Optimized Trajectories to the Nearest Stars Using Lightweight High-velocity Photon Sails

Abstract

New means of interstellar travel are now being considered by various research teams, assuming lightweight spaceships to be accelerated via either laser or solar radiation to a significant fraction of the speed of light (c). We recently showed that gravitational assists can be combined with the stellar photon pressure to decelerate an incoming lightsail from Earth and fling it around a star or bring it to rest. Here, we demonstrate that photogravitational assists are more effective when the star is used as a bumper (i.e. the sail passes "in front of" the star) rather than as a catapult (i.e. the sail passes "behind"or "around" the star). This increases the maximum deceleration at α Cen A and B and reduces the travel time of a nominal graphene-class sail (mass-to-surface ratio 8.6 × 10 −4 gram m −2 ) from 95 to 75 yr. The maximum possible velocity reduction upon arrival depends on the required deflection angle from α Cen A to B and therefore on the binary's orbital phase. Here, we calculate the variation of the minimum travel times from Earth into a bound orbit around Proxima for the next 300 yr and then extend our calculations to roughly 22,000 stars within about 300 ly. Although α Cen is the most nearby star system, we find that Sirius A offers the shortest possible travel times into a bound orbit: 69 yr assuming 12.5% c can be obtained at departure from the solar system. Sirius A thus offers the opportunity of flyby exploration plus deceleration into a bound orbit of the companion white dwarf after relatively short times of interstellar travel.

Interstellar communication. I. Maximized data rate for lightweight space-probes

“…Photovoltaic energy is available at a level of kW m −2 at au distance from the star, so that a probe in orbit (perhaps decelerated by stellar photons, Heller & Hippke (2017); Heller et al . (2017)) has no power issues for transmissions. A fly-by probe at 20% c, however, transverses the au distance in 17 min, translating into a data volume of order Mbits m −2 if the whole time were used for transmission (which is unrealistic, given that the target exoplanet is to be observed).…”

“…Only recently, Heller & Hippke (2017) and Heller et al . (2017) suggested to decelerate using the stellar radiation and gravitation in a maneuver they referred to as photogravitational assist. A project by the ‘Breakthrough Initiatives’ 1 provides monetary support (of order 100 m USD) for research on gram-scale robotic spacecrafts, using a light sail for propulsion (Lubin, 2016; Popkin, 2017).…”

Interstellar communication: The colors of optical SETI

“…The beam falls below the naked eye visibility (6 mag) at a distance of ∼ 2 kpc. Astrometry, proper motion estimates and pointing accuracy must be of the same order (µas) as required for spaceflight, a level which is achievable with future telescopes for nearby stars (Heller et al 2017).…”

Photon-Sail Equilibria in the Alpha Centauri System

“…However, little is known about the dynamics of the photon sail once it arrives in the other star system, especially in a multi-star system like Alpha Centauri. To date, the only works investigating these dynamics include References [8] and [9]. Both articles focussed on the dynamics in the binary-star system composed of the stars Alpha Centauri A and B, and investigated the possibility of decelerating the spacecraft after arrival, assuming a graphene-based sail covered with a highly reflective coating.…”