In his free time, McDowell conducts research into the
history of spaceflight, and since 1989 has written and edited ''
Jonathan's Space Report'', a free internet newsletter documenting technical details on satellite launches. This information, obtained from original sources including declassified Department of Defense documents and Russian-language publications, can also be found on McDowell's web site. In 1994, McDowell published a history of the
North American X-15 spaceplane, in which he suggested that should be adopted as the
boundary of space. In the
mesosphere, 80 km is nearly equal to 50 mi, the altitude used by the United States to confer astronaut status on pilots, as in the X-15 program itself. It also differs from the internationally accepted
Kármán line altitude of 100 km, used by the
Fédération Aéronautique Internationale for the same purpose. In 2018, McDowell published a refereed journal paper in
Acta Astronautica making detailed physical arguments for the 80 km value. ==Media==