When Paul Murdoch received the commission to design the Flight 93 National Memorial in 2005, he never imagined the job’s final stages would be taken up with figuring out how to build a massive — and massively complex — musical instrument.
The memorial marks the site in Western Pennsylvania where United Flight 93 struck the earth on the morning of Sept. 11, 2001, killing everyone aboard. Flight 93 was originally destined to travel to San Francisco from Newark, N.J., but Al Qaeda hijackers seized control of the aircraft after takeoff and redirected the plane toward Washington, D.C., where it is believed they planned to attack the U.S. Capitol.
The flight’s passengers and crew, however, banded together to overtake the four hijackers, and the plane never hit its intended target. Instead, it crashed into a decommissioned coal mine outside of Shanksville, Penn., a tiny hamlet in the Allegheny Mountains that lies about 30 miles south of Johnstown.
For the last 15 years, Murdoch and a team at his Los Angeles firm, Paul Murdoch Architects, have served as lead designers on the memorial to those aboard Flight 93. In collaboration with the Virginia-based landscape architecture firm Nelson Byrd Woltz, they have turned what was once a barren industrial clearing into a real deal national park. (The site is managed by the National Park Service.)
The bowl of what was once the open-pit mine is now a picturesque meadow planted with wildflowers and native grasses. A curving allée fringed with maple trees leads visitors on a solemn walk from the visitor center to a memorial plaza, where a series of marble panels bear the names of the passengers and crew. From the plaza, the plane’s final resting place is visible, marked by a boulder.
But even though much of the site’s design and construction has been complete since 2015, a key component was missing.
As part of the original proposal, Murdoch had designed “The Tower of Voices,” which would greet visitors to the site. Standing at a height of 93 feet — a nod to the flight number — the latticed concrete tower was intended to provide a visible marker at the park’s entrance off nearby Route 30. It was also designed to function as a massive wind chime, using air currents to activate a variety of acoustic tubes within.
“We were moved by the fact that the last contact that people had with loved ones or others on the plane was through phone calls,” says Murdoch, referring to the frantic last phone calls some passengers made in the wake of the hijacking. “Somehow those voices were a lingering memory of these people before they died. So, we wanted to do something in the memorial with sound.”
“By using the wind, it’d be an ever-changing memorial expression,” he adds, “because it would alway reflect the changing conditions on the site.”
The tower was to be outfitted with 40 aluminum chimes, one in honor of each passenger and crew member. But though the construction of the tower was completed in 2018, this unusual musical instrument did not become fully operational until last week when its 40 custom wind chimes, along with the elaborate mechanisms that allow them to ring, were craned into place and installed. (Until then, the tower had operated with eight unfinshed prototypes.)
The memorial tower is now ready to sing, and its completion couldn’t be timelier.
Friday marks the 19th anniversary of the 9/11 attacks, when Al Qaeda hijackers seized commercial jetliners and plunged them into New York City’s World Trade Center and the Pentagon in Arlington, Va. — killing almost 3,000 people. And though it has been almost two decades since the attack, Shanksville remains an important site of pilgrimage: In attendance at this year’s commemoration ceremony will be President Trump and Democratic presidential nominee Joe Biden. (The park is currently open to the public, with COVID-19protocols in place.)
Designing a public monument is never an easy process. Designing a public monument that occupies a 2,200-acre site and includes a 93-foot musical instrument takes the challenge to another level.
To get the wind chimes built required a battery of experts, including a wind-engineering consultant, an acoustics engineer and a fabricator of musical instruments — one comfortable producing aluminum chimes at a scale of 5 to 10 feet. Also on board was composer and Hamilton College professor Samuel Pellman, who devised the chimes’ pitch. Pellman died in a 2017 cycling accident after completing work on the project.
From the get-go, there were challenges.
“I thought we’d be making models and testing them in wind tunnels,” says Murdoch. “But the models we needed to make wouldn’t fit in the wind tunnels that are available.”
This meant trucking prototype chimes out to Simi Valley, the Arizona desert and Morton, Ill., for testing — sites that had similar wind conditions to Pennsylvania.
The other difficulty: devising an efficient striker to make the chimes ring. Think of that wooden circle in the middle of a backyard chime, which, when agitated by the wind, bumps into the chimes and makes them resonate. In the case of the Tower of Voices, the striker would need to be heavy enough to produce sound when hitting a 10-foot chime but light enough to be dynamic in the wind. And, oh, it would have to be durable, able to survive summer heat, winter snows, high-velocity wind storms and plenty of precipitation.
In addition, because the chimes were staggered along the inside of the tower at various heights, no single striker would be able to hit all of the notes. That meant designing a striker for each chime. To prevent a tangle of cables within the tower, each striker had to be embedded within the body of each chime.
“That made the technical challenge really difficult,” says Murdoch. “While you get a really robust sound when you strike a chime externally, internally you only have have a couples of inches to move the striker enough.”
Acoustics expert Elizabeth Valmont of the design firm Arup, who worked on the project, told Popular Science the design was unprecedented: “Having a chime work like a bell, where there’s a hammer inside the tubes, had not been tested before.”
They were able to devise a striker that worked efficiently. But the team was then faced with the issue of wear and tear. After a single day of testing in Simi Valley, cables were already fraying. If they replaced these with more heavy-duty chains, the additional weight made the striker less responsive to the wind.
“On the one hand, it needed to be robust, but it needed to be lightweight enough to be responsive,” says Murdoch. “Reconciling those two things was turning out to be a real challenge.”
It was at this point that a friend suggested Murdoch turn to an unusual source for design advice: Nord Embroden, a devotee of land sailing, a sport in which boat-like vehicles on wheels use the wind to reach speeds of more than 100 miles per hour.
“What they basically do is create a vehicle that is powered by the wind,” says Murdoch. “It has to be responsive to the wind — especially when they are racing. And it has to hold up against high speeds and a lot of grinding. I said, ‘This sounds like the right combination.’"
Originally from Long Beach, Embroden runs a small industrial design firm called Nord Design that has worked on everything from specialty household fixtures to gear for oil drilling rigs. He is now based out of Piñon Hills, a small desert community at the edge of the Mojave, which puts him in close proximity to a dry lake for land sailing. In the past, he has set speed records in the sport.
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Intrigued by the challenge, Embroden joined the team — and immediately got to work producing prototype sail mechanisms that could efficiently move the strikers within the body of the chime without falling apart. These they tested under live wind conditions in Morton, Ill. They all worked. Since then, the team has worked on refining the design and its materials so that it would be rugged enough to withstand the elements over the long-term.
In May, Embroden traveled to Pennsylvania to run his first on-site test.
“There’s an old homestead site there from the 1800s, and I walked up there into the trees, and you could hear that chime, and it was so clear,” he recalls. “It was really emotional to have all of that happen and to have been a part of making that happen.”
“It was beautiful.”
For Murdoch, the installation of the finished chimes marks the culmination of more than 15 years of work.
In 2004, he was one of more than 1,000 designers to submit a concept to the public competition for the Flight 93 memorial. A year later, his firm had landed the commission in conjunction with Nelson Byrd Woltz.
The proposal featured an entrance that brought visitors to the site through a pair of concrete walls bisected by a footpath that mirrors Flight 93’s final trajectory. From there, a crescent-shaped path, lined by 40 groves of trees in memory of the dead, embraced what had once been the bowl of the open-pit mine. This led to the memorial plaza with views of the crash site.
The design was less about creating a single iconic monument structure than a contemplative procession through the 2,200-acre site.
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“It’s a choreography of natural and commemorative moments,” says Murdoch. “You can drive around the bowl, but those who can walk, it gives them time to reflect on what they’ve seen. By the time they get to the memorial plaza, they are in a different frame of mind.”
Murdoch was used to public processes when he landed the gig. His small firm specializes in public buildings, such as libraries and community centers. But this was his first memorial — one that not only occupies a vast area but whose design would be scrutinized at a national level while memories of the events in question were still fresh.
He recalls poignant early meetings with the family members of those killed. “It was very difficult,” says Murdoch. “Very emotional.”
Add to this a cocktail of politics.
In the early phases of design, the National Park Service had not yet acquired all of the necessary parcels of land, which meant the firm was producing construction documents without having surveyed key parts of the site.
In addition, after the designs were presented to the public, a self-ordained minister in a nearby town publicly theorized the crescent-shaped path secretly alluded to the crescent and the star, a symbol commonly associated with Islam. This led various right wing commentators and Tom Tancredo (then a congressman from Colorado) to stage a conspiracy pile-on. A passenger’s father asked to have his son’s name removed from the site, a request the National Park Service declined.
“It became a political hot button,” says Murdoch. “But once the design was explained directly to people — instead of some fringe online group misinforming — they backed off.”
Despite the challenges, Murdoch believes the memorial that has emerged from this process is one that transcends the debates of any given moment. He credits the forward-thinking nature of the families who were involved in the design process.
“One thing that impressed us was that they had a more transcendent perspective of why the memorial should be done,” he says, “not just for their healing but for future generations.”
That is a concept that has resonated with visitors. Parks superintendent Stephen M. Clark says that even though it has been almost 20 years since the attacks of 9/11, the Flight 93 National Memorial continues to be a draw.
“It was stated over and over that people would stop coming,” says Clark. “Plane crashes happen, and this is very solemn and very sad, but visitation will come to a very slow pace. However, it has been anything but. Visitation has continued to increase to an average of 400,000 visitors a year.”
Clark says he is particularly moved by the tower and the sounds it produces.
“That tower really puts me in a frame of mind of what those people in the plane witnessed, and that they had the courage to fight back against unbelievable circumstances,” he says. “The symbolism of those voices, that really speaks to me.”
Murdoch says the story of the passengers and crew on Flight 93 is one that remains meaningful to him as well.
“This is a group of 40 people who got on an airplane together one morning and somehow figured out what was happening and, very quickly, came together despite the fact that they didn’t know each other,” he says. “They didn’t stay passive. Nor did they get split up by a bunch of differences. They came together with purpose and took a stand.”
“Every generation has its challenges to keep our democracy healthy and vital,” he adds. “What these people did is really important to this country.”
At the memorial, their voices continue to echo.