Electric sails are potentially more effective than light sails near most stars (1911.02765v3)

Abstract: Electric sails are propulsion systems that generate momentum via the deflection of stellar wind particles through electric forces. Here, we investigate the relative merits of electric sails and light sails driven by stellar radiation pressure for F-, G-, K- and M-type stellar systems. We show that electric sails originating near M-dwarfs could attain terminal speeds of $\sim 500$ km/s for minimal payload masses. In contrast, light sails are typically rendered ineffective for late-type M-dwarfs because the radiation pressure is not sufficiently high to overcome the gravitational acceleration. Our analysis indicates that electric sails are better propulsion systems for interplanetary travel than light sails in proximity to most stars. We also delineate a method by which repeated encounters with stars might cumulatively boost the speeds of light sails to $\gtrsim 0.1\,c$, thereby making them more suitable for interstellar travel. This strategy can be effectuated by reaching $\sim 10^5$ stars over the span of $\sim 10$ Myr.

• The paper evaluates electric sails and light sails for space propulsion, finding electric sails potentially more effective near most stars, especially M-dwarfs.
• Analysis shows electric sails initiated near M-dwarfs can achieve high terminal velocities (~500 km/s) for small payloads, overcoming light sail limitations in such environments.
• Quantitative insights reveal electric sails offer advantages below a stellar mass threshold of approximately 0.75 solar masses, outperforming light sails across a broad spectrum of stellar environments dominated by stellar winds.

Evaluating Electric and Light Sails for Space Propulsion

The paper "Electric sails are potentially more effective than light sails near most stars" by Manasvi Lingam and Abraham Loeb investigates the comparative efficacy of electric sails and light sails as propulsion mechanisms across different types of stellar environments. The primary focus of this work is to assess the suitability of these two propulsion technologies for interplanetary and interstellar travel, particularly around F-, G-, K-, and M-type stars.

Electric Sails: A Viable Alternative

Electric sails harness momentum by deflecting charged particles in stellar winds via electric forces, suggesting potential advantages in certain stellar environments. The authors provide a detailed analysis indicating that electric sails initiated near M-dwarfs can achieve terminal velocities on the order of 500 km/s for minimal mass payloads. This performance contrasts with the limitations of light sails in similar environments, where insufficient radiation pressure from late-type M-dwarfs renders solar radiation-driven propulsion ineffectual.

The paper formulates a method through which repeated encounters with stars could cumulatively increase the speeds of light sails to velocities exceeding 0.1c, suitable for interstellar voyages. However, such a strategy entails visiting approximately 10^5 stars over a timespan of about 10 million years, highlighting a significant temporal investment when viewed against human timescales.

Performance Across Stellar Types

The research delineates the dependency of electric sail efficacy on stellar parameters, primarily focusing on mass and rotational velocity. The work’s quantitative insights reveal that the initial acceleration and eventual velocities achieved by electric sails offer significant advantages over light sails across a broad spectrum of stellar environments, especially those dominated by stellar winds. Notably, the analysis establishes a stellar mass threshold (~0.75 M☉) below which electric sails outperform their light-driven counterparts, particularly for M-type stars that account for the majority of stellar objects in the galaxy.

Theoretical and Practical Implications

Practically, this paper underscores the potential of electric sails to serve as more effective propulsion mechanisms than light sails in proximal stellar vicinities, especially for less massive stars. Theoretical implications suggest that, while electric sails might provide an impetus for interplanetary missions by exploiting stellar wind conditions, light sails remain advantageous for certain high-energy applications such as those reliant on laser arrays—a possibility highlighted by ongoing projects like Breakthrough Starshot.

Future Directions

The paper intimates several avenues for continued research, particularly in refining the models to include comprehensive stellar parameters and real-world engineering constraints. Further empirical paper will be required to substantiate the feasibility of these propulsion systems in practical, mission-specific contexts.

In conclusion, this research offers a robust foundation for considering electric sails as a promising technology for space propulsion. Their possible superiority in low-mass stellar contexts overcomes some of the traditional obstacles associated with light sail technologies, thus paving the way for future exploratory missions within our solar system and beyond. This work enriches the dialogue on propulsion technologies, offering both theoretical insight and practical guidance for the future design of interstellar exploration missions.