Analytical mechanics of asteroid disassembly using the Orbital Siphon effect

Abstract

A chain of tether-connected payload masses assembled from the surface material of a spherical rotating asteroid is envisaged as a means of delivering a fraction of the asteroid mass into orbit, without the need of external work to be done. Under conditions to be discussed, a net radial force is established on the chain which can be exploited to initialize an orbital siphon effect: new payloads are connected to the chain while top payloads are removed and released into orbit. Adopting simplifying assumptions, the underlying dynamics of the problem is entirely analytical and is investigated in detail. The amount of mass extractable from the asteroid is then discussed, according to a range of strategies. It is proposed that the scheme could in future provide an efficient means of extracting material resources from rotating Near Earth Asteroids.

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

“…Contrary to the model used in Ref. [14], no support structure is envisaged here and the chain does not rotate as a rigid body. However, it will be shown not only that the siphon reaches a finite steady state speed as in Ref.…”

“…When a bucket reaches the anchor pulley, it is refilled with a new payload. In References [14,15] this event was modeled as an inelastic impact, resulting in a discontinuous velocity change of the system (note that the "waiting" payload is at rest with respect to the siphon, in the asteroid reference frame). This choice may cause numerical instabilities in this model.…”

“…Consider the simplified model shown in Fig.2, (as the one studied in [14]), where a chain of masses is anchored at the equator of a spherical asteroid, with the masses aligned and normal to the asteroid surface and extending beyond the synchronous orbit radius. For simplicity any distinction between 'payloads' and 'buckets' is here avoided and the term 'mass' is used to indicate an element of the chain.…”

“…The excess of centrifugal force implies a constant acceleration of the chain. However, it has been shown in [14] that the momentum exchange between the mass to be connected (initially at rest) and the rest of the chain eventually leads the siphon to reach the steady state…”

“…In Reference [14] the siphon dynamics is studied assuming that the chain of masses can slide on a rigid support anchored to the equator of a spherical asteroid. This avoids any rotation of the chain generated by inertial forces.…”