Space architecture of space and a space transportation infrastructure can be accelerated. Virgin Galactic has indicated plans for an orbital craft, SpaceShipThree. The demand for space tourism is one without bound. It is not difficult to imagine lunar parks or cruises by Venus. Another impetus to become a spacefaring species is planetary defense. The classic space mission is the Earth-colliding asteroid interception mission. Using nuclear detonations to split or deflect the asteroid is risky at best. Such a tactic could actually make the problem worse by increasing the amount of asteroid fragments that do end up hitting the Earth. Robert Zubrin writes:
Vision for Space Exploration be directed toward reducing human spaceflight costs sufficiently for the betterment of low Earth orbit research, business, and tourism. Alternatively, VSE could afford advances in other scientific research (astronomy, selenology), in-situ lunar business industries, and lunar-space tourism. The VSE budget required termination the Space Shuttle by 2010 and of any US role in the International Space Station by 2017. This would have required, even in the most optimistic plans, in a period of years without human spaceflight capability from the US. Termination of the Space Shuttle program, without any planned alternatives, in 2011 ended virtually all US capability for reusable