Engineering topics

Allen, H. Julian

Publications and source records attributed to Allen, H. Julian.

5 records

NASA NTRS1960

Problems in Atmosphere Entry from Parabolic Orbits

Up to the present time we have been concerned with sending small instrumented probes into interplanetary space and larger bodies into near-earth satellite orbits. Only recently we have begun to recover intact some of these orbiting bodies and soon we will carry on this program to the recovery of manned satellites. In the not-too-distant future we will be concerned with transit to and from the moon and the planets. It is with the problems of entry into our atmosphere of these higher speed vehicles that this paper will be concerned.

Allen, H. Julian↗

NASA NTRS1953

A Study of the Motion and Aerodynamic Heating of Missiles Entering the Earth's Atmosphere at High Supersonic Speeds

A simplified analysis is made of the velocity and deceleration history of missiles entering the earth's atmosphere at high supersonic speeds. It is found that, in general, the gravity force is negligible compared to the aerodynamic drag force and, hence, that the trajectory is essentially a straight line. A constant drag coefficient and an exponential variation of density with altitude are assumed and generalized curves for the variation of missile speed and deceleration with altitude are obtained. A curious finding is that the maximum deceleration is independent of physical characteristics of a missile (e.g., mass, size, and drag coefficient) and is determined only by entry speed and flight-path angle, provided this deceleration occurs before impact. This provision is satisfied by missiles presently of more usual interest.

Allen, H. Julian↗

NASA NTRS1947

A Theory of Unstaggered Airfoil Cascades in Compressible Flow

By use of the methods of thin airfoil theory, which include effects of compressibility, rela.tio^as are developed which permit the rapid determination of the pressure distribution over an unstaggered cascade of airfoils of a given profile, and the determination of the profile shape necessary to yield a given pressure distribution for small chord gap ratios, For incompressible flow the results of the theory are compared with available examples obtained by the more exact method of conformal transformation. Although the theory is developed for small chord/gap ratios, these comparisons show that it may be extended to chord/gap ratios of order unity, at least for low speed flows. Choking of cascades, a phenomenon of particular importance in compressor design, is considered.

Spurr, Robert A.↗

NASA NTRS1945

An Experimental Investigation of Several Low-Drag Wing-Nacelle Combinations with Internal Air Flow

The results of an experimental investigation of several low-drag wing-nacelle combinations, incorporating internal air-flow systems, are presented. The external-drag increments due to these nacelles are between one-half and two-thirds of those of conventional nacelle forms. This improvement is accomplished with only minor effects on the lift and moment characteristics of the wing. The procedure employed to determine the external shape of such low-drag nacelles is considered in detail. The design of an efficient internal-flow system with or without a blower or throttle, presents no serious problems. The energy losses in the expansion before the engine and the contraction thereafter can be kept small. It is believed that these nacelles have a wide application in housing engine pusher-propeller units and, with some alteration, jet-propulsion devices. It is probable that the low external drags may not be realized if such nacelles are used with a tractor propeller because of the high level of turbulence in the propeller slipstream.

Allen, H. Julian↗

NASA NTRS1943

The Effect of Compressibility on the Growth of the Laminar Boundary Layer on Low-Drag Wings and Bodies

The development of the laminar boundary layer in a compressible fluid is considered. Formulas are given for determining the boundary-layer thickness and the ratio of the boundary-layer Reynolds number to the body Reynolds number for airfoils and bodies of revolution. It i s shown that the effect of compressibility will profoundly alter the Reynolds number corresponding to the upper limit of the range of the low-drag coefficients . The available data indicate that for low-drag and high critical compressibility speed airfoils and bodies of revolution, this effect is favorable.

Allen, H. Julian↗