Talk:Kármán line

FAA and NASA recognition of 50mi rather than 100km

Should the article list the FAA and NASA stating the boundary of space is 50mi or 100km?Garuda28 (talk) 00:22, 14 July 2021 (UTC)

@Nux: The source you added does not directly state that the FAA recognizes the 100km Karan line, instead stating that "Many people believe that in order to achieve spaceflight, a spacecraft must reach an altitude higher than 100 kilometers (62 miles) above sea level." The majority of RS state that the FAA utilized the same 50 miles used by the Air Force as defining the boundary between air and space and for awarding astronaut wings (https://www.washingtonpost.com/technology/2021/07/11/richard-branson-virgin-galactic-live-updates/; https://www.nationalgeographic.com/science/article/where-is-the-edge-of-space-and-what-is-the-karman-line; https://www.technologyreview.com/2019/06/26/238928/where-does-space-begin/; https://www.nbcnews.com/science/space/branson-virgin-galactic-space-launch-n1273547)

The FAA itself states to earn astronaut wings "Must demonstrate flight beyond 50 statute miles above the surface of the Earth as flight crew on an FAA licensed or permitted launch reentry vehicle." (https://www.faa.gov/news/fact_sheets/news_story.cfm?newsId=19074)

NASA also acknowledges this 50mi boundary in the majority of reliable sources (https://www.space.com/will-richard-branson-reach-space-virgin-galactic; https://www.cnet.com/news/blue-origin-and-jeff-bezos-get-faa-approval-for-july-20-trip-to-space/)

Do you have secondary sources that state that the FAA recognizes the Karman Line (100 km) rather than the 50 mi indicated by all these secondary sources?Garuda28 (talk) 00:22, 14 July 2021 (UTC)

I think that treating news articles as better sources is wrong for science articles. Most articles do not cite any sources so they might as well be copying from each other or from wiki ¯\_(ツ)_/¯... I guess the exception is nat-geo article which does cite some sources. Interestingly it says that for the purpose of astronaut wings NASA does conform to Air Force definition, but it also says "NASA Mission Control places the line at 76 miles (122 kilometers), because that is “the point at which atmospheric drag becomes noticeable,” Bhavya Lal and Emily Nightingale of the Science and Technology Policy Institute write in a 2014 review article." [1]. So I think saying that NASA agrees to 50 miles as space boundary is missleading.

I also find it weird that multiple people try to re-define what Karman line means. Not FAA nor NASA define Karman line differently. Karman line is a Karman line. A law journal with multiple references [2] clearly says that Karman line was defined as 100 km. It was named after Karman (not by Karman) and agreed upon by many countries. Most importantly by those actually going to space -- U.S. and Russia (then Soviet Union).

--Nux (talk) 01:24, 14 July 2021 (UTC)

Pdf pg14of27 of this 1964 tech paper explains that Free Molecular Flow happens at an altitude above “75-80 Km”:

https://apps.dtic.mil/sti/pdfs/AD0457278.pdf

The word ‘space’ essentially means a realm where the space between molecules has gotten very large. Free Molecular Flow means that the atoms move significant distances without bumping into each other. You can artificially create a realm of space in a vacuum chamber. Or if you fly high enough, space occurs naturally in the realm known as Outer Space. Stated more simply, the 100km threshold was picked arbitrarily. Whereas there is excellent rationale for using 50 miles (=80km =FreeMolecularFlow =Space). —Tdadamemd19 (talk) 03:24, 14 July 2021 (UTC)

Cool, but the article is about the Karman line... Well it is named Karman line, but seems to be more and more about random space related things. Nux (talk) 08:14, 14 July 2021 (UTC)

Hardly random. The point is that a specific transition happens above 50 miles (80 km). And that this fits with the very notion of what space is. A significant amount of space between the molecules. The Karman Line is all about arriving at a definition of where the transition to space has happened. The concept of free molecular flow goes a long way toward informing that threshold. —Tdadamemd19 (talk) 09:06, 14 July 2021 (UTC)

I'm still skeptical of whether this provides a relevant definition of the edge of space:

• Do you know if any organisation or authority has ever proposed such a definition?
• Doesn't the point of transition depend on the length scales involved? The paper is about small metal strips. I guess for something the size of a human or spaceship the transition would happen at a higher altitude.

--BlauerFuchs (talk) 20:15, 1 August 2021 (UTC)

Definitely. Free molecular flow happens when the mean free path of the molecules is ten or more times greater than the length of the object in question. So the larger the object is, the higher the altitude required for it to be in free molecular flow. Fcrary (talk) 21:29, 1 August 2021 (UTC)

Yeah but you cannot redefine what meter means. There is an international body that defined and named Karman line. You can discuss what space is not what Karman line is. Nux (talk) 10:04, 14 July 2021 (UTC)

Suggestion to delete Free molecular flow paragraph

In its current form, the paragraph about "free molecular flow" in the section about alternative definitions does not appear to have a concrete connection to the Karman Line. In particular, the part about "space between molecules" sounds rather esoteric and not very scientific.

In particular, closer study of the cited article reveals that the altitude (or density of the atmosphere) at which aerodynamics is best described by the equations of free molecular flow depends heavily on the size of the object in question. Therefore, the sentence " It has been known since at least as early as 1964 that the transition to free molecular flow happens at an altitude above “75-80 Km”" is not a correct citation (or at least is misleading) IMO.

Certainly, the concept of "free molecular flow" is not widely accepted to be "A key consideration" with respect to the Karman line as the first sentence of that paragraph suggests.

In summary, I suggest to delete the paragraph in its current form, since it does not represent scientific consensus. (talk) 16:45, 30 August 2021 (UTC)

Good point. Whilst free molecular flow occurs naturally in outer space, that does not figure into the variegated factors which define the Kármán line. As a practical matter outer space begins where aerodynamics ends, and as just as practical a matter orbital mechanics would hold sway some distance beyond that– it's not as if the line is only several meters thick! It's a liminal space. kencf0618 (talk) 13:38, 22 June 2022 (UTC)

Should the article be revised now the US Department of Defense also recognises the 100 km boundary?

Currently the article extensively discusses the US military's position on the 50 miles / 80 km boundary, though it is only implied to have accepted this boundary due to the astronaut definition and the retroactive free molecular flow consideration. Yet neither of these has any official status, and there seems to be no evidence that the 50 miles boundary is used in an official capacity whatsoever with all US government organisations either recognising the 100 km boundary (FAA, NASA) or being ambiguous about it (US delegation to UN COPUOS). Some of the references used to present this view are quite dated or not sourced directly from a public organisation.

Now, since at least November 2021, the US Department of Defense has explicitly adopted the 100 km boundary as well in the Dictionary of Military and Associated Terms: "Space domain: The area surrounding Earth at altitudes of greater than or equal to 100 kilometers above mean sea level". A PDF version of the dictionary can be found here on the website of the Federation of American Scientists: https://fas.org/irp/doddir/dod/dictionary.pdf Previously the DoD did not take an explicit stance, as previous versions of the same publication did not include such a definition, though the related air domain was defined in the 2014 version as "The atmosphere, beginning at the Earth's surface, extending to the altitude where its effects upon operations become negligible" which implies 'space' to be beyond that undefined altitude.

With the DoD seemingly being the final major American actor to explicitly adopt the Kármán line, and the current position in the COPUOS likely being a discussion on legal boundaries of sovereignty rather than the definition of the edge of space discussed in the article, do you think a rewrite of the article is in order in which alternative to Von Kármán are mentioned but the 'US being the exception' is removed and the aforementioned uses of the 50 miles boundary are more clearly presented as implied reasoning rather than official views? SabasNL (talk) 13:38, 30 June 2022 (UTC)

March 2023 edits

I believe the latest changes are made in good faith, but is in need of an expert before we commit them to the page.

The chief reason is that the article has been changed in a major way: from making clear there is no internationally agreed upon limit that is legally binding to describing the Karman line as a done deal: "the conventional line" and then discussing the importance of defining the edge of space in the context of "this is that definition". But it isn't.

Yes, defining the edge of space is is important for legal and regulatory purposes. But the Karman Line is not the accepted answer.

I have provisionally rolled back to the previous version where our article isn't as categorical. If a third party, preferably an expert in the field, were to look at the changes and reapply them, I would not object further.

To Deeday-UK: thank you for your good-faith edits. Please hold off further edits to the article for a week or two. If nobody has taken action or commented here, feel free to reapply your changes, as silence is consensus. Regards, CapnZapp (talk) 03:31, 15 March 2023 (UTC)

I'm not an expert, but I agree that the edits seem to be too categorical. On the other hand, the previous version (an attempt to define) goes perhaps a bit too much the other way. Maybe we can find a compromise between the two... Rosbif73 (talk) 07:44, 15 March 2023 (UTC)

This can be easily accommodated by saying e.g. that "The Kármán line is a proposed conventional boundary between Earth's atmosphere and outer space", instead of the conventional boundary, and then adding earlier on that there is no universal agreement on where this boundary should lie, and that a widely accepted value is the one set by the FAI at 100 km. I'm going to reword it along this line, unless there are strong objections. --Deeday-UK (talk) 11:58, 18 March 2023 (UTC)

Water'n it down

It seems there's been a long-term effort to water down the relevance and established nature of the Karman line, which might be politically-aligned POV-pushing.

The lede used to say:

The Kármán line lies at an altitude of 100 km (approx. 62 miles) above the Earth's sea level, and is commonly used to define the boundary between the Earth's atmosphere and outer space.[2] This definition is accepted by the Fédération Aéronautique Internationale (FAI), which is an international standard setting and record-keeping body for aeronautics and astronautics.

This turned into:

represents both the attempt to define a boundary between Earth's atmosphere and outer space, and offers a specific definition set by the Fédération aéronautique internationale (FAI), an international record-keeping body for aeronautics.

and later:

is an attempt to define a boundary between Earth's atmosphere and outer space, and offers a specific definition set by the Fédération aéronautique internationale (FAI), an international record-keeping body for aeronautics.

and currently:

is a proposed conventional boundary between Earth's atmosphere and outer space set by the international record-keeping body FAI (Fédération aéronautique internationale) at an altitude of 100 kilometres (54 nautical miles; 62 miles; 330,000 feet) above mean sea level. However, such definition of the edge of space is not universally adopted.

—ReadOnlyAccount (talk) 23:15, 28 March 2024 (UTC)