Where exactly is "the edge of space" ?

In the mid-20th century, scientists tried to set that limit at how low you can go and still sustain an orbit — an altitude known as the Karman line, named after aerospace engineer Theodore von Karman. At some point atmospheric drag becomes too big a factor to sustain even a highly elliptical orbit — one that swings in close and then out much farther.

For years, the official Karman line has been set at 100 kilometers. But that was not the value Karman set for it. In a paper published earlier this year in the journal Acta Astronautica, McDowell recalculated the Karman line, and found it’s considerably closer — just close enough to make SpaceShipTwo a space-faring craft.

When North Korea launched a missile last year, reportedly over Japanese airspace, it was actually higher than the International Space Station, McDowell said. “Of course it’s in space, and it doesn’t make sense to say it’s in Japanese airspace,” he said, but without an international agreement about the boundary between air and space, such confusion is inevitable.

https://www.bloomberg.com/opinion/articles/2018-12-15/virgin-galactic-s-spaceshiptwo-may-or-may-not-have-gone-to-space