the Postmasters General of all members of the Universal Postal Union, and so on, from United States Postmaster General Arthur E. Summerfield. Their postage (four cents domestic, eight cents international) had been cancelled "USS Barbero Jun 8 9.30am 1959" before the submarine put to sea. At Mayport, the Regulus missile was opened and the mail forwarded to the post office in Jacksonville, Florida, for sorting and routing. Upon witnessing the missile's landing, Summerfield stated, "This peacetime employment of a guided missile for the important and practical purpose of carrying mail, is the first known official use of missiles by any Post Office Department of any nation." Summerfield proclaimed the event to be "of historic significance to the peoples of the entire world", and predicted that "before man reaches the moon, mail will be delivered within hours from New York to California, to Britain, to India or Australia by guided missiles. We stand on the threshold of rocket mail." Despite the Postmaster General's enthusiasm, the Department of Defense saw the measure more as a demonstration of U.S. missile capabilities. Experts believe that the cost of using missile mail could never be justified. While during the 1920s a letter between Europe and the United States would not arrive for at least a week after mailing, by the 1950s air mail crossed the Atlantic Ocean in as little as one day. One of the mail containers which was on board the Regulus missile fired by Barbero is in the collection of the United States Submarine Force Museum in Groton, Connecticut. Reusable launch vehicles Rocket expert Willy Ley speculated in 1954 that using small cruise missiles to rapidly deliver mail might be possible for as little as three times the rate for airmail, in part because they could be reusable. Technologists like Robert Zubrin, of Mars Society fame, think that rocket mail, or at least ultra-elite business package delivery, may become commercially viable with the development of fully reusable launch systems, particularly single-stage to orbit vehicles. Such systems would allow package delivery anywhere in the world in 30–45 minutes. This idea has been forwarded by Zubrin and was the original business plan behind Pioneer Rocketplane (later Rocketplane Limited, Inc.), which he co-founded. Zubrin has since left the company, which is now focused on pursuing a somewhat more conventional space tourism strategy. The potential of package delivery with reusable launch vehicles is discussed in Zubrin's