For the class of high Mach number scramjet known as the inlet-fueled radical farming scramjet, the manner in which the ignition and heat release regions scale with pressure (that is, altitude) for different ﬂight Mach numbers, has been studied by means of shock tunnel experiments and high ﬁdelity numerical computations. The generic two-dimensional Busemann-like scramjet conﬁguration of Odam  has been re-designed and lengthened, so that the variation of combustion length scales with altitudes, can be examined. A set of experimental conditions were examined over a range of total pressures varying from 5MPα to 40MPα and total enthalpies from 3MJ/kg to 6MJ/kg, corresponding to an equivalent ﬂight Mach number ranging from Mα_flight=8 to Mα_flight=11 and a ﬂight dynamic pressure ranging from q_flight=58kPα to q_flight=194kPα. All tests conducted during the experimental campaign were run fuel-off, fuel into nitrogen and fuel into air in order to dissociate the effects of injection and how they modiy the ﬂow structure within the engine, from the effects of combustion heat release and pressure rise. The experimental results presented here have been generated from surface pressure measurements and Schlieren diagnostic. For all test conditions, a careful numerical analysis of the scramjet inﬂow was ﬁrst produced using computation of the facility nozzle outﬂow, enabling the non-uniformity present within the freestream ﬂow to be accounted for. This computed nozzle outﬂow was then used as the inﬂow boundary of the scramjet CFD simulations. This methodology allowed for greater accuracy and better understanding of the complex and coupled phenomena of supersonic ﬂows and supersonic combustion. The comparison between the experimental results and their numerical reconstruction provided insight into the behaviour of scramjet across a broad range of ﬂight conditions and demonstrated the capabilities of CFD at capturing the trends of supersonic combustion in inlet-fueled scramjets. Building on the coupled experimental / numerical study, a detailed numerical study of the combustion process was performed over a much broader range of ﬂight conditions. This study included and extended the conditions achievable in the shock tunnel, and removed all the ﬂow complexities that make shock tunnel experiments different from ﬂight. The analysis uncovered regimes where different combustion scaling laws apply, depending on both the altitude and the equivalent ﬂight Mach number. It was found that at an equivalent ﬂight Mach number of Mα_flight=7.96, the combustion process in the scramjet engine behaves as the radical farming scramjet. There was limited chemical activity in the inlet, with radicals being formed only at the end of the intake ramps in the small regions of ﬂow separations. Combustion was not enabled in the ﬁrst “radical farm”, or shock-induced hot structure, in the combustion chamber, due to low reaction rates at that ﬂight Mach number. Further convection and mixing of air and fuel is required, and ignition occurs at one subsequent hot structure, depending on the pressure (dynamic pressure, altitude). The pressure sensitivity of the ignition and reaction phases of the combustion process was systematically extracted from the results. It is demonstrated that for this ﬂight Mach number and range of dynamic pressures q, that the ignition length correlation parameters qn∙L is constant for a value of the exponent n such that 1.1 ≤ n ≤ 1.2. In other words, the scaling parameter required to conserve the ignition length relative to the geometric scale of the combustor in the event of changes to the geometric scale is qn∙ L=const where 1.1 ≤ n ≤ 1.2. The fact that n is close to unity highlights the strong dependency of ignition on two-body reactions. On the other hand, the reaction length was found to scale as qn∙ L with n ≃ 1.5. During the length required for heat release reactions, both two-body reactions and three-body heat release reactions are signiﬁcant (n is between 1 and 2). As the total ﬂow enthalpy is increased, for conditions corresponding to equivalent ﬂight Mach number of Mαflight=9.17, Mαflight=10.30 and Mαflight=11.33, it was found that the inlet plays a major role in radical production. The chemical activity in the inlet is high, with intense production of H radicals as early as the injection location. For an equivalent ﬂight Mach number of Mαflight=9.17, at ﬂight dynamic pressure in the range of 47kPα ≤ qflight ≤ 144kPα, the ignition length correlation parameter can be written q1.1∙L=const. For ﬂight dynamic pressure in the range of 167kPα ≤ qflight ≤ 240kPα, the ignition location is anchored at the second hot structure in the combustor, after which the reaction length scales as qn∙L with n ≃ 1.7. For the two higher Mach numbers, the local pressure and temperature combined with the high level of radicals generated in the inlet permit combustion to anchor to the ﬁrst hot structure at all altitudes considered. The reaction length scaling parameter qn∙L is constant for a value of 1.7 ≤ n ≤ 1.8 at Mαflight=10.30, and 1.8 ≤ n ≤ 1.9 at Mαflight=11.33, showing that the reaction process was strongly governed by three-body reactions. This study combined the use of experiments and CFD computations to systematically investigate the combustion behaviour in the inlet-fueled radical farming scramjet. It contributes to the science of scramjets by demonstrating that the ignition lengths and reaction lengths can be successfully scaled applying the adequate correlation parameter, depending on the ﬁght Mach number and the ﬂight dynamic pressure (that is, altitude).