Anthony Robert Martin

Modelling of non-thermal plasma aftertreatment of exhaust gas streams

A reaction mechanism has been developed that is appropriate for the plasma aftertreatment of diesel exhaust gas. It is based on a simulated gas mixture containing propene, nitric oxide, nitrogen dioxide, oxygen and nitrogen. The reaction mechanism has been used to determine the end-products from the plasma processing and their concentrations using a chemical kinetics modelling procedure. It has been validated by a range of experiments using the same gas mixture with a packed bed, a dielectric barrier plasma reactor and a wide range of end-product analysis techniques. Using a wide range of experimental conditions has enabled us to validate the model and its predictions and to critically evaluate several alternative reaction mechanisms for the oxidation of propene and the formation of end-products in a more systematic and reliable manner than before.

The promise of electric propulsion for low-cost interplanetary missions

Interplanetary science missions often require a significant propulsive capability. Electric propulsion provides a means of avoiding the large propellant masses associated with chemical systems. Such an approach can lead to the use of small spacecraft, consistent with a low cost mission philosophy. Example applications of electric propulsion to low-cost interplanetary science missions are discussed, including use in cis-Lunar space, Lunar missions, and missions to a range of asteroids.

Concept studies for a laser powered orbital transfer vehicle

Abstract The concept of beamed energy propulsion, where power from a remote source is transmitted to a space vehicle and then converted into useful thrust, is an attempt to decouple the energy source from the rocket vehicle. It is hoped that in this way high thrust levels and high exhaust velocities can be produced while eliminating the need for a heavy on-board source. Instead of using energy from chemical reactions to heat a propellant, a powerful beam of energy is employed. The efficiency of microwave power generation, transmission, collection and rectification is much higher than for laser beams. However, rectennae dimensions of about 1 km radius are required for propagation over a few thousand kilometres, and a geostationary orbit system would need a radius of about 10 km. While such large systems are feasible, they are well beyond current technical capabilities, and hence the use of microwaves for powering space vehicles must be ruled out in favour of the use of laser powered systems, at least for the present. This paper describes concept studies carried out on a continuous laser power system. The studies suggested that the possibilities for the use of lasers in such a role were optimistic, with the vehicle involving nothing that was outside current technology. A round trip mission with a velocity increment of 10 km/s was considered. A vehicle with an initial mass of about 18 tonnes could propel a 7 tonnes payload on a round trip from low Earth orbit to geostationary altitude and back. The time taken for the mission would be of the same order as chemical systems, with transfer times measured in hours rather than days.

Starships and their Detectability

The feasibility of interstellar vehicles journeying among the stars is considered. The starting point is the results of Project Daedalus, which demonstrated that a relatively crude interstellar probe would be possible with only modest extrapolations of present- day science and technology. The discussion is then extended to consideration of fast starships, relatively small vehicles which travel at a reasonable percentage of the speed of light, and much slower, much larger world ships which spend millenia on their journey. Some of the characteristics of such vehicles are commented upon, in a more general examination of the impact that the existence of star-ships has upon the detectability of advanced technical civilisations in the Galaxy.

The development status of the UK-10 and UK-25 ion thruster systems☆

Abstract The paper describes the development status of two ion thruster systems intended for a wide variety of future applications. The UK-10 system is based on the 10 cm dia T5 thruster which was originally designed to produce 10 mN thrust using mercury propellant. It has not been shown to give up to 70 mN, with xenon, while retaining the high efficiency and stable operation demonstrated earlier. The associated power and propellant supply systems are described, together with plans to test fly the system. The UK-25 ion thruster is a new device intended for primary propulsion tasks. It is of 25 cm dia and was designed using the scaling laws formulated during the development of the UK-10 system. Its performance has been mapped up to a thrust of 250 mN, a value limited by the available test facility, not the thruster itself. Its application to European deep space missions has been studied, also other roles in low Earth orbit.

The U.K. ion propulsion programme: Past status and new results

Abstract During the decade 1967–1977, the U.K. developed a highly efficient Kaufman-type ion thruster specifically for the north-south station-keeping role on geostationary communications satellites, although many other applications of this device were feasible. With a design thrust of 10 mN using mercury propellant, throttling between 7 mN and 17 mN was possible at an exhaust velocity of 30 km/s. At the selected operating point, the fully corrected mass utilisation efficiency was 87.6%, the electrical efficiency 70.4%, the specific impulse 2730 s, and the input power 223 W. Although discontinued in 1977, the market opportunities for such devices have improved since that date, so the project was restarted in 1985, using rare gas propellants to avoid potential problems caused by the contamination of spacecraft surfaces with mercury. It has been found that the performance with xenon is outstanding, matching the high levels set earlier and providing a much wider throttling range, especially at increased beam accelerating voltages. Thrusts of up to 34.5 mN have been achieved. In addition to the results of this new work, the paper also reports progress with the design and test of a larger, 200 mN thruster intended for primary propulsion