew compartment was compromised... and that was even with individual oxygen tanks. One of the changes after that accident was that the crews had to ware pressure suits during launch and reentry.

Approximately half of the Personal Egress Air Packs on Challenger were found to have been activated. Michael Smiths' (the pilot) was positioned in such a way that he could not activate it himself, Judith Resnik or Ellison Onizuka did it for him.

The Rogers commission report does not indicate if or when cabin integrity was lost.

More salient to this conversation is that these were designed to provide safe egress from the shuttle on the ground. Essentially, they dumped air into a helmet that was not much more than something you'd wear on a motorcycle.

Sorry if my recollections weren't exact enough... they were based on a 1989 read of the Rogers' report and a short 1991 discussion with one of my physics professors about the findings and her personal opinions.

The report is online here (which is a better source than Wikipedia), but I wasn't aware that this informal dialog would warrant such scrutiny.

 

[Alpha_Geek]

Hi Shaw,

No worries. We'll never get a concrete answer from NASA on it. Even if NASA knew for certain, they would never, ever tell the public that the crew was conscious all the way to impact.

Personally, I think the most damning evidence isn't in the Rogers Commission report, but in the words of Joe Kerwin , both his investigationh and the Rogers commission report use the word "possible" and not even "probable" when stating the likelyhood that the crew was incapacitated before impact.

Jay Barbree of NBC also did an investigative report on STS-51L. It incuded an interview with Bob Overmyer, a shuttle astronaut who was one of the investigators assigned to the accident. I knew the possibility from the day they announced the PEAPs, but to hear Overmeyers words "“They were alive, they were alive.” chills me to this day.