The biennial Paris Air Show is supposedly the world’s largest, oldest and the most prestigious air show of them all. This means that the big players in the aero industry feel compelled to make hyped up announcements to wow the crowd. This year there were two announcements of supersonic jetliners_ EADS first announced the ZEHST and then HyperMach Europe Aeronautics disclosed the SonicStar. While the ZEHST shall run on seaweed bio-fuel, the latter will run on regular jet fuels (Jet A, JP-4 and JP-7). Both aircraft are tailor made with, as the HyperMach website claims, “custom super luxury for the VVIP executive class, government officials and diplomats” or in other words, the snobs and the obnoxious elites only. Even though it may only seat 20 VVIPs, there will be special cryogenically climate controlled compartments for “specialty and luxury high worth transport items such as thoroughbred race horses”. The HyperMach’s “Contact Us” page has a broken form script and has been returning an error message for days as of this writing. (The contact details for the executives are available.) Nevertheless, the company is inviting investors. £100 will buy you one share. Better hurry because they want to do the first test flight in 2021.
Take a look at the picture below. The first thing that gives away the vehicle’s speed rating is the pointed nose, denoting a supersonic regime. (Hypersonic planes have blunt noses, note the Space Shuttle’s nose.) HyperMach claims that it has a top speed of Mach 3.8, limited by aerothermodynamic heating at higher Mach numbers (heat caused by the shock waves) resulting in ionization of air and formation of super-heated plasma around the vehicle.
The HyperMach site claims that the SonicStar is supported by the UK and French governments (just as the Concorde was). However, the SonicStar’s design specifications are quoted in imperial units, suggesting that the designers could be American. Although the site does not directly suggest the US government’s involvement, the artist’s conceptual drawing of the engine nacelles show the US flag along with the French and British flags. The site does state that the craft will be certified with the FAA.
A lot of technical specifications are provided on The Science page for those technically minded. The drawings look very pleasing to the eyes. But the drawing of the engines do not look realistic. For starters, the engine inlets do not look like they will catch the shocks well and the large area of cross-section of the turbofan engine will create tremendous drag penalties. The exhaust nozzles do not look supersonic. The little canards are pretty much useless at subsonic speeds for lift or control. Perhaps they may be useful for control at high subsonic speeds, especially in the transonic regime (Mach 0.85 to 1.1). They seem to have done a well enough job with the preliminary conceptual design, probably enough to sell the ideas to prospective investors, who may think the canard idea is very cool.
The two futuristic hybrid engines give the craft a cruising speed of Mach 3.3 at 60,000 ft (18 000 m). The Concorde had a top speed of Mach 2.04. Unlike the turbojets on the Concorde, the SonicStar is going to have a conceptual engine that they call the Supersonic-Magnetic Advanced Generation Jet Electric Turbine (S-MAGJET). This engine lacks a direct shaft or gear coupling of the turbine to the compressor and fan. Instead, the turbine will drive a generator to produce electric power. The compressor and fan will be driven by electric motors and will be rotated at different speeds independently. “The bypass fans running independently from the compressor can be run at much slower speeds than the compressor, this means a more efficient RPM for the fan blade design of the S-MAGJET, a low bypass fan supersonic engine design.” The lack of shafts and gears (and bearings, etc.) may result in weight and cost savings, but then generators and motors are not exactly light weight. They have copper coils and copper is heavy. What about batteries? Another source of added weight. Power converters (ac to dc, dc to dc, etc.) are also heavy because they need coils for inductors/transformers and large capacitors. Plus, their generators are superconducting generators, which require heavy cryogenic systems. Where are the heat exchangers going to be, how large are they going to be and how much do they weigh? There are more design flaws with this engine concept but I’ll pass for now.
I think the S-MAGJET engine is too far fetched and unrealistic. If they go with these engines, they may not be able to achieve the target dates of 2021. My advice is to just go for the old fashioned turbo-jet plus ramjet combination like the SR-71 (the Pratt & Whitney J58-P4). That idea worked well enough back in the 60s and they certainly can get them working again by 2021. That engine concept will also give them the fast turn around time required for the intercontinental return flight.