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• Document Type: FOIA
• Collection: FOIA Collection
• Document Number (FOIA) /ESDN (CREST): 05752619
• Release Decision: RIPPUB
• Original Classification: U
• Document Page Count: 5
• Document Creation Date: March 9, 2023
• Document Release Date: February 10, 2021
• Case Number: F-2011-01575

Approved for Release: 2021/01/13 C05752619 CONTROL NO. 114
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Induced Magnetic Moment: It is well known that a body, when placed in an
external magnetic field, will have an induced magnetic moment caused by the external
field. The technique used in the variable-mu detection system is composed of two
parts: 1) the generation of an "artificial" magnetic moment in the target by creating
an external field, and 2) the detection of the field produced by this induced moment.
Phase Detection: The heart of the variable-mu system is the active field
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source ( coi I ) which introduces a magnetic dipole field at a discrete frequency, and
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a high frequency variable-mu magnetometer. With the use of coherent detection
techniques, it is apparent that a number of target effects cannot be explained by a
change in magnitude of magnetic field. Thus, in some manner, the target appears to
the sensor as not only a magnitude change of the induced field, but also as a change
in phase of this field as referenced to the coil field. The introduction of phase
changes (time delay) by ferromagnetic material is treated by Richard M. Bozorth
('Ferromagnetism," D. Van Nostrand Co., Inc., 1951), but the sum knowledge of
this effect is not sufficient to use phase detection as a means of target identification
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Experimental Models:
The extent of the work to date is such that equipment for an experimental
model of the detection system can be fabricated and installed in a light plane for
basic testing. The tests to be performed with this first flyable system are critical
and will dictate the design of a prototype system.
Mechanical Rigidity: The prime objective of the initial tests will be to
determine the mechanical rigidity required for successful operation. The basic
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electronics of the system is now capable of eliminating a large portion of the noise
problems generated by plane vibration. However, the problems associated with flying
such a system will not become apparent until flight tests are made.
Electronic Design: Most of the electronics has been designed for an experi-
mental model. For a flyable system, however, design sophistication will be required
in order to improve the operational reliability and to simplify the system operation.
System Geometry: Much of the work which will yield optimum sensitivity
patterns will be done in the laboratory. These results must be translated into a design
capable of operation in rather limited available space. For the experimental model,
provisions will be made for making small geometry changes so that optimum sensitivity
patterns can be obtained while in flight.
Prototype Model:
The work done on the prototype model will reflect the results of the laboratory
and experimental studies. The initial task will be to study the aircraft to be provided
by the customer so that the design of the experimental models will be compatible with
the environment with which it will interface and in which it will operate. This will
permit the fabrication of a prototype with a minimum of redesign.
The prototype will be installed in the aircraft provided by the customer. Data
readout and displays will be designed to meet the customer's requirements and will be
provided as a part of the prototype.
Technical Program:
The tasks to be performed will be aimed at the ultimate objective of fabricating
a magnetic variable-mu sensor and detection techniques recently developed at The
Electro-Mechanics Company.
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Emphasis will be placed on the electronic design and fabrication, the opti-
mization and fabrication of the system geometry, and on field and flight tests for the
system evaluation.
The emphasis on electronic design and fabrication will be primarily concerned
with upgrading the existing instrumentation, designing the system to operate on air-
craft power, and designing data readout and display systems.
The optimization of the system geometry will require a theoretical study of
the sensitivity patterns of the coil and sensor. This work will be completed as soon
as possible by using computer techniques for the analysis. The results of this study
will be examined in field tests.
The field and flight tests will be emphasized throughout the work period.
Aside from determining the sensitivity patterns and the optimum geometry of the
system, work is required on structural design problems inherent in fabricating an
airborne system.
The tasks to be completed include the following:
1.
2. System geometry optimization:
a. theoretical studies, and
b. laboratory and field tests,
3. Synchronous detector design and fabrication,
4. Power available and required,
5. Structural design,
6. Flight and field tests,
7. Prototype design and fabrication, and
8. Data readout design.
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