Asteroid Resources Research Articles

Synergistic approach of asteroid exploitation and planetary protection

The asteroid and cometary impact hazard has long been recognised as an important issue requiring risk assessment and contingency planning. At the same time asteroids have also been acknowledged as possible sources of raw materials for future large-scale space engineering ventures. This paper explores possible synergies between these two apparently opposed views; planetary protection and space resource exploitation. In particular, the paper assumes a 5 tonne low-thrust spacecraft as a baseline for asteroid deflection and capture (or resource transport) missions. The system is assumed to land on the asteroid and provide a continuous thrust able to modify the orbit of the asteroid according to the mission objective. The paper analyses the capability of such a near-term system to provide both planetary protection and asteroid resources to Earth. Results show that a 5 tonne spacecraft could provide a high level of protection for modest impact hazards: airburst and local damage events (caused by 15–170 m diameter objects). At the same time, the same spacecraft could also be used to transport to bound Earth orbits significant quantities of material through judicious use of orbital dynamics and passively safe aero-capture manoeuvres or low energy ballistic capture. As will be shown, a 5 tonne low-thrust spacecraft could potentially transport between 12 and 350 times its own mass of asteroid resources by means of ballistic capture or aero-capture trajectories that pose very low dynamical pressures on the object.

Asteroid Resource Map for Near-Earth Space

Most future concepts for the exploration and exploitation of space require a large initial mass in low Earth orbit. Delivering this required mass from the Earth’s surface increases cost due to the large energy input necessary to move mass out of the Earth’s gravity well. An alternative is to search for resources in-situ among the near Earth asteroid population. The near Earth asteroid resources that could be transferred to a bound Earth orbit are determined by integrating the probability of finding asteroids inside the Keplerian orbital element space of the set of transfers with an specific energy smaller than a given threshold. Transfers are defined by a series of impulsive maneuvers and computed using the patched-conic approximation. The results show that even moderately low energy transfers enable access to a large mass of resources.

Status report of the electric sail in 2009

The electric sail is a new propulsion concept which uses charged tethers to extract momentum from the solar wind by Coulomb interaction. We give a status report of the electric sail as of October 13, 2009. We report progress during the last two years in plasma physical thrust estimation, tether manufacture methods, navigability, test mission planning and applications. The thrust estimates have gone up recently by a factor of about five, samples of final-type tether have been manufactured, accurate navigability of the sail in variable solar wind has been shown numerically, a CubeSat test mission for measuring the electric sail force in orbit is in Phase-A study and trajectory calculations for many classes of missions have been made. Using existing technology, it seems possible to build an electric sail of ∼ 1 N thrust, ∼ 100 kg mass and ∼ 10 year lifetime. In terms of lifetime produced impulse per unit propulsion system mass, such a near-term and general-purpose device would be about 1000 times more efficient than a chemical rocket and about 100 times more efficient than a contemporary ion engine. This level of performance is enough to enable a host of important applications, such as in situ measurements in interstellar space, sample return from most solar system targets, non-Keplerian orbit probes for space weather forecasting and helioseismology and economical utilisation of asteroid resources.

Nonexplosive Approach to Fragment Subkilometer Asteroids with a Tether Centrifuge

A THOUGH we have some clues about the mineralogy and surface properties of different families of asteroids and comets we still know very little about the structure and physical properties of their interior. Such information would be extremely precious to plan future missions to divert asteroids from their collision course with our planet or to shatter them in small dispersed fragments. Additionally, a better knowledge of asteroid internal composition, structure, and morphology can provide invaluable insight into the history and formation of our solar system and the development of life. So far, the approaches proposed in the literature toward improving our knowledge of asteroids structure and interior have been based on indirect measurements through radar tomography [1] and seismology [2] and on direct measurements through subsurface sampling [3]. Although the former can only provide limited resolution measurements of the interior the latter are restricted to the outer layers of the celestial object. This Note presents a new approach to study the internal structure and mechanical properties of small asteroids and comets by artificially increasing their spin rate up to a level where the stress induced by the centrifugal load triggers out a fragmentation process. It is shown that the spin-up process can be effectively carried out using a counter-rotating tether satellite anchored to the asteroid surface as a means to exchange energy and angular momentum with the celestial body. By monitoring the mechanical response of the asteroid to the increased centrifugal load scientific data about its strength and structure can be gathered. Most important though, once the fragmentation process is activated a direct access to the inner layers of the celestial body becomes possible providing unique scientific information for asteroid mitigation missions, planetary science, and astrobiology. In addition, once the complex fragmentation dynamics and asteroid mechanical properties are better understood, the concept could provide an alternativemeans for asteroid fragmentation aswell as an important tool in asteroidmining technology. It isworthmentioning that tethered satellite systems of up to 20 km in length have already been successfully deployed during low-cost space missions [4]. Besides, tethered sling systems attached to asteroids have been studied in the past as reusable propellantless transportation systems for planetary missions [5–7] or for recovering asteroid resources to be used as construction material for solar power satellites or space habitats [8]. Although such proposed tether applications differ considerably from the present one, these references have addressed the basic dynamic issues of asteroid-based tether slings. In particular, Puig-Suari et al. [5] discussed the need for a tapered-cross-section tether to minimize the required tether mass and derived a formula for the optimum taper profile, whereas Kuchnicki et al. [6] investigates the spin-up and deployment dynamics of the sling accounting for the inertial characteristics of the tapered tether.

Biological Potential of Extraterrestrial Materials

Meteoritic materials are investigated as potential early planetary nutrients. Aqueous extracts of the Murchison C2 carbonaceous meteorite are utilized as a sole carbon source by microorganisms, as demonstrated by the genetically modifiedPseudomonas fluorescenceequipped with theluxgene. Nutrient effects are observed also with the soil microorganismsNocardia asteroidesandArthrobacter pascensthat reach populations up to 5 × 107CFU/ml in meteorite extracts, similar to populations in terrestrial soil extracts. Plant tissue cultures ofAsparagus officinalisandSolanum tuberosum(potato) exhibit enhanced pigmentation and some enhanced growth when meteorite extracts are added to partial nutrient media, but inhibited growth when added to full nutrient solution. The meteorite extracts lead to large increases in S, Ca, Mg, and Fe plant tissue contents as shown by X-ray fluorescence, while P, K, and Cl contents show mixed effects. In both microbiological and plant tissue experiments, the nutrient and inhibitory effects appear to be best balanced for growth at about 1:20 (extracted solid:H2O) ratios. The results suggest that solutions in cavities in meteorites can provide efficient concentrated biogenic and early nutrient environments, including high phosphate levels, which may be the limiting nutrient. The results also suggest that carbonaceous asteroid resources can sustain soil microbial activity and provide essential macronutrients for future space-based eco- systems.

Asteroidal resources for space manufacturing

Earth-approaching asteroids (Apollos and Amors) may be competitive candidates as raw materials for space manufacturing. The total energy per unit mass required to transfer material from some of these bodies to high Earth orbit is comparable to that for lunar material. Recent optical studies suggest ordinary and carbonaceous chondrite compositions for these asteroids, with some containing large quantities of metallic iron and nickel, and others, carbon, hydrogen and nitrogen. Discoveries of several new candidate asteroids over the next few years will allow for a better selection of materials and mission possibilities. Material from one of these asteroids, either in raw or manufactured form, could be returned to the vicinity of the Earth by a solar-powered mass-driver reaction engine. With a requirement of ∼60 shuttle flights, and with minimal development costs, an automated mission to a 200-m dia. (10 7 ton) metal-rich asteroid could be carried out by a mass-driver tug assembled in low Earth orbit using shuttle tankage as reaction mass. Such a tug could, within a few years, move the asteroid into high Earth orbit for the manufacturing of ∼ 20 satellite power stations using a portion of the asteroid itself as reaction mass. In the next few years over 100 asteroids in this size range could be discovered, orbits determined and composition types classified using existing earthbased and spaceborne search techniques.

Mining the Apollo and Amor Asteroids

Earth-approaching asteroids could provide raw materials for space manufacturing. For certain asteroids the total energy per unit mass for the transfer of asteroidal resources to a manufacturing site in high Earth orbit is comparable to that for lunar materials. For logistical reasons the cost may be many times less. Optical studies suggest that these asteroids have compositions corresponding to those of carbonaceous and ordinary chondrites, with some containing large quantities of iron and nickel; others are thought to contain carbon, nitrogen, and hydrogen, elements that appear to be lacking on the moon. The prospect that several new candidate asteroids will be discovered over the next few years increases the likelihood that a variety of asteroidal resource materials can be retrieved on low-energy missions.

Mining the Apollo and Amor Asteroids

Earth-approaching asteroids could provide raw materials for space manufacturing. For certain asteroids the total energy per unit mass for the transfer of asteroidal resources to a manufacturing site in high Earth orbit is comparable to that for lunar materials. For logistical reasons the cost may be many times less. Optical studies suggest that these asteroids have compositions corresponding to those of carbonaceous and ordinary chondrites, with some containing large quantities of iron and nickel; others are thought to contain carbon, nitrogen, and hydrogen, elements that appear to be lacking on the moon. The prospect that several new candidate asteroids will be discovered over the next few years increases the likelihood that a variety of asteroidal resource materials can be retrieved on low-energy missions.