# Optimized trajectories to the nearest stars using lightweight high-velocity photon sails

## TL;DR

This paper explores optimized interstellar trajectories using lightweight photon sails, demonstrating that photogravitational assists near stars like Sirius A can significantly reduce travel times to about 69 years, enabling potential flyby and orbiting missions.

## Contribution

It introduces an improved method of using stellar photon pressure as a bumper for deceleration, optimizing trajectories for faster interstellar travel to nearby stars.

## Key findings

- Photogravitational assists are more effective when the star acts as a bumper.
- Travel time to Sirius A can be reduced to 69 years at 12.5% light speed.
- Deceleration allows for orbiting the target star system after flyby.

## 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 $\alpha$ Cen A and B and reduces the travel time of a nominal graphene-class sail (mass-to-surface ratio 8.6e-4 gram m$^{-2}$) from 95 to 75 yr. The maximum possible velocity reduction upon arrival depends on the required deflection angle from $\alpha$ 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 $\alpha$ 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.