There's a great book by Milt Thompson, At The Edge of Space, covering the X-15 program. All of those guys clanked when they walked.
Great book. He had a follow-on about the lifting bodies but didn't finish it before he passed. The folks who did finish it didn't do a great job but it's one of the few records of another neat program by someone who was in the thick of it.
Who of my generation can forget the opening of this? http://www.dailymotion.com/video/x910ca_six-million-dollar-man-intro-openin_shortfilms
or this