A barrage balloon is a type of airborne barrage, a large uncrewed tethered balloon used to defend ground targets against aircraft attack, by raising aloft steel cables which pose a severe risk of collision to hostile aircraft, making the attacker's approach difficult and hazardous. Early barrage balloons were often spherical. The kite balloon, having a shape and cable bridling which stabilises the balloon and reduces drag, could be operated at higher wind speeds than could a spherical balloon. Some examples carried small explosive charges that would be pulled up against the aircraft to ensure its destruction. Barrage balloons are not practical against high-altitude aircraft—the long cable required for a high-altitude balloon would be too heavy.
US Marine Corps barrage balloon, Parris Island, South Carolina, in May 1942
Landing ships putting cargo ashore on one of the invasion beaches during the Battle of Normandy. Note the barrage balloons, raised by the 320th Barrage Balloon Battalion.
Balloons could be launched from specialised vehicles.
A kite balloon is a tethered balloon which is shaped to help make it stable in low and moderate winds and to increase its lift. It typically comprises a streamlined envelope with stabilising features and a harness or yoke connecting it to the main tether and a second harness connected to an observer's basket.
Drachen kite balloon, showing its characteristic shape
Caquot kite balloon with basket near the ground