Guests: Leonard David, Mark Mayfield. Topics: Human spaceflight history, commercial space, NASA policy. Please note that you are invited to comment, ask questions, and rate this program on the new Space Show blog, http://thespaceshow.wordpress.com. Mark Mayfield's book, "The Spaceflight Vault: A History Of NASA's Manned Missions," is available from the One Giant Leap Foundation website as an Amazon partner. If you buy the book from OGLF, Amazon makes a contribution to The Space Show.