The positions of the eighteen shells were plotted and updated on a real-time map displayed on a big monitor. They were spread out like beads on a string along a trajectory that rose straight up from the Flying S Ranch and then spiraled down through Mexican airspace. They all seemed to be following the same basic flight plan, like cars in an aerial train. Each had two video cameras, one aimed forward and the other aimed back. The twin feeds from one shell were up on the video screens. They couldn’t have been more different. The view forward was of a black sky above a curved horizon limned in blue. The view back was an endless series of flashes, which became so visually annoying that the pane had to be minimized. But it confirmed that the sulfur-burning pulse jet had ignited and was farting away.