Rockoon

A rockoon (from rocket and balloon) is a solid fuel sounding rocket that, rather than being lit immediately while still on the ground, is first carried into the upper atmosphere by a gas-filled balloon, then separated from the balloon and ignited. This allows the rocket to achieve a higher altitude, as the rocket does not have to move under power through the lower and thicker layers of the atmosphere. A 2016 study by Acta Astronautica concluded that low-mass and high altitude launches give the best results.^[1]

The original concept was developed by Cmdr. Lee Lewis, Cmdr. G. Halvorson, S. F. Singer, and James A. Van Allen during the Aerobee rocket firing cruise of the U.S.S. Norton Sound on March 1, 1949.

A serious disadvantage is that unpiloted balloons cannot be steered,^[2] and consequently the location from which the rocket is launched can be uncertain. Therefore, a large area for the fall of the rocket is required for safety reasons. The rockoons that Robert Ellis worked with cost around a tenth the cost of rockets.^[3]