Scilence the Boom

Mark Hansen

Tonight, I wantto talk about two things, both of which are futuristic in nature. The first reminds me of something we might have seen on theJetsons, the second we actually saw for 3 or 4 decades starting almost 60 years ago.

In mid-November I had the opportunity to go golfing with some friends in Scottsdale, Arizona. While there, one of the guys expressed that he really wanted to experience a WAYMO ride. I had to ask what a WAYMO was and was told that it was an autonomous -driverless taxi or Uber. I reluctantly agreed when I realized that I was to be the designated driver that night if we drove our own car.

At the exact designated time and spot arranged on the WAYMO app, the WAYMO vehicle slid up to the curb and the four of us piled in -I made sure that I sat safely in the back seat.

As it turned out, we ended up taking several WAYMO rides over the weekend, and every ride was smooth, with seemingly effortless lane changes, right turns, left turns, normal accelerations, as well as handling stop lights and stop signs with ease.

Towards the end of our stay in Scottsdale, I was becoming more comfortable riding in the WAYMO, so I decided to sit in the front passenger seat so I could see the large radar display better. I was fascinated to observe that the WAYMO was watching traffic in front and behind us, traffic in our lanes and oncoming traffic plus cross traffic at corners. It was even watching pedestrians on the sidewalks and in crosswalks!

The current WAYMO vehicle is an especially equipped, all electric Jaguar I-PACE SUV. It uses radar, cameras, and light detection and ranging or LIDAR and Al programing to navigate safely on surface streets. It turns out that safety statistics for Waymo vehicles have been better than human drivers. WAYMOs so far have not ventured out in northern climates where driving in snow and ice present a potential challenge for its programming. If a WAYMO vehicle finds itself in a peculiar situation like flooded streets or a traffic jam at a corner, it stops and a human back at support headquarters can give it suggestions on what to do nextto get out of the situation.

By the time the weekend was over, we were able to takefourWAYMO rides, and because I'm here standing before you tonight, you know that I survived this "Jetson-like experience!

The second futuristic item that I thought was fascinating was the recent resurgent interest in Supersonic passenger flight. You may remember the Concorde Supersonic Transport with its iconic droop-nose silhouette, which took its last flight in 2003, over 20 years ago.

The Concorde's ultimate success was dealt with a huge blow in 1973 when the US and other countries outlawed supersonic flights over land. This was because of the damage that associated sonic booms could cause. The extremely loud and sudden cracks of the sonic booms not only were startling to humans but were blamed for causing buildings to shake, and fragile building materials like masonry, plaster, tiles and windows to break or be damaged.

The Concorde was therefore relegated primarily to transatlantic flights between New York and Paris and London. Ultimately, the limited flight options and the costs of operations doomed the Concorde and its promise to make this world seem more accessible and smaller.

On January 28, 2025, a company called Boom Supersonic flewtheirX-B1 test plane at Mach 1.1 to 1.2 without any sonic booms recorded on the ground while it broke the sound barrier 6 times over the Mojave Desert.

Boom Supersonics' CEO, Blake Scholl stated that this test proved that what he calls "Boomless Cruise" is real and now can be applied to passenger airline flights over land in the nearfuture.

Just to review, a sonic boom is the thunder-like clap of noise we hear on the ground as an aircraft flies overhead taster than the speed of sound which is around 760 miles an hour. As an aircraft flies through the air, it pushes and compresses the air out of the way. The air pressure waves begin to pile up ahead of the plane and compress, forming shock waves. The shock waves move out and away from the aircraft, creating a very sudden change in pressure. When the energy from the crashing shockwaves reaches our ears, it is heard as the loud, momentary crack of a sonic boom.

Boom Supersonics' Boomless Cruise is a result of a phenomenon called "Mach Cutoff". The application of Mach Cutoff depends on complicated coordination of flying at speeds of Mach 1.1 to 1.3, plane flight altitudes of around 35,000 feet, and atmospheric conditions where denser air closer to the earth reflects or deflects the sonic boom sound waves from earth back up into the sky. This is much like a wave in a swimming pool being deflected off the wall of the pool back into the pool.

As a result of these successful supersonic tests, Boom Supersonic is in the development stage of creating a brand-new supersonic passenger plane which it has named "Overture".

If Overture is able to fly from Mach 1 to Mach 1.3 without creating sonic booms, flight times overland will be reduced by 50% over conventional passenger air travel. As an idea of how this might impact passenger flights, a flight from New York to San Fransico could be completed in 3 and½ hours instead of 5 hours. This means that you could take off from New York at 9:00AM Eastern Time and land in San Francisco at9:30AM Pacific Time. Because Overture will be able to fly at Mach 1.7 over the ocean, a flightfrom New York to London would take 3 hours and 40 minutes instead of 7 hours and 20 minutes, which is twice as fast as current plane flights.

With its anticipated 4800-mile range, Overture would be able to make trips to several European cities. Trans-Pacific flights would require a refueling stop somewhere halfway there. Even with a refueling stop, these flights will be able to save several hours over today's conventional flights.

Overture will have many improvements over the Concorde that are the results of advancements in technology, design, and materials that can be used now compared to what was available in the 1960s. These advancements may allow Overture to fly faster and quieter but also may allow itto be easier for the pilots to fly and to be more fuel efficient.

New real-time cameras and heads up display systems for pilots will allow Overture to do away with the distinctive droop nose that was required on Concorde during take-off and landing so the pilots could see the ground and runway. This drooping nose added weight and complexity to the plane. Overture pilot's direct vision to the front will be replaced by many external, high-resolution cameras that will be displayed on 3 large touch screens. Heads up display visors will be worn that will project the outside images to the pilot's eyes where the image from outside will move exactly like what they would see if they were looking out the nonexistent front window.

The nose of Overture will be very pointed with the fuselage sleekly angling back to modified delta-shaped wings. The delta wing shapes of both Concorde and Overture require that the planes land and take off at a higher attack angle, so the plane's nose is blocking the pilot's view of the ground. Delta wings are much better for supersonic speeds than traditional aircraft wings, which are better for subsonic flight speeds. As a tradeoff for the speed advantages of delta wings is lift.

There will be digital flight systems available to the pilot that will replace the multitude of analog systems of the Concorde. This will allow Overture to fly with 2 pilots instead of the 3 required on Concorde. It is estimated that with Overtures' new onboard computer flight systems, 80-90% of takeoffs and landings will be done under computer control.

Boomless cruise will require continuous and up to the second decisions and adjustments of air speed, altitude, and evaluation of weather and air density data. These will be made by onboard Al capable computer systems that certainly were not available to Concorde.

Since Boomless cruise was proven to be possible, Boom has been working on propulsion systems. Current passenger jets use what is called "High Bypass Turbofans". In a high bypass turbo fan, 90% of the air goes around the core of the jet with 10% of the air going through the jet where the jet fuel is ignited and burned to spin the jet turbine fans.

These high bypass turbo fans can improve fuel consumption levels, but when flying at supersonic speeds, the big openings of these engines cause too much drag for supersonic speeds.

Military supersonic planes use low or medium bypass turbofans which are usually tucked close to the body of the plane or its wings and have smaller square openings that reduce aerodynamic drag.

Boom wanted an engine that would be of this lower bypass variety, but it also wanted it to ultimately be able to be powered by100% sustainable aviation fuel. The designers of most jet engines, Rolls Royce, General Electric, and Prat & Whitney, were not interested in designing this new jet, so Boom had to develop their own.

Boom Supersonics' new engine is in the early testing phase now. They named it "Symphony". Boom's Symphony low bypass engine has not been yet tested on airplanes, but because of its anticipated ability to run continuously and reliably for long periods of time, modified Symphony engines are being designed for compact electrical generation that could be used for Al data centers to supplement their extremely large electrical needs. The generating systems will be about the size of a shipping container and will require no water.

Boom Supersonic has a lofty goal of rolling out the 65 to 80 passenger Overtures before the end of the decade. It is anticipating price points for tickets to be around $500 for flights in the US. Airline carriers such as United, American, and Japan Airlines have ordered 35 of the new planes with options to purchase 95 more.

On another front, NASA is approaching boomless cruising from another angle. They are using aerodynamics, wind tunnels and artificial intelligence to develop shapes of the plane that might allow itto break the sound barrierwithoutthe sonic boom.

Their X-59 experimental plane uses the fact that airspeeds are actually different on different parts of the plane. For example, the airspeed at the nose of the plane may be different than the airspeed atthewing or tail. Using these airspeed differences, the idea is to lessen the shockwaves produced by air compression much like noise canceling headphones.

The X-57 plane which NASA named "QueSST" for Quiet Supersonic Transport, was developed with cooperation of Lockheed Martin. It took its maiden flight on October 29, 2025. Wind tunnel testing and advanced computer modeling led them to develop an elegantly shaped plane with a very long flattened nose, about 38 feet of the total 99 feet.

It sports smallish, sharply swept delta wings and wings on its large tail. Its engine is located on the top of the plane to further disrupt shock wave distribution. Although the plane has only flown at 230 mph during testing so far, their hope is that ultimately, the plane will be able reduce the loud clap of the sonic boom, which is about 105 decibels, to around 75 decibels, which is the sound of a car door closing. So this means that instead of a sonic boom, you get a sonic thump.

Acknowledging these advancements in quieter supersonic flight and to encourage further research and development, President Trump lifted the blanket ban on supersonic flight over the United States. In his executive order, he stated that due to advances in aerospace engineering, material science, and noise reduction technologies, he is tasking the FAA to establish new standards for noise certification for aircraft exceeding Mach 1 for overland flights as long as the aircraft does not produce an audible boom on the ground.

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The near future holds promising and exciting new travel options, whether on the ground or in the air. There are still some hurdles and challenges these emerging technologies mustface. As we come back from break, we could discuss some of these challenges, but I would also be interested if any of you would take a ride in an autonomous vehicle, or if you would want to take a flight in the first days of paid supersonic plane travel.

I'd like to thank you for your attention tonight and for the opportunity to present tonight's paper. We'll see you after the break!