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Extremely Small Balance Technology


OBJECTIVE: Development of small balance technologies having the capability for measuring forces and moments on extremely small wind tunnel test models. 

DESCRIPTION: The size of models tested in the AEDC 16-ft wind tunnels, particularly models of stores used in Captive Trajectory System (CTS) testing, can be unusually small for large vehicles due to the small scales needed for the parent vehicle to fit within the wind tunnel. These small models cannot be tested using traditional force and moment balances since the size of the supporting stings can be much larger than the models, making the small forces upon the models to fall within the noise measured by the balance. A small six degree of freedom (DOF) force and moment balance system is needed to enable the forces and moments on wind tunnel models whose characteristic outer dimension is down on the order of .5 inches or smaller. This implies the balance itself needs to by .2 inches in diameter or smaller. Time resolved measurements up to frequencies of 2000 Hz are desirable. This technology will be used in wind tunnel testing with flow fields ranging in Mach number from 0.1 to 2.5, altitude pressures from -1,000 to 100,000 ft, and temperatures ranging from -50 to 140 °F. The approach may be a traditional sting with extremely small components, but other concepts such as a tethered system or holding of the store with a magnetic field will be considered. The hardware material must be sufficiently strong to withstand the aerodynamic forces created by the facility and be tolerant to the temperature, which can be extremely cold due to the expansion of the flow before the test section. 

PHASE I: Develop a conceptual design for a small balance/force and moment measurement capability and a development plan for a prototype system and demonstration. 

PHASE II: Develop a prototype system and demonstrate the capability for measuring the force and moments in a relevant environment. 

PHASE III: The prototype system should be standardized with components that can easily be procured. Any software/data reduction capabilities needed with the system will be refined to integrate with facility test measurement data systems. 


1: G. BRIDEL and H. THOMANN. "Wind-tunnel balance based on piezoelectric quartz force transducers", Journal of Aircraft, Vol. 17, No. 5 (1980), pp. 374-376.

2:  R. L. BLACK. "High-speed store separation - Correlation between wind-tunnel and flight-test data." Journal of Aircraft, Vol. 6, No. 1 (1969), pp. 42-45.

3:  Frank Steinle, Jr., "Modeling of anelastic effects in calibration of a six-component wind tunnel balance", AIAA-2000-0105, 38th Aerospace Sciences Meeting and Exhibit.

KEYWORDS: Balance, Flight Vehicles, Wind Tunnel, Force Measurement 


Joseph Wehrmeyer 

(931) 454-4345 

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