and air friction on the body of an aircraft, especially at the nose and leading edges, becomes considerable, as the temperature is proportional to the square of the Mach number. That is why hypersonic speeds are problematic with respect to the strength of materials and are often referred to as the heat barrier. Ayaks uses thermochemical reactors (TCRs): the heating energy from air friction is used to increase the heat capacity of the fuel, by cracking the fuel with a catalytic chemical reaction. The aircraft has double shielding between which water and ordinary, cheap kerosene circulates in hot parts of the airframe. The energy of surface heating is absorbed through heat exchangers to trigger a series of chemical reactions in presence of a nickel catalyzer, called hydrocarbon steam reforming. Kerosene and water spits into a new fuel reformate: methane (70–80% in volume) and carbon dioxide (20–30%) in a first stage: CnHm + H2O CH4 + CO2 Then methane and water reform in their turn in a second stage into hydrogen, a new fuel of better quality, in a strong endothermic reaction: CH4 + H2O CO + 3H2 CO + H2O CO2 + H2 Thus, the heating capacity of the fuel increases, and the surface of the aircraft cools down. The calorific value of the mixture CO + 3H2 produced from 1 kg of methane through water steam reforming (62,900 kJ) is 25% higher than that of methane only (50,100 kJ). Besides a more energetic fuel, the mixture is populated by many free radicals that enhance the degree of ionization of the plasma, further increased by the combined use of e-beams that control electron concentration, and HF pulse repetitive discharges (PRDs) that control electron temperature. Such systems create streamer discharges that irrigate the ionized flow with free electrons, increasing combustion effectiveness, a process known as plasma-assisted combustion (PAC). Such concept was initially named Magneto-Plasma-Chemical Engine (MPCE), and the working principle referred to as Chemical Heat Regeneration and Fuel Transformation (CHRFT). In subsequent literature, the accent has been put more on magnetohydrodynamics than on the chemical part of these engines, which are now simply referred to as a scramjet with MHD bypass as these concepts intimately require each other to work efficiently. The idea of thermally shielding the engine is detailed in the fundamental analysis of an ideal turbojet for maximum thrust analysis in the aerothermodynamics literature. That is, putting the turbine