If you had been a resident of La Rinconada, Peru, all your life, living at approximately 16,732.28 feet (the highest-listed continuous human habitation on Earth) and say as a perfectly robust 30-year-old, was somehow on the first mission to Mars, and say once your spaceship landed and it was high noon on a Martian summer day – at noon, at the equator in the summer, where the temperature is 70°F (20°C) and you were equipped with gear designed to keep you warm at the top of Mt. Everest, and had the same oxygen gear provided to climbers who summit Everest, how long could you reasonably expect to be able to wander around your spaceship, NOT wearing full astronaut-type pressurized gear – just you, just like on Everest, with no special "Mars"gear?
Would you be immediately struck down by the intense radiation, or would you be able to conduct somewhat normal activities for minutes, if not hours?
I know it’s hard to believe that it is ever 70° F on Mars, but it is – so how long would you last, if say, you dropped your key to the door to the spaceship and couldn’t get back in?
You would not survive long–20 or 30 seconds, tops.
The pressure is really the fundamental problem. Pure oxygen does you nothing if you can’t breathe it, and you can’t breathe air at 14 psi, or even 1 psi, if the outside pressure is effectively 0 (it’s something like 0.07 psi on Mars).
There are designs for compact space suits that provide mechanical pressure instead of air pressure. Stretchable material like spandex holds pressure on your chest and other areas and would in principle allow you to breathe. These suits would do worse in temperature regulation, but as per your OP we’ve allowed comfortable temperatures. At any rate, I don’t think the kinks have been worked out, but they suits are possible in principle.
You wouldn’t last long at all. The Armstrong Limit would get you. The atmosphere of Mars has a pressure of only 0.087 psi compared to 14.69 psi on the Earth. The water in your body would boil at normal human body temperature. A pilot on Earth who who was only equipped with an oxygen mask and flew at an altitude where the air pressure was equivalent to that on the Martian surface (generally between 62,000 and 63,500 feet) would die in just a few minutes as all his bodily liquids would boil away.
Incidentally, radiation is really not a problem. If you spent years on the surface, you might have a slightly elevated risk of cancer, but there’s no acute radiation hazard. If you can solve the pressure and temperature problems, you could spend hours outside.
If you had an accurate replica of the Martian atmosphere in a room in a lab on Earth, you would call that room a vacuum chamber and its contents a vacuum. Not a very good vacuum, maybe, but it’d still kill you just the same.
You’re off by a decimal. Earth’s atmospheric pressure at 63,000 feet is about 0.91 psi, according to my model. If you want 0.087 psi, you need to go to about 114,000 feet. Not that the difference matters much; either way, you won’t last long.
The problem with only compressing part of the body is that the blood will tend to flow to the parts that are not compressed. So, if you compress the chest mechanically and keep the head in a pressure-controlled environment, blood with flow into the extremities and the heart will have to work very hard to pump it back out. For this reason, the “simple” mechanical pressure suits that you sometimes hear about are actually quite complex. They also have to be fit just so there are no variations in tension or anyplace for the fabric or undersuit to fold or press a seam, as this will rapidly produce the astronaut equivalent of bedsores.
To answer the o.p. what will happen is that your sinuses and conjunctiva, which are the most delicate, “exposed” parts of the body will expand, inflate, and shortly start hemorrhaging fluids. Exposed skin will also dry out quickly but not before you start passing out due to pressure being drawn away from your head. Consciousness will be somewhere between 5 and 30 seconds, irreversible brain damage due to cerebral hypoxia starting in five minutes, death shortly thereafter.
Apparently not true. From the Wikipedia page on the Armstrong limit:
This is not a complete containment suit, and I’m guessing that pilots in those circumstances (a depressurized F-22 cockpit at ~60K feet) aren’t oozing out of the unsqueezed parts.
It isn’t? My reading of that paragraph says that the positive-pressure sealing mask completes the covering. Where do you think the pilot is not covered, and why would they allow this? The image on the Wikipedia page you link to doesn’t show the entire body but assuming gloves nothing would be left uncovered.
You would survive a bit longer than that. Jim Leblanc was testing a space suit for NASA in a vacuum chamber when a tube broke loose. Jim passed out after about 15 seconds or so. It took 25 or 30 seconds for someone to get the door open (and this was only to a partial pressure room just outside the door), and it was over a minute before the chamber was repressurized (normal procedures required about 30 minutes, so roughly a minute was pretty darn good under the circumstances). By the time the doctor came in to examine him, Jim had pretty much fully recovered. He complained about his ears aching a bit, but was otherwise ok.
While having only 10 to 15 seconds of useful consciousness is pretty well proven, exactly how long you would survive is a bit debatable. Since this hasn’t been tested on humans, the best data we have comes from animal tests. In these tests, changes in blood pressure due to gases coming out of solution after about a minute or so resulted in an effective stoppage of blood flow. After about 60 to 90 seconds or so, the animal’s hearts would often go into fibrillation. If their hearts hadn’t gone into fibrillation, the animals would usually survive at that point. For those that did go into fibrillation, resuscitation efforts after repressurization,were usually unsuccessful.
NASA documentation notes that if a person were to try to hold their breath, their lungs would rupture with almost certainly fatal results. So if you climb out of your Mars lander without a suit, don’t hold your breath.
If repressurization occurs within about 90 seconds or so and your heart didn’t go into fibrillation, there’s a very good chance that you would experience blindness and other neurological effects, but these effects would be only temporary and chances are you would recover very quickly.
The scenario of an almost instant death due to your bodily fluids boiling was disproved by Jim Leblanc and various animal tests. It is however worth noting that after he recovered from his experience, Jim said that his last memory before blanking out was of the sensation of the saliva on the back of his tongue boiling off.
Obviously if you take a human pressurized to sea level and then expose that person to a (near-) vacuum, bad things will happen. But what if we supply pure oxygen at, say, 0.2 atmospheres? At that pressure, the boiling point of water is still well above body temperature, so boiling wouldn’t be an issue. The difference between parts of the body covered by pressure and the exposed parts would also be quite small (0.2 atmospheres), so I’m thinking you could leave small areas exposed without trouble, as long as you use compression garments that cover the face, neck and chest/abdomen, which contain air. Even here on earth blood may pool in the legs because it has to fight gravity on its way back to the heart, but on mars there’s less gravity so maybe swollen feet would actually not even be a problem.
At this pressure the partial pressure for pure oxygen would be the same as the oxygen partial pressure we normally experience. Oxygen is also easily harvested from silicates and CO2, while nitrogen is hard to come by once you leave the earth, so pure oxygen makes a lot of sense from that perspective, too.
What I mean is that it is not hermetically sealed or designed to apply pressurized gas to the entire surface of the body. It applies mechanical pressure to the torso, enabling the pilot to exhale against the gas pressure being applied via the mask that seals against his face. Without that torso pressure, the mask would inflate his lungs and he would be unable to exhale. It also inflates air bladders around the pilot’s legs to prevent blood from pooling there. If this goes on for extended periods then blood will start pooling elsewhere (arms, hands, etc.), but it’s not supposed to go on for long: this setup is supposed to buy the pilot enough time to descend rapidly to a pressure-safe altitude.
Basically gas pressure is applied to the area around his nose and mouth, and mechanical pressure is applied to his torso and legs - and that’s about it.
Wow. The pressure thing was a surprise. Then how come on Everest people’s fluids don’t start to boil, even a teensy-weensy bit? What is the altitude on Earth at which, even if you were at a comfortable temperature (70°Ï) and had on a mask – dunno whether oxygen would be the optimum gas for the task – would it start to get noticeable, and what would the first symptoms be?
My mind always goes to that scene in “2001: A Space Odyssey” where Bowman explodes himself out of the pod and into the pod bay and repressurizes, all without a helmet on. Obviously Kubrick would have done his homework – he had Arthur C. Clarke as an adviser, after all – and so that scene in Total Recall where Arnie’s eyes start to bug out of his head (obviously Paul Verhoeven didn’t do his homework for that scene --) is a Total Exaggeration? Or somewhere in between?
I’m fascinated by these types of stories – like the one about deep-sea diving accidents where the diver was literally sucked through the tube connected to his helmet – did that really happen? (Sorry, off topic, but still to do with pressurization issues).
Right. I’m rather curious about this myself. Suppose you were on a spaceship where sudden catastrophic pressure loss was a possibility. You live on the ship, so wearing a suit around all the time is not feasible. You can’t reduce the risk of pressure loss to zero for <sci fi reason here>.
What’s the minimum amount of gear you could wear around to survive a sudden decompression? It sounds like you could wear a shirt that contains a gas driven compression system. The shirt would be like an ordinary shirt but contain tubes crossing across the torso. In a low pressure environment, a gas cartridge would inflate the tubes to provide torso pressure. The user would then need to grab an oxygen mask stored somewhere on their person and put it on before passing out. A chemical oxygen generator or some kind of compressed oxygen bottle would supply pure oxygen at 2-3 psi.
That means the pressure pushing your body out of this hypothetical “shirt” would be about 2-3 psi. Human tissue is tough, it might resist those forces for a while. This emergency kit would only contain enough oxygen for a few minutes anyway.
Blood boiling : the rough answer is thischart. Body temperature is 37 celsius, or 310 kelvin. On the chart, find 310, and mouse pointer down to the line between liquid and vapor. Observe the pressure it is at. It looks to be a bit under 1/10 of 1 ATM. Now, blood contains dissolved solids, so it actually experiences what is called boiling point elevation. So the actual point your blood would boil is a bit under that. And blood won’t easily boil through your intact skin because the capillaries maintain pressure for as long as your heart functions (which won’t be very long if you can’t get oxygen)
As for the minimum pressure you can survive : the simple answer is you need a minimum “partial pressure” of oxygen. To make a long explanation short, if you are breathing 100% oxygen the partial pressure of the oxygen is the same as the pressure your lungs are at when you are breathing the oxygen. According to wiki, you need about 0.16 atmospheres of oxygen to live. Then you just look at an altitude chart and find at what altitude the pressure is under 0.16 atmospheres. It’s above 10k meters, the chart on wikiperiod doesn’t include that critical portion of the graph.
A real life person has survived a similar experience to what Bowman underwent in 2001, so it’s plausible. Google Jim Leblanc.
Mythbusters confirmedthat that deep sea diving catastrophe is possible. I don’t know if it actually happened to anyone, but it’s not a hard accident to have, so, probably. It only requires failure of a check valve and pressure loss in the air supply line.
Well, pushed into rather than sucked into, but you’re basically right. If the non-return valve on an old-style diving helmet fails, you’re toast. Or rather, pate.
My calculations may have been off on Earth’s air pressure at a particular altitude, but my decimal places are correct. Mars’ air pressure is 600 pascals, or 0.087 psi. I think where I got mixed up was that 62,000 feet is where the Armstrong limit begins on Earth, not the actual altitude where the pressure is equal to that on the Martian surface.
I’ll concede that you have to reach a higher altitude on Earth for the air pressure to be that low. At least we can agree that stepping out onto the Martian surface without a pressure suit is a Very Bad Idea.