On the stability of a space vehicle riding on an intense laser beam

TL;DR

This paper investigates the stability conditions of a nanocraft propelled by intense laser radiation, analyzing how shape and configuration affect its ability to maintain position and orientation within the laser beam for potential interstellar travel.

Contribution

It provides stability criteria for nanocraft designs with spherical and conical sails, highlighting the importance of the StarChip placement and sail shape for stable laser propulsion.

Findings

Stable configurations require the StarChip to be positioned away from the sail center.

Flat sails are inherently unstable regardless of spinning.

Stability depends on sail shape and the relative position of the nanocraft components.

Abstract

The Breakthrough Starshot Initiative is suggested to develop the concept of propelling a nano-scale spacecraft by the radiation pressure of an intense laser beam. If such a nanocraft could be accelerated to 20 percent of light speed, it could reach the vicinity of our nearest potentially habitable exoplanet within our life time and capture its images and obtain other scientific data. In this project the nanocraft is a gram-scale robotic spacecraft comprising two main parts: StarChip and Lightsail. To achieve the goal of the project it is necessary to solve a number of outstanding scientific problems. One of these tasks is to make sure that the nanocraft position and orientation inside the intense laser beam column is stable. The nanocraft driven by intense laser beam pressure acting on its Lightsail is sensitive to the torques and lateral forces reacting on the surface of the sail. These forces influence the orientation and lateral displacement of the spacecraft, thus affecting its dynamics. If unstable the nanocraft might be expelled from the area of laser beam. In choosing the models for nanocraft stability studies we are using several assumptions: 1. configuration of nanocraft is treated as rigid body (applicability of Euler equations); 2. flat or concave shape of circular sail; 3. mirror reflection of laser beam from surface of the Lightsail. We found conditions of position stability for spherical and conical shape of the sail. The simplest stable configurations require the StarChip to be removed from the sail to make the distance to the center of mass of nanocraft bigger than curvature radius of the sail. Stability criteria do not require the spinning of the nanocraft. A flat sail is never stable (even with spinning).