ON MEASURING DRAG COEFFICIENTS IN A BALLISTICS RANGE USING A MICROWAVE RESONANT CAVITY
Abstract
A microwave resonant cavity has been constructed from a 4.5-inch diameter pipe, ten feet long. Hollow sleeves are inserted into the ends. A frequency-controlled reflex klystron is used to excite a standing wave within the cavity at a frequency of 1910 mc. The interaction of an axially moving projectile with the electromagnetic field produces a change in the cavity resonant frequency in proportion to the magnitude of the displaced field. The changing frequency is observed as a periodic variation in the power absorbed by the cavity. The time length of each period is the time required for the projectile to transit one half of a waveguide wavelength. As the projectile proceeds through the cavity the similar successive time intervals are measured by a high-speed chronograph. The resultant time-distance information is reduced to a drag coefficient by ordinary ballistics range techniques. The accuracy with which drag coefficients can be obtained depends upon, among other things, the length of the resonant cavity. Two sets of sphere drag coefficients which have been obtained with the microwave resonant cavity are presented. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1962
- Accession Number
- AD0276056
Entities
People
- Robert J. Haislmaier
Organizations
- Naval Ordnance Laboratory