Showing papers in "Journal of the Aerospace Sciences in 1962"

Change of Satellite Orbit Plane by Aerodynamic Maneuvering

Abstract: M a n e u v e r s in which t h e o rb i t a l p l a n e of a n e a r t h sa te l l i te is changed b y m e a n s of a e r o d y n a m i c forces d u r i n g one or m o r e skips i n to a n d o u t of t h e a t m o s p h e r e a r e ana lyzed . T h e cha r ac te r i s t ic veloci t ies r equ i r ed of r o c k e t s t o deflect t h e vehic le i n to t h e a t m o s p h e r e in i t ia l ly a n d t o reacce le ra te i t t o o rb i t a l speed af ter l eav ing t h e a t m o s p h e r e a r e ca lcu la ted as func t ions of t h e change in inc l ina t ion , t h e l i f t -drag r a t io , a n d t h e e n t r y angle , a n d a r e c o m p a r e d w i t h t h e c h a r a c t e r i s t i c veloci t ies r equ i red for p u r e l y e x t r a a t m o s p h e r i c rocke t m a n e u v e r s . I n add i t i on , a e r o d y n a m i c h e a t i n g , acce le ra t ions , a n d t i m e t o c a r t y ou t t h e m a n e u v e r s a r e e s t i m a t e d .

Stagnation-Point Shock-Detachment Distance for Flow Around Spheres and Cylinders in Air

Abstract: This equation and the data are plotted in Fig. 1. Deviations between the equation and the data were computed and it was found that the average of the absolute magnitudes of the differences \X\ is 4.48 percent and the algebraic average X is 0.07 percent, with a standard deviation ax of 5.60 percent. Data for spheres from Refs. 1, 3, and 4 have been plotted in Fig. 2 along with Eq. (1) derived by Serbin, and it can be seen that the fit is not very good, particularly at the lower Mach numbers. An equation (also plotted in Fig. 2) tha t more accurately fits the data for spheres is

Propeller-Nacelle Whirl Flutter

Abstract: An analytical investigation is made of a heretofore unimportant flutter phenomenon that may occur in a propeller-nacellewing combination—a flutter condition which involves propeller and nacelle precession, and which has been of major concern recently. One of the objects of the investigation is to isolate and show the influence of those parameters which appear to be most strongly linked with this whirl-type instability. Considered, for example, are various combinations of pitch and yaw stiffnesses of the nacelle, structural damping, and propeller speed. To understand the behavior of the system better, the motion due to various initial disturbances is also studied for both subcritical and supercritical conditions. The results presented are derived by digital and analog means, the analog setup being used primarily for the motion studies. Part of the study is devoted to a further examination of the propeller aerodynamics. Finally, a comparison is made of analytically determined critical conditions with results obtained in some wind-tunnel tests.

The Homogeneous Boundary Layer at an Axisymmetric Stagnation Point With Large Rates of Injection

Abstract: This report presents a theoretical analysis of the boundary layer at an axisymmetric stagnation point with large rates of air injection. The results of a previous investigation indicated that for localized mass transfer in the stagnation region, the rates of injection are considerably greater than those usually treated. The exact stagnation-point boundary-layer equations are integrated numerically for an approximate representation of the gas properties. The two-point boundary conditions are treated in a new manner which is useful for various boundarylayer and mixing problems. The exact solutions indicate that for large rates of injection the boundary layer is closely represented by an inner isothermal shear flow and by an exterior, relatively thin region, in which the flow variables change to their free-stream values. An integral method based on profiles suggested by the exact solutions is developed and shown to lead to accurate predictions of the integral thicknesses which are of interest for a study of the downstream influence of the stagnation-point mass transfer.

The stability under axial compression and lateral pressure of circular-cylindrical shells with a soft elastic core.

Abstract: : The stability under axial compressionoion and lateral prpressure of a finite ciircular-cylindrical shell with an elastic core is treated by means of Donnell's equations. For lateral pressure it is found that a previous solution treating the cylinder as a ring or a long cylinder is adequate for a wide range of combinations of length-radius ratio, radius-thickness ratio, and ratio of moduli of core and cylinder. Results for axial compression are included for completeness and to correct a previous analysis of the same problem. (Author)

Stresses and Deformations of the Thin-Walled Pressurized Torus

Abstract: The thin-walled pressurized torus is an example of a configuration that cannot be treated properly by means of linear membrane theory. Though the stress distributions that result from this theory do not exhibit any irregularities themselves, they lead to deformations which are incompatible with the assumption of a continuous shell. The deformation incompatibilities are such that superficially they would seem to require the introduction of bending and shear stresses. If this suspicion were correct, as has been assumed previously, this would not only invalidate the physical concept of an ideal membrane but it would also lead to a more complicated torus analysis than appears to be warranted by the nature of the problem. Indeed, such an analysis seems never to have been performed. In the present paper the concept of an ideal membrane is revalidated by showing that an adequate nonlinear membrane solution exists. This membrane solution can be derived with relatively little numerical effort. Numerical results are given which demonstrate the required corrections to the results of linear membrane theory. As a side result, a lemma is derived concerning the invariance with respect to Poisson's ratio of certain deformations which arise as thin shells of revolution are pressurized.

Determination of Lift or Drag Programs to Minimize Re-Entry Heating

Abstract: A study of single-pass re-entry from escape speed and from circular satellite speed is made to determine the lift program for a hypersonic glider and the drag-modulation program for a nonlifting vehicle that minimize the heating of the vehicles within acceleration or range constraints. A new method of numerical solution is used, similar to Kelley's "method of gradients," that permits rapid convergence to the optimum lift program starting with an original good estimate. This method avoids the twopoint boundary-value problem of the calculus-of-variations formulation, and is applicable to any optimum-programing problem. An acceleration-tolerance limit is introduced which describes the human pilot's capability to withstand acceleration more accurately than a simple acceleration limit. at tack program, must be determined in order to minimize the total heat and satisfy the desired terminal constraints. The straightforward approach to solving such complicated problems has not met with any significant success, despite the fact t ha t the formulation is clear.7 Recently Kelley and the present authors developed, almost simultaneously, a "steepest descent" technique which is capable of solving such complicated variational problems in a practical way using highspeed digital computers. This technique is presented in the next section and then it is applied to the two problems described above.

Vibrations of a Rectangular Cantilever Plate

Abstract: A Fourier sine-series method is used to solve the differential equation, together with the boundary conditions, for the transverse vibrations of a thin rectangular cantilever plate. Frequencies of vibration and the corresponding nodal lines are calculated and plotted as functions of the ratio of sides for five symmetric and four antisymmetric modes. Because of the large number of calculations made, some interesting phenomena appear which have not previously been reported in the literature.

Radiating Effectiveness of Annular-Finned Space Radiators, Including Mutual Irradiation Between Radiators Elements

Abstract: The heat transfer characteristics of annular fin and tube radiators have been determined analytically. The complex interaction problem resulting from mutual irradiation between neighboring fins and between fins and the tube surface has been fully accounted for by applying a newly-devised contour-integral method for deriving the radiant interchange factors. The mathematical description of the simultaneous heat transport by conduction and radiation leads to a nonlinear integro-differential equation. This has been solved for a wide range of the pertinent physical parameters. The heat transfer from the fin-tube system has been calculated and is presented graphically in dimensionless form. The separate contributions to the total of the fin and of the tube are also shown. The results definitely indicate that the use of fins leads to a significant increase in heat transfer compared with the unfinned tube.

Axisymmetric Viscous Flow Past Very Slender Bodies of Revolution

Abstract: Axisymmetric viscous flow past unyawed very slender bodies of revolution is treated within the category of the perfect gas. Attention is paid especially to the effect of transverse curvature of the body. From the transformed equations, the similarity conditions are deduced, and the parameter characterizing the effect of transverse curvature is obtained. Several numerical solutions of similarity equations for hypersonic flows are presented, and upon the basis of these results, the effect of the transverse-curvature parameter is discussed. A method of applying the local-similarity approximation to obtain the approximate solution for nonsimilar cases is described, as are practical applications to incompressible flow past a long cylinder and to hypersonic flow past a very slender cone. Comparison with experimental results shows fair agreement with calculations using the local-similarity approximation in the present range of experimental flow conditions.

Calculation of Potential Flow About Bodies of Revolution Having Axes Perpendicular to the Free-Stream Direction

Abstract: A general method is described for calculating, with the aid of an electronic computer, the potential flow about arbitrary bodies of revolution whose axes are perpendicular to the free-stream direction. When combined with the solution for the axisymmetric flow about these bodies, this method makes it possible to calculate the pressure distribution on any body of revolution at angle of attack forward of any separated region of the flow, and also to calculate the flow at points off the body surface. After the basic equations of the method have been derived, its accuracy is exhibited by comparison with analytic solutions for ellipsoids of revolution. Calculated pressure distributions are then compared with experimental data for a variety of bodies. The agreement is quite satisfactory in all cases. The calculated velocities for other selected bodies are presented to exhibit certain properties of this type of flow.

Boundary-Layer Transition in the Presence of Streamwise Vortices

Abstract: Results of an experimental investigation of instability leading to transition in the subsonic boundary-layer flow along a flat plate are presented. A series of wings was placed outside the boundary layer to produce streamwise vortices, which in turn made the boundary layer three-dimensional—i.e., periodic in thickness in the spanwise direction. Hot-wire measurements were made to trace the downstream development of the disturbance or wave created by the vibrating ribbon. As the wave travels downstream, it is deformed into a three-dimensional configuration by the three-dimensionality of the boundary-layer flow, but it is eventually damped out so long as it remains small in intensity. I t is only after the wave intensity exceeds a certain amount (which depends on the degree of boundary-layer threedimensionality) that the nonlinear effect manifests itself by the rapid amplification of wave intensity, the rapid increase in wave three-dimensionality, and the distortion in mean velocity profile. The appearance of nonlinear development inevitably leads to the breakdown of laminar flow, and hence the onset of turbulence. There is present a mechanism by which the energy is transferred from one spanwise position to another so that the breakdown of laminar flow occurs as a consequence of three-dimensional development of the wave as a whole.

The downstream influence of mass transfer at the nose of a slender cone

Abstract: : The influence of localized mass transfer at the nose of a slender cone under hypersonic flow conditions was studied by experimental and theoretical means. Two gaseous coolants, nitrogen and helium are injected through a porous plug subtending a half angle of 30 degrees. The effect of the mass transfer on the shock shape, pressure distribution, heat transfer and transition are investigated. The theoretical analysis involved a study of the effect of mass transfer on the shock stand-off distance and leads to an inviscid flow parameter permitting the experimentally determined shock shape and pressure distribution to be extrapolated to other than test conditions and to other coolant gases. Significant reductions in heat transfer are obtained with injection. Indeed with small amounts of helium injection the peak heating is found to occur downstream on the cone and to be an order of magnitude less than would occur at the stagnation point without mass transfer. With nitrogen early transition is found to occur so that local heating rates are actually increased over those prevailing at the same Reynolds number without injection.

Modified Crocco-Lees Mixing Theory for Supersonic Separated and Reattaching Flows

Abstract: Re-examination of the Crocco-Lees method has shown that the previous quantitative disagreement between theory and experiment in the region of flow up to separation was caused primarily by the improper C(K) relation assumed. A new C(K) correlation, based on low-speed theoretical and experimental data and on supersonic experimental results, has been developed and found to be satisfactory for accurate calculation of two-dimensional laminar super sonic flows up to separation. A study of separated and reattaching regions of flow has led to a physical model which incorporates the concept of the "dividing" streamline and the results of experiment. According to this physical model, viscous momentum transport is the essential mechanism in the zone between separation and the beginning of reattachment, while the reattachment process is, on the contrary, an essentially inviscid process. This physical model has been translated into Crocco-Lees language using a semi-empirical approach, and approximate C(K) and F(K) relations have been determined for the separated and reattaching regions. The results of this analysis have been applied to the problem of shock wave-laminar boundary layer interaction, and satisfactory quantitative agreement with experiment has been achieved.

Compressive Stability of Orthotropic Cylinders

Abstract: By utilizing linear stability theory, solutions for elastic buckling of short and moderate length orthotropic cylinders under axial compression are presented for the axisymmetric and asymmetric modes. The plastic buckling of short and moderate length isotropic cylinders is then investigated in considerable detail and the theoretical results are correlated with available experimental data. Plastic buckling of orthotropic cylinders is also treated. Finally, a discussion of the effects of finite deflections and initial imperfections is presented.