3 ms·
Wikipedia [1] quotes from Kármán's autobiography where he discusses the origin of his idea, and he used an example of 300,000 ft. (91 km.) As the paper you link
by mannykannot 7y ago
Wikipedia [1] quotes from Kármán's autobiography where he discusses the origin of his idea, and he used an example of 300,000 ft. (91 km.) As the paper you link to shows, it is one of several candidates for the 'edge' of space, and they are all inherently vague. The paper shows how, by picking one reasonable set of parameters, you can put a Kármánesque line at 80 km., but its strongest argument for space beginning there is that several different candidates overlap at around that altitude.
[1] https://en.wikipedia.org/wiki/K%C3%A1rm%C3%A1n_line https://en.wikipedia.org/wiki/K%C3%A1rm%C3%A1n_line
- lutorm 7y agoMaybe space should be defined as the altitude you need to have to not have your orbit decay in less than one orbit. I wonder what altitude that is, actually.
- mannykannot 7y agoThe paper linked to by aerophilic goes into that issue in some detail, but it does not lead to a sharp distinction, either - for one thing, the ballistic coefficient ranges over a couple of orders of magnitude, with smaller objects coming down sooner. If we confine the discussion to circular orbits, it suggests that 100km is a better number than anything lower, but elliptic orbits can get away with lower perigees, which is a concern when the boundary of space is being defined for national territory purposes (e.g. spy satellites with a perigee over the nation being spied on.)