Hypersonic Aircraft return. Some Are Waiting This, Others Fear It

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Written by Marat Kushaev; Originally appeared at TASS, translated by AlexD exclusively for SouthFront

Supersonic passenger aircraft (SSPA) are likely to take to the skies in ten years. TASS – the difficulties facing engineers and the political struggle for speed

“Sometimes it seems that the disputes between experts will end in a fight. Europe is categorically against a supersonic aircraft that does not satisfy Chapter 14 on noise. But all understand that to build such an aircraft is a complicated challenge. The Americans avoid this question. They have a prototype almost ready, and it is clear that they will launch planes. Russia’s position for the moment is not to commit to anything but watch how everything will develop”, says the head of the Department of aero-acoustics and aircraft ecology of the Central Aero-Hydrodynamic Institute (CAHI) Victor Kopyev. The man in the front row agrees whole-heartedly.

In a room without windows, inside the immense “Sirius” Park – five years ago, thousands of journalists transmitted reports from the Sochi Olympics – brought together experts on transport, gathered at the forum “Science of the Future”. I arrived the day before and was tired: an hour and a half to the airport, still the same before take-off, two fifteen in the air, an hour on the hot parking lot in Adler (the driver did not want in any circumstances leave until the chartered bus was filled, and the quirky taxi drivers jacked up the prices and laughed at the greedy “Muscovites” (I myself am from the Urals and I laughed in response), then another half hour on the freeway to the hotel.

On a supersonic liner during this time I would have reached Vladivostok and, maybe even had time to swim in the Pacific Ocean. While such fast travel is impossible for the moment, in ten years time for sure for someone it will become commonplace. Only, of course, if the experts and regulators of different countries do not kill each other.

Why did the Tu-144 and Concorde have gone down in history?

Supersonic passenger transport once existed. On December 31, 1968, the Soviet Tu-144 took off for the first time, and a few months later, the Franco-British Concorde. They were not to be confused with anything: a narrow, elongated fuselage with a pointed nose, long deltoid wings, like feathering arrows, from the bottom, barely noticeable engines with angular shapes, reminiscent of old cameras of video surveillance. These were the aircraft of the future, able to accelerate to more than 2 thousand km/h, about twice the speed of sound and conventional passenger liners. But that future didn’t really arrive.

Supersonic passenger aircraft Tu-144. IMAGE: Boris Korzin/TASS

The speed of sound is not just a beautiful comparison. If you fly even faster, there is additional air resistance. The unusual subtle silhouettes of the Concorde and the Tu-144 allowed to overcome the sound barrier, but at a high price: despite the design tricks, both aircraft consumed an exorbitant amount of fuel, and could only accommodate a little more than a hundred passengers. Seats in the last Concorde flight between London and New York cost £4350 one way (adjusted for inflation at the current rate is about $8261.92 USD).

Fuel consumption is half the problem: the Concorde and the Tu-144 were a real calamity for people on the ground. To better understand this, I went to the Moscow region city of Zhukovsky, 40 minutes by metro and half an hour by train, to the scientific director of the CAHI and the project to develop the concept of a supersonic passenger aircraft of the second generation. “Here you see a ship is sailing. The wave coming from the nose of the ship spreads over a great distance, a lot of energy is used,” comes along from afar Academician Sergei Chernishev. With supersonic aircraft it is the same, but instead of water, it is air; the shock wave from the aircraft takes away some of the energy of the engine. Where the shockwave hits the ground, there is an explosion.

In reality nothing explodes, only a loud pop due to the pressure drop. This drop is only a few ten-thousandths of atmospheric pressure, but it is perceived by the ear as a distant rumble of thunder as if from nowhere. “People get scared. At night they wake up, and in the afternoon because of the suddenness it is unpleasant,” says Sergei Chernyshev. There were cases of breaking glass because of the low flying Tu-144 and combat vehicles, buildings developed cracks. Moreover, the sonic boom occurs not only under the flying aircraft, it covers the ground like a carpet tens of kilometres wide, which creeps under the aircraft, while the speed remains supersonic.

Supersonic passenger plane Concorde. Ian Waldie/Getty Images

In the US, the rumble of future aircraft so alarmed officials that the US Federal Aviation Administration banned the Concorde from flying over land even before they first took to the air with passengers on board (the United Nations International Civil Aviation Organisation, or ICAO, later adopted a resolution stating that supersonic aircraft should not create “unacceptable situations for people”). The potentially popular routes between the East and West coasts of the country were dropped, and since the world in the 1970s was not as globalised and rich as it is now, the Franco-British aircraft were left to fly over the Atlantic from New York to Paris, London and back.

Carriers suffered losses, despite the expensive tickets, in 2000, one Concorde crashed, killing more than 100 people, soon the civilian aviation industry suffered difficult times because of the September 11 attacks and rising oil prices in 2003, the Concorde made a final flight. No one remembers the Tu-144 of that time: the Soviet aircraft was decommissioned only seven months after the first commercial flight. Supersonic aircraft remained only at the Ministry of Defence and research institutes.

What do airplanes and swings have in common?

While still the Concorde flew over the Atlantic skies, the development of supersonic passenger aircraft of the second generation began. The state agencies and institutions of the EU, USA, Japan, Russia, corporations with a long history in the aircraft industry and recently opened firms are involved. Until the 2010s, only experts heard about it, but the closer the tests of new prototypes, the stronger the interest, and worries, of ordinary people.

Since the laws of physics have not changed in 50 years, the problems are the same: sonic boom and fuel consumption. There is something else – a deafening noise on take-off and landing. “Whistling from the first generation of aircraft was well, just beyond”, says Sergei Chernyshev. Jet spray from the engines literally tore the air. The volume of the engines can be reduced by increasing the diameter, but along with the overall dimensions air resistance will grow, the aircraft will consume more fuel or even be unable to overcome the sound barrier.

What have changed, unlike the laws of nature, are ICAO’s requirements for noise on take-off and landing. The Concorde and the Tu-144 made a painful hiss, but it was not contravened the then international standards. For the new aircraft to meet the current rules (Chapter 14, which Victor Kopyev mentioned in Sochi), it should have a 16 times lower noise level of the supersonic passenger aircraft (SPA) of the first generation. To do this, engineers are looking for new technical solutions, for example, trying to hide the engines in the design of the aircraft, so that the sound is shielded by the body and does not spread down to the ground.

Test model prototype aircraft in a wind tunnel, which is developed in CAHI

For sonic booms there are no such rules yet. According to Sergei Chernyshev, the Committee on Aviation Environmental Protection from the effect of aviation (CAEP ICAO) did not even agree on how to measure it: the pressure jump, the spectrum of sound frequencies or something else. In the last ten years, the sonic boom has been seen as pulse noise, the volume of which can be measured in decibels. “In a large city such as Moscow, Tokyo, Paris, background noise during the day corresponds to the level of 65-67 dB. It is logical to assume that this threshold is the permissible noise level, because no one will notice a flying plane. The noise of slamming car doors is also pulsed and relatively chose to 60-65 dB. Many experts believe that a sound stroke with an equivalent volume of 65 dB is acceptable during the day. Of course, at night the requirements should be tougher,” explains Sergei Chernyshev.

But even if the aircraft with such characteristics will be able to be created, it may not be enough. At the October ICAO conference, the representative of Austria expressed the opinion of the European countries: “Technical data show that the level of sonic boom during acceleration will be comparable to that of the Concorde at cruising speed. This level of noise has led to a ban on flights at supersonic speeds over populated areas”. And even a reduced sonic boom at cruising speed, according to the report’s authors, will cause people inconvenience. The debate about this has not subsided so far.

The Concorde had to slow down over land. “But to make an aircraft that is effective as subsonic, and supersonic, is simply impossible from the point of view of physics. Subsonic requires a long wing for good aerodynamics, but with such a wing it is impossible to accelerate the aircraft to supersonic speed – there will be huge resistance, as if the plane hit a wall” says Sergei Chernyshev. “To overcome the sound barrier, you need a short wing with a large sweep angle, but in subsonic such an aircraft is ineffective because of high fuel consumption. The second-generation SPA must be optimally tuned for a long, extended cruise flight at supersonic speed, and for such aircraft to get a start in life, it is necessary to adopt norms for a low sonic boom.”

Designing a supersonic passenger plane is like swinging on a swing. Long wings improve aerodynamics at low speeds, but do not allow overcoming the sound barrier. Engines with a large cross-section reduce noise while increasing resistance and fuel consumption. For a minimum sonic boom on the ground, the nose of the fuselage must be blunted, but this leads to an increase in air resistance and fuel consumption. Nevertheless, several supersonic machines are being developed around the world, and a couple of American companies are already accepting pre-orders from carriers.

How long do we have to wait?

For the supersonic passenger aircraft to appear in the sky, first it needs to show that they do not bother people. This is done with the help of prototypes-experimental aircraft to test the technology in action. The Lockheed Martin Corporation commissioned by NASA developed one such prototype. The X-59 QueSST prototype looks more like a futuristic fighter than a liner. Because of the very long nose, it does not even have windshields; the pilot is fed about what is happening overboard thanks to a pair of 4K video cameras. According to the designers’ idea, due to the small size and elongated shape of the prototype, it will produce a sonic boom no louder than the hum of the highway.

In 2023, the X-59 QueSST will fly over American cities several times a day, and NASA experts will ask residents about their experience. What answers they will get is hard to predict, even if the prototype exceeds expectations. Discussing supersonic aircraft, aviation historian Janet Bednarek told BuzzFeed that any noise is a problem. Although ordinary planes are becoming quieter, people still complain: one gets used to good things quickly.

Also, the public is sure to be outraged because of the high fuel consumption. In 2018, analysts at the International Clean Transportation Council, the very non-profit that found Volkswagen understating emissions in cars with diesel engines, simulated the flight of such a prototype. It turned out that the supersonic aircraft would burn 5-7 times more fuel per passenger than the subsonic, and emissions of carbon dioxide and nitrogen oxides will exceed the existing norms by 40 and 70%, respectively. Sergei Chernyshev’s assessment is more optimistic: fuel consumption will be higher by only 1.5-2 times. “You have to pay for speed”, he says.

According to the European Commission, aviation accounts for more than 2% of all greenhouse gases entering the atmosphere, and travel from New York to London and back leads to about the same emissions as heating a house for one European during the year. ICAO constantly increases requirements on engines, but for supersonic aircraft it changed the old rules but has not introduced new ones yet. Anyway, carriers in any case can buy quotas for additional emissions of harmful gases. Only because of this, transport tickets of the future will rise in price even more.

How much a trip will cost is unknown. The American company Boom Supersonic expects to set a price comparable to a business class flight. Boom Supersonic is one of three American firms that develop supersonic aircraft, and the only one whose prototype is designed for several dozen passengers. The other two, Spike Aerospace and Aerion Supersonic, are preparing small business jets that will be even more expensive to fly.

Boom Supersonic Overture aircraft project. IMAGE: Boom Technology, Inc.

“If you look at the needs of humanity, the market is ready. The first ones to fly will be those that fly business class at the corporations’ expense. Then there will be large-size aircraft. For whom? For Japan: they fly to Australia, the US and Europe. All their flights are either with a transfer, or direct, but exhaustingly long. The Japanese already want a plane for 100 passengers. Same in Australia. Europe – supersonic aircraft will be in demand on all transatlantic flights. And take our country: to Khabarovsk or Vladivostok in eight hours – the road is not pleasant,” says Sergei Chernyshev.

It won’t be long now. Boom Supersonic is going to test the prototype XB-1 next year, and by the mid-2020s, build the full-size liner Overture for 55-70 passengers. Sergei Chernyshev is more reserved in the estimates: in his view, the first prototypes will appear in the US only in 2023-2025, then the project needs to pass the Central Institute of Aerohydrodynamics security, and the first manned flights will take place no earlier than 2030. “By that time, all the norms for sonic boom and noise during take-off and landing should be adopted,” says the scientific director of the institute.

Why fly fast?

Only when supersonic aircraft of the second generation will be built, it will become clear what they are capable of and why they are really needed. When the Tu-144 was designed, they also dreamed of the Far East, but a commercial flight to Khabarovsk never appeared: the planes flew between Moscow and Alma-Ata. On Boom Supersonic’s website it is mentioned that Overture will be able to fly about 8.3 thousand km without refuelling, that is, on ultra-long flights, for example, from Australia to Europe, it will have to make an intermediate stop.

Refuelling, transfers, red tape at the airport, check-in, luggage, metal detectors, customs control, and the road to the airport takes a lot of time. I went to Sochi at the crack of dawn, and only got in time for lunch, after spending a little more than two hours in the air. Supersonic planes won’t fix these tedious procedures, so people won’t travel twice as fast.

However, travel time on long-distance routes will still be reduced. But these days the price of this accomplishment will seem too high to many. Income inequality is rising in almost all countries, and the planet is going to hell because of the changing climate. Someone will be outraged: “And rich people are rushing through across the world just because they don’t use video calling?”

Sergei Chernyshev looks upon this differently: “We are moving to another state, this is the second attempt, more elaborate. Distances are shrinking, the world is becoming even more globalised, horizons are opening up that may not be clear now. Who thought that mobile communications would be as it is now?” The faster humanity moves, the more advanced civilisation becomes. Maybe there is no causality, but the world of walking tribes with chisels is clearly different from the world of wagons and gunpowder, and that one, from the time when the car arrived. The return of supersonic aircraft, apparently, is inevitable, and then life will change again before our eyes.

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