Reply by Author to Ernst D. Geissler
1963; American Institute of Aeronautics and Astronautics; Volume: 1; Issue: 2 Linguagem: Inglês
10.2514/3.54840
ISSN1533-385X
Autores Tópico(s)Spacecraft Dynamics and Control
ResumoG comments are quite appropriate, and they indicate that such generalizations as were drawn in Ref. 1 must not be accepted without careful study for the specific application. In this regard, some information is available from the detailed study of a three-stage Nova-type booster vehicle made recently by Lockheed Missiles and Space Company. The vehicle considered was 45 ft in diameter and 394 ft in length; the eight F-l engines provided an initial thrust-toweight ratio of 1.25. Vehicle dynamics analysis was based on an optimum ascent trajectory under a synthetic wind profile derived from the 99% design-wind criteria of NASA. A simple autopilot with gain programmed to yield approximately constant natural frequency, but without angle-of-attack control, was found adequate for the requirements. Vehicle parameters for this design are summarized as follows: First bending frequency 0.85 cps Air frame-autopilot natural frequency /o 0.12 cps Maximum useful F-l gimbal angle 5° Damping (attitude rate gain) critical Under the design conditions, control was effected with a gimbal deflection not exceeding 2°, the vehicle angle of attack reaching a maximum of 11°. The effect of variations in the design parameters was studied, and stability analyses were made incorporating the first two body bending modes and first two slosh modes for each of the six tanks. The following conclusions are quoted from Ref. 3:
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