Nov 19, 2019 / Travel
Understanding the supersonic flight experience
What should passengers aboard a supersonic commercial jet expect upon breaking the sound barrier? The answer may surprise you.
How does it feel to fly supersonically? Descriptions of breaking the sound barrier are rife with hair-raising myths and legends that promise an exhilarating sense of speed. But if truth be told, the experience is barely noticeable — even in a fighter jet. Speed alone doesn’t deliver the supersonic thrills of popular imagination.
This week, we’ll take a deep dive into the supersonic flight experience and shed light on what passengers can expect when flying Overture, our supersonic airliner.
Breaking Mach 1.0
Without instruments to indicate an aircraft has exceeded Mach 1.0 (the speed of sound), most pilots won’t recognize the exact moment their aircraft transitions to supersonic speed. In fact, passengers on Concorde may not have known they broke the sound barrier at the very instant it happened.
Lourdes Maurice, a retired FAA expert and advisor to Boom, flew Concorde once in 1998 from New York to London. Maurice traveled with her husband and eight-year-old son to celebrate the completion of her PhD in mechanical engineering. “Flying on the Concorde was an awe-inspiring experience, but without the display to indicate that we were flying supersonically, I wouldn’t have known it,” recalls Maurice. “Climbing to 60,000 feet was incredibly smooth. There was no turbulence. We knew we were flying supersonically, but our bodies didn’t give us any signs.”
In aircraft designed to fly supersonically, there are no sudden changes that indicate speed is changing. It’s difficult to sense movement. At cruising altitude, there is no sensation of speed because there is no reference — you don’t see landmarks on the ground that enable you to recognize your speed.
The Higher the Climb
The higher the climb, the thinner the air. This fact doesn’t solely apply to mountain climbers; it has implications for all aircraft. At higher altitudes, thinner air means less resistance for the aircraft and a smoother ride, in addition to fuel savings.
Today, most commercial airliners cruise between 33,000 and 42,000 feet. At 60,000 feet — Overture’s cruising altitude — the air will be extremely thin, resulting in little to no turbulence.
Transonic Regime: In the supersonic neighborhood
Commercial airline passengers often come close to supersonic speed without knowing it. This occurs when aircraft travel in the lower spectrum of the transonic regime, which ranges from Mach 0.8 to 1.2. Several commercial aircraft in operation today can achieve transonic speeds, including the Boeing 747–8i (cruising speed of Mach 0.86) and Airbus 380 (cruising speed of Mach 0.85). Private jets also fly in the transonic regime: the Cessna Citation X+ has a maximum speed of Mach 0.935 and the Dassault Falcon 7X can reach Mach 0.90.
While these speeds are impressive, they won’t shave much time off a journey. The Boeing 737–800 — flown by Alaska, Delta and United Airlines to name a few — cruises at a notable Mach 0.785. Its faster counterparts, which reach cruising speeds ranging from Mach 0.8 to Mach 0.9, may arrive at a destination about 10 minutes faster.
Weather and wind, as opposed to maximum aircraft speed, can offer a “boost” to beat the clock. Tailwinds (the jet stream) can accelerate an aircraft’s speed traveling east over the Atlantic or east over the North Pacific Ocean during the winter months. In fact, commercial aircraft used the jet stream to set new records for subsonic transatlantic crossings during February 2019’s winter storm. A Virgin Atlantic flight from Los Angeles to London reached ground speeds of up to 801 mph — faster than Mach 1. But it wasn’t flying supersonically. It was swept along in the fast-moving air, which clocked in at 231 mph.
Roller Coaster Ride
Thankfully, supersonic flight isn’t the roller coaster ride we might imagine. Speed alone doesn’t create the Top Gun moments known as pulling Gs or G forces.
Pulling Gs is the physical effect of a sudden change in velocity. While gravitational force remains constant, the incremental acceleration felt is due to a sudden change in direction or abrupt turn. Pilots describe it as the sensation of the body being pulled into the bottom of the aircraft: stressed muscles, dizziness and a sense of being weighed down — a feeling of otherworldliness. Pulling Gs is a matter of acceleration (positive or negative), direction, and the duration of time that G forces are experienced. It can lead to loss of consciousness or “tunneling out” when blood pools in the legs — known as a G-LOC (G-induced loss of consciousness).
Aerobatic aircraft maneuvers are a good example of G forces: think swoops and circles and turns. On a roller coaster ride, you will feel G forces, but it’s unlikely that it will be anything more than a thrill. Roller coasters are designed to delight, and the G forces they generate are tolerated by most people. You might even feel a second of pulling Gs when an elevator “dips” before reaching the correct floor.
Apart from a moment or two during takeoff, it’s unlikely that commercial airline passengers will feel significant G forces because aircraft maintain a steady speed and direction.
In commercial aircraft, speed transitions are rarely noticed. And in supersonic aircraft, passengers who drift off to sleep might be surprised to wake up and learn they’re traveling at Mach 1.7.
Imagine flying on Overture at 60,000 feet above the earth — and experiencing zero turbulence. The only sign that you have surpassed the speed of sound is a display that indicates Overture’s speed. Out your window is a stunning view of the curvature of the earth: a view usually reserved for astronauts… That’s the supersonic flight experience.