Rockoon

A rockoon (from rocket and balloon) is a solid fuel sounding rocket that, rather than being immediately lit while on the ground, is first carried into the upper atmosphere by a gas-filled balloon, then separated from the balloon and automatically ignited. This allows the rocket to achieve a higher altitude, as the rocket does not have to move unde...
Found on http://en.wikipedia.org/wiki/Rockoon

rockoon

A Navy rockoon just after a shipboard launch. A Deacon rocket is suspended below the balloon A high-altitude balloon from which a small sounding rocket could be launched. The first rockoon was sent up in 1952 from the icebreaker Eastwind off Greenland by a research group headed by James Van All...
Found on http://www.daviddarling.info/encyclopedia/R/Rockoon.html
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