| Research Abstract |
1.An analytical model is made on the basis of airframe and mass distribution of Japanese SSTO space plane which has been studied in National Aerospace Laboratory. The wings of the model are fixed on the fuselage at one point similarly to the X-30 demonstrator vehicle. The second order piston theory is used as the unsteady aerodynamic force at hypersonic speed, and the stability is calculated in the use of four modes, i.e. rigid translation, rigid rotation, first and second bending modes. The results have disclosed that there is a possibility of the occurrence of body flutter depending on the body flexibility and the wing position in the hypersonic speed lower than its body divergence speed.
2.Flutter experiments have been carried out in a low speed wind tunnel of which maximum speed is 30 m/s by using a flexible model supported vertically in its wing surface so as to be able to move freely to side direction in horizontal plane. Four models different in span and position of the wing have been tested. Theoretical analysis has been carried out by using Ueda's doublet-point method for non-planer surface in calculation of unsteady aerodynamic force. The results have revealed the following characteristics.
(1) In all experiments the body flutter speed has been measured and the body divergence has not occurred.
(2) For the flutter speed, flutter frequency and flutter mode, good agreement is observed between experimental and theoretical results.
(3) The U-g diagram obtained by theoretical analysis has disclosed the characteristic that the flutter speed depends on the value of structural damping coefficient.
(4) The experimental result has shown that this body flutter is mild. Namely, a steady selfexcited vibration has been observed at the wind speed a little bit higher than the flutter speed. Then this flutter does not lead to a catastrophic failure at once.
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