1985 Fiscal Year Final Research Report Summary
Nonlinear Dynamic Characteristics of Recovery Bodies
| Project/Area Number |
59420021
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| Research Category |
Grant-in-Aid for General Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Research Field |
Aerospace engineering
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| Research Institution | Institute of Space and Astronautical Science |
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Principal Investigator |
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| Project Period (FY) |
1984 – 1985
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| Keywords | recovery body / nonlinear dynamic stability / 非線型動特性 / 減速特性 |
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| Research Abstract |
It is the purpose of this project to clarify nonlinear dynamic characteristics of the recovery bodies at subsonic and supersonic speeds. The project consists of four subresearch programs, the title and the associated results of each program may be summarized briefly as follows.
1) Dynamic stability characteristics in pitching motions : The pitching motion of the recovery bodies having 2-stage cylindrical geometry has two kinds of nonlinear oscillatory modes, depending on whether the large cylinder is directed upwind or not. The one is a monotonously damping oscillation and the another is a non-damping one that tends finally to a limiting cycle. The numerical simulation based on the present curve-fitting method reveals that the model is aerodynamically unstable in both cases.
2) Deceleration characteristics of supersonic parashutes : The drag coefficient of the parashutes obtained in the present experiment at M = 2 is in the range from 0.15 to 0.20, which seems to give a promising feasibility to practical use of the supersonic parashutes.
3) A method of flat spin prevention : The experiment conducted in a low speed wind tunnel clearly reveals that the antennae mounted on slender recovery bodies have a remarkable effect for reduction of tumbling of the bodies. This results suggests that, if the antennae are allocated adequately, the spin will be prevented effectively.
4) Transient characteristics to flat spin of slender bodies : There are two transient processes that the bodies are brought to rotation, depending on Reynolds number and body geometry. This implies the existence of a single or double equilibrium angular velocities that a steady flat spin is possible. Furthermore, variation of moment coefficient with angular velocity is nonlinear, which can be calssified into the following three categories. Those are the cases of (a) monotonous decrease, (b) having maximum, and (c) having maximum after monotonous decrease.
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