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Saturday, February 27, 2016

Reading List: Tesla

Carlson, W. Bernard. Tesla: Inventor of the Electrical Age. Princeton: Princeton University Press, 2013. ISBN 978-0-691-16561-5.
Nicola Tesla was born in 1858 in a village in what is now Croatia, then part of the Austro-Hungarian Empire. His father and grandfather were both priests in the Orthodox church. The family was of Serbian descent, but had lived in Croatia since the 1690s among a community of other Serbs. His parents wanted him to enter the priesthood and enrolled him in school to that end. He excelled in mathematics and, building on a boyhood fascination with machines and tinkering, wanted to pursue a career in engineering. After completing high school, Tesla returned to his village where he contracted cholera and was near death. His father promised him that if he survived, he would “go to the best technical institution in the world.” After nine months of illness, Tesla recovered and, in 1875 entered the Joanneum Polytechnic School in Graz, Austria.

Tesla's university career started out brilliantly, but he came into conflict with one of his physics professors over the feasibility of designing a motor which would operate without the troublesome and unreliable commutator and brushes of existing motors. He became addicted to gambling, lost his scholarship, and dropped out in his third year. He worked as a draftsman, taught in his old high school, and eventually ended up in Prague, intending to continue his study of engineering at the Karl-Ferdinand University. He took a variety of courses, but eventually his uncles withdrew their financial support.

Tesla then moved to Budapest, where he found employment as chief electrician at the Budapest Telephone Exchange. He quickly distinguished himself as a problem solver and innovator and, before long, came to the attention of the Continental Edison Company of France, which had designed the equipment used in Budapest. He was offered and accepted a job at their headquarters in Ivry, France. Most of Edison's employees had practical, hands-on experience with electrical equipment, but lacked Tesla's formal education in mathematics and physics. Before long, Tesla was designing dynamos for lighting plants and earning a handsome salary. With his language skills (by that time, Tesla was fluent in Serbian, German, and French, and was improving his English), the Edison company sent him into the field as a trouble-shooter. This further increased his reputation and, in 1884 he was offered a job at Edison headquarters in New York. He arrived and, years later, described the formalities of entering the U.S. as an immigrant: a clerk saying “Kiss the Bible. Twenty cents!”.

Tesla had never abandoned the idea of a brushless motor. Almost all electric lighting systems in the 1880s used direct current (DC): electrons flowed in only one direction through the distribution wires. This is the kind of current produced by batteries, and the first electrical generators (dynamos) produced direct current by means of a device called a commutator. As the generator is turned by its power source (for example, a steam engine or water wheel), power is extracted from the rotating commutator by fixed brushes which press against it. The contacts on the commutator are wired to the coils in the generator in such a way that a constant direct current is maintained. When direct current is used to drive a motor, the motor must also contain a commutator which converts the direct current into a reversing flow to maintain the motor in rotary motion.

Commutators, with brushes rubbing against them, are inefficient and unreliable. Brushes wear and must eventually be replaced, and as the commutator rotates and the brushes make and break contact, sparks may be produced which waste energy and degrade the contacts. Further, direct current has a major disadvantage for long-distance power transmission. There was, at the time, no way to efficiently change the voltage of direct current. This meant that the circuit from the generator to the user of the power had to run at the same voltage the user received, say 120 volts. But at such a voltage, resistance losses in copper wires are such that over long runs most of the energy would be lost in the wires, not delivered to customers. You can increase the size of the distribution wires to reduce losses, but before long this becomes impractical due to the cost of copper it would require. As a consequence, Edison electric lighting systems installed in the 19th century had many small powerhouses, each supplying a local set of customers.

Alternating current (AC) solves the problem of power distribution. In 1881 the electrical transformer had been invented, and by 1884 high-efficiency transformers were being manufactured in Europe. Powered by alternating current (they don't work with DC), a transformer efficiently converts current from one voltage and current to another. For example, power might be transmitted from the generating station to the customer at 12000 volts and 1 ampere, then stepped down to 120 volts and 100 amperes by a transformer at the customer location. Losses in a wire are purely a function of current, not voltage, so for a given level of transmission loss, the cables to distribute power at 12000 volts will cost a hundredth as much as if 120 volts were used. For electric lighting, alternating current works just as well as direct current (as long as the frequency of the alternating current is sufficiently high that lamps do not flicker). But electricity was increasingly used to power motors, replacing steam power in factories. All existing practical motors ran on DC, so this was seen as an advantage to Edison's system.

Tesla worked only six months for Edison. After developing an arc lighting system only to have Edison put it on the shelf after acquiring the rights to a system developed by another company, he quit in disgust. He then continued to work on an arc light system in New Jersey, but the company to which he had licensed his patents failed, leaving him only with a worthless stock certificate. To support himself, Tesla worked repairing electrical equipment and even digging ditches, where one of his foremen introduced him to Alfred S. Brown, who had made his career in telegraphy. Tesla showed Brown one of his patents, for a “thermomagnetic motor”, and Brown contacted Charles F. Peck, a lawyer who had made his fortune in telegraphy. Together, Peck and Brown saw the potential for the motor and other Tesla inventions and in April 1887 founded the Tesla Electric Company, with its laboratory in Manhattan's financial district.

Tesla immediately set to make his dream of a brushless AC motor a practical reality and, by using multiple AC currents, out of phase with one another (the polyphase system), he was able to create a magnetic field which itself rotated. The rotating magnetic field induced a current in the rotating part of the motor, which would start and turn without any need for a commutator or brushes. Tesla had invented what we now call the induction motor. He began to file patent applications for the motor and the polyphase AC transmission system in the fall of 1887, and by May of the following year had been granted a total of seven patents on various aspects of the motor and polyphase current.

One disadvantage of the polyphase system and motor was that it required multiple pairs of wires to transmit power from the generator to the motor, which increased cost and complexity. Also, existing AC lighting systems, which were beginning to come into use, primarily in Europe, used a single phase and two wires. Tesla invented the split-phase motor, which would run on a two wire, single phase circuit, and this was quickly patented.

Unlike Edison, who had built an industrial empire based upon his inventions, Tesla, Peck, and Brown had no interest in founding a company to manufacture Tesla's motors. Instead, they intended to shop around and license the patents to an existing enterprise with the resources required to exploit them. George Westinghouse had developed his inventions of air brakes and signalling systems for railways into a successful and growing company, and was beginning to compete with Edison in the electric light industry, installing AC systems. Westinghouse was a prime prospect to license the patents, and in July 1888 a deal was concluded for cash, notes, and a royalty for each horsepower of motors sold. Tesla moved to Pittsburgh, where he spent a year working in the Westinghouse research lab improving the motor designs. While there, he filed an additional fifteen patent applications.

After leaving Westinghouse, Tesla took a trip to Europe where he became fascinated with Heinrich Hertz's discovery of electromagnetic waves. Produced by alternating current at frequencies much higher than those used in electrical power systems (Hertz used a spark gap to produce them), here was a demonstration of transmission of electricity through thin air—with no wires at all. This idea was to inspire much of Tesla's work for the rest of his life. By 1891, he had invented a resonant high frequency transformer which we now call a Tesla coil, and before long was performing spectacular demonstrations of artificial lightning, illuminating lamps at a distance without wires, and demonstrating new kinds of electric lights far more efficient than Edison's incandescent bulbs. Tesla's reputation as an inventor was equalled by his talent as a showman in presentations before scientific societies and the public in both the U.S. and Europe.

Oddly, for someone with Tesla's academic and practical background, there is no evidence that he mastered Maxwell's theory of electromagnetism. He believed that the phenomena he observed with the Tesla coil and other apparatus were not due to the Hertzian waves predicted by Maxwell's equations, but rather something he called “electrostatic thrusts”. He was later to build a great edifice of mistaken theory on this crackpot idea.

By 1892, plans were progressing to harness the hydroelectric power of Niagara Falls. Transmission of this power to customers was central to the project: around one fifth of the American population lived within 400 miles of the falls. Westinghouse bid Tesla's polyphase system and with Tesla's help in persuading the committee charged with evaluating proposals, was awarded the contract in 1893. By November of 1896, power from Niagara reached Buffalo, twenty miles away, and over the next decade extended throughout New York. The success of the project made polyphase power transmission the technology of choice for most electrical distribution systems, and it remains so to this day. In 1895, the New York Times wrote:

Even now, the world is more apt to think of him as a producer of weird experimental effects than as a practical and useful inventor. Not so the scientific public or the business men. By the latter classes Tesla is properly appreciated, honored, perhaps even envied. For he has given to the world a complete solution of the problem which has taxed the brains and occupied the time of the greatest electro-scientists for the last two decades—namely, the successful adaptation of electrical power transmitted over long distances.

After the Niagara project, Tesla continued to invent, demonstrate his work, and obtain patents. With the support of patrons such as John Jacob Astor and J. P. Morgan he pursued his work on wireless transmission of power at laboratories in Colorado Springs and Wardenclyffe on Long Island. He continued to be featured in the popular press, amplifying his public image as an eccentric genius and mad scientist. Tesla lived until 1943, dying at the age of 86 of a heart attack. Over his life, he obtained around 300 patents for devices as varied as a new form of turbine, a radio controlled boat, and a vertical takeoff and landing airplane. He speculated about wireless worldwide distribution of news to personal mobile devices and directed energy weapons to defeat the threat of bombers. While in Colorado, he believed he had detected signals from extraterrestrial beings. In his experiments with high voltage, he accidently detected X-rays before Röntgen announced their discovery, but he didn't understand what he had observed.

None of these inventions had any practical consequences. The centrepiece of Tesla's post-Niagara work, the wireless transmission of power, was based upon a flawed theory of how electricity interacts with the Earth. Tesla believed that the Earth was filled with electricity and that if he pumped electricity into it at one point, a resonant receiver anywhere else on the Earth could extract it, just as if you pump air into a soccer ball, it can be drained out by a tap elsewhere on the ball. This is, of course, complete nonsense, as his contemporaries working in the field knew, and said, at the time. While Tesla continued to garner popular press coverage for his increasingly bizarre theories, he was ignored by those who understood they could never work. Undeterred, Tesla proceeded to build an enormous prototype of his transmitter at Wardenclyffe, intended to span the Atlantic, without ever, for example, constructing a smaller-scale facility to verify his theories over a distance of, say, ten miles.

Tesla's invention of polyphase current distribution and the induction motor were central to the electrification of nations and continue to be used today. His subsequent work was increasingly unmoored from the growing theoretical understanding of electromagnetism and many of his ideas could not have worked. The turbine worked, but was uncompetitive with the fabrication and materials of the time. The radio controlled boat was clever, but was far from the magic bullet to defeat the threat of the battleship he claimed it to be. The particle beam weapon (death ray) was a fantasy.

In recent decades, Tesla has become a magnet for Internet-connected crackpots, who have woven elaborate fantasies around his work. Finally, in this book, written by a historian of engineering and based upon original sources, we have an authoritative and unbiased look at Tesla's life, his inventions, and their impact upon society. You will understand not only what Tesla invented, but why, and how the inventions worked. The flaky aspects of his life are here as well, but never mocked; inventors have to think ahead of accepted knowledge, and sometimes they will inevitably get things wrong.

Posted at 21:34 Permalink

Saturday, February 13, 2016

Reading List: The Wright Brothers

McCullough, David. The Wright Brothers. New York: Simon & Schuster, 2015. ISBN 978-1-4767-2874-2.
On December 8th, 1903, all was in readiness. The aircraft was perched on its launching catapult, the brave airman at the controls. The powerful internal combustion engine roared to life. At 16:45 the catapult hurled the craft into the air. It rose straight up, flipped, and with its wings coming apart, plunged into the Potomac river just 20 feet from the launching point. The pilot was initially trapped beneath the wreckage but managed to free himself and swim to the surface. After being rescued from the river, he emitted what one witness described as “the most voluble series of blasphemies” he had ever heard.

So ended the last flight of Samuel Langley's “Aerodrome”. Langley was a distinguished scientist and secretary of the Smithsonian Institution in Washington D.C. Funded by the U.S. Army and the Smithsonian for a total of US$ 70,000 (equivalent to around 1.7 million present-day dollars), the Aerodrome crashed immediately on both of its test flights, and was the subject of much mockery in the press.

Just nine days later, on December 17th, two brothers, sons of a churchman, with no education beyond high school, and proprietors of a bicycle shop in Dayton, Ohio, readied their own machine for flight near Kitty Hawk, on the windswept sandy hills of North Carolina's Outer Banks. Their craft, called just the Flyer, took to the air with Orville Wright at the controls. With the 12 horsepower engine driving the twin propellers and brother Wilbur running alongside to stabilise the machine as it moved down the launching rail into the wind, Orville lifted the machine into the air and achieved the first manned heavier-than-air powered flight, demonstrating the Flyer was controllable in all three axes. The flight lasted just 12 seconds and covered a distance of 120 feet.

After the first flight, the brothers took turns flying the machine three more times on the 17th. On the final flight Wilbur flew a distance of 852 feet in a flight of 59 seconds (a strong headwind was blowing, and this flight was over half a mile through the air). After completion of the fourth flight, while being prepared to fly again, a gust of wind caught the machine and dragged it, along with assistant John T. Daniels, down the beach toward the ocean. Daniels escaped, but the Flyer was damaged beyond repair and never flew again. (The Flyer which can seen in the Smithsonian's National Air and Space Museum today has been extensively restored.)

Orville sent a telegram to his father in Dayton announcing the success, and the brothers packed up the remains of the aircraft to be shipped back to their shop. The 1903 season was at an end. The entire budget for the project between 1900 through the successful first flights was less than US$ 1000 (24,000 dollars today), and was funded entirely by profits from the brothers' bicycle business.

How did two brothers with no formal education in aerodynamics or engineering succeed on a shoestring budget while Langley, with public funds at his disposal and the resources of a major scientific institution fail so embarrassingly? Ultimately it was because the Wright brothers identified the key problem of flight and patiently worked on solving it through a series of experiments. Perhaps it was because they were in the bicycle business. (Although they are often identified as proprietors of a “bicycle shop”, they also manufactured their own bicycles and had acquired the machine tools, skills, and co-workers for the business, later applied to building the flying machine.)

The Wrights believed the essential problem of heavier than air flight was control. The details of how a bicycle is built don't matter much: you still have to learn to ride it. And the problem of control in free flight is much more difficult than riding a bicycle, where the only controls are the handlebars and, to a lesser extent, shifting the rider's weight. In flight, an airplane must be controlled in three axes: pitch (up and down), yaw (left and right), and roll (wings' angle to the horizon). The means for control in each of these axes must be provided, and what's more, just as for a child learning to ride a bike, the would-be aeronaut must master the skill of using these controls to maintain his balance in the air.

Through a patient program of subscale experimentation, first with kites controlled by from the ground by lines manipulated by the operators, then gliders flown by a pilot on board, the Wrights developed their system of pitch control by a front-mounted elevator, yaw by a rudder at the rear, and roll by warping the wings of the craft. Further, they needed to learn how to fly using these controls and verify that the resulting plane would be stable enough that a person could master the skill of flying it. With powerless kites and gliders, this required a strong, consistent wind. After inquiries to the U.S. Weather Bureau, the brothers selected the Kitty Hawk site on the North Carolina coast. Just getting there was an adventure, but the wind was as promised and the sand and lack of large vegetation was ideal for their gliding experiments. They were definitely “roughing it” at this remote site, and at times were afflicted by clouds of mosquitos of Biblical plague proportions, but starting in 1900 they tested a series of successively larger gliders and by 1902 had a design which provided three axis control, stability, and the controls for a pilot on board. In the 1902 season they made more than 700 flights and were satisfied the control problem had been mastered.

Now all that remained was to add an engine and propellers to the successful glider design, again scaling it up to accommodate the added weight. In 1903, you couldn't just go down to the hardware store and buy an engine, and automobile engines were much too heavy, so the Wrights' resourceful mechanic, Charlie Taylor, designed and built the four cylinder motor from scratch, using the new-fangled material aluminium for the engine block. The finished engine weighed just 152 pounds and produced 12 horsepower. The brothers could find no references for the design of air propellers and argued intensely over the topic, but eventually concluded they'd just have to make a best guess and test it on the real machine.

The Flyer worked the on the second attempt (an earlier try on December 14th ended in a minor crash when Wilbur over-controlled at the moment of take-off). But this stunning success was the product of years of incremental refinement of the design, practical testing, and mastery of airmanship through experience.

Those four flights in December of 1903 are now considered one of the epochal events of the twentieth century, but at the time they received little notice. Only a few accounts of the flights appeared in the press, and some of them were garbled and/or sensationalised. The Wrights knew that the Flyer (whose wreckage was now in storage crates at Dayton), while a successful proof of concept and the basis for a patent filing, was not a practical flying machine. It could only take off into the strong wind at Kitty Hawk and had not yet demonstrated long-term controlled flight including aerial maneuvers such as turns or flying around a closed course. It was just too difficult travelling to Kitty Hawk, and the facilities of their camp there didn't permit rapid modification of the machines based upon experimentation.

They arranged to use an 84 acre cow pasture called Huffman Prairie located eight miles from Dayton along an interurban trolley line which made it easy to reach. The field's owner let them use it without charge as long as they didn't disturb the livestock. The Wrights devised a catapult to launch their planes, powered by a heavy falling weight, which would allow them to take off in still air. It was here, in 1904, that they refined the design into a practical flying machine and fully mastered the art of flying it over the course of about fifty test flights. Still, there was little note of their work in the press, and the first detailed account was published in the January 1905 edition of Gleanings in Bee Culture. Amos Root, the author of the article and publisher of the magazine, sent a copy to Scientific American, saying they could republish it without fee. The editors declined, and a year later mocked the achievements of the Wright brothers.

For those accustomed to the pace of technological development more than a century later, the leisurely pace of progress in aviation and lack of public interest in the achievement of what had been a dream of humanity since antiquity seems odd. Indeed, the Wrights, who had continued to refine their designs, would not become celebrities nor would their achievements be widely acknowledged until a series of demonstrations Wilbur would perform at Le Mans in France in the summer of 1908. Le Figaro wrote, “It was not merely a success, but a triumph…a decisive victory for aviation, the news of which will revolutionize scientific circles throughout the world.” And it did: stories of Wilbur's exploits were picked up by the press on the Continent, in Britain, and, belatedly, by papers in the U.S. Huge crowds came out to see the flights, and the intrepid American aviator's name was on every tongue.

Meanwhile, Orville was preparing for a series of demonstration flights for the U.S. Army at Fort Myer, Virginia. The army had agreed to buy a machine if it passed a series of tests. Orville's flights also began to draw large crowds from nearby Washington and extensive press coverage. All doubts about what the Wrights had wrought were now gone. During a demonstration flight on September 17, 1908, a propeller broke in flight. Orville tried to recover, but the machine plunged to the ground from an altitude of 75 feet, severely injuring him and killing his passenger, Lieutenant Thomas Selfridge, who became the first person to die in an airplane crash. Orville's recuperation would be long and difficult, aided by his sister, Katharine.

In early 1909, Orville and Katharine would join Wilbur in France, where he was to do even more spectacular demonstrations in the south of the country, training pilots for the airplanes he was selling to the French. Upon their return to the U.S., the Wrights were awarded medals by President Taft at the White House. They were feted as returning heroes in a two day celebration in Dayton. The diligent Wrights continued their work in the shop between events.

The brothers would return to Fort Myer, the scene of the crash, and complete their demonstrations for the army, securing the contract for the sale of an airplane for US$ 30,000. The Wrights would continue to develop their company, defend their growing portfolio of patents against competitors, and innovate. Wilbur was to die of typhoid fever in 1912, aged only 45 years. Orville sold his interest in the Wright Company in 1915 and, in his retirement, served for 28 years on the National Advisory Committee for Aeronautics, the precursor of NASA. He died in 1948. Neither brother ever married.

This book is a superb evocation of the life and times of the Wrights and their part in creating, developing, promoting, and commercialising one of the key technologies of the modern world.

Posted at 20:28 Permalink