Deceleration of High-velocity Interstellar Photon Sails into Bound Orbits at α Centauri

Abstract

At a distance of about 4.22 ly, it would take about 100,000 years for humans to visit our closest stellar neighbor Proxima Centauri using modern chemical thrusters. New technologies are now being developed that involve highpower lasers firing at 1 gram solar sails in near-Earth orbits, accelerating them to 20 % the speed of light (c) within minutes. Although such an interstellar probe could reach Proxima 20 years after launch, without propellant to slow it down it would traverse the system within hours. Here we demonstrate how the stellar photon pressures of the stellar triple α Cen A, B, and C (Proxima) can be used together with gravity assists to decelerate incoming solar sails from Earth. The maximum injection speed at α Cen A to park a sail with a mass-to-surface ratio (σ) similar to graphene (7.6 × 10 −4 gram m −2 ) in orbit around Proxima is about 13, 800 km s −1 (4.6 % c), implying travel times from Earth to α Cen A and B of about 95 years and another 46 years (with a residual velocity of 1280 km s −1 ) to Proxima. The size of such a low-σ sail required to carry a payload of 10 grams is about 10 5 m 2 = (316 m) 2 . Such a sail could use solar photons instead of an expensive laser system to gain interstellar velocities at departure. Photogravitational assists allow visits of three stellar systems and an Earth-sized potentially habitable planet in one shot, promising extremely high scientific yields.

Universal scaling relation for magnetic sails: momentum braking in the limit of dilute interstellar media

“…The extended cruising time of the order 10 4 years implies however that slow cruising trajectories are only an option for mission, such as for life-carrying Genesis crafts [12], not expected to yield near-term results in terms of a tangible scientific return. as the inner magnetic field strength and the working-regime current I wr from (16). For the Earth the Larmor radius of solar wind protons at the shock location = z R 15 is with ∼24 km much lower than the extension of the bow shock.…”

“…For the last possibility a photon sail is used [14,15], just in the reverse modus operandi [16]. For the first two options momentum is transferred to charged particles, with the difference being that the particle density of stellar winds is somewhat higher than that of the interstellar space.…”

“…. Using the optimality condition (16), that is = = = ( )| ( ) a z log 1, 18 z e one may evaluate the deceleration profile for a given deceleration ratio v v 0 .…”

“…The quality of the superconducting tapes is the key parameter determining overall mission requirements. The hard cutoff (6) determines directly the minimal current at which the sail stops working, with a reasonable working regime for the current being given by (16). For a given type of superconducting tape the mass per length necessary to support the field generating current is therefore dependent solely on the initial velocity v 0 .…”

Electromagnetic Forces on a Relativistic Spacecraft in the Interstellar Medium

“…If entering the stellar corona as contemplated by Heller & Hippke (2017), the spacecraft will be rapidly heated to a high temperature by gas collisions (Hoang et al 2017b). The typical density in active regions of solar corona declines with radius R as n i ∼ 10 4 (100R ⊙ /R) 2 cm −3 (Sittler & Guhathakurta 1999).…”