A scale model of a future supersonic business jet (SSBJ) took center stage at the stand of TsAGI, the Russian acronym for Central Aerohydrodynamic Institute, at the MAKS 2019 airshow in Moscow in late August. While bearing some resemblance to earlier models showcased two years ago, such as a gull-like shape of the wing, it differs in having a wider forward fuselage to house a passenger cabin.
In addition, the empennage of two vertical and two horizontal surfaces has been replaced by a V-like tail, while tunnels for air intakes leading to a pair of rear-mounted engines are longer. Sweep angles for the leading edges of both inner and outer wing sections have also been reduced, and the wing-to-fuselage attachment is extended by means of forward, rather than backward, sweep of the wing’s trailing edge.
Explaining these and other changes, TsAGI said, “Reducing sonic boom remains the key issue that keeps in the focus of attention for scientists from all over the world. The optimized layout of the future aircraft model on display at MAKS 2019 shall provide a lower level of the sonic boom and of the noise footprint on the ground, as well as higher fuel efficiency. The [aforementioned] model comes with an unusual shape of the wing: that featuring a characteristic V-like geometry and variable thickness along the wing-to-fuselage attachment. The air intakes leading to engines are positioned on top of the rear fuselage."
The company also addressed some issues to do with load-bearing structure and materials for future supersonics. A wide application of polymeric composites and metal-composite structures promises to reduce the SSBJ’s weight, it explained.
There is no information on SSBJ powerplant except for mentioning “use of liquid hydrogen as fuel for gas-turbine engines” being studied for application to “supersonic long-range flights” in a booklet at TsAGI’s booth at MAKS.
Shortly after MAKS closed, minister Denis Manturov said investments already made into SSBJ development amount to 1.4 billion roubles ($21.1 million). The ongoing effort is being led by TsAGI and six other scientific research establishments. He gave seating capacity at 16 to 19 and cruise speed at 2,000 to 3,000 kilometers per hour (1,090 to 1,620 knots).
Detailed specifications will be worked out in the 2020 to 2022 timeframe, along with construction of a technology demonstrator. Documentation for serial aircraft is expected to be developed between 2022 and 2026. Much investment is needed into powerplants because no existing engines appear suitable for the Russian SSBJ. Rough estimates render a deliverable SSBJ to be twice as expensive compared to subsonic business jets of similar seating capacity, Manturov said.
Also at MAKS 2019, TsAGI demonstrated a mockup of a load-bearing structure intended for the forward section of an SSBJ airframe. Main structural members are made of composite materials, while outer and inner skins are made of “advanced non-metallic materials."
TsAGI made a special point that this mockup employs parts made by additive manufacturing. It further notes that the mockup represents “a hybrid metal-and-composite forward section of the airframe” and “features a non-conventional load-bearing structure with implementation of modern engineering decisions arising from bionic principles." Such structures are also applicable to prospective long- and medium-haul passenger jets, the company said.
Another exhibit at MAKS was described as “a multi-walled composite panel of integral nature.” It consists of two outer skins, longitudinal walls, and lightweight filling. This exhibit is “a specimen for production” as “an element in load-bearing structure for high-loaded sections of the airframe.” Apart from stiffness and strength, such elements provide high resistance to impact, good thermal insulation, and noise-reduction qualities, as required for supersonic jets.
On August 26, TsAGI held a ceremony at the town of Zhukovsky, where TsAGI is located. As part of the event,a surviving example of the Tu-144 first-gen supersonic transport was placed as a memorial. Academician Sergei Chernyshev, the head of science at the institute, said: “The Tu-144 is a legend and an interesting page in TsAGi’s history. We commenced studies into supersonic transports even before the Tu-144 launch and have never stopped working on the theme since then. Today, we do this work with other priorities and standards in mind. As part of the ongoing effort, we work on some technical issues related to tough ecological requirements."
Earlier this year, speaking on the occasion of the 50th anniversary of the Tu-144's first flight, TsAGI general director Cyril Sypalo said the institute works with Tupolev on “a project not less challenging than the Tu-144 was”—development of second-generation supersonic transports. “It may well turn out that what we do today would prove a task more difficult…as we are moving from the technology demonstration phase to actual creation of a commercially viable means of transportation. Of particular interest is a supersonic business jet project being executed jointly by Tupolev and TsAGI."
Sypalo further said that, under orders from Russia’s ministry for industry and trade, the two companies are to work out “compromise technologies” that balance a required level of sonic boom versus cost, as well as operational performance of a future supersonic aircraft. Last year, the aforementioned ministry forecast that, at a unit cost between $100 and $120 million, the demand for next-gen supersonic transports would come to 30 aircraft in Russia and “many more” outside the country. It added that the research and development effort could take seven to eight years.