In this work, an embedded heat source vapor chamber (EHS-VC) is proposed for efficient and cost-effective heat dissipation in a limited space of aerospace electronics. The effect of the filling liquid mass and the layers of copper mesh under different working conditions on the heat transfer performance is systematically investigated. EHS-VCs are filled by deionized water with different filling liquid mass of 0.5 g, 0.75 g, 1.0 g, 1.25 g, and 1.5 g. The layer numbers of 250 in⁻¹ copper mesh in EHS-VC are 3, 5, and 7. The results indicate that the optimized EHS-VC with a filling liquid mass of 1.0 g and 5 layers of copper mesh shows superior thermal performance among all tested working conditions. The surface temperature distribution of the optimized EHS-VC remains relatively stable and the surface temperature of the optimized EHS-VC increases linearly with heat load. The optimized EHS-VC can achieve a minimum thermal resistance of 0.19°C/W and a maximum critical power of 140 W. Compared with diamond/copper composite plate (D/C CP), EHS-VC shows great potential for efficient and cost-effective heat dissipation in a limited space of aerospace electronics, resulting in a 25% reduction in thermal resistance at the same heat load of 140 W.