SOUNDER

SOUNDER was a vehicle designed to be launched and ascend like a balloon but instrumented to fly like a blimp. Batteries charged by a single solar array positioned inside the transparent envelope drive an electric motor and propeller in the back of the balloon-turned-blimp. The Sounder vehicle is designed to loiter and maintain a pre-determined position for extended periods of time. Although the launch appeared to be perfect one of three fragile tail fins may have been damaged during the launch, and the flight was terminated due to system failures.

Balloon launched on: 4/27/1999 at 11:00 local
Launch site: Hondo Airport, New Mexico, US  
Balloon launched by: Joint Command and Control Warfare Center, Kelly AFB, Texas / Southwest Research Institute
Balloon manufacturer/size/composition: Stratospheric Airship 1500 m3
End of flight (L for landing time, W for last contact, otherwise termination time): 4/27/1999 at 17:15 local
Balloon flight duration (F: time at float only, otherwise total flight time in d:days / h:hours or m:minutes - ): ~ 6 h
Landing site: S of Jourdanton, Texas, U.S.

• Autonomous stratospheric airship description of the Sounder system in the U.S. patent registry
• Development of a small stratospheric Station Keeping Balloon system Proceedings, 22nd ISTS, Morioka, Japan (2000)
• Spokesman On Line July 1999 (via Archive.Org)