He has worked with the Dutch Navy, the USAF and NASA.
He is the author of several books.
His first book, The Theory of Orbits, is an important text on orbital mechanics[?].
... are 65 years of age or older. The median age is 39 years. For every 100 females there are 104.2 males. For every 100 females age 18 and over, there are 97.8 males. The ...