Asteroid deflection and exploitation : possible synergies

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 spacecraft 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 to 170 meters 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 335 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

Use of orbiting reflectors to decrease the technological challenges of surviving the lunar night

In this paper the feasibility of using lunar reflectors to decrease the technological challenges of surviving the lunar night is investigated. This is achieved by attempting to find orbits in the two-body problem where the argument of periapsis is constantly Sun-pointing to maximise the time spent by the reflectors over the night-side of the Moon. Using these orbits the ability of reflectors of varying sizes to provide sufficient illumination to a target point on the surface is determined for scenarios where a latitude band is constantly illuminated and a scenario where a specific point is tracked. The optimum masses required for these far-term scenarios are large. However, a nearer-term scenario using low altitude orbits suggest that the effective duration of the lunar night can be reduced by up to 50% using a set of 300 parabolic reflectors of 100m radius with a total system mass of 370 tonnes. A system is also demonstrated that will allow a partial illumination of the craters in the Moon’s polar region for a mass up to 700kg

Planetary protection efficiency by a small kinetic impactor

This paper re-examines the deflection concept with, arguably, the highest technological readiness level: the kinetic impactor. A baseline design for the concept with a 1,000 kg spacecraft launched from Earth is defined. The paper then analyses the capability of the kinetic spacecraft to offer planetary protection, thus, deflecting asteroids on a collision trajectory with Earth. In order to give a realistic estimate, the paper uses a set of more than 17 thousand Earth-impacting trajectories and has computed the largest asteroid mass that could be deflected to a sufficiently safe distance from Earth. By using the relative impact frequency of the different impact orbits, which can be estimated by modeling the asteroid population and the collision probability of the different impact geometries, a figure on the level of planetary protection that such a system could offer can be estimated. The results show that such a system could offer very high levels of protection, around 97% deflection reliability, against objects between 15 to 75 meters, while decreases for larger sizes

The feasibility of using an L1 positioned dust cloud as a method of space-based geoengineering

In this paper a method of geoengineering is proposed involving clouds of dust placed in the vicinity of the L1 point as an alternative to the use of thin film reflectors. The aim of this scheme is to reduce the manufacturing requirement for space-based geoengineering. It has been concluded that the mass requirement for a cloud placed at the classical L1 point, to create an average solar insolation reduction of 1.7%, is 7.60x1010 kg yr−1 whilst a cloud placed at a displaced equilibrium point created by the inclusion of the effect of solar radiation pressure is 1.87x1010 kg yr−1. These mass ejection rates are considerably less than the mass required in other unprocessed dust cloud methods proposed and are comparable to thin film reflector geoengineering requirements. Importantly, unprocessed dust sourced in-situ is seen as an attractive scheme compared to highly engineered thin film reflectors. It is envisaged that the required mass of dust can be extracted from captured near Earth asteroids, whilst stabilised in the required position using the impulse provided by solar collectors or mass drivers used to eject material from the asteroid surface

Towards Designing a Credible Hazardous NEA Mitigation Campaign of Dual-deflection Act

Given a limited warning time, an asteroid impact mitigation campaign would hinge on uncertainty-based information consisting of remote observational data of the identified Earth-threatening object, general knowledge on near-Earth asteroids, and engineering judgment. Due to these ambiguities, the campaign credibility could be profoundly compromised. It is therefore imperative to comprehensively evaluate the inherent uncertainty in deflection and plan the campaign accordingly to ensure successful mitigation. This research demonstrates dual-deflection mitigation campaigns consisting of primary and secondary deflection missions, where both deflection performance and campaign credibility are taken into consideration. The results of the dual-deflection campaigns show that there are trade-offs between the competing aspects: the total interceptor mass, interception time, deflection distance, and the confidence in deflection. The design approach is found to be useful for multi-deflection campaign planning, allowing us to select the best possible combination of deflection missions from a catalogue of various mitigation campaign options, without compromising the campaign credibility

Opportunities for asteroid retrieval missions

Asteroids and comets are of strategic importance for science in an effort to uncover the formation, evolution and composition of the Solar System. Near-Earth Objects (NEOs) are of particular interest because of their accessibility from Earth, but also because of their speculated wealth of material resources. The exploitation of these resources has long been discussed as a means to lower the cost of future space endeavours. In this chapter, we analyze the possibility of retrieving entire objects from accessible heliocentric orbits and moving them into the Earth’s neighbourhood. The asteroid retrieval transfers are sought from the continuum of low energy transfers enabled by the dynamics of invariant manifolds; specifically, the retrieval transfers target planar, vertical Lyapunov and halo orbit families associated with the collinear equilibrium points of the Sun-Earth Circular Restricted Three Body problem. The judicious use of these dynamical features provides the best opportunity to find extremely low energy transfers for asteroidal material. With the objective to minimise transfer costs, a global search of impulsive transfers connecting the unperturbed asteroid’s orbit with the stable manifold phase of the transfer is performed. A catalogue of asteroid retrieval opportunities of currently known NEOs is presented here. Despite the highly incomplete census of very small asteroids, the catalogue can already be populated with 12 different objects retrievable with less than 500 m/s of Δv. All, but one, of these objects have an expected size in the range that can be met by current propulsion technologies. Moreover, the methodology proposed represents a robust search for future retrieval candidates that can be automatically applied to a growing survey of NEOs

Hazardous Near Earth Asteroid Mitigation Campaign Planning Based on Uncertain Information on Asteroid Physical Properties

Given a limited warning time, an asteroid impact mitigation campaign would hinge on uncertainty-based information consisting of remote observational data of the identified Earth-threatening object, general knowledge on near-Earth asteroids (NEAs), and engineering judgment. Due to these ambiguities, the campaign credibility could be profoundly compromised. It is therefore imperative to comprehensively evaluate the inherent uncertainty in deflection and plan the campaign accordingly to ensure successful mitigation. This research demonstrates dual-deflection mitigation campaigns consisting of primary and secondary deflection missions, where both deflection performance and campaign credibility are taken into consideration. The results of the dual-deflection campaigns show that there are trade-offs between the competing aspects: the total interceptor mass, interception time, deflection distance, and the confidence in deflection. The design approach is found to be useful for multi-deflection campaign planning, allowing us to select the best possible combination of deflection missions from a catalogue of various mitigation campaign options, without compromising the campaign credibility

Near-Earth asteroid resource accessibility and future capture mission opportunities

In-Situ Resource Utilization (ISRU) has always been suggested for ambitious space endeavours; and asteroids and comets in particular are generally agreed to be ideal sources, both in terms of its accessibility and wealth. The future utilisation of asteroid resources is here revisited by, firstly, providing an estimate of the total amount of accessible resources in the Earth’s neighbourhood and, secondly, by envisaging a series of missions in order to retrieve resources from the most accessible objects known today. An analytical multi-impulsive transfer model is proposed in order to define the region in Keplerian space from which resources are accessible, and mapped subsequently into a near-Earth asteroid model, to understand the availability of material. This estimate shows a substantial amount of resources can be accessible at relatively low energy-cost; on the order of 1014 kg of material could potentially be accessed at an energy cost lower than that required to access the resources in the Moon. Most of this material is currently undiscovered, but the current surveyed population of near-Earth asteroid provides a good starting point for a search for future capture opportunities. The possibility of capturing, i.e., placing the asteroid into an orbit in permanent close proximity to Earth, a small-size NEO or a segment from a larger object would be of great scientific and technological interest in the coming decades. A systematic search of capture candidates among catalogued NEOs is presented, which targets the L2 region as the destination for the captured material. A robust methodology for systematic pruning of candidates and optimisation of capture trajectories through the stable manifold of planar Lyapunov orbits around L2 has been implemented and tested. Five possible candidates for affordable asteroid retrieval missions have been identified among known NEOs, and the transfers to the L2 region calculated. These transfers enable the capture of bodies with 2-8 meters diameter with modest propellant requirements. Because of the optimal departure dates, two of them have been identified as attractive targets for capture missions in the 2020-2030 time frame

Sustainability in the boardroom: An empirical examination of Dow Jones sustainability world index leaders

In recent years, there has been a virtual explosion of interest in corporate governance. Corporate scandals and the need to protect minority shareholders' interests, for example, are some of the reasons behind the development of corporate governance codes in numerous countries and corporations. At the same time, the concepts of "sustainable development", "corporate responsibility", and "corporate citizenship" have taken root in the business world. Although an extensive body of research treats the fields of corporate governance and sustainable development separately, less attention has been paid to the interaction between both fields. This paper attempts to bridge this gap by examining how corporate governance systems are evolving in order to integrate sustainable development thinking into them. We do so by analyzing the governance systems of the 18 corporations that are leading the market sectors considered by the Dow Jones Sustainability World Index (DJSWI). We present the results of our in depth analysis of the 18 cases and propose the Sustainable Corporate Governance Model that emerges from that analysis.Corporate governance; sustainable corporate governance; sustainable enterprise; sustainable development; business in society;