Ballute (Balloon-Parachute)

Its a dynamic decelerator developed by the Goodyear Aerospace Corporation, of Akron, Ohio. The name came from the combination of the words "Balloon" and "Parachute".

Ballute was introduced in 1958 to satisfy space requirements of deceleration, stabilization, and recovery of payloads from high altitudes and supersonic velocities. The then known parachute
configurations were unable to perform adequately in this space environment.

The basic principle underlying the operation of the BALLUTE is that the ram-air inlet oriented into the airflow allows pressurization of the body to a level equal to the sum of the dynamic and ambient pressures of the flow. This internal pressure acting normal to the membrane is always greater than a combination of the external ambient pressure and the dynamic forces that act externally and obliquely on the membrane.

The first developmental models worked by towing a pressurized sphere in the form of a cone-shaped balloon, behind the recoverable article. Although this approach supplied the required drag forces, the balloon was violently unstable in subsonic and transonic velocity regimes. So to stabilize the sphere, an inflated torus called a "burble fence" was added around the balloon to act as a vortex generator and to ensure flow separation at a constant station around the ballute.

The ballute, unlike the parachute, has a relatively small inflation inlet that takes longer to inflate than the parachute. Conversely, in the event of a gust or wind shear, inflation air cannot be rapidly expelled, permitting the ballute to maintain its geometric and, therefore, its aerodynamic characteristics. For this reason, the ballute is considered aerodynamically as a rigid body.

As detailed analysis and wind tunnel testing proceeded, the inflation of the balloon which initially was made by canned gas, was later replaced by ram-air inflation.

Ballutes replaced common parachutes in meteorological rockets, to allow a stable descent phase of the nosecone. Nowadays, different types of ballutes are used as retarding device for freefall bombs dropped from aircraft, and are being studied for use during aerocapture and aerobraking maneuvers, and also for deorbit and recovery of low-mass satellites from low-Earth orbit.

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