two individuals had displayed interest in purchasing seats with contract negotiations expected to be concluded by the end of the year. In January 2011, Space Adventures founder Eric Anderson announced that one of the two seats on the flight had been sold at a price of US$150 million, and negotiations for the second seat were under way. In 2011, Space Adventures projected the first mission could occur by 2015. By 2014 this had slipped to 2018, and the company's website subsequently changed to indicate they expected their first mission to launch before the end of the decade then changed again to remove any suggested timeline. Criticism Mark Wade, author of the Encyclopedia Astronautica, has argued that the Zenit rocket is not powerful enough for this mission and that the larger Proton rocket will in fact be needed. These same calculations have also shown that a fully fueled and outfitted Block DM would be beyond the capabilities of the Zenit rocket, and the DM would have to fire for a short time in order to stabilize its orbit. See also Space tourism Space Adventures List of current and future lunar missions References External links Encyclopedia Astronautica: DSE-Alpha Commercial spaceflight Human spaceflight programs Space Adventures Space tourism Missions to the Moon Proposed space probes