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Subsonic wind tunnel experiments on a GETOL wing are reported. The main results relevant to performance, stability and control are presented, and applied to a hypothetical vehicle. Short-field capability is demonstrated to be possible. Stability and control problems are analysed, and shown not to be prohibitive.

Recent experimental information on low-level atmospheric turbulence is first reviewed. It is suggested that the assumptions of homogeneity and isotropy customarily adopted for high altitudes are still useful in this regime, and that the integral scale is roughly equal to 9/10 of the altitude up to about 1000 ft. Next, the previously published theory of the 'power-series approximation' as applied to the vertical component of the gust is extended to include all three velocity components simultaneously. Fourteen different one- dimensional input power spectra and cross spectra are found of which only five are important. Of these five, only one is a cross-spectrum involving two different velocity components (u and v). Formulae for them are calculated and curves are presented. The 'gust derivatives' required for calculating airplane response are defined and discussed, and the most important ones are shown to be simply the negatives of classical stability derivatives. Methods of approach for calculating the remaining ones are suggested., Presented at the AGARD Specialists' Meeting on Stability and Control, 10-14 Apr 61, held at Rhode-Saint-Genese, Belgium.

A wind tunnel study was made of the bending moment response of a cylindrical structure exposed to a turbulent wind. A theory, developed by Etkin, of the response of a slender structure in the stream direction to a turbulent wind was compared with the experimental results. The structure used for the study was an approximate aeroelastic model of an existing radio antennas. A turbulence field was generated in the wind tunnel by a square mesh grid. With a ratio of longitudinal turbulence scale to model diameter of L/D = 21 and an intensity of 20% the model in this turbulence field was then representative of a full scale structure in atmospheric turbulence. Bending moment spectra in the drag and lift directions were obtained for various turbulence conditions. It was found that close agreement was obtained between theory and experimental results in the turbulence field. This indicates that the drag coefficient for this cylinder is very similar under turbulent and steady wind conditions. Some measurements of lift-drag correlation were also made which indicated that essentially zero correlation exists in the turbulent field. It was concluded that the theory provides a reasonably accurate method of predicting the response of a slender structure to a turbulent wind. (Author)

A study is presented of the interaction with the solar radiation field of a spinning satellite having long flexible rods. The dynamics of thermal bending of the rods is analyzed, including the effect of vehicle rotation, and the shape, amplitude and phase are calculated. The radiation pressure on the periodically bent rods produces a net average despin torque that depends critically on the phase lag of the thermal bending. The theory is compared with flight data from the Alouette I and S48 satellites, and the agreement indicates that the mechanism studied is the primary cause of despin of these vehicles. A means of preventing despin is proposed. It consists of polished plates mounted on the tips of the rods. The torque produced by the solar pressure acting on them is opposite to that on the rods. The plate area required for complete cancellation of the despin torque is of order 1/4 to 1/2 of the projected rod area. (Author)

ONE FAMILY OF SOLUTIONS IS PRESENTED FOR A MONOTONIC TRANSITION FROM A CIRCULAR ORBIT TO AN EQUILIBRIUM GLIDE. It is performed at high lift coefficient and low L/D, and terminates at a match point where the prescribed conditions of the glide are met. The vehicle then continues on the glide at a higher value of L/D. The high rag required during transition entails the use of a large auxiliary light-weight drag body, which is jettisoned upon arrival at the match point. The presence of this drag body results in a reduction of the total heat load on the vehicle itself. The exact amount of this reduction depends on the details of the design, but it can be typically of the order of 3/4 in an entry with a peak acceleration of the order of 7 g. As a result, the maximum average vehicle temperature can be made relatively low, with consequent advantages in the structural design, and in the thermal protection of the payload. (Author)