Talk:Armstrong limit

Comments
The trivia of "2001" omits that Kubrick asked permision to NASA technics for that scene. They said man can suport the vacuum presion for some seconds. In the movie, the presure of the capsule and the explosion can act too as softeners.

Even in the main text is a link that explains something similar. I sugest to erase that trivia.
 * I agree. Having read a bit on the subject, I think it may be possible to survive such a situation, so I removed the trivia section. Philbert2.71828 03:25, 21 August 2006 (UTC)

Origin of the name?
The article doesn't explain why this is called the Armstrong limit. Is it related to Neil Armstrong ? Probably not for his astronaut career, but when he was a X-15 pilot... fr:user:case 11:51, 7 February 2007 (UTC)
 * Nine months later, the questions is answered - nothing to do with Neil. - DavidWBrooks 20:09, 11 November 2007 (UTC)

Boil in their own body fluids
Currently the page reads "A human would eventually boil in their own body fluids (a process known as ebullism)". This seems misleading to me, because it gives the idea that they are somehow cooked (the obvious comparison is with stewing some kind of meat to eat). And that's wrong. Ebullism (which sounds horrible) is described via the link and it's effectively an extreme form of "the bends" that divers get - bubbles of gas form inside your body.

I guess I could just change it, but I was wondering if I'd missed something (I'm a physicist, not a biologist). —Preceding unsigned comment added by 201.222.151.83 (talk) 19:29, 26 September 2009 (UTC)

You didn't miss anything. It was nonsense, and wrong, and I removed it. Ariel. (talk) 11:03, 17 November 2009 (UTC)


 * This version of the article was an abomination unto the eyes of the factual gods. It contained this whopper of Original Research borne out of not understanding one iota of sixth-grade physics: Contrary to the sources below this doesn't have any relation to the blood pressure as the blood pressure in the venous system is close to or even lower than zero. Yeaaaah… notwithstanding what NASA says, someone thinks blood pressure can be lower than zero. I’ve completely revised the article and, as of this writing, now looks like this. Greg L (talk) 01:53, 25 January 2011 (UTC)

The venous pressure in the brain can actually drop slightly below ambient pressure (i.e. negative with respect to the central venous pressure near the heart) when sitting or standing in a 1G environment. This is simple physics, due to the effect of gravity on the ~12 inch hydraulic column of venous blood. This greatly complicates neurosurgery, since a puncture in the venous side of the cerebral vasculature can cause a serious air embolism. But the reason that I mention this is that in the brain, the differential pressure between the intravascular space WRT the outside of the body is indeed slightly negative. However there is still a strong osmotic contribution from all the proteins and salts dissolved in the circulating blood, and this acts like antifreeze in that it reduces the effective vapor pressure of water in blood. So from an ebullism standpoint, dilute urine or saliva will boil before the blood will.129.55.200.20 (talk) 22:17, 10 November 2016 (UTC)

At or above the Armstrong limit?
"At or above the Armstrong limit, exposed bodily liquids such as saliva, tears, and the liquids wetting the alveoli within the lungs... will boil away without a pressure suit"

Shouldn't this read "At or below the Armstrong limit".... I would assume near the Armstrong limit would still be very dehydrating as water's vapor pressure would be comparitively high.

So, this describes the effect on mucous membranes. The skin is generally a good moisture barrier. So, it would seem as if the limit on the skin exposure would be different than say face and eye exposure.--Keelec (talk) 04:57, 10 August 2012 (UTC)

Caption for the photo
I find the caption for the photo a bit confusing because the pilot in the aircraft is in a pressurized cockpit and should be able to transverse the Armstrong limit without negative effects. Or am I missing something? I'd offer the alternative photo http://en.wikipedia.org/wiki/File:B-8_winter_helmet_%26_A-14_oxygen_mask_(1944).jpg from the cabin pressurization article. Or a slight rewording of the caption might be a better idea. Perhaps I'm a nut and the only one that thought, wait a second, that F-16 pilot would be fine. Velophile (talk) 21:04, 2 April 2013 (UTC)

Modern?
"For modern military aircraft such as the United States’ F‑22 and F‑35" Even the venerable(1950s) McDonnell Douglas F-4 Phantom II & English Electric Lightning operate at high altitudes. Kitchen Knife (talk) 14:36, 11 December 2013 (UTC)

Not to mention the U-2 & the SR-71. They flew so high the pilots had to wear space suits. U-2 versions are also still in service today (not for long). If you want operational fighters however, why not use the F-15C? It's service ceiling is 65k feet - 20k meters - & you can bet it's gone way above that with NASA & the Air Force. That aside, this article states the operational altitude for the F-35(no model listed) is in excess of 59k feet. No models of the F-35 are or have ever been operational. None will be until the Marines go operational with an F-35B squadron in 2018. So it's literally impossible for the F-35 to have an operational altitude of even 1 foot.

Units
I have gone through the article and standardized the usage of units of measurement. In all cases, I have used the convert template so that units are displayed in both customary and SI at each instance. However, since most of the sources for the article are US sources or regulations, I have led with feet when mentioning altitude, or miles in the few cases that is used instead. These units, feet and miles, are also required to be used by international aviation regulations, which I think makes it appropriate to lead with them in this article.

When discussing pressure, I have led with the SI unit hectopascal. Where it is used to discuss blood pressure, I left the secondary displayed unit as mmHg, as these units are normally used in the medical world. Where discussing pressure altitude, or tire pressure, I have set the secondary displayed unit as psi, since that makes the most sense in those contexts.

I understand that there is frustration on the part of some editors that the US uses non-SI units in many a major way, and failed to convert to mainly SI units like most of the rest of the world in the 1970s. But this is the situation we are stuck with, and here on Wikipedia we cannot fix or change it, only deal with it. Just remember that all units of measurement, SI or otherwise, are essentially arbitrary anyway. Is the length of the path traveled by light in vacuum during a time interval of 1/299792458 of a second really that much less arbitrary than the average length of 16 men's left feet? And does the usage of one over the other really confer upon you the moral high ground? Darkest Tree  Talk  18:42, 5 February 2016 (UTC)

2001: A Space Odyssey: Any chance that Dave Browman could survive his "stunt"?
In the film 2001: A Space Odyssey David Browman, who had left the helmet of his space suit behind, had to enter to an emergency airlock. Doing so, he was exposed to space vakuum for several seconds until he managed to activate / pressurize the airlock. Is there any chance that in real live an astronaut can survive this "stunt" and stay at health and consciosness, so that he could do things like deactivating HAL immediately after the "stunt"? --Andi47 (talk) 04:33, 12 June 2016 (UTC)


 * The movie scene might be possible. In that scene 7.3 seconds elapsed from hatch jettison until Bowman's hand initiates the closing and repressurization sequence. By about 11 seconds the door is mostly closed. Current experience indicates a human may remain conscious in a vacuum for about 12 seconds. If the Apollo environmental control system is any guide, it doesn't wait until the hatch is closed to begin emergency repressurization -- it immediately starts dumping gas into the cabin at the highest possible flow rate. On Apollo that emergency flow rate was so high it could sustain cabin pressure for several minutes with a five-inch diameter hole in the hull.


 * Another issue is that of "barotrauma" when the hatch is jettisoned. On Apollo the cabin environment was pure O2 at a low pressure -- about 4.7 psi, and pressure in the suit was 3.8 psi. Before opening the door of the lunar module they dialed down the pressure to zero -- it was under complete manual control. A human can survive and remain conscious for many minutes at 1 psi pure O2 or less. In the 2001 movie it shows Bowman manipulating controls prior to jettisoning the hatch. In a real scenario one of those actions would be reducing cabin pressure to the lowest level which could briefly sustain life. That would greatly reduce barotrauma from the final pressure loss. Even then, holding your breath in such a situation would be damaging, as the air tried to escape your lungs. The movie does fleetingly show Bowman grimacing before jettisoning the hatch, but was this holding his breath or protecting his face from any debris? It is just an entertainment movie, but the actions and timing depicted in that scene are not far off from what would be possible in the real world. Joema (talk) 15:43, 27 December 2016 (UTC)

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Terminology problem
This term has a problem in that sources commonly confuse the definition of term as this article does. At the risk of being anal I believe the article needs to be crisp in its definition.

There are two definitions that are used for this term:
 * The pressure at which water begins to boil at the average human body temperature.
 * The average altitude at which the air has this pressure. This value is harder to establish an accepted value.

Though related these are two separate numbers. The article introduces the topic using the second definition but then says that being "below" the limit is unsafe, which is illogical. From what I have seen most sources introduce the topic with the second definition but then discuss it as the first (as this article is doing). Confusing to me.

-- MC — Preceding unsigned comment added by 2605:6000:EC16:C000:F06C:ADB6:9333:C12C (talk) 21:40, 19 August 2017 (UTC)
 * I modified the intro paragraph to address this concern. What do you think?
 * Riventree (talk) 11:28, 27 February 2018 (UTC)

Grammar problem? -- altitude and pressure
The article reads: "Commercial jetliners are required to maintain cabin pressurization at a cabin altitude of not greater than 2,400 m (8,000 ft)." Why "not greater than"? Shouldn't it be simply "greater than"? --1000Faces (talk) 12:56, 20 July 2021 (UTC)
 * Clearly not. If it were greater than, then the cabin pressurization altitude would be at a higher altitude and therefore lower pressure. You'd want higher pressure to prevent people from passing out. The wording is correct, the proposed wording removing the "not" is the opposite meaning and therefore wrong -- 65.92.246.142 (talk) 10:51, 4 May 2022 (UTC)

-- 65.92.246.142 (talk) 10:57, 4 May 2022 (UTC)
 * Cabin pressure altitude (cabin altitude), the altitude at which a pressure of X is expected
 * Aircraft altitude, the altitude at which an aircraft is flying
 * These are not the same thing, a pressure altitude is a different way of defining pressure as measured in feet/metres. It is not an actual altitude, it is the equivalent altitude for a given pressure.

Contradictory statements
In the "Historical significance" section, it is written "At 11,900 m (39,000 ft), breathing pure oxygen through an unsealed face mask, one is breathing the same partial pressure of oxygen as one would experience with regular air at around 3,600 m (11,800 ft) above sea level." This link however states that at 40000 ft (12190 m) breathing pure oxygen under positive pressure maintains the equivalent altitude of 10000ft, i.e., a lower altitude than the sentence above is mentioning one would have at a lower altitude. The NASA link must be correct because the pressure at 40k ft is 2.72 psi which results at 100% oxygen around 10000 ft in as much oxygen as man can survive with. So the sentence concerning 39000 ft (11.9 km) is obviously wrong, isn't it? Glasfaser Wien (talk) 08:30, 1 May 2023 (UTC)