Tag Archives: The_Institute/IEEE_History

General Electric Device That Revolutionized Electrical Machines Is Now an IEEE Milestone

Post Syndicated from Joanna Goodrich original https://spectrum.ieee.org/the-institute/ieee-history/general-electric-device-that-revolutionized-electrical-machines-is-now-an-ieee-milestone

The silicon-controlled rectifier, or thyristor, can be found in flash bulbs, motors and manufacturing equipment

THE INSTITUTEMore than 60 years after General Electric introduced the silicon-controlled rectifier, it is still a dominant control device in the power industry because of its efficiency. The SCR, also known as the thyristor, is a three-terminal p-n-p-n device that has an anode, a cathode, and a gate. It was introduced in 1957 and developed at a GE facility in Clyde, N.Y.

The invention of the SCR led to improvements in the control of the rectification, or conversion, of line voltage from AC to DC and became the basis of modern speed control in both AC and DC motors. The device’s application to motor control made possible the displacement of DC motors by the more efficient and reliable AC motors, particularly in trains, according to the Engineering and Technology History Wiki. SCRs also allowed for DC electrical transmission at much higher voltages and power levels than previously obtainable, says IEEE Life Senior Member Sreeram Dhurjaty, chair of the IEEE Power Electronics Society’s Rochester Section chapter.

The SCR was dedicated as an IEEE Milestone on 14 June. Administered by the IEEE History Center and supported by donors, the Milestone program recognizes outstanding technical developments around the world. The Rochester Section’s Power Electronics Society chapter was the sponsor.


Prior to 1955, triode vacuum tubes, which control the flow of electric current between electrodes, were used for machine control. They were difficult to operate and frequently failed in large machines.

To fix those issues, IEEE Member John Bardeen and Walter H. Brattain of Bell Laboratories in 1947 developed the point-contact transistor, an interconnection between two transistors.

According to IEEE Life Fellow Edward Owen, who wrote the article “SCR Is 50 Years Old” about the technology in the IEEE Industry Applications Magazine, the complexity of the point-contact transistor’s circuits and the fragile nature of the technology spurred GE power engineers Frank Gutzwiller and Gordon Hall to develop a new technology in 1956 that would improve upon Bardeen and Brattain’s device. But, as IEEE Life Fellow Gerard Hurley, history chair of the IEEE Power Electronics Society, explained during the Milestone ceremony, the two engineers encountered several issues.

Hurley said Gutzwiller and Hall did not realize until later in their research that silicon, not germanium, was the appropriate semiconductor material to use for the SCR. Germanium has a smaller band gap—which means less energy is required to pull electrons into conduction. That makes it easier for the material to heat up and degrade.

Gutzwiller and Hall also encountered problems with false triggering. Heat alone could cause the device to turn on. The device also could be triggered by induced current, when the anode to cathode voltages rose too fast. Both instances could cause leakage, which could increase power consumption or result in complete circuit failure.

The first SCRs that Gutzwiller and Hall built could tolerate only low voltages, but refinements to the manufacturing process ultimately produced devices capable of handling voltages exceeding 10 kilovolts. Gutzwiller and Hall also designed a silicon-wafer bonding process capable of better accommodating thermally induced stresses.

Modern SCRs are used for AC power control for lights and motors, AC power switching circuits, and photographic flashes.

The SCR also made an impact on manufacturing, according to IEEE Life Fellow John Kassakian, founding president of the IEEE Power Electronics Society.

“The steel, electrochemical, automotive, and welding industries, among many others, benefited greatly by the improved efficiency, more precise control, and reduced cost made possible by the application of SCR-based equipment to their processes,” Kassakian said at the Milestone ceremony.

A plaque honoring the SCR was mounted at the entrance of the Advanced Atomization Technologies headquarters, in Clyde. AAT is a joint venture between GE Aviation and Parker Aerospace.

The plaque reads:

General Electric introduced the silicon-controlled rectifier (SCR), a three-terminal p-n-p-n device, in 1957. The gas-filled tubes used previously were difficult to operate and unreliable. The symmetrical alternating-current switch (TRIAC), the gate turn-off thyristor (GTO), and the large integrated gate-commutated thyristor (IGCT) evolved from the SCR. Its development revolutionized efficient control of electric energy and electrical machines.

This article was written with assistance from the IEEE History Center, which is funded by donations to the IEEE Foundation’s Realize the Full Potential of IEEE campaign.

Katherine Johnson, the Hidden Figures Mathematician Who Got Astronaut John Glenn Into Space

Post Syndicated from Joanna Goodrich original https://spectrum.ieee.org/the-institute/ieee-history/katherine-johnson-the-hidden-figures-mathematician-who-got-astronaut-john-glenn-into-space

The NASA technologist received the IEEE President’s Award for her work on Apollo 11

THE INSTITUTEKatherine G. Johnson’s mathematical calculations of orbital mechanics at NASA were critical to the success of Friendship 7 and several other U.S. human spaceflights. She was one of the women featured in the 2016 Oscar-nominated film Hidden Figures.

IEEE last month recognized her work with its President’s Award, “for fundamental computational contributions to the success of American’s first and subsequent manned spaceflights, including Apollo 11.” Johnson, who turned 100 in August, was unable to travel to the ceremony. Her daughters, Katherine Goble Moore and Joylette Goble Hylick, accepted the award on her behalf at the IEEE Honors Ceremony, held on 17 May in San Diego. Johnson “has a real passion for learning, and always aspired to teach others everything she knew,” Hylick said. You can watch the presentation on IEEE.tv.

As IEEE marks the 50th anniversary of the moon landing and spaceflight through the Footsteps: IEEE’s Commemoration of Human Space Travel effort, The Institute is highlighting IEEE members and other pioneers, like Johnson, and the technologies that helped propel the program forward.


In a 2017 interview with The Washington Post, Johnson said she always wanted to be a mathematician. She attended high school when she was 10 years old, but due to segregation at the time, she wasn’t allowed to attend her county’s high school in Greenbrier, W.Va. Her family moved to Institute, W.Va., and she attended West Virginia State College, now West Virginia State University, which offered high school courses to black students.

She finished high school at age 14 at West Virginia State, then continued taking college courses there. She graduated in 1939 summa cum laude with a bachelor’s degree in mathematics and French. She planned on continuing her education and was selected as the first black woman in the state to attend the graduate school program at West Virginia University, in Morgantown. She withdrew from the program after one semester, however, to start a family with her husband, James Goble. Johnson worked as a math teacher at a black public school in Marion, Va.

According to her biography on the NASA website, Johnson always knew she would eventually leave teaching to become a research mathematician. In 1953 she joined NASA’s predecessor, the National Advisory Committee for Aeronautics, at its Langley laboratory, in Hampton, Va., as a pool mathematician. Those mathematicians, called computers, analyzed data collected from flight tests and airplane black boxes.

 Thanks to her understanding of analytical geometry, just two weeks after she joined NACA, she was assigned to the maneuver-loads branch of the Flight Research Division. She spent the next four years analyzing data from flight tests and plane crashes.


When the Russian satellite Sputnik was launched in 1957, the United States was already working on sending satellites into space, but Sputnik’s debut led to the formation of NASA. Due to Johnson’s work at NACA, she was among the first employees hired by NASA in 1958.

Working as a technologist for the spacecraft controls branch, she calculated the path for astronaut Alan Shepard’s Freedom 7 mission in 1961, America’s first human spaceflight.

In 1960 she became the first woman to receive credit as an author of a research report, “Determination of Azimuth Angle at Burnout for Placing a Satellite Over a Selected Earth Position.” In it, Johnson and her coauthor, engineer Ted H. Skopinski, explained the equations describing an orbital spaceflight in which the craft’s landing position is specified.

Her life changed in 1962, when astronaut John Glenn asked for Johnson to double-check the trajectory calculations for Friendship 7. Because of the mission’s complexity, the space agency collaborated with IBM in the construction of a worldwide communications network. They built and linked tracking stations to IBM computers in Bermuda, Cape Canaveral, and Washington, D.C., so engineers could follow the flight live. The computers had been programmed with orbital equations that would control the trajectory of the Friendship capsule from blastoff to landing. Glenn, however, was nervous about putting his life in the hands of machines, which he believed to be prone to mistakes, according to NASA.

According to the NASA biography on Johnson, Glenn asked engineers to “get the girl”—meaning Johnson—during the preflight check, because of her experience with trajectory analysis. He wanted her to run the same numbers that had been programmed into the computer, but by hand, on her desktop calculator. In an interview with CNN, Johnson recalls Glenn saying while she was working, “If she says they’re good, then I’m ready to go.”

For her work on Friendship 7, in 2015 she was awarded the U.S. Presidential Medal of Freedom, the nation’s highest civilian honor. At the White House ceremony, President Barack Obama said, “No one knows that John Glenn wouldn’t fly unless Katherine Johnson checked the math.”

In 2017 NASA unveiled the Katherine G. Johnson Computational Research Facility at the Langley Research Center, in Hampton, Va., the same location where she started her career at NACA. Earlier this year, the agency renamed a facility in Fairmont, W. Va., that housed a program that monitors the software used to track NASA’s high-profile missions. It’s now called the Katherine Johnson Independent Verification and Validation Facility.

Project Diana Honored With an IEEE Milestone

Post Syndicated from Joanna Goodrich original https://spectrum.ieee.org/the-institute/ieee-history/project-diana-honored-with-an-ieee-milestone

The demonstration prompted the United States to enter the race to space

THE INSTITUTEOn 10 January 1946 four standard-array antennae at Camp Evans, on the grounds of Fort Monmouth in New Jersey, sent a radar pulse toward the moon as it rose above the horizon. Just 2.5 seconds later, the signal had bounced off the lunar surface, its echo appearing clearly on an oscilloscope.

That seemingly modest demonstration, called Project Diana, had a lasting impact, marking the birth of radar astronomy, which has been used to map other planets. It also set the stage for the space race in the United States.

Project Diana was dedicated as an IEEE Milestone on 17 May. Administered by the IEEE History Center and supported by donors, the Milestone program recognizes outstanding technical developments around the world.


During World War II, scientists emitted short bursts of microwave signals from one point on the Earth to another by bouncing them off the ionosphere. The so-called skywave-communication technique, which reached up nearly 400 kilometers, was used mainly to detect enemy aircraft.

The Camp Evans laboratory, called Site Diana, built a large transmitter, receiver, and reflective-array antenna to bounce radar signals off the moon. The transmitter, a modified SCR-271 radar set from the war, was connected to the antenna, composed of an 8-by-8 array of half-wave dipoles and reflectors.

The receiver compensated for the shift in frequency of the reflected signal because the motion toward or away from the line of sight differed each day. The receiver’s rotation angles were carefully calculated for each trial. The antenna could be rotated only in azimuth, meaning it could be turned only from side to side, not up and down. The attempt could be made only as the moon passed through the 12-degree-wide patch in the sky the antenna was aimed at during moonrise and moonset, because the antenna’s elevation angle was fixed. Scientists could observe for only about 40 minutes due to the transition of the moon and the lobes of the antenna pattern.

Engineer John H. DeWitt Jr. and chief scientist E. King Stodola received the first reflected signals at 11:58 a.m. EDT on 10 January. It took a little more than 2 seconds for the signals to be reflected, the same amount of time required for light to travel to the moon and back. The experiment demonstrated that radio communication could be conducted through the ionosphere.

Since 1946, mapping of astronomical objects has been done with radar, although it’s more sophisticated than what the Project Diana crew did. But the basic technique of bouncing radio signals off distant bodies that was developed for the project has been used to gather data about the geological and dynamic properties of many of the solar system’s planets and other heavenly bodies. Additionally, the technique has been used to determine the distance from the earth to the sun and the scale of the solar system itself.

Project Diana was honored on 17 May on the former grounds of Fort Monmouth, in Wall Township, N.J. The post was selected for closure in 2005 by the U.S. Defense Department’s Base Realignment and Closure Commission and officially closed in 2011. The site is now being redeveloped.

“Project Diana brought promise of a coming golden age of science and technology arising from the aftermath of World War II,” IEEE Life Member Albert Kerecman said at the plaque’s unveiling ceremony. “It refocused engineers and scientists to establish new goals centered on benefiting humanity, and created a need for developing solid-state technologies capable of surviving space launch and environments.”

The plaque, mounted near the entrance of the building that housed the laboratory, reads:

On 10 January 1946, a team of military and civilian personnel at Camp Evans, Fort Monmouth, New Jersey, USA, reflected the first radar signals off the moon using modified SCR-270/1 radar. The signals took 2.5 seconds to travel to the moon and back to the Earth. This achievement, Project Diana, marked the beginning of radar astronomy and space communications.

This article was written with assistance from the IEEE History Center, which is funded by donations to the IEEE Foundation’s Realize the Full Potential of IEEE campaign.

A Look Through the History of U.S. Space Travel

Post Syndicated from Joanna Goodrich original https://spectrum.ieee.org/the-institute/ieee-history/a-look-through-the-history-of-us-space-travel

Photographs show key moments of the effort to land on the moon

IEEE is marking the 50th anniversary of the moon landing and spaceflight through the Footsteps: IEEE’s Commemoration of Human Space Travel effort.  These images were provided by the IEEE History Center, which is funded by donations to the IEEE Foundation’s Realize the Full Potential of IEEE Campaign.