The quest to explore Mars has long been fueled by technological innovation and strategic trade-offs. Traditional chemical propulsion systems have dominated space missions, providing rapid journeys at a substantial fuel cost. However, a team of scientists from Spain has delved into the realm of electric propulsion systems, envisioning a more efficient approach for Mars exploration. In this article, we explore the advantages, trade-offs, and the preliminary study conducted on sending a probe to Mars utilizing entirely electric propulsion—a groundbreaking concept that could reshape the future of deep space exploration.
Advantages of Electric Propulsion
Electric propulsion systems offer a paradigm shift in the efficiency of space travel, particularly once a spacecraft has left Earth’s atmosphere. While chemical rockets demand a significant portion of their launch mass as fuel (70%-90%), electric propulsion systems operate with remarkable efficiency, requiring only 10%-40% of launch mass as fuel. This trade-off, however, manifests in the form of reduced thrust, making electric propulsion systems slower in space. The focus of this study was to analyze the impact of electric propulsion on a Mars mission and determine the feasibility of this alternative approach.
Preliminary Study Parameters
Published in Acta Astronautica, the study focused on a trajectory aiming to place a 2,000 kg spacecraft into a polar orbit around Mars at an altitude ranging from 300 km to 1,000 km. This weight constraint was chosen to match the payload capacity of scientific packages equivalent to the ExoMars orbiter developed by the European Space Agency (ESA). The researchers evaluated different electric propulsion systems and set a crucial requirement—operating at the minimum thrust level of .1 N to successfully enter orbit around Mars.
Selection of BHT-6000 Electric Propulsion System
In their quest for a suitable electric propulsion system, the researchers chose the BHT-6000 as the primary propulsion system for the mission. The BHT-6000 is a Hall Effect thruster, capable of operating with 2 kW to 6 kW of power and utilizing common electric propulsion propellants like Xenon and Krypton. The selection of this system laid the foundation for further modeling and simulations, exploring the mission’s trajectory and comparing it with traditional chemical propulsion options.
Modeling the Mission
Employing a multi-body model, the scientists meticulously mapped out the gravitational influences on their chosen trajectory. Subsequent simulations compared the mission’s outcomes using the BHT-6000 electric propulsion system against a standard chemical propellant. The results were consistent with expectations, showcasing the advantages of electric propulsion in terms of cost-effectiveness.
Trade-Offs: Speed vs. Cost
While a chemical rocket displayed a faster travel time to Mars, completing the journey in just under a year, the BHT-6000-powered mission required approximately 3.2 years from launch. However, the weight of the chemical propulsion system was 2.4 times that of the electric propulsion system. The cost savings of choosing electric propulsion, even with a more extended travel time, amounted to almost $30 million, assuming a conservative launch cost of $10,000/kg.
Future Implications
The trade-off between speed and cost is a critical consideration for space exploration agencies facing budget constraints. Although there are currently no planned deep space missions utilizing electric propulsion as the primary system, the evolving technological landscape makes it increasingly likely for future unmanned missions to opt for this efficient alternative. The preliminary study sheds light on the potential benefits of electric propulsion, hinting at a transformative future in deep space exploration, particularly in the quest to unlock the mysteries of Mars. As advancements continue, electric propulsion systems may become the driving force behind cost-effective and sustainable journeys into the depths of our solar system.
Source:
Marco Casanova-Álvarez et al, Feasibility study of a Solar Electric Propulsion mission to Mars, Acta Astronautica (2024). DOI: 10.1016/j.actaastro.2024.01.001