One of the amidoamine-structured hyperbranched polymers is developed as an efficient macroinitiator to enhance the endothermic capacity of hydrocarbon fuels to meet the stringent cooling requirement of hypersonic aircrafts. Hyperbranched poly(amidoamine) (PAMAM) is treated with palmitoyl chloride to modify a lipophilic shell on the hydrophilic core, and the amphiphilic product, palmitoyl-hyperbranched poly(amidoamine) (PPAMAM), can be well-dissolved in hydrocarbon fuels. The long alkyl chains in PPAMAM break away from the core at about 200 degrees C, and the PAMAM core destructs around 400 degrees C. The high decomposition temperature of the core enables PPAMAM to be performed as a macroinitiator for hydrocarbon fuels. Thermal cracking of methylcyclohexane (MCH) from 600 to 720 degrees C with the addition of PPAMAM is carried out in an electrically heated tubular reactor under the pressure of 3.5 MPa. Significant improvements of the conversion, gas yield, and heat sink of MCH with PPAMAM are observed. The conversion of MCH is increased from 39.5 to 56.3 wt % at 690 degrees C, and the corresponding heat sink has been raised from 2.48 to 2.91 MJ/kg. Furthermore, PPAMAM with the optimum molecular weight is employed for the cracking of aviation kerosene. The heat sink is also improved significantly in comparison to that from the thermal cracking of bare kerosene, which confirms the effective application of PPAMAM in endothermic hydrocarbon fuels.