The thesis focusses on the effects that an intercooler (IC) and an inter­turbine burner (ITB) have on the cycle performance of a UBPR engine. The IC is located between the low­pressure compressor (LPC) and the high­pressure compressor (HPC). It exchanges heat between the core flow and the bypass flow reducing the temperature in the core flow. This has the advantage of a lower HPC­inlet temperature reducing the work needed to reach maximum compression. This also reduces the combustion inlet temperature which reduces the turbine inlet temperature (TIT) or increases the power density of the core. The ITB reduces the TIT by transferring some of the fuel to the ITB. This reduces NOx emissions. The objective is to analyze the effect that several design parameters have on the on­design performance and to analyze the optimized cycles to compare the advantages and disadvantages of each. Both the IC and ITB improve the thrust specific fuel consumption (TSFC) of the cycle. They also reduce NOx emissions. The ITB reduces NOx emissions more because of the extra degree of freedom during take­off. Varying the ITB energy fraction dependent on the ambient conditions has a positive effect on the NOx emissions during take­off at a slight TSFC increase. Combining an IC and an ITB in the cycle does not add the benefit of each for the TSFC but does add the benefit for NOx emissions as it reduces this even more. The IC­ITB engine is thus found to be optimal over the other engines because the NOx emissions are substantially lower than for the other investigated cycles.