A simulator is described which generates and transmits a beam of audible sound energy mathematically similar to the solar power satellite (SPS) power beam. The simulator provides a laboratory means for analysis of ground based closed loop SPS phase control and of ionospheric effects on the SPS microwave power beam

Ott, J. H.

Rice, J. S.

English

NASA Technical Reports Server

A POWER SATELLITE SONIC SIMULATOR
James H. Ott and James S. Rice
Novar E]ectr0nics Corporation, Barberton, Ohio
N82'
ABSTRACT
A simulator is described which generates and transmits a beam of audible
sound energy mathematically similar to the SPS power beam. The simulator
provides a laboratory means for analysis of ground based closed loop SPS
phase contro] and of ionospheric effects on the SPS microwave power beam.
INTRODUCTION
Novar Electronics Corporation has built and is currently testing a
Satellite Power System Microwave Transmission Simulator. In a ground based
laboratory environment, the simulator generates and transmits a beam of
audible sound energy which is mathematically similar to the microwave beam
which would transmit energy to earth from a Solar Power Satelllte.
SIMULATOR DESCRIPTION
Figure I shows the major functional parts of the simulator. The Sonic
Spacetenna (Figure 2) is 1.3 meters in diameter and contains 3200 Independent
transmitting elements. These elen_nts are connected in a 64 row by 64 coi_n
matrix. Each column is driven by a driver which multiplexes each of the 64
rows 32,000 times per second. This enables the simulator's computer to
control the amplitude, phase, and frequency of each of the 3200 transducers.
The simulator is designed to transmit a coherent sonic power beam at 12 kHz.
Any illumination taper, e.g., Gaussian, can be programmed and the resultant
ground pattern studied. A computer, _ Memory, 300 MB disc drive, and
line printer are incorporated to provide a very high degree of experimental
flexlbility.
SIMULATOR CAPABILITIES
A unique feature of Novar's Sonic Simulator ls its ability to provide
actual photographs of the transmitted power beam. Figure 3 shows a scanning
system which provides an intensity modulated raster of the sonic beam. By
adding a phase signal to the intensity modulator, the phase coherence can
also be photographe_. This technique, developed at Bel! Labs in the early
]950's 1, will provide photographic records similar to Figure 4.
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The Sonic Simulator is current]y being used to generate collimated co-
herent sonic beams to verify that the beam divergence and sideIobe character-
istics are in satisfactory agreement with the aperture lIiuminatlon equations
which have been used to define the SPS microwave beam.
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FIGURE 1
SONIC SPS PHASE CONTROL SIMULATOR
MAJOR FUNCTIONAL BLOCKS
The concept of "ground based" phase control implies a closed loop phase
control system which makes corrections In deviations in SPS beam pointing and
focusing from ground based measurements of the received power beam. In other
words, ground based phase control is a servo control system which like any
servo system has a measureable transfer function, frequency response, step
response, noise factor, resolution, loop stablllty, etc. Novar is using Its
interferometer phase contro] technique to focus and point the sound beam 2. The
open and closed loop characteristics of the Sonic Simulator will be measured.
A descriptive servo loop diagram and transfer function wi]i be developed and
all measured characteristics will be tested for agreement with control system
theory. The next step will then be to analyze and mitigate the effects of
unwanted interfering inputs such as air currents in the laboratory and the
reflection of the sonic beam off.wails.
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The Sonic Simulator can be readily forced to deal with the same noise
characteristicsas the ior_sphere would introduce into the real world SPS
phase control system, This would be accomplished by altering the propagation
of the simulator's sonic beam through the use of sculptured reflecting sur-
faces and controlled air turbulence.
Ionospheric effects will impact an SPS Phase Control System similar to
the way that noise and offset error impact any closed loop servo system.
Therefore, conventional control system synthesis techniques should be able to
reduce SPS phase control errors due to ionospheric effects.
Ayalytical techniques will be developed to permit the validation of these
sonic propagation models against measured'ionospheric parameters. This would,
for example, lead to thequantitative correlation of ionospheric electron
density patterns with the sound reflecting surfaceis roughness and placement.
I
FIGURE 2
SONIC SPACETENNA
FIGURE 3
PHOTOGRAPHIC SCANNING SYSTEM
A precision mechanical scanning system provides an
actual photograph of the sonic beam• The camera
lens remllns open In a darkened room while the sound-
to-light modulator (device being pointed at) provides .
a light output proportional to the Intensity of the
sonic beach. The modulator is scanned up and down
and for_iErd and backward to provide a photograph of"
a cross section of the beam.
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FIGURE 4
REPRESENTATIVE PHOTOGRAPH OF A
MECHANICALLY SCANNED SONIC BEAM
(Be]] System Technical Journal,
1951 .)
CONCLUSIONS
It is expected that a number of concl.usions can be provided regarding
the applicability of the sonic simulation technique to the future development
of the SPS power transmission system. If'conclusions are favorable, we
would expect that the sonic simulator will provide a low cost alternative to
many of the time consuming orbiting satellite experiments that would other-
wise be necessary.
REFERENCES
I ° W. E. Kock and F. K. Harvey, "A Photographic Method for Displaying Sound
Waves and Microwave Space Patterns," Bell System Technical Journal, Voi.
30, July 1951, pp. 564-587.
. J. H. Ott and J. S. Rice: "Digital SPS Phase Control Using Traveling
Wave Interferometry" Novar Electronics Corporation Technical Report,
October, 1978.
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296


A power satellite sonic simulator

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