Recent years have proven that sending humans to Mars may be challenging but not impossible. Earlier tests have proven that nuclear rockets can be more efficient than chemical rockets. In a chemical rocket, the propellant requirements are enormous, which means higher launching costs. This, in turn, will result in a longer trip time. Meanwhile, nuclear rockets have at least twice the propellant efficiency of chemical propulsion systems, allowing a reduction in propellant requirement and launching costs, decreasing the trip time by almost a half, thus, making them more desirable for beyond low earth orbital missions. In this study, a nuclear thermal rocket (NTR) was designed with U235 enrichment of 19.75% to power up the rocket and produce a high specific impulse (Isp) that ranges between 850s-900s. Two different configurations were designed using Monte Carlo code Serpent 2 to test their material performance (including fuel, tie tube, and moderator) under operation. Hence, they put together an optimum configuration to withstand a harsh operating environment to achieve the mission goals. Moreover, temperature analysis was done using MATLAB to extract the power distribution from Serpent 2 to find the average value of the exit temperature for the propellent in addition to the fuel temperature and, thus, perform Isp calculations. The obtained results reflected the ability of the reactor to operate at temperatures as high as 2500 K to deliver a sufficient value of Isp that is equal to 864.15 s, which is a high value compared to any other convention chemical rocket.