AD-2 1 3749N2 AD-261 375Div. 1U (16 Aug 61) OTS price $1.00 National Aeronautics and Space Administr tion, Washington, D.C. SOUND PRESSURES AND CORRELATION OF NOISE ON THE FUSELAGE OF A JET AIRCRAFT IN FLIGHT, by Russell D. Shattuck. Aug 61, 32p. incl. illus. tables (NASA technical note no. D-1086) Unclassified reportAlso available from NASA, Wash. 25, D.C., as NASA Technical note D-1086. DESCRIPTORS: *Jet plane oi, Fus lages, Pressure, Flight testing, Boundary layer, *Jet engine noise, Flight, Velocity, Jet bombers, Acoustics, Microphones, Sound, Jet planes, Measurement. Open-ended Terms: B-57. T s r co uc l itu es of 10,000, 20,000, and 30,000 feet at speeds of Mach 0.4, 0.6, and 0.8. It was found that the sound pressure levels on the aft fuselage of a jet aircraft in flight can be estimated using an equation involving the tru airsp d an th fr e air d n ity. The cross-correlation coefficient over a spacing of 2.5 feet was generalized with Strouhal number. The spectrum of the noise in flight is comparatively flat up to 10,000 cycles per second. (Author).

While it is common knowledge that ion beams are easily neutralized using a variety of means, the precise process of neutralization remains unknown. With the increasing popularity of electric propulsion, and in particular micropropulsion systems, this question is of significant importance. Additionally, it has a bearing on thruster design, space instrument calibration, electrodynamic tethers, and ionospheric research. A review of the present state of knowledge on this topic is presented as well as results from ion beam simulations using 2D and 3D Particle-in-Cell codes. The grid generation methodology, adaptation, charged-particle transport, and field solver methodologies of the 3D code are reviewed. The simulations show electrons moving to neutralize the ion beam from background and neutralizer sources. The simulations show the dependence of neutralization on beam energy and the electron/ion velocity ratio. The results are compared favorably with previous computations and experimental observations.

Throughout most of the twentieth century, electric propulsion was considered the technology of the future. Now, the future has arrived. This important new book explains the fundamentals of electric propulsion for spacecraft and describes in detail the physics and characteristics of the two major electric thrusters in use today, ion and Hall thrusters. The authors provide an introduction to plasma physics in order to allow readers to understand the models and derivations used in determining electric thruster performance. They then go on to present detailed explanations of: Thruster principles Ion thruster plasma generators and accelerator grids Hollow cathodes Hall thrusters Ion and Hall thruster plumes Flight ion and Hall thrusters Based largely on research and development performed at the Jet Propulsion Laboratory (JPL) and complemented with scores of tables, figures, homework problems, and references, Fundamentals of Electric Propulsion: Ion and Hall Thrusters is an indispensable textbook for advanced undergraduate and graduate students who are preparing to enter the aerospace industry. It also serves as an equally valuable resource for professional engineers already at work in the field.