Bold Statement: "Speed is life" might seem dramatic, but when you consider the future of aviation, it’s spot on. Imagine cutting in half the time it takes to fly from New York to Los Angeles, transforming a six-hour flight into less than three. This is no mere daydream, but the potential reality offered by the groundbreaking X-59 Quest. We’ll be peeling back the layers of this revolutionary aircraft, from its power source, a modified General Electric F414 GE100 engine, to the intriguing theory of perceived loudness, a unique measure of the sonic boom's intensity.
Tantalizing Teaser: Of course, it’s impossible to discuss supersonic flights without paying homage to the legendary Concorde. This iconic aircraft reached blazing speeds with its delta wings and slim fuselage, but what led to its retirement? We're going to unravel the complexities of supersonic flight economics and the not-so-small issue of noise. As we look ahead to the X-59 and the promise it holds, we also keep our eyes on the horizon for further technological advancements in the field, ever eager for the next big breakthrough that brings us closer to an era of quiet, supersonic flight. Hold on tight; it's going to be a thrilling ride!
You're listening to the Pilot Photog podcast, where every airplane has a story. This strange looking aircraft will soon take to the skies with an unusual mission to be as quiet as possible. Designated the X-59, this NASA research vehicle is also known as the Quiet Supersonic Technology Demonstrator, or Quest. Let's take a look at how this unconventional jet could lead to two-hour New York to London flights and supersonic airliners that are faster than the Concorde, and why there may be some unique military applications for this technology. Time is money and speed is life. The faster you can get somewhere, the more time you will have to do the tasks you need to do at your destination. In aviation, more speed typically gives you more options in case things go wrong. This is true of personal travel on airlines or military aircraft en route to a target. When it comes to airlines, there's been an unofficial speed limit of about 600 miles per hour. For a typical airline flight from New York to London, travel time is around 6 and a half hours, and that hasn't changed in 50 years. It's not that we can't design aircraft which can travel faster than that. In fact, the Concorde was an airliner that could fly at over 1300 miles per hour. More on this incredible airplane later. So why does this speed limit exist for airliners? Well, it comes down to two main reasons efficiency and noise. For an aircraft to travel faster, it must produce more thrust, which in turn requires more fuel, and more fuel equals more cost. More efficient engines and more streamlined designs can help, but to this point most airliners have been optimized to fly around 600 miles per hour or just under the speed of sound. Flying faster than the speed of sound is represented by a Mach number, where Mach 1 is supersonic. Today's airliners and biz jets fly at speeds around Mach 0.7 to 0.8. Surprisingly, this speed limit has nothing to do with technology limitations, but with noise. When an airplane goes supersonic, a loud shockwave or sonic boom is heard. This loud noise can be annoying or even disturbing to people on the ground and, as a result, many countries, including the United States, have banned overland sonic booms for civilian aircraft. But what if we could make sonic booms quieter or virtually unnoticeable to people on the ground? Nasa is working on exactly this and has developed the X-59 Quest.
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To understand how the X-59 solves the noise problem, we first have to look at how sonic booms are generated. As an aircraft flies through the air, it is continuously creating pressure waves that emanate from the airplane. These waves travel at the speed of sound, which is about 678 miles per hour at 30,000 feet. The pressure waves travel in all directions like the ripples formed from a drop of water. When an aircraft goes supersonic, these pressure waves begin to pile up ahead of the airplane and compress, forming shock waves. This is similar to how waves pile up in front of a boat as it moves through the water. As an aircraft approaches the speed of sound, these shock waves will move out and away from the aircraft, creating a sudden change in pressure. This change occurs so quickly that we hear it as a loud boom or crack, known as a sonic boom.
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Remember the Concorde. While it could travel at Mach 2 or 1350 miles per hour, the sonic boom it generated was loud enough for several nations to restrict its supersonic travel to just over the ocean. An incredible feat of engineering and one of the most beautiful aircraft ever to grace the skies. The Concorde made use of delta wings and a slim fuselage, in service from 1976 until 2003,. The Concorde's technology worked, but the economics and acoustics didn't. It was too expensive to fly and too loud to operate supersonic over populated areas. But the dream of commercial supersonic travel did not die with the Concorde.
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In fact, prior to the X-59, nasa experimented with an unusually shaped F-16. Known as the F-16XL, this aircraft was initially a competitor to the now famous F-15E Strike Eagle. While the XL lost that competition, nasa soon pressed this double delta winged fighter into service to study, among other things, quiet sonic booms. The pair of XL aircraft were designated numbers 848 and 849 and were fitted with aerodynamic gloves with tiny holes to study laminar flow over the wings. These gloves did reduce the noise generated by sonic booms, but the cost to produce such gloves on civilian airliners was deemed too expensive and the program was cancelled in 1999.
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Fast forward to today and the quest for silent sonic booms has once again resumed in the form of the purpose-built X-59. This long and slender design helps shape the volume and lift distribution of the aircraft, which spreads out the buildup of shock waves so that they do not group or coalesce into very strong front or rear shocks, which typically are the cause of a loud sonic boom. Additionally, the X-59 is designed to fly at higher altitudes, around 55,000 feet. Today, most airliners operate between 30 and 40,000 feet. This increased distance from the ground also reduces the noise heard from the sonic boom. The X-59 is powered by a modified General Electric F414 GE100 engine, which is similar to engines found in the Navy's Super Hornet A proven and durable engine. It should allow the X-59 to fly at speeds of Mach 1.4 or just above 1000 miles per hour.
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And while it will fly supersonic, the real question is how loud will it be? You're probably familiar with decibels, which are used to measure sound, loudness or intensity. What you may not be familiar with is a metric known as perceived loudness or PL. Pl is used in the field of psychoacoustics to measure the subjective perception of the loudness of a sound by a listener. In other words, pl is a way to measure how loud a sound seems to us, considering how our ears and brain understand sound. For example, a firework going off 500 feet away would have a PL value of 113.6. The Concord Sonic Boom had a PL of 105. The X-59's Sonic Boom is estimated to have a PL of 75, which is equivalent to the PL of a car door being slammed across the street. So the X-59's Sonic Boom is more of a sonic thump.
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Aside from its design shape to reduce noise, the X-59 also features a flush cockpit, this along with a long and pointed nose effectively obstructs all forward vision. In order to see the pilot makes use of an enhanced flight vision system, or EVS, which consists of a forward 4K video camera. This flush canopy allows for a more streamlined aircraft and will likely become the norm as supersonic and eventually hypersonic airlines become viable. So what would one of these quiet supersonic airliners look like? Here is one such concept, which features an elongated fuselage and a windowless cockpit with black markings representing where the windows would be on a more traditional design. This aircraft also makes use of variable or swing wing technology Wing swept outward for takeoffs and landings and then wing swept back for supersonic or possibly even hypersonic flight. At speeds of Mach 2.2, this aircraft could make the New York to London trip in 3.5 hours, compared to the 6.5 hours it takes today. If this airplane were able to achieve Mach 3 speeds, then that same trip would take just 2.5 hours. Keep in mind that, while the sound problem appears to have been solved by the technology demonstrated in the X-59, we still have to contend with the efficiency problem, specifically fuel. An airplane flying at Mach 3 or even Mach 2.2 would burn enormous amounts of fuel, but perhaps, if these designs prove viable, then flying passengers may be willing to spend a little bit more to get somewhere much faster. There's also the economy of scale. As more supersonic aircraft are built and carry passengers. Then costs will go down Again. This was tried before with the Concorde, but perhaps today we are at a point in aviation technology where we can make supersonic commercial travel a reality.
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What about military applications? At first, a silent sonic boom does not seem all that important. Military operations are loud and in a contested environment noise doesn't matter, or does it? The latest push in military aircraft is all about stealth, which is the ability to remain undetected or unobservable for as long as possible. To this point, stealth aircraft have primarily focused on reducing the radar cross signature, or RCS, by shaping the aircraft to direct away as much radar energy as possible. Another aspect of stealth is heat or thermal management. Military aircraft generate large heat signatures, especially when an engine's afterburner is being used. Some stealth aircraft, like the F-117 Nighthawk, had shrouds over their engines to conceal and dissipate their heat exhaust. Interestingly, the Nighthawk is subsonic, with a maximum speed of Mach 0.92. Another component of stealth is sound. If an aircraft can be made to be as quiet as possible, then this would be another way for it to avoid detection. Perhaps designing a manned aircraft, or even drone that would have a reduced sonic boom could be an advantage. After all, a quiet, unseen aircraft that can strike targets before being detected would be valuable.
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Nasa's X-59 Quest represents a unique moment in the adventure that is aviation. Quiet, sonic booms or sonic thumps will likely open up possibilities for commercial supersonic overland travel that were once inconceivable and would redefine what we consider as fast travel. Flights from New York to Los Angeles, which currently take about six hours, could potentially be completed in less than three hours. This incredible speed could revolutionize international and cross-country business, enabling quicker transactions, faster deliveries and a significant boost in global productivity. It brings new weight to the phrase speed is life, as the impact of this technology could be truly transformative for a wide range of industries.
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As the technological development around the X-59 Quest continues, there will be many more milestones and breakthroughs to discuss. These may include progress in the testing phases, regulatory developments allowing supersonic flight overland, or perhaps even the first commercial offerings from aviation companies. As each development unfolds, I will continue to chronicle this exciting journey by creating new videos to keep you informed. The evolution of aviation is a compelling narrative and the X-59 Quest is a major chapter in that story. I look forward to keeping up to date with every twist and turn along the way.