How to capture an asteroid – and why we should go to such trouble

No abstract available

Harvesting Near Earth Asteroid Resources Using Solar Sail Technology

Near Earth asteroids represent a wealth of material resources to support future space ventures. These resources include water from C-type asteroids for crew logistic support; liquid propellants electrolytically cracked from water to fuel crewed vehicles and commercial platforms; and metals from M-type asteroids to support in-situ manufacturing. In this paper the role of solar sail technology will be investigated to support the future harvesting of near Earth asteroid resources. This will include surveying candidate asteroids though in-situ sensing, efficiently processing asteroid material resources and returning such resources to near-Earth space. While solar sailing can be used directly as a low cost means of transportation to and from near Earth asteroids, solar sail technology itself offers a number of dual-use applications. For example, solar sails can in principle be used as solar concentrators to sublimate material. If a metal-rich M-type asteroid is processed through solar heating, then the flow of metal resources made available could be manufactured into further reflective area. The additional thermal power generated would then accelerate the manufacturing process. Such a strategy could enable rapid in-situ processing of asteroid resources with exponential scaling laws. It is proposed that solar sailing therefore represents a key technology for harvesting near Earth asteroids, using sunlight both as heat for asteroid processing and radiation pressure for resource transportation

On the stability of approximate displaced lunar orbits

In a prior study, a methodology was developed for computing approximate large displaced orbits in the Earth-Moon circular restricted three-body problem (CRTBP) by the Moon-Sail two-body problem. It was found that far from the L(1) and L(2) points, the approximate two-body analysis for large accelerations matches well with the dynamics of displaced orbits in relation to the three-body problem. In the present study, the linear stability characteristics of the families of approximate periodic orbits are investigated

Feedback stabilization of displaced periodic orbits : Application to binary asteroid

This paper investigates displaced periodic orbits at linear order in the circular restricted Earth-Moon system (CRTBP), where the third massless body utilizes a hybrid of solar sail and a solar electric propulsion (SEP). A feedback linearization control scheme is implemented to perform stabilization and trajectory tracking for the nonlinear system. Attention is now directed to binary asteroid systems as an application of the restricted problem. The idea of combining a solar sail with an SEP auxiliary system to obtain a hybrid sail system is important especially due to the challenges of performing complex trajectories

Cylindrically and spherically constrained families of non-Keplerian orbits

This paper introduces new families of Sun-centered non-Keplerian orbits (NKOs) that are constrained to a three-dimensional surface such as a cylinder or sphere. As such, they are an extension to the well-known families of two dimensional NKOs. For both the cylindrical and spherical types of orbits, the equations of motion are derived in an appropriate reference frame, constraints are introduced to confine the orbit to a cylindrical or spherical surface and further constraints allow the definition of the set of feasible orbits. Additionally, the phase spaces of the orbits are explored and a numerical analysis is developed to find periodic orbits within the set of feasible orbits. The richness of the problem is further enhanced by considering both an inverse square acceleration law (mimicking solar electric propulsion) and a solar sail acceleration law to keep the spacecraft on the cylindrical or spherical surface. These new families of NKOs generate a wealth of new orbits with a range of interesting applications ranging from solar physics to astronomy and planetary observation

Reclaim the inventive spirit of James Watt for an energy-rich, lower-carbon world

No abstract available

Azimuthal repositioning of payloads in heliocentric orbit using solar sails

FUTURE solar physics missions will require the ability to reposition multiple spacecraft at different azimuthal positions relative to the Earth, while remaining close to a one year circular orbit. Such azimuthal repositioningwill allow stereoscopicviews of solar features to be generated and will allow imaging of coronal mass ejections as they transit the sun-Earth line. The NASA STEREO mission, which is scheduled for launch in 2005, will utilize two spacecraft to perform such tasks. Both spacecraft will be launched on a Delta II 7925 and will use multiple lunar gravity assists to maneuver the spacecraft onto leading and trailing heliocentric orbits. The two spacecraft will then drift ahead of and behind the Earth on free-drift trajectories,with increasingEarth-sun-spacecraft angles

On the stability of displaced two-body lunar orbits

In a prior study, a methodology was developed for computing approximate large displaced orbits in the Earth-Moon circular restricted three-body problem (CRTBP)by the Moon-Sail two-body problem. It was found that far from the L1 and L2 points, the approximate two-body analysis for large accelerations matches well with the dynamics of displaced orbits in relation to the three-body problem. In the present study, the linear stability characteristics of the families of approximate periodic orbits are investigated

Pattern transition in spacecraft formation flying using bifurcating potential field

Many new and exciting space mission concepts have developed around spacecraft formation flying, allowing for autonomous distributed systems that can be robust, scalable and flexible. This paper considers the development of a new methodology for the control of multiple spacecraft. Based on the artificial potential function method, research in this area is extended by considering the new approach of using bifurcation theory as a means of controlling the transition between different formations. For real, safety or mission critical applications it is important to ensure that desired behaviours will occur. Through dynamical systems theory, this paper also aims to provide a step in replacing traditional algorithm validation with mathematical proof, supported through simulation. This is achieved by determining the non-linear stability properties of the system, thus proving the existence or not of desired behaviours. Practical considerations such as the issue of actuator saturation and communication limitations are addressed, with the development of a new bounded control law based on bifurcating potential fields providing the key contribution of this paper. To illustrate spacecraft formation flying using the new methodology formation patterns are considered in low-Earth-orbit utilising the Clohessy-Wiltshire relative linearised equations of motion. It is shown that a formation of spacecraft can be driven safely onto equally spaced projected circular orbits, autonomously reconfiguring between them, whilst satisfying constraints made regarding each spacecraft

Analysis and control of displaced periodic orbits in the Earth-Moon system

We consider displaced periodic orbits at linear order in the circular restricted Earth-Moon system, where the third massless body is a solar sail. These highly non-Keplerian orbits are achieved using an extremely small sail acceleration. In this paper we will use solar sail propulsion to provide station-keeping at periodic orbits above the L2 point. We start by generating a reference trajectory about the libration points. By introducing a first-order approximation, periodic orbits are derived analytically at linear order. These approximate analytical solutions are utilized in a numerical search to determine displaced periodic orbits in the full nonlinear model. Because of the instability of the collinear libration points, orbit control is needed for a spacecraft to remian in the vicinity of these points. The reference trajectory is then tracked using a linear Quadratic Regulator (LQR). Finally, simulations are given to validate the control strategy. The importance of finding such displaced orbits is to obtain continuous communications between the equatorial regions of the Earth and the polar regions of the Moon