Photogravimagnetic assists of light sails: a mixed blessing for Breakthrough Starshot?

Abstract

Upon entering a star system, light sails are subject to both gravitational forces and radiation pressure, and can use both in concert to modify their trajectory. Moreover, stars possess significant magnetic fields, and if the sail is in any way charged, it will feel the Lorentz force also. We investigate the dynamics of so-called "photogravimagnetic assists" of sailcraft around $\alpha$ Centauri A, a potential first destination en route to Proxima Centauri (the goal of the Breakthrough Starshot program). We find that a 10m${}^2$ sail with a charge-to-mass-ratio of around 10 $\mu$C/g or higher will need to take account of magnetic field effects during orbital maneouvres. The magnetic field can provide an extra source of deceleration and deflection, and allow capture onto closer orbits around a target star. However, flipping the sign of the sailcraft's charge can radically change resulting trajectories, resulting in complex loop-de-loops around magnetic field lines and essentially random ejection from the star system. Even on well-behaved trajectories, the field can generate off-axis deflections at $\alpha$ Centauri that, while minor, can result in very poor targetting of the final destination (Proxima) post-assist. Fortunately for Breakthrough Starshot, nanosails are less prone to charging en route than their heavier counterparts, but can still accrue relatively high charge at both the origin and destination, when travelling at low speeds. Photogravimagnetic assists are highly non-trivial, and require careful course correction to mitigate against unwanted changes in trajectory.

arXiv comment10 pages, 8 figures, accepted for publication in MNRAS

References in corpus (25)

• A terrestrial planet candidate in a temperate orbit around Proxima Centauri
• Proxima's orbit around Alpha Centauri
• The habitability of Proxima Centauri b II. Possible climates and Observability
• 55 Cancri (Copernicus): A Multi-Planet System with a Hot Super-Earth and a Jupiter Analogue
• The habitability of Proxima Centauri b. I. Irradiation, rotation and volatile inventory from formation to the present
• Magnetically Aligned HI Fibers and the Rolling Hough Transform
• Is Proxima Centauri b habitable? -- A study of atmospheric loss
• Prospects for Characterizing the Atmosphere of Proxima Centauri b
• Coronal activity cycles in nearby G and K stars - XMM-Newton monitoring of 61 Cygni and Alpha Centauri
• Are Proxima and Alpha Centauri Gravitationally Bound?
• No Conclusive Evidence for Transits of Proxima b in MOST photometry
• The interaction of relativistic spacecrafts with the interstellar medium
• The Habitability of Proxima Centauri b I: Evolutionary Scenarios
• Deceleration of high-velocity interstellar photon sails into bound orbits at $\alpha$ Centauri
• Combining Magnetic and Electric Sails for Interstellar Deceleration
• Optimized trajectories to the nearest stars using lightweight high-velocity photon sails
• Compact HI clouds from the GALFA-HI survey
• Bound Orbits of Solar Sails and General Relativity
• Slingshot Dynamics for Self Replicating Probes and the Effect on Exploration Timescales
• Electromagnetic forces on a relativistic spacecraft in the interstellar medium
• Relativistic Generalization of the Incentive Trap of Interstellar Travel with Application to Breakthrough Starshot
• Spacecraft Charging and Hazards to Electronics in Space
• Relativistic Gas Drag on Dust Grains and Implications
• Universal scaling relation for magnetic sails: momentum braking in the limit of dilute interstellar media
• Direct Exoplanet Investigation using Interstellar Space Probes

Cited by in corpus (4)

• Orbital inclination and mass of the exoplanet candidate Proxima c
• Interstellar communication network. I. Overview and assumptions
• Challenges in Scientific Data Communication from Low-Mass Interstellar Probes
• Reflection from Inclined, Relativistic Light Sails