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

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

A continuum model for the orbit evolution of self-propelled 'smart dust' swarms

A continuity equation is developed to model the evolution of a swarm of self-propelled ‘smart dust’ devices in heliocentric orbit driven by solar radiation pressure. These devices are assumed to be MEMs-scale (micro-electromechanical systems) with a large area-to-mass ratio. For large numbers of devices it will be assumed that a continuum approximation can be used to model their orbit evolution. The families of closed-form solutions to the resulting swarm continuity equation then represent the evolution of the number density of devices as a function of both position and time from a set of initial data. Forcing terms are also considered which model swarm sources and sinks (device deposition and device failure). The closed-form solutions presented for the swarm number density provide insights into the behaviour of swarms of self-propelled ‘smart dust’ devices an can form the basis of more complex mission design methodologies

Orbit design for future SpaceChip swarm missions in a planetary atmosphere

The effect of solar radiation pressure and atmospheric drag on the orbital dynamics of satellites-on-a-chip (SpaceChips) is exploited to design equatorial long-lived orbits about the oblate Earth. The orbit energy gain due to asymmetric solar radiation pressure, considering the Earth's 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

Hybrid solar sail and SEP propulsion for novel Earth observation missions

In this paper we propose a pole-sitter spacecraft hybridising solar electric propulsion (SEP) and solar sailing. The intriguing concept of a hybrid propulsion spacecraft is attractive: by combining the two forms of propulsion, the drawbacks of the two systems cancel each other, potentially enabling propellant mass saving, increased reliability, versatility and lifetime over the two independent systems. This almost completely unexplored concept will be applied to the continuous monitoring of the Earth’s polar regions through a pole-sitter, i.e. a spacecraft that is stationary above one pole of the Earth. The continuous, hemispherical, real-time view of the pole will enable a wide range of new applications for Earth observation and telecommunications. In this paper, families of 1-year-periodic, minimum-propellant orbits are found, for different values of the sail lightness number and distance from the pole. The optimal control problem is solved using a pseudo-spectral method. The process gives a reference control to maintain these orbits. In addition, for stability issues, a feedback control is designed to guarantee station-keeping in the presence of injection errors, sail degradation and temporary SEP failure. Results show that propellant mass can be saved by using a medium-sized solar sail. Finally, it is shown that the feedback control is able to maintain the spacecraft on-track with only minimal additional effort from the SEP thruster

Control of Lagrange point orbits using solar sail propulsion

Several missions have utilised halo orbits around the L1 and L2 previous termLagrangenext term points of the Earth-Sun system. Due to the instability of these orbits, station-keeping techniques are required to prevent escape after orbit insertion. This paper considers using solar sail propulsion to provide station-keeping at quasi-periodic orbits around L1 and L2. Stable manifolds will be identified which provide near-Earth insertion to a quasi-periodic trajectory around the libration point. The possible control techniques investigated include solar sail area variation and solar sail pitch and yaw angle variation. Hill's equations are used to model the dynamics of the problem and optimal control laws are developed to minimise the control requirements. The constant thrust available using solar sails can be used to generate artificial libration points Sunwards of L1 or Earthwards of L2. A possible mission to position a science payload Sunward of L1 will be investigated. After insertion to a halo orbit at L1, gradual solar sail deployment can be performed to spiral Sunwards along the Sun-Earth axis. Insertion -V requirements and area variation control requirements will be examined. This mission could provide advance warning of Earthbound coronal mass ejections (CMEs) responsible for magnetic storms

Novel solar sail mission concepts for Space weather forecasting

This paper proposes two novel solar sail concepts for space weather forecasting: heliocentric Earth-following orbits and Sun-Earth line confined solar sail manifolds. The first exploits a solar sail acceleration to rotate the argument of perihelion such that aphelion, where extended observations can take place, is always located along the Sun-Earth line. The second concept exploits a solar sail acceleration to keep the unstable, sunward manifolds of a solar sail Halo orbit around a sub-L1 point close to the Sun-Earth line. By travelling upstream of space weather events, these manifolds then allow early warnings for such events. The orbital dynamics involved with both concepts will be investigated and the observation conditions in terms of the time spent within a predefined surveillance zone are evaluated. All analyses are carried out for current sail technology (i.e. Sunjammer sail performance) to make the proposed concepts feasible in the near-term. The heliocentric Earth-following orbits show a reasonable increase in useful observation time over inertially fixed, Keplerian orbits, while the manifold concept enables a significant increase in the warning time for space weather events compared to existing satellites at the classical L1 point

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