50 years ago, NASA launched the Explorer 9 from Wallops Island, Virginia. It was one of many missions the space agency sent into orbit as the United States raced to catch up with the Soviet Union in the space race. Strapped to a Scout rocket, the Explorer was a prime example of a largely forgotten part of NASA's history: the inflatable spacecraft.

The first was the Echo 1, which you can see inflated inside the Navy's dirigible hangar at Weeksville, North Carolina. The reason for using inflatable craft is simple: they're light, which meant that you didn't need as much thrust from your rocket to get into orbit. John Pierce, Bell Laboratory's director of research in communication principles, and William O'Sullivan of the National Advisory Committee for Aeronautics became relentless promoters of the idea of balloon satellites for telecommunications and research. People called them -- seriously -- "satelloons."

The Echo satellite was made of aluminum-coated mylar and could be used a mirror to reflect communications signals around the globe. It carried only two FM transmitters, which you can see in the photo above as the round white blobs on the left and right near the balloons center. They were powered by 70 solar cells that fed storage batteries. The Echo was packed into a container 26 inches across and launched into space on a Thor-Delta booster rocket on August 12, 1960. After deploying in orbit, a pre-recorded message from President Dwight D. Eisenhower was bounced off the satellite.