Effects of the Reentry Plasma Sheath on Microwave Antenna Performance PDF Download
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Author: J. Leon Poirier
Publisher:
ISBN:
Category : Antenna radiation patterns
Languages : en
Pages : 82
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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 : 82
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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
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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
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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
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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 : Breakdown (Electricity)
Languages : en
Pages : 58
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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: Nicholas V. Karas
Publisher:
ISBN:
Category : Electron distribution
Languages : en
Pages : 62
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Book Description
The microstrip plasma probe, a new diagnostic tool for use in the investigation of ionized media, has been developed and successfully tested both in the laboratory and in an actual flight. It is flush mounted (therefore causes no aerodynamic disturbances); simple in geometric shape (therefore can be modified to fit curved surfaces and ruggedized to withstand shock and vibration); only a fraction of the operating wavelength in length (therefore saves on payload space); and operates with low power (therefore does not disturb the plasma which it is measuring). Experimental results, obtained from both the laboratory and from an actual flight, have been compared to theory and to experimental data from other probes. In both instances the results are close.
Author: John F. Lennon
Publisher:
ISBN:
Category : Plasma sheaths
Languages : en
Pages : 86
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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 : Microwave antennas
Languages : en
Pages : 46
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Book Description
The purpose of the third AFCRL Trailblazer II reentry vehicle flight was to study the effects of shock ionized air on the performance of a microwave antenna system located in the expansion region of the nose cone. The system consisted of a pair of cavity-backed circumferential slot antennas mounted one behind the other on the conical afterbody of the reentry vehicle. During reentry, measurements of antenna impedance mismatch, interantenna coupling, signal attenuation and antenna pattern distortion were made. The data have been compared with computed values and found to be in good agreement. This experiment thus establishes the validity of the various microwave and flow field models and calculations used to obtain the theoretical values in the shoulder region of the reentry body. These results will now serve as a standard against which to compare the properties of various chemical alleviants which are being studied in other flights. (Author).
Author: Nicholas V. Karas
Publisher:
ISBN:
Category : Afterglow (Physics)
Languages : en
Pages : 60
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Book Description
Experimental data resulting from an investigation of the electroacoustic probe in an argon afterglow plasma for a planar geometry indicates the value of the probe as a diagnostic tool. It is suited to airborne payloads because of its small size and rugged construction. In carrying out the study, some of the parameters that were varied were the pressure (range = 100 to 1000 micro m), input power to the probe (range = 40 dB), and frequency of input signal (350 to 600 MHz). The effect of changing physical dimensions of the probe was also considered. Electroacoustic probe predictions of the electron density gradients close to a surface were found to compare closely with the electron density gradients obtained with a floating double Langmuir probe. Treating the electroacoustic probe as similar to a resonant circuit produced some preliminary results that show up as familiar Q values. Both linear and nonlinear responses of the electroacoustic probe are illustrated. One nonlinear phenomenon--induced oscillations in sections of the resonance curve--is discussed in detail. (Author).
Author: John F. Lennon
Publisher:
ISBN:
Category : Fluorohydrocarbons
Languages : en
Pages : 52
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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).
