The ballute (a portmanteau of balloon and parachute) is a parachute-like braking device optimized for use at high altitudes and supersonic velocities. Invented by Goodyear in 1958, the original ballute was a cone-shaped balloon with a toroidal burble fence fitted around its widest point. A burble fence is an inflated structure intended to ensure flow separation. This stabilizes the ballute as it decelerates through different flow regimes (from supersonic to subsonic).
The ballute is inflated either by a gas generator or by air forced into the structure by ram air inlets.
Ballutes have also been proposed in stacked toroidal and tension cone form factors, in addition to the more standard isotensoid ballute.
The ballute has been used as a retarding device for freefall bombs dropped from aircraft.
It has been proposed for use during aerocapture and aerobraking. In the 1984 film 2010: The Year We Make Contact, a ballute is used on the space vehicle Leonov to shield it from the effects of heating during aerobraking. This allowed the Leonov to slow itself without expending fuel and establish an orbit around Jupiter's moon Io.
In April 2018 SpaceX's Elon Musk tweeted "SpaceX will try to bring rocket upper stage back from orbital velocity using a giant party balloon."
In August 2019 Peter Beck of Rocket Lab announced that they would attempt to recover their Electron rocket's lower stage utilizing a ballute for supersonic deceleration.
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