EFFECT OF STING STIFFNESS ON MEASURED DERIVATIVES FOR A MODEL DESCRIBING PITCH OSCILLATIONS OF LOW REDUCED FREQUENCY,
Abstract
Experimental pitch damping derivatives are usually obtained from wind tunnel tests by using either forced or free oscillation techniques. In both cases the model is as a rule sting mounted. The effect of sting stiffness on measured derivatives for a model oscillating in pitch is analyzed. The method of forced oscillations is used in the analysis but the conclusions are valid also for the free oscillation technique. It is shown that, for a representative re-entry body model, a sting with a natural frequency at least 4 times higher than the model pitch frequency is needed if the effect of 'sting plunging' is to be kept below 5%. The relations derived make it possible to estimate the sting plunging effect by use of static data and the requirements on sting stiffness may, therefore, be reduced somewhat. It is essential, however, that the sting natural frequency is appreciably larger than the model pitch frequency if reliable data are to be obtained. Such a sting will give too low (conservative) damping derivatives for a statically stable model if the plunging effect is neglected. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 20, 1960
- Accession Number
- AD0829502
Entities
People
- L. E. Ericsson
Organizations
- Lockheed Martin Missiles and Space