The agency has already spent billions of dollars on the National Aerospace Plane, the X-33, X-34, X-37, X-38 and the Orbital Space Plane.

FORBES: Magazine Article

Latest example of NASA bloated spending: The agency has already spent billions of dollars on the National Aerospace Plane, the X-33, X-34, X-37, X-38 and the Orbital Space Plane.

FORBES: Magazine Article

He flew the X-15 rocket plane to the edge of space - 200, 000 feet up at 4, 000 mph.

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This appears to be the mindset of the Air Force regarding its experimental X-37B space plane, the billion-dollar robotic vehicle's orbital flight being extended beyond the 270 days it was initially designed for.

ENGADGET: Air Force X-37B space plane books additional time on orbital cruise, orders another margarita

Before being chosen in 1962 as one of the "Group II" astronauts -- which included Apollo 13 commander James Lovell along with such legends as Frank Borman, Pete Conrad and John Young -- Armstrong was one of the elite pilots selected to fly the X-15 rocket plane up to five times the speed of sound and toward the edge of space.

CNN: Neil Armstrong, a hero who shunned fame

For its part, the Navy has a prototype for an unmanned strike plane, the X-47B, which looks like a gigantic matte-gray flying saucer, with a 62-foot wingspan.

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Nowadays, behind Skunk Works' highly secure perimeter, engineers reportedly are working on the aviation wonders of tomorrow, including a lightweight cargo plane called the X-55A and a bizarre, blimp-like airship called the P-791 Hybrid Air Vehicle, which has special technology that allows it to take off and land just about anywhere.

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His first rocket plane flight in the Bell X-1B experienced a nose gear failure on landing.

FORBES: Neil Armstrong's Immortal Footprint