Commercial aerospace firm Space X announced plans Thursday to develop the world\'s first completely resuable rocket, which chief executive Elon Musk said could revolutionize space travel. Past space travel has involved reusable vessels such as the space shuttle, but the rockets that propelled the system into space could be used just once. Space X is working to bring its existing designs for the spacecraft \"in line with reality\" to develop the reusable rocket, Mus said. The rocket\'s first and second phases would fly themselves back to Earth, landing accurately at the launch pad, simulations by Space X showed. Musk told reporters at the National Press Club in Washington that such a ssytem would reduce launch costs by \"100-fold\" and make possible longer distance missions, such as to Mars. Space X is currently among those developing commercial spacecraft to transport cargo and astronauts to the International Space Station, as NASA shifts its focus after the retirement of the 30-year-old shuttle fleet.