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:
Space tourism returned aboard Soyuz TM-11. As of 2018, no suborbital space tourism has yet occurred, but since it is projected to be more affordable, many companies view it as a money-making proposition. Most are proposing vehicles that make suborbital flights peaking at an altitude of . Passengers would experience three to six minutes of weightlessness, a view of a twinkle-free starfield, and a vista of the curved Earth below. Projected costs are expected to be about $200,000 per passenger. At the end of the 1990s, MirCorp, a private venture that was by then in charge of the space station, began seeking