Assessing General Propulsion Architectures for Fast Transit Times to Mars for Crewed Missions

As NASA and commercial contractors, such as SpaceX, continue to develop their programs with Artemis and Starship respectively, it is becoming apparent that the program developments are ultimately leading to a method to transport humans to Mars. However, the current travel time to Mars requires 6–9-months one way using a Hohmann transfer. Due to this, human spaceflight to Mars is more dangerous as exposure to risks such as solar radiation, long exposure to low gravity fields, and isolation. These are some of the many hazards of interplanetary space travel for humans. However, most of the effects of these hazards can be reduced by reducing the transit time it takes to travel to Mars. To this end, while current approaches use only chemical rockets, it is important to study the effects of a hybrid architecture on performance. Hybrid systems are defined as a chemical-electric propulsion system or a chemical-nuclear thermal propulsion system. While there are many other variations, this study focuses on chemical-electric propulsion systems and how the hybrid architecture affects the overall time of flight. To implement this, a model was developed that used real time acceleration on the spacecraft to accurately model the effects of the electrical portion of the propulsion system to reach Mars. The study varies the specific impulse from 1000 to 10,000 seconds with each specific impulse being tested with a range of mass flow rates from 0.00001 kg/s to 0.001 kg/s. The chemical portion was represented by departure delta velocities of 3.8, 4.0, 4.2, and 4.4 km/s. These inputs were used in the model and calculated a time of flight for each combination which then was used to calculate the time savings compared to a pure chemical rocket for each departure delta velocity value. Finally, a cost estimate was considered to determine if the hybrid propulsion system is feasible compared to chemical only systems. It was determined that by using lower Isp while keeping the thruster efficiency to about 80%, it is indeed possible for a hybrid propulsion system to reach faster transit times thus introducing the possibility of future investment.