The asphalt runway stretches for a mile on Yucca Flat, deep in the Nevada National Security Site about 80 miles northwest of Las Vegas. Built in 2005, the runway covers a dirt landing strip from the 1950s, when the wide, flat valley was used for atomic bomb test shots. A small complex of buildings dominated by a large hangar with unusual clamshell doors dominates the southern end of the asphalt strip. The complex has no official name. Not many people even know it’s there. As secret airbases go, the single runway in the test site’s Area 6 is easily overshadowed by the world’s most famous secret military base, Area 51, a dozen miles northeast. Area 51’s existence was only recently acknowledged, even after decades of speculation by UFO enthusiasts that the aircraft development and test facility also houses space aliens and extraterrestrial technology. Unlike Area 51, which is protected by shoot-to-kill security and shielded from outside view by mountain ranges, Area 6 has only fences and visitor checkpoints. It can be seen at a distance from tour buses on the highway to historic bomb craters at the northern end of Yucca Flat. But exactly what goes on at the much smaller and much newer Area 6 is still top-secret defense research-and-development work. It’s so hush-hush that the security site’s spokesman can say little about it. Darwin Morgan, a spokesman for the National Nuclear Security Administration, said the low-key Area 6 facilities have been used by the Defense and Homeland Security departments. “They come here to test their own sensors,” he recently said after spending months fending off questions about the Area 6 runway