By Justin Bachman, Bloomberg News In the future, military dominance will depend partly on how fast you can fly and how quickly you can get into space. That’s one of the guiding principles behind an advanced Pentagon project to build a spacecraft able to launch smaller payloads into low-earth orbit on short notice, and at lower cost. Boeing Co.’s XS-1 (Experimental Spaceplane), which the company dubs “Phantom Express,” got a green light this week by the Defense Advanced Research Projects Agency, or Darpa.