Propulsion of Spacecrafts to Relativistic Speeds Using Natural Astrophysical Sources

Abstract

In this paper, we explore the possibility of using natural astrophysical sources to accelerate spacecrafts to relativistic speeds from a conceptual standpoint. We focus on light sails and electric sails, which are reliant on momentum transfer from photons and protons, respectively, because these two classes of spacecrafts are not required to carry fuel on board. The payload is assumed to be stationed near the astrophysical source, and the sail is subsequently unfolded and activated when the source is functional. By considering a number of astrophysical objects such as massive stars, microquasars, supernovae, pulsar wind nebulae, and active galactic nuclei, we show that terminal speeds approaching the speed of light might be realizable under idealized circumstances provided that sufficiently advanced sail materials and control techniques exist. We also investigate the constraints arising from the sail's material properties, the voyage through the ambient source environment, and the passage through the interstellar medium. While all of these considerations pose significant challenges to spacecrafts, our analysis indicates that they are not insurmountable in optimal conditions. Finally, we sketch the implications for carrying out future technosignature searches.

Inverse design of lightweight broadband reflector for efficient lightsail propulsion

“…As shown in Fig. 4 (a), the optimal structure is exclusively a 1D grating (orange region) throughout the entire range of thickness [10,1000] nm. The reason for ruling out the two other shapes as optimal solutions is as follows: at deep subwavelength thicknesses, reflection increases less dramatically than mass with filling ratio so that the uniform slabs that obtained for the high index material are not viable optimized solution here; at larger thicknesses, there is still much room for improvement of reflectivity, eliminating the need of cutting down on mass with 2D structuring.…”

“…While such a project requires multidisciplinary efforts [6] such as materials science [9], mechanical engineering, astrophysics [10], and telecommunications [11], many key challenges can be alleviated via probing the boundary of photonic design, including efficient propulsion [8], heat management [12], laser beam focusing [13], and self-stabilization [14][15][16][17]. They all contain many tradeoffs that were so far optimized by tuning few geometric parameters of simple photonic structures, leaving possibly much room for improvement by systematically studying more complicated structures.…”