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Author: John F. Lennon Publisher: ISBN: Category : Plasma sheaths Languages : en Pages : 86
Book Description
The properties of the reentry plasma sheath are being studied by AFCRL in a series of Trailblazer II rocket flights. This program is divided into two phases. The first phase has been concerned with the structure of the ionized layer that forms around the test vehicles during reentry and in particular its effect on electromagnetic signals, while the second phase is concerned with enhancing microwave transmitter performance under such conditions by introducing chemicals into the flow to reduce the free electron concentrations. This report surveys some aspects of the first phase which consisted of three flights. The first part of the report describes the flight performance of the vehicles including trajectory, velocity history, aerodynamic heating, spin-and-precession, and overall orientation of each payload during its reentry, while the second part presents a theoretical description of the high temperature shock layer for the various flight conditions. Since the purpose of the calculations was to obtain predictions of experimental performance, a number of different models were used. The resulting flow properties are presented in some detail; in particular, the various electron density distributions are shown both in the nose region and around the vehicle. These results are analyzed and then compared with the extensive experimental data. On the conical afterbody where three-dimensional effects due to vehicle angle of attack become important, the observed conditions could not be completely represented by the theoretical models--all of which assumed the flow to be axisymmetric. The general conclusion, however, is that the theoretical properties satisfactorily predict the actual test performance for a wide range of situations. (Author).
Author: John F. Lennon Publisher: ISBN: Category : Plasma sheaths Languages : en Pages : 86
Book Description
The properties of the reentry plasma sheath are being studied by AFCRL in a series of Trailblazer II rocket flights. This program is divided into two phases. The first phase has been concerned with the structure of the ionized layer that forms around the test vehicles during reentry and in particular its effect on electromagnetic signals, while the second phase is concerned with enhancing microwave transmitter performance under such conditions by introducing chemicals into the flow to reduce the free electron concentrations. This report surveys some aspects of the first phase which consisted of three flights. The first part of the report describes the flight performance of the vehicles including trajectory, velocity history, aerodynamic heating, spin-and-precession, and overall orientation of each payload during its reentry, while the second part presents a theoretical description of the high temperature shock layer for the various flight conditions. Since the purpose of the calculations was to obtain predictions of experimental performance, a number of different models were used. The resulting flow properties are presented in some detail; in particular, the various electron density distributions are shown both in the nose region and around the vehicle. These results are analyzed and then compared with the extensive experimental data. On the conical afterbody where three-dimensional effects due to vehicle angle of attack become important, the observed conditions could not be completely represented by the theoretical models--all of which assumed the flow to be axisymmetric. The general conclusion, however, is that the theoretical properties satisfactorily predict the actual test performance for a wide range of situations. (Author).
Author: J. Leon Poirier Publisher: ISBN: Category : Antenna radiation patterns Languages : en Pages : 82
Book Description
A Trailblazer II rocket was launched on 18 June 1967 from the NASA wallops Island (Va.) Rocket Test Facility to study the properties of the reentry plasma sheath and its effects on microwave antenna performance. The reentry payload consisted of three major subsystems: a plasma diagnostic system, an S- band transponder system, and an X-band telemetry system. The flight data yielded (1) measurements of the influence of the plasma on the radiation pattern distortion, signal attenuation, and impedance mismatch for an S-band slot antenna located at the stagnation point of the nose cone; (2) measurements of the plasma sheath effects on the interantenna coupling between two S-band antennas on the nose cone; and (3) determinations of the electron density profile and gradients in the boundary layer about the nose cone.
Author: J. Leon Poirier Publisher: ISBN: Category : Antenna radiation patterns Languages : en Pages : 0
Book Description
A Trailblazer II rocket was launched on 18 June 1967 from the NASA wallops Island (Va.) Rocket Test Facility to study the properties of the reentry plasma sheath and its effects on microwave antenna performance. The reentry payload consisted of three major subsystems: a plasma diagnostic system, an S- band transponder system, and an X-band telemetry system. The flight data yielded (1) measurements of the influence of the plasma on the radiation pattern distortion, signal attenuation, and impedance mismatch for an S-band slot antenna located at the stagnation point of the nose cone; (2) measurements of the plasma sheath effects on the interantenna coupling between two S-band antennas on the nose cone; and (3) determinations of the electron density profile and gradients in the boundary layer about the nose cone.
Author: Publisher: ISBN: Category : Languages : en Pages : 75
Book Description
A Trailblazer II rocket was launched on 18 June 1967 from the NASA wallops Island (Va.) Rocket Test Facility to study the properties of the reentry plasma sheath and its effects on microwave antenna performance. The reentry payload consisted of three major subsystems: a plasma diagnostic system, an S- band transponder system, and an X-band telemetry system. The flight data yielded (1) measurements of the influence of the plasma on the radiation pattern distortion, signal attenuation, and impedance mismatch for an S-band slot antenna located at the stagnation point of the nose cone; (2) measurements of the plasma sheath effects on the interantenna coupling between two S-band antennas on the nose cone; and (3) determinations of the electron density profile and gradients in the boundary layer about the nose cone.
Author: Dallas T. Hayes Publisher: ISBN: Category : Ablation (Aerothermodynamics) Languages : en Pages : 84
Book Description
To develop alternative solutions to Air Force problems relating to signal transmission in the presence of ionization, AFCRL undertook an extensive investigation of techniques for modifying reentry plasmas. The program included laboratory tests and a series of reentry flight experiments. This report describes the flight test of one successful technique, Teflon ablation, a passive approach that requires no internal support systems. A reentry vehicle fitted with a Teflon-coated nosecap was instrumented to measure antenna impedance mismatch, interantenna coupling, signal attenuation, and charged-particle density. The probe data showed that the local boundary-layer electron density decreased by as much as a factor of 200. The Teflon coating effected a 25-dB decrease in S-band signal attenuation. High-power antenna breakdown was modified by the presence of the ablation products. Details of the vehicle design, flight dynamics, and ablation, are presented, and the results of the Teflon-ablation technique are contrasted with those of a successful liquid-injection technique that was tested on a previous flight.
Author: John F. Lennon Publisher: ISBN: Category : Fluorohydrocarbons Languages : en Pages : 52
Book Description
The effect of injecting an electrophilic liquid into the ionized flow field surrounding a reentry vehicle was observed during the flight of a trailblazer 2 on 28 July 1972. The report describes the rationale used to initially screen candidate additives and the experimental evaluation that finally resulted in the selection of Freon 114B2 for operational use. Injection system design and preliminary testing are discussed, and the predicted and actual performance during flight are compared. Data from on-board antennas and electrostatic probes confirmed that the additive reduced the electron density and improved transmission. A number of factors characterizing the injection are presented as a basis for analyzing the flow-additive interaction. (Author).
Author: J. Spencer Rochefort Publisher: ISBN: Category : Plasma sheaths Languages : en Pages : 76
Book Description
Two Trailblazer II rockets were launched at Wallops Island, Virginia, to study the properties of the shock-ionized flow field and its effects on microwave radiation. Description of the apparatus carried by the two vehicles is presented in this report. The instrumentation to measure the flow field during reentry included such diagnostic sensors as electrostatic probes, stripline probe and a conductivity probe. S-band microwave systems were employed to determine plasma effects on antennas. The measurements included phase and magnitude of the reflection coefficient, variations in mutual coupling between two on board antennas and transmitted signal attenuation. A pulsed liquid injection apparatus was used to perform a plasma alleviation experiment. Performance of the instrumentation and general results obtained from unprocessed data are discussed.
Author: John F. Lennon Publisher: ISBN: Category : Breakdown (Electricity) Languages : en Pages : 58
Book Description
This is one of a series of reports on the Trailblazer II program. The particular aspect treated here involves the unmodified expansion-region plasma and its effect on an antenna located on the vehicle shoulder. This report describes some of the theoretical approaches used, discusses the levels of approximation involved, and shows the agreement between these various methods and the test data. The failure of a single set of assumptions to yield consistent agreement over a range of altitudes confirms the need to adopt flow models appropriate to the changing regimes encountered during reentry. One significant conclusion is that performance characteristics such as reflection and interantenna coupling which depend mostly on the level of peak electron density can be represented by simple plane wave, as well as by the more sophisticated slot antenna models. The latter approach, however, is necessary to describe propagation across the entire plasma sheath.
Author: J. L. Poirier Publisher: ISBN: Category : Plasma sheaths Languages : en Pages : 32
Book Description
A simple method of simulating the variation in the amplitude of microwave signals from rocket-borne transmitters is presented. The technique reproduces signal changes caused by vehicle motion as well as those induced by plasma effects. The simulator uses a voltage controlled attenuator which is programmed to vary the output power of a test transmitter to produce the variations in signal amplitude which would be observed during a flight. An analog system which is suitable for variations of simple cyclical shape and a digital simulator which can reproduce changes of any complexity are presented. Use of the simulator before flight allows the dynamic behavior of a microwave link to be determined, permits optimum receiver and recorder parameters to be selected, increases operator confidence, and enhances flight test reliability. (Author).
Author: John F. Lennon
Author: John F. Lennon
Author: J. Leon Poirier
Author: J. Leon Poirier
Author: 
Author: Dallas T. Hayes
Author: John F. Lennon
Author: J. Spencer Rochefort
Author: John F. Lennon
Author: J. L. Poirier
Author: