ON TV: Area 51 Declassified premieres on the National Geographic Channel on Saturday, May 28, at 10:00 p.m. ET/PT.

No word yet on alien starships, but now that many Cold War-era Area 51 documents have been declassified, veterans of the secret U.S. base are revealing some of the clever—and surprisingly low-tech—ways they hid futuristic prototypes from prying eyes.

The CIA created Area 51 in 1955 to test and develop top secret U.S. military projects in the remote Nevada desert. More than 50 years later, the base still doesn't officially exist and appears on no public U.S. government maps.

In the 1950s and '60s, Area 51 was the epicenter of the OXCART project, intended to create the successor for the U-2 spy plane.

The OXCART plane was expected to be undetectable in the air as it flew surveillance and information-gathering missions over the Soviet Union. But Area 51 personnel soon found it necessary to conceal the craft from the Soviets eyes even when it was still being tested on the ground.

Cat and Mouse at Area 51

It was discovered that Soviet spy satellites, dubbed ash cans by Area 51 staff, were making regular rounds over Nevada.

U.S. intelligence agencies, though, provided Area 51 workers with a decisive advantage in this international "game of cat and mouse," according to T.D. Barnes, a former hypersonic flight specialist at Area 51 whose expertise was in electronic counter measures.

No longer sworn to secrecy by the CIA, Barnes said, "In our morning security meetings, they'd give us a roster of the satellites that the Soviets had in the air, and we'd know the exact schedule of when they were coming over.

"It was like a bus schedule, and it even told us whether it was an infrared satellite or what type it was," Barnes told National Geographic news.

The Area 51 Hoot and Scoot

Often hoisted atop tall poles for radar tests of the planes' stealthiness, OXCART prototypes were tested outside—making the Soviet spy satellites especially aggravating.

"We had hoot-and-scoot sheds, we called them," Barnes says in the new National Geographic Channel documentary Area 51 Declassified. (The Channel is part-owned by the National Geographic Society, which owns National Geographic News.)

"If a plane happened to be out in the open while a satellite was coming over the horizon, they would scoot it into that building."

Former Area 51 procurement manager Jim Freedman adds, "That made the job very difficult, very difficult.

"To start working on the aircraft and then have to run it back into the hangar and then pull it out and then put it in and then pull it out—it gets to be quite a hassle," Freedman says in the film.

Shadows of Area 51

It turned out that even laborious hooting and scooting weren't enough. Spies had learned that the Soviets had a drawing of an OXCART plane—obtained, it was assumed, via an infrared satellite.

As a plane sat in the hot desert, its shadow would create a relatively cool silhouette, visible in infrared even after the plane had been moved inside.

"It's like a parking lot," Barnes told National Geographic News. "After all the cars have left you can still see how many were parked there [in infrared] because of the difference in ground temperatures."

To thwart the infrared satellites, Area 51 crews began constructing fanciful fake planes out of cardboard and other mundane materials, to cast misleading shadows for the Soviets to ponder. (Not intended to be seen, the decoys themselves were scooted out of sight before satellite flyovers.) Sometimes staff even fired up heaters near imaginary engine locations to make it look as if planes had just landed.

"We really played with the infrared satellites," Barnes recalled.

Ahead of Its Time—And Gone Before Its Time?

As for the real U-2 successor, the Soviets never solved the secrets of OXCART before the program was made public in the mid-1960s.

But during the course of some 2,850 top-secret test flights numerous people did see an oddly shaped (for the time), Mach-3 aircraft. Unidentifiable even to air controllers or commercial pilots, the gleaming titanium craft no doubt helped fuel the persistent rumors connecting UFOs with Area 51.

In the end, the result of all the subterfuge was the Archangel-12, or A-12, considered by some to be the first true stealth plane. (Related: "'Hitler's Stealth Fighter' Re-created.")

The A-12 could travel over 2,000 miles an hour (3,220 kilometers an hour) and cross the continental U.S. in 70 minutes—all while taking pictures that could resolve foot-long objects on the ground from an altitude of 90,000 feet (27,430 meters).

But despite being "the most advanced aircraft ever built," as CIA historian David Robarge writes, the A-12 never saw spy service over the Soviet Union. And just as the Archangel was to be deemed ready for operation, its successor, the U.S. Air Force's famed SR-71 Blackbird, was already in the works.