The Reaction Engines Limited LAPCAT Configuration A2 is a design study for a hypersonic speed jet airliner intended to provide environmentally friendly, long range, high capacity commercial transportation.
The requirement of LAPCAT is to reduce travelling time of long-distance flights. This requires a new flight regime with Mach numbers ranging from 4 to 8. At these high speeds, classical turbo-jet engines need to be replaced by advanced airbreathing propulsion concepts and hence related technologies need to be developed.
The LAPCAT A2 vehicle flying at Mach 5 was carried out by Reaction Engines. The vehicle study indicates that a 400ton, 300 passenger vehicle could achieve antipodal range without marginality. The vehicle relies on pre-cooled turbo-based engines employing a cycle based on the Reaction Engines SABRE spaceplane engine.
The great circle route is not used in this example because the route travels mostly over land. The sonic boom generated by travelling at supersonic speed can cause great discomfort for people on the ground, which was why Concorde was prohibited from flying supersonically over land.
SABRE, which stands for Synergistic Air-Breathing Rocket Engine, utilizes “atmospheric air” to propel it at first before switching to “rocket mode” to reach space. According to the ESA, “The end result of this made-in-Europe technology would be low-cost, reliable, and reusable engines, potentially enabling future vehicles that could perform the equivalent job of today’s rockets while operating like an aircraft – revolutionizing access to space.”
Although hydrogen can be ignited, the risks of an explosion or fire are lower compared to conventional airline kerosene fuel
Normally, as air enters a jet engine, it is compressed by the inlet, and thus heats up. It needs much more power to compress that heated air further by the engine’s compressor section, which reduces the compressor’s efficiency dramatically. Furthermore, this means that high-speed engines need to be made of materials that can survive extremely high temperatures. In practice, this inevitably makes the engines heavier and also reduces the amount of fuel that can be burned, to avoid melting the gas turbine section of the engine. This in turn reduces thrust at high speed.
Anything travelling at Mach 5 and above has to withstand surface temperatures of up to 1,000C. Aluminium and titanium melt like butter at this speed. Ceramic panels will have to be used.
During tests, the heat that accumulated at Mach 8 was up to 30% less than at Mach 5.
Race for the skies
Other companies are already working to make the supersonic business-aviation market a reality. Airbus has just patented a delta-wing Mach 4.5 hypersonic design that could be used to create business jets. Also, they are working with US-based start-up Aerion to make available a fleet of supersonic jets for wealthy clients.
Spike Aerospace, another US company, plans to launch a similar supersonic business passenger plane, with internal video screens linked to external cameras instead of windows. And Lockheed Martin has a commercial plane, the N+2, that will travel at Mach 1.7.
Data from Reaction engines
Capacity: 300 passengers (plus baggage)
Length: 139 m (456 ft 0 in)
Wingspan: 41 m (134 ft 6 in)
Wing area: 900 m2 (9,700 sq ft)
Max takeoff weight: 400,000 kg (881,849 lb)
Fuel capacity: 198 t (437,000 lb) liquid hydrogen
Powerplant: 4 × Reaction Engines Scimitar Precooled jet engine
Cruise speed: Mach 5.2 (6,370.2 km/h) supersonic, or Mach 0.9 (1,102.54 km/h; 685.09 mph; 595.32 kn) subsonic
Range: 18,700 km (11,600 mi, 10,100 nmi) plus a 5,000 km (3,100 mi; 2,700 nmi) reserve
Service ceiling: 28,000 m (92,000 ft) or 5,900 m (19,400 ft) subsonic
Lift-to-drag: 5.9 at 25 km, Mach 5.2; 11 at 5.9 km, Mach 0.9;
Specific fuel consumption: 40.9 kN‑s/kg (0.86 lb/(lbf⋅h)) at Mach 5.2; 96 kN‑s/kg (0.37 lb/(lbf⋅h)) at Mach 0.9
Noise: 101 dBa at 450 m (1,480 ft) lateral