a superior grade of chemicals which now are called "semiconductor grade," with greater purity than the previous chemi­cally pure materials available. The in­dustry can bé proud of that.

One might very well ask whether there are any problems still unsolved in the technology of preparing silicon for semi­conducting devices. The answer is that during the last few years, considerable effort has been concentrated on what is considered to be the last major problem to be licked before silicon is considered a

-foolproof and readily manufacturable ma­terial.

A troublesome characteristic of silicon persisted until very recently in that when the silicon is heated to elevated tempera­tures during the manufacturing process of a device, it loses minority carrier life­time—a valuable electrical property. The minority carrier lifetime indicates the distance an electron travels in the material before becoming trapped by an atom. This reduced lifetime has the effect of diminishing the amount of current that a transistor can handle inasmuch as the current is lost in transit through the device.

This deficiency in silicon has been par­tially circumvented in various ways by alternate device technologies but the ab­solute maximum of utilization of silicon still requires that the lifetime problem be solved. Significant breakthroughs in this field have appeared. It now is assumed that with continued effort one will be able to say that silicon in all of its properties is under control, and can be made by pro­duction methods to fulfill the most ex­acting requirements of any device. Thus, the requirements for a nearly ideal semiconducting material are reaching fulfillment.

Tremendous progress has been made out all problems are not solved. The full potential of silicon has not yet been realized and there are challenging prob­lems ahead. Scientific research in the

Hughes Aircraft Company Photo

HOT RIDE on moving belt through electric heating coil of partly assembled semicon­ductors insures good electrical connections in the tiny devices, which replace conventional vacuum tubes in electronic circuits.

fast-growing semiconductor industry has been intensified to such a degree that, at least in the previously mentioned case, an important new product has been intro­duced to volume production within six months after its conception.

Dr. D. M. Van Winkle, head of semi­conductor research and development for Hughes Aircraft Company, Culver City, Calif., told a press conference recently that "we cannot afford to spend years in a laboratory to come up with a new product." He cited the case of a fast re­covery silicon diode now in heavy produc­tion at the company's Los Angeles plant.

About two years ago, it was determined that there was a growing need for just such a device in the company product line. The firm's laboratory was put to work and, within six months customers were offered the newly developed diode to use.

Dr. Van Winkle told business, financial, and trade writers that so rapid have been technical developments in silicon diodes, transistors, and rectifiers that a whole new line of these tiny products has been made available to industry in less than 4 years.

During this period of remarkable

THE SUPERSONIC B-58 "Hustler"-the world's fastest bomber—was developed for the U.S. Air Force for the primary mis­sion of bombing and reconnaissance by the Fort Worth, Texas, plant of the Convair Division of General Dynamics Corporation.

The needle-like fuselage, supported by a triangular wing and driven by four turbojet engines, carries beneath it an equally slim disposable pod that can be a devastating bomb, a battery of cameras, or a container for electronic counter-measures.

Virtually an automatic airplane, the Hustler requires only a three-man crew; pilot, navigator-bombardier, and defen­sive systems operator. It is capable of altitudes and speeds (Mach 2) far beyond those of any bomber now in existence.

Although performance details are classified, it has been revealed that it pro­vides a greater gain in top-speed advan­tage over the latest operational bomber than that bomber had over the Wright brothers' airplane!

Control System Development

The problem of controlling supersonic flight was begun in 1949 under a U.S. Air Force research contract by Bendix Avi­ation Corporation's Eclipse-Pioneer Divi­sion, Teterboro, N.J., to explore the possi­bilities of a system that would make possible manned flight at about three times the speed of anything then in the air.

The objective was a fligh» control sys­tem that would control an airplane under all flight conditions. These included com­binations of low and high altitude, sub­sonic, transonic, and supersonic speeds:

growth, scientific advancements demanded by the industry of its suppliers have had far-reaching effects in the metallurgical, chemical, and pharmaceutical fields, as previously mentioned.

Dr. Van Winkle disclosed that a pro gram to obtain higher purity quartz from which to make crucibles was under­taken and that its success led to the present high-volume production of sili­con semiconductor devices. A goodly amount of credit is due the efforts of Hughes Research Laboratories.

To a great extent they have been pio­neers in a new frontier of science tech­nology and, as a consequence and with the tremendous efforts of manufacturing technological personnel, have produced more silicon semiconductor devices than any other company in the world and silicon applications are its most impor tant products.

Laboratories are working on still more advanced products, utilizing still more advanced basic materials, and developing still more advanced techniques for still more advanced semiconductor applica­tion in industry, in the military, as well as in the home.

changes in gross weight and location ot center of gravity, and the presence or absence of an external "pod" such as the Hustler carries. The system must provide the pilot with the means for controlling the airplane manually under all condi tions and at the same time, give him maximum performance capabilities.

The system must prevent the pilot from causing maneuvers beyond the. structural limitations of the plant, provide stability augmentation, control-stick steering, atti

PLANE PLOTTERS flight-test the world's fastest "pilot," or automatic control system at the Eclipse-Pioneer Division plant, Bendix Avia­tion Corporation. The engineers in the analog-computer facility are connected by headsets to a laboratory mock-up of the Hustler.

Control System for B-58 Supersonic Reconnaissance Bomber

464 Of Current Interest ELECTRICAL ENGINEERING

AIR RAMS equipment has been put together just to simulate mechani­cally the forces exerted by air on the control surfaces of the supersonic B-58 Hustler bomber. The row of hydraulic actuators slams a force of 240,000 pounds per square inch against the trailing edge of the wing (left above). The enormous external force must be overcome by the Hustler's automatic "power thinking" control system. Engineers of the Eclipse-Pioneer Division, Bendix Aviation Corporation, have "flown" the supersonic jet thousands of hours on the flight control test rig shown.

POWER-THINKING STEERING is done by Bendix Aviation Corporation engineer who holds the stick of the automatic control system developed by the company's Eclipse-Pioneer division for the supersonic B-58 Hustler. The stick is connected through a unique linkage system that will facilitate a further step into space in manned aircraft by trans­lating motions of the stick through its electronically and hydraulically actuated circuits into delicate control-surface motions adjusted to vary­ing flight conditions.

tude or altitude hoW, Mach hold, head­ing hold, automatic approach, station-keeping, and similar functions.

Control System Elements The control system consists essentially

of three parts: sensing, computing, and actuation. Sensing includes the measuring of all data, or "inputs." These inputs come from the pilot controls and switches, airplane attitude reference system, head­ing and navigation data, radio guidance for range and approach, altitude and speed data from the air data system, body rates and accelerations, actuatoi posi­tions and velocities, and similar informa­tion.

This sensed input information, is translated into mechanical motion and control of the airplane through the am­plifier computer, power control linkage assembly, and surface actuation system interconnected systems.

Amplifier Computer

The amplifier computer is the "brain" of the Hustler flight-control system. Within a volume of 2.2 cubic feet (com parable in size and shape to a "two-suiter" traveling bag) are packed 140 transistors, more than 2,000 resistors and capacitors, three miles of wire and 10 electromechanical units containing 14 mo­tors, 60 potentiometers, 15 synchros, and gearing with ratios varying from 900:1 to 1,235,000:1. In this unit the "commands" or signals that control the airplane are computed and distributed to other parts of the over-all control system.

Built into the amplifier computer is a "G"—limiting feature that automatically prevents either the automatic pilot or the human pilot from "commanding" a ma­

neuver that exceeds the structural limita tions of the Hustler. This is an essential aspect of supersonic flight, because a violent maneuver could disintegrate the plane. The system also permits automatic control of speed to achieve the best fuel economy (Constant Mach Mode).

Once the B-58 is airborne, the pilot can maneuver to any desired altitude and speed and smoothly engage the auto­matic pilot. In addition, the pilot may maneuver the Hustler through the con­trol stick without disengaging the auto­pilot. In this maneuver, the autopilot is temporarily bypassed but follows the ma­neuver and automatically resumes flying the plane on the new7 course when the pilot returns the control stick to neutral.

Heading control can be magnetic, along a radio beam, or a gyro-directed course selected by the navigator.

The system constantly computes the gross weight of the plane (including fuel present and any equipment being car­ried), modifies this value in terms of ac­celeration, and maintains Mach and altitude through automatic trim signals as part of the over-all control function.

AMERICAN INDUSTRY is keenly aware of the problem of air pollution and spends hundreds of millions of dollars per year to reduce pollution. Many types of equip­ment are used from mechanical collectors through cyclone-type collectors to high-efficiency electrostatic precipitators. Al-

Surface Actuation

Two separate hydraulic systems, each ex­erting a force of 3,000 pounds per square inch, are used to drive the control-surface actuators. Ten rams are used to move each elevon, five of these being fed from one hydraulic supply and five from the other. This sérvomechanism system is so sensitive that it compensates for de­flections in the control surfaces caused by their sudden movement (acceleration) by the power control system. The rams and' valves are manufactured by the Bendix Corporation, Pacific Division, North Holly­wood, Calif.

Four rams are used to control the rud­der. They are also designed to permit only one of the hydraulic systems to oper­ate the rudder if their is a failure of the second system.

The elevon surface actuators are ca pable of exerting a torque of 240,000 foot pounds, approximately 6,000 times greater than the actuator torque used on airliners and equivalent to the torque output of approximately 500 Cadillac engines.

though mechanical collectors remove larger and heavier particles from indus^ trial gases, electrostatic precipitation is required to remove particles of small size from 0.1 to 40 microns.

An electrical laboratory and research department has been operated by Re-

Model Studies Save Money in Designing of Flues

M A Y 1 9 5 8 Of Current Interest 465