Velocity field path-planning for single and multiple unmanned ariel vehicles

Unmanned aerial vehicles (UAV) have seen a rapid growth in utilisation for reconnaissance, mostly using single UAVs. However, future utilisation of UAVs for applications such as bistatic synthetic aperture radar and stereoscopic imaging, will require the use of multiple UAVs acting cooperatively to achieve mission goals. In addition, to de-skill the operation of UAVs for certain applications will require the migration of path-planning functions from the ground to the UAV. This paper details a computationally efficient algorithm to enable path-planning for single UAVs and to form and re-form UAV formations with active collision avoidance. The algorithm presented extends classical potential field methods used in other domains for the UAV path-planning problem. It is demonstrated that a range of tasks can be executed autonomously, allowing high level tasking of single and multiple UAVs in formation, with the formation commanded as a single entity

Orbits in a generalized two-body problem

The two-body problem is a well-known case of the general central force problem with an attractive, inverse square force. However, there are forms of spacecraft propulsion, such as solar sails and minimagnetospheric plasmapropulsion, which generate a repulsive, inverse square force. Because this force can be modulated, a more general central force problem is then formed. Such a problem is investigated and the families of orbits available using both forward integration and an inverse approach are explored. Both are used to explore various modes of transfer between circular coplanar orbits and to determine strategies for escape

Solar sailing: mission applications and engineering challenges

Solar sailing is emerging as a promising form of advanced spacecraft propulsion, which can enable exciting new space-science mission concepts. By exploiting the momentum transported by solar photons, solar sails can perform high-energy orbit transfer manoeuvres without the need for reaction mass. Missions such as planetary sample return, multiple small-body rendezvous and fast missions to the outer Solar System can therefore be enabled with the use of only a modest launch vehicle. In addition, new families of highly non-Keplerian orbits have been identified that are unique to solar sails, and can enable new ways of performing space-science missions. While the opportunities presented by solar sailing are appealing, engineering challenges are still to be solved before the technology finally comes to fruition

Mars climate engineering using orbiting solar reflectors

The manned mission is seen as a first step towards a Mars surface exploration base-station and, later, establishing permanent settlement. The location and use of Mars's natural resources is vital to enable cost-effective long-duration human exploration and exploitation missions as well as subsequent human colonization. Planet resources include various crust-lodged materials, a low-pressure natural atmosphere, assorted forms of utilizable energy, lower gravity than Earth's, and ground placement advantages relative to human operability and living standards. Power resources may include using solar and wind energy, importation of nuclear reactors and the harvesting of geothermal potential. In fact, a new branch of human civilization could be established permanently on Mars in the next century. But, meantime, an inventory and proper social assessment of Mars's prospective energy and material resources is required. This book investigates the possibilities and limitations of various systems supplying manned bases on Mars with energy and other vital resources. The book collects together recent proposals and innovative options and solutions. It is a useful source of condensed information for specialists involved in current and impending Mars-related activities and a good starting point for young researchers

Orbital dynamics of earth-orbiting 'smart dust' spacecraft under the effects of solar radiation pressure and aerodynamic drag

This paper investigates how the perturbations due to asymmetric solar radiation pressure, in presence of Earth's shadow, and atmospheric drag can be balanced to obtain long-lived Earth centered orbits for swarms of SpaceChips, without the use of active control. The secular variation of Keplerian elements is expressed analytically through an averaging technique. Families of solutions are then identified where a Sun-synchronous apse-line precession is achieved passively. The long-term evolution is characterized by librational motion, progressively decaying due to the non-conservative effect of atmospheric drag. Therefore, long-lived orbits can be designed through the interaction of energy gain from asymmetric solar radiation pressure and energy dissipation due to drag. In this way, the short life-time of high area-to-mass spacecraft can be greatly extended (and indeed selected). In addition, the effect of atmospheric drag can be exploited to ensure the end-of life decay of SpaceChips, thus preventing long-lived orbit debris

Orbit design for future SpaceChip swarm missions

The effect of solar radiation pressure and atmospheric drag on the orbital dynamics of satellites-on-a-chip (SpaceChips) is exploited to design long-lived orbits about the Earth. The orbit energy gain due to asymmetric solar radiation pressure, considering the Earth shadow, is used to balance the energy loss due to atmospheric drag. Future missions for a swarm of SpaceChips are proposed, where a number of small devices are released from a conventional spacecraft to perform spatially distributed measurements of the conditions in the ionosphere and exosphere. It is shown that the orbit lifetime can be extended and indeed selected through solar radiation pressure and the end-of-life re-entry of the swarm can be ensured, by exploiting atmospheric drag

Analytical control laws for interplanetary solar sail trajectories with constraints

An indirect method is used to obtain an analytical control law for a spacecraft with a low-thrust propulsion system which is constituted by a solar sail coupled with a solar electric thruster. Constraints on the control inputs for such as the system need to be taken into account for the design of a control law to avoid reducing control performance, even though the solar electric thruster is employed as an auxiliary system capable of increasing the thrust magnitude of the sailcraft. The aim of this paper is to derive an analytical control law for a system with input constraints. A barrier function is used to analytically obtain a control law without a computationally expensive iterative algorithm. Therefore, using the analytic method presented, a transfer orbit can be readily calculated with an onboard computer. Pontryagin's maximum principle is also used to obtain an optimal control law to compare with the proposed control law. The proposed control law is demonstrated as suitable for an example transfer problem between circular and coplanar orbits

Social potential model to simulate emergent behaviour for swarm robots

Swarm robotics has a wide range of applications in numerous fields from space and sub-sea exploration to the deployment of teams of interacting artificial agents in disposal systems. In this paper, we introduce a model to simulate the emergent behaviour of multi-agent robot systems, based on principles from physical mechanics. The model is based on mutual interactions among the swarm individuals. The main elements of these interactions are repulsion forces, attraction forces, alignment forces and dissipative forces generated by the swarm members. Using statistical tools, which are used to investigate simulated group behaviour, we discuss the importance of introducing some dissipation to the system as well as the effect of the interaction parameters on various components of the model

The orbital siphon : A new space elevator concept

A new concept for propellantless payload transfer from the surface of the Earth to Earth escape is presented. Firstly, a simple model of a payload ascending or descending a conventional space elevator is developed to explore the underlying dynamics of the problem. It shown that an unconstrained payload at rest on a space elevator at synchronous radius is in an unstable equilibrium, and that this instability can be used to motivate the development of a new concept for payload transfer. It will be shown that a chain of connected payloads stretching from the surface of the Earth to beyond synchronous radius can be assembled which will lift new payloads at the bottom of the chain, while releasing payloads from the top of the chain. The complete system therefore acts as an 'orbital siphon', transporting mass from the surface of the Earth to Earth escape without the need for external work to be done. Indeed the system performs net work by transferring energy from the Earth's rotation to the escaping mass. The dynamics of the siphon effect are explored and key engineering issues are identified

Solar sail mission applications and future advancement

Solar sailing has long been envisaged as an enabling technology. The promise of open-ended missions allows consideration of radically new trajectories and the delivery of spacecraft to previously unreachable or unsustainable observation outposts. A mission catalogue is presented of an extensive range of potential solar sail applications, allowing identification of the key features of missions which are enabled, or significantly enhance, through solar sail propulsion. Through these considerations a solar sail application-pull technology development roadmap is established, using each mission as a technology stepping-stone to the next. Having identified and developed a solar sail application-pull technology development roadmap, this is incorporated into a new vision for solar sailing. The development of new technologies, especially for space applications, is high-risk. The advancement difficulty of low technology readiness level research is typically underestimated due to a lack of recognition of the advancement degree of difficulty scale. Recognising the currently low technology readiness level of traditional solar sailing concepts, along with their high advancement degree of difficulty and a lack of near-term applications a new vision for solar sailing is presented which increases the technology readiness level and reduces the advancement degree of difficulty of solar sailing. Just as the basic principles of solar sailing are not new, they have also been long proven and utilised in spacecraft as a low-risk, high-return limited-capability propulsion system. It is therefore proposed that this significant heritage be used to enable rapid, near-term solar sail future advancement through coupling currently mature solar sail, and other, technologies with current solar sail technology developments. As such the near-term technology readiness level of traditional solar sailing is increased, while simultaneously reducing the advancement degree of difficulty along the solar sail application-pull technology development roadmap