Spacecraft Conceptual Design for Returning Entire Near-Earth Asteroids

Abstract

In situ resource utilization (ISRU) in general, and asteroid mining in particular are ideas that have been around for a long time, and for good reason. It is clear that ultimately human exploration beyond low-Earth orbit will have to utilize the material resources available in space. Historically, the lack of sufficiently capable in-space transportation has been one of the key impediments to the harvesting of near-Earth asteroid resources. With the advent of high-power (or order 40 kW) solar electric propulsion systems, that impediment is being removed. High-power solar electric propulsion (SEP) would be enabling for the exploitation of asteroid resources. The design of a 40-kW end-of-life SEP system is presented that could rendezvous with, capture, and subsequently transport a 1,000-metric-ton near-Earth asteroid back to cislunar space. The conceptual spacecraft design was developed by the Collaborative Modeling for Parametric Assessment of Space Systems (COMPASS) team at the Glenn Research Center in collaboration with the Keck Institute forSpace Studies (KISS) team assembled to investigate the feasibility of an asteroid retrieval mission. Returning such an object to cislunar space would enable astronaut crews to inspect, sample, dissect, and ultimately determine how to extract the desired materials from the asteroid. This process could jump-start an entire ISRU industry.

Technology for a robotic asteroid redirect mission

“…Assuming a 2-m moment arm with two 0.9-N thrusters firing in a couple it is estimated that only about 50 kg of propellant would be needed to de spin the asteroid and that it would take about 15 hours to complete the despin process. Note, this is less propellant than calculated by the COMPASS team [3] due to the slower asteroid rotation rate assumed in the this study.…”

“…The feasibility of capturing and returning to cislunar space an entire small near-Earth asteroid (NEA), with a mass of up to approximately 1,000 metric tons, was the subject of a 2011-2012 study by the Keck Institute for Space Science (KISS) at the California Institute of Technology [1][2][3][4][5] and more recently by NASA [6,7]. An earlier study investigated the feasibility or capturing and delivering smaller NEAs directly to the International Space Station [8,9].…”

Attitude Control and Stabilization of Spacecraft with a Captured Asteroid

“…This conceptual ARM spacecraft, with dry mass of 5, 500 kg and wet mass of 15, 500 kg, could carry 13 × 10 3 kg of Xenon propellant for the 40 kW SEP system and an additional 900 kg of liquid propellant for the roll control thrusters. 8 The various propulsion systems on board the conceptual ARM spacecraft are shown in Fig. 3(b).…”

“…(7) in order to ensure that the system is always within the technological capability of the sensors and actuators onboard the ARM spacecraft. It is desired that after time T ∈ R, the asteroid and spacecraft combination should be oriented in the desired attitude orientation, represented by the MRP q final , as shown in the steady-state condition (8). Note that if the system has to hold its attitude within the given steady-state error bound ε ss , then the desired angular velocity ω final of the stabilized system should be sufficiently close to 0 rpm.…”

“…1(a) is proposed for this mission, which weighs 15, 500 kg and carries a 40 kW solar electric propulsion (SEP) system. 8 In this paper, we provide a detailed analysis of one of the main control challenges for this ARM mission concept: despinning and three-axis stabilizing the asteroid and spacecraft combination after the tumbling asteroid is captured by the ARM spacecraft. In case a suitable NEO asteroid is not found, an alternate ARM mission concept is to pick up a rock from a much larger asteroid.…”