Dynamics of a Nonrigid Orbital Siphon at a Near-Earth Asteroid

Abstract

The orbital siphon is a novel concept for propellantless payload transfer from the surface of a rotating body to orbit. In the context of asteroid mining, the orbital siphon represents an efficient solution to deliver mined material from the asteroid surface to an orbiting station for later processing or storage. The key idea is that the centrifugal-induced force exerted on a tether-connected chain of payload masses assembled from the surface of a rotating body can be large enough to pull the lower masses to initialize an orbital siphon effect: new payloads are connected to the chain while upper payloads are removed. In this paper, the dynamics of an orbital siphon anchored to two irregularly shaped near-Earth asteroids is investigated. The siphon is modeled as a closed chain of tether-connected buckets kept taut by two pulleys: one at the asteroid surface and one attached to an orbiting collecting spacecraft. Buckets are filled with asteroid material to be delivered to the collecting spacecraft. It is shown that the irregularities of the gravitational field do not introduce instabilities to the orbital siphon system for the scenarios presented in this paper. Without any braking mechanism required, the average speed of the siphon does not diverge but reaches a constant value at a steady state. Moreover, it is shown that the siphon effect is still generated when the anchor moves on the asteroid surface, allowing the mining location to be moved without interrupting the flow of material to the collecting spacecraft.