Safety criteria for flying E-sail through solar eclipse

TL;DR

This paper analyzes the thermal and mechanical stresses on electric solar wind sail tethers during planetary eclipses using numerical simulations, establishing safe approach distances for various celestial bodies.

Contribution

It provides the first detailed numerical analysis of eclipse-induced stresses on E-sail tethers and determines safe approach distances for multiple planetary and small body environments.

Findings

Eclipsing is safe beyond approximately 2.5 au from the Sun.

Safe distances around terrestrial planets depend on orbital parameters.

For Mars, safe distance with 20 km tether is between Phobos and Deimos orbits.

Abstract

The electric solar wind sail (E-sail) propellantless propulsion device uses long, charged metallic tethers to tap momentum from the solar wind to produce spacecraft propulsion. If flying through planetary or moon eclipse, the long E-sail tethers can undergo significant thermal contraction and expansion. Rapid shortening of the tether increases its tension due to inertia of the tether and a Remote Unit that is located on the tether tip (a Remote Unit is part of typical E-sail designs). We analyse by numerical simulation the conditions under which eclipse induced stresses are safe for E-sail tethers. We calculate the closest safe approach distances for Earth, Moon, Venus, Mars, Jupiter, Ceres and an exemplary 300 km main belt asteroid Interamnia for circular, parabolic and hyperbolic orbits. We find that any kind of eclipsing is safe beyond approximately 2.5 au distance, but for terrestrial planets safety depends on the parameters of the orbit. For example, for Mars the safe distance with 20 km E-sail tether lies between Phobos and Deimos orbits.