All Set to Go Supersonic?

Is it not strange that in the world of aviation, where “Faster, higher, farther” is a cherished mantra, business jets seem perpetually stuck at a maximum speed of 900 to 1,000 kmph? Ever since the M2.02 Anglo-French Aérospatiale/BAC Concorde, a turbojet-powered supersonic passenger airliner, was retired from service in October 2003, no civilian transport aircraft has crossed the speed of sound (1,235 kmph). Consequently, there are scores of commercial flights today that stretch over 15 hours. If this seems like refined torture for travellers, think of the torment of businesspeople – a breed not noted for patience.

However, help may be at hand courtesy supersonic business jets (SSBJ). An SSBJ, surely the ultimate status symbol, would be ideal for a harried CEO who wishes to attend a distant conference and be back in the office the same day. The 18-hour Singapore Airlines’ Flight 22 from Changi to Newark, New Jersey – the world’s longest by time – has only business class seats, a pointer to significant latent demand for SSBJs, so long as ticket prices are comparable to those of business class.

ADVANTAGE AERION?

A handful of corporations in the United States are striving to provide tangible wings to supersonic dreams and SSBJs that can slash long flight times by half or more may be operational in just five to seven years. Among the more promising is Spike Aerospace located in Boston with its M1.6 18-passenger S-512 SSBJ. Boom Technology in Colorado has even more ambitious plans – a M2.2, 55-seat supersonic airliner. But analysts reckon that Aerion Corporation of Reno, Nevada, has the best chance of being the first to bring its Aerion AS2 SSBJ to the market.

Unlike other more recent entrants in the field, Aerion Corporation is well funded and has been working on supersonic jets since 2004. In fact, it had planned the service entry of its first Aerion SSBJ way back in 2011. However, consequent to the global economic crisis of 2008, the bottom fell out of the business jet market, forcing Aerion to put its plans on hold. The current AS2 variant of the Aerion was announced in May 2014 at the European Business Aviation Convention and Exhibition (EBACE) held in Geneva, Switzerland. Aerion is now collaborating with industry leaders such as GE Aviation, Boeing and Honeywell to develop this redesigned and updated version of the original Aerion with a larger cabin, longer range and power by three engines.

The AS2 has a cabin designed by Honeywell that will accommodate 12 passengers. Building on a century of Boeing’s aerospace technology advances, the jet will have a swept wing configuration, incorporating supersonic laminar flow technology and a new fuselage design that will reduce wing drag by 60 per cent and overall aerodynamic drag by 20 per cent. Other features, including the use of carbon-fibre composites known for their strength and light weight, will make it more efficient and economical to operate, promising lower fuel consumption and increased travel ranges of approximately 4,200 nautical miles. The AS2 will have a service ceiling of 60,000 ft, will be capable of super-cruise at Mach 1.4 over water and fly overland at Mach 1.2 without the sonic boom reaching the ground. This will be achieved by exploiting the “Mach cut-off” phenomenon. Mach cut-off occurs under suitable conditions of flight speed and atmosphere, in which the thicker air at lower altitude refracts the sonic boom away from the ground.

AERION AND AFFINITY – MADE FOR EACH OTHER

Developing a supersonic aircraft is not difficult. The sound barrier was broken as far back as in 1947 and today, there are thousands upon thousands of supersonic military aircraft in service around the world. However, apart from the Concorde, there has been only one other commercial supersonic jet – the Tupolev Tu-144, developed by the aerospace industry in the then Soviet Union. Unfortunately, the Tu-144 turned out to be ill-fated and was permanently retired from passenger service in 1978 due to intractable safety and budget concerns after it had logged just 55 passenger flights. The reason for the stark contrast between military success and civilian failure is that while fighter jets are largely free of noise and fuel burn constraints, commercial aircraft must meet stringent standards that will only keep getting tighter. That is why the engine is probably the most crucial part of SSBJ development. While subsonic engines aim for a high-bypass ratio design for best fuel economy, supersonic power plants need balanced performance across both subsonic and supersonic regimes, for which a medium-bypass design is the best.

Unlike other more recent entrants in the field, Aerion Corporation is well funded and has been working on supersonic jets since 2004

Aerion’s confidence about the AS2’s development prospects stems largely from GE Aviation’s recent announcement that it has completed the initial design of its 16,000 to 20,00lb Affinity turbofan. Affinity, which as per GE, is a hybrid between an airline engine and a combat aircraft engine, will be the first supersonic engine specifically designed for business jets. It is a twin-shaft, twin-fan turbofan controlled by a next generation Full Authority Digital Engine Control (FADEC) for enhanced reliability and on-board diagnostics. Built around the iconic GE CFM56 engine core, it is claimed to have good fuel economy characteristics that will exceed current Greenhouse Gas (GHG) emissions standards. It is also purposefully designed to meet stringent Chapter 14/Stage 5 airport noise requirements that will be a mandatory requirement for aircraft certified after 2020. The Aerion’s cruise speed has been intentionally reduced from M1.6 to M1.4 to facilitate a modest compression ratio and keep ram drag – loss of thrust caused by increasing the velocity of the air entering the engine – under control.

PITFALLS AHEAD

However, while SSBJ technology is advancing apace, there is as yet no assurance that there will be enough global demand to justify the huge investment required. Even assuming some major technological breakthroughs, supersonic flight will never be at low cost. And however advanced their engine, SSBJs will inevitably burn far more fuel per passenger than subsonic jets do. With each day bringing further dire warnings about global warming from the Intergovernmental Panel on Climate Change (IPCC) and others, supersonic business travel that spews tonnes of GHG into the upper atmosphere, may appear rather reprehensible. Although their overall impact on climate change may not be significant, SSBJs could attract punitive taxes or regulatory hurdles that make it impossible for them to operate as intended.

Aerion however, remains optimistic. It is striving to avoid the pitfalls that grounded the Concorde which were high operating and maintenance cost, prohibitive ticket prices and regulatory hassles. The US Federal Aviation Administration (FAA) and other bodies are also working with the International Civil Aviation Organisation (ICAO) to develop international noise and emissions standards specific to supersonic flight.

In December 2017, Aerion revealed its planned timeline for the AS2. The SSBJ will take to the air for the first time in 2023 and make its first transatlantic flight on October 24 that year – to mark 20 years of the Concorde’s last commercial flight. The company hopes to achieve certification by the end of 2025 and bring the $120 million jet into service in early 2026. Aerion will produce about 500 AS2 SSBJs in all and reinvest the proceeds in larger and faster follow-on designs, including perhaps a supersonic airliner. According to Aerion CEO Tom Vice, “Our mission is to enhance global mobility with supersonic speed, starting with business aviation and following with successively faster and larger designs for business and commercial aviation.” Time will tell if the Aerion AS2 and other SSBJs will be economical and technologically advanced enough to mitigate climate change concerns and thus operate freely, on par with other business jets.