The average age of NASA employees is 46.2 years and rising, and the space agency forecasts that more than 4,000 of its full-time workers will retire over the next six years. The numbers tell the story behind NASA's experiment with social networking as a way to capture and share knowledge before those employees wave goodbye.

I wrote recently about NASA's pilot test of Socialcast's social-networking-as-a-service platform. (See One Small Step For Socialcast, One Giant Leap For Enterprise Social Networking.) It's easy enough to see the demographic data that's driving NASA in this direction. The agency makes its workforce data publicly available via Cognos PowerPlay business-intelligence software. You can view NASA's workforce data cubes on the NASA site here.

NASA's not ready to talk about its use of Socialcast, but there's background on its knowledge management program, also on the Web site.

If NASA were to move beyond the experimental stage with Socialcast, it would represent a high profile early adopter for the social networking startup. Here's my recent interview with Socialcast CEO Tim Young.