3 ms·
I'm aware. I'm not saying the altitude is the exact same altitude at all times under all conditions. I'm saying there is a specific altitude where centrifugal f
by _moof 5y ago
I'm aware. I'm not saying the altitude is the exact same altitude at all times under all conditions. I'm saying there is a specific altitude where centrifugal force becomes the dominant force if you want to stay aloft. And that was Kármán's original conception. Yes, that altitude will vary with the atmospheric tides (and with C_L, as another commenter points out). But it is still a definite altitude and not at all arbitrary.
arbitrary: "based on random choice or personal whim, rather than any reason or system"
It is not based on random choice or personal whim. It is the result of a systematic analysis of the relationship between the forces required to sustain flight.
- mannykannot 5y ago>I'm not saying the altitude is the exact same altitude at all times under all conditions. You were disputing a post in which this was literally the only point I made: https://news.ycombinator.com/item?id=27801257 https://news.ycombinator.com/item?id=27801257
- SonicScrub 5y agoNothing says "arbitrary" more than a quantity that was deliberately rounded up 9km just for the heck of it. Things can be guided by math/logic and still have arbitrary elements. The Karmen line definition is a logical definition with certain arbitrary constant selections, and therefore it's not specific. This doesn't mean it's random, only that there are band of valid definitions. It's correct to state a boundary defined by centrifugal force dominance is somewhere between 80ish and 100ish km, and the specific number is somewhat arbitrary. It's not correct to say its for 20km (for example), which would be a truly random selection.