The nation's aviation infrastructure is again under scrutiny, following a series of paralyzing communications and radar outages at some of the country's busiest airports.
On Sunday, systems at the Terminal Radar Approach Control facility in Philadelphia, which guides planes in and out of Newark Liberty International Airport, went blank, according to the Federal Aviation Administration. The disruption caused it to lose communication with all of the planes in the sky, meaning air traffic controllers couldn't see or reach pilots for 90 seconds. That prompted the FAA to order a temporary ground stop, triggering flight delays and cancellations.
The incident came just days after a nearly identical technology mishap on April 28, during which controllers lost contact with aircraft for 30 seconds.
What has followed has been weeks of chaos and fear over passenger safety, especially months after a fatal midair collision near Ronald Reagan International Airport in Washington, D.C. killed 67 people. The failures have highlighted inadequacies of current radar systems that are supposed to work together to provide air traffic controllers a comprehensive view of all activity on the runways and over airspace.
In an effort to address some of those worries, Secretary of Transportation Sean Duffy announced plans to overhaul the antiquated telecommunications, radio and surveillance systems. According to the FAA, some airports still rely on systems that use floppy disks and copper wire.
Talk of the broader revamp has spurred conversations about the latest innovations in radar technology. Here is a look at the scientific origins of radar.
Where did the word come from?
The word, radar, is a near acronym that stands for RAdio Detection And Ranging. It was coined by the U.S. Navy in either 1940 or 1941, according to the FAA and Merriam-Webster dictionary.
It works a lot like an echo, but rather than sound waves, pulses of radio waves are emitted that then bounce off of an object. By timing how long it takes for the signal to go out and come back, one can calculate how far away something is. And, depending on the angle of the incoming signal, one can also work out the elevation, speed and trajectory of whatever is out there.
Though it seems like thoroughly modern technology, the application dates back to the late 19th century. German physicist Heinrich Hertz was the first to prove that pulsing radio waves are reflected by metallic surfaces. However, credit for the first invention to use what we now think of as radar, belongs to German physicist Christian Hülsmeyer. Hülsmeyer built on Hertz's work to create the Telemobiloskop, an invention patented in 1904. The device contained both a transmitter and receiver and was designed to detect and help passing ships avoid colliding into one another.
But it was the British military that unleashed the true potential of radar technology under pressure from the Germans in the 1930s. World War II was looming and the British were desperate for a weapon to stave off attacks. Their answer: The death ray.
The British military put their best and brightest on the case, including Robert Watson-Watt, a Scottish physicist.
The government had had the idea for some time.
"For 10 years, it had a standing reward of £1,000 to anyone who developed a ray that could kill a sheep at 100 yards," Robert Buderi, author of The Invention That Changed the World, told NPR. That's roughly $50,000 in today's money.
Watson-Watt quickly realized such a weapon was out of the realm of possibility but he offered an alternate solution: "The idea of radio detection as opposed to radio destruction," Buderi said.
It was a huge development.
By the outbreak of the war in 1939, the government had built a system — called Chain Home — that could detect enemy aircraft within a 100 mile range. Historians cite this as a massive turning point in the war, preventing the Nazis from ever landing on British soil.
Buderi noted, even more pivotal to the allied war effort was the top secret invention of a device about the size of a hockey puck, called the cavity magnetron. Developed by two British scientists, it was a powerful transmitter of radio waves that was much more compact and powerful than anything that existed until then.
"This gave the promise of actually fitting radar systems onto planes themselves," Buderi explained.
The U.K. shared the advances with American scientists. That led to the founding of a secret lab at the Massachusetts Institute of Technology called the Radiation Lab to develop microwave radar systems for use during the war.
"It is frequently said that, although the atomic bomb ended World War II, it was radar that won the war," MIT says of the lab's role in the war effort.
How has radar changed over time?
Radar is a common technology today, even though it was once a highly kept secret.
(In fact, radar was such a highly regarded secret, that in order to cover their success in shooting down enemy bombers with the new technology, they claimed Royal Air Force pilots simply ate lots of carrots. Thus spawning the myth that carrots drastically improve nighttime vision, according to The Smithsonian.)
Today modern aircraft are reliant on radar to avoid midair collisions. That wasn't always the case.
Shortly after the war, air travel exploded. Through the early 1950s, a hodgepodge of state and industry agencies controlled what happened within the 158,000 miles of airways over the country.
It wasn't until mid-1952, after five years of testing by the U.S. Navy, that Washington National Airport became the first in the U.S. to use radar. The FAA says pilots resisted the innovation saying they worried about losing control.
That all changed after a devastating collision on June 30, 1956, when a United Airlines plane crashed into a TWA flight over the Grand Canyon, killing all 128 passengers and crew from both planes.
An investigation said the probable cause "was that the pilots did not see each other in time to avoid the collision."
A little more than a year later, President Eisenhower signed the Airways Modernization Act into law, streamlining regulations and practices, and ensuring that planes would now be monitored from take off to landing.
Why does the word matter today?
The Department of Transportation's plan to "equip facilities with better technology to reduce outages, improve efficiency, and reinforce safety" would mean years of upgrades at airports across the country paid for with billions of taxpayer dollars.
"We have a system that is built for the past, we are proposing a system built for the future," the FAA said in a statement.
Among the specifics outlined by the agency are new fiber, wireless and satellite technologies at over 4,600 sites, 25,000 new radios and 475 new voice switches. Additionally, the FAA said, it would like to replace 618 radars "which have gone past their life cycle."
Duffy has repeatedly stated that the entire project is doable in under four years. But the Government Accountability Office estimates that a revamp of this scope will take 10 to 13 years to accomplish properly.
There is also some discrepancy on the cost of such an endeavor. As NPR reported, the House Transportation and Infrastructure Committee has estimated the cost at about $12.5 billion. But aviation industry experts, pilot association representatives and others, put the tally at a minimum of $18.5 billion.
On a more day to day level, the current problems with today's radar systems will continue to disrupt passenger's flight plans.
Speaking to NBC's Meet the Press, Duffy said he plans to reduce the number of flights in and out of Newark for the "next several weeks."
"I want you to get to where you're traveling. And if that means slowing down flights into Newark, we slow them down to make sure we can do it safely," Duffy said.
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