Arcjet rocket

About: Arcjet rocket is a research topic. Over the lifetime, 1121 publications have been published within this topic receiving 9687 citations. The topic is also known as: Arcjet.

Recombination lasing in a magnetoplasmadynamic arcjet

Abstract: The plasmadynamic recombination laser concept is verified experimentally in a high power quasi-steady MPD arcjet operating at 4 kA and 12 g/sec of argon. Measurements of the spatial variation of electron temperature, electron density, and population densities in the arc exhaust flow confirm that inverted populations of the 4p to 4s Ar II transitions are established by collisional-radiative recombination of the Ar III ion. Using an optical cavity aligned transversely to the flow, recombination lasing of four such transitions, 5145, 4880, 4764 and 4727 A, is observed spectro-photographically and photoelectrically over the entire 1-msec discharge.

A two-dimensional, non-equilibrium numerical model of an alkali seeded hydrogen arcjet thruster

Abstract: The largest source of loss in efficiency in a conventional arcjet thruster is the energy required to dissociate and ionize the propellant so that an electric arc can pass through the gas. The ions do not recombine so the energy required to create them cannot be converted into thrust. The addition of a small amount of a readily ionizable material such as an alkali metal should provide adequate electrical conductivity, without the main propellant being ionized. Simplified analysis predicts that this can cut the frozen losses from nearly fifty percent to less one percent. To study in detail the effects of seeding a hydrogen arcjet with cesium, a two-dimensional numerical model was developed, which accounts for hydrogen molecules, atoms, and ions and cesium atoms and ions. The electrons are treated as one fluid and the heavy species as a second, with separate temperatures and a heat transfer rate between the two. The flow was modelled by Navier-Stokes equations modified to account for thermal and chemical nonequilibrium, and are numerically integrated by MacCormacks predictor-corrector scheme on a structured grid, and the elliptical equation for the electric potential was solved by successive over-relaxation. The model predicts that it is possible for the seeded arcjet to be run with the cesium nearly fully ionized but the hydrogen having minimal dissociation or ionization. When the flow passes through the arc attachment point on the anode, which is a region of high current density, it was originally feared that the hydrogen may ignite and revert to conventional operation with all the frozen losses. No evidence was found for such behaviour, even when run at comparatively high currents. The cesium was found to be fairly uniformly spread throughout the constrictor, and so also was the current density, which means that there was no formation of a narrow arc in the centre of the constrictor as there is in conventional arcjets. This implies that if the constrictor is made of a conductor the arc will attach at the earliest possible point and not pass down the length of the constrictor as desired. Consequently the constrictor must be an insulator for proper operation of a seeded arcjet. Author: Darrel Kim Robertson E-mail: dkrl@mit.edu Thesis Supervisor: Manuel Martinez-Sanchez Professor of Aeronautical and Astronautical Engineering Acknowledgments I would first like to thank my thesis supervisor Professor Manuel Martinez-Sanchez for the opportunity to work on such an interesting and exciting project. I would especially like to thank him for his help in understanding the physics involved in arcjet operation, particularly as to which phenomena were important and which could be neglected. When I occasionally got stuck, he proved to be a great source of new ideas on how to tackle problems with the modelling of the physics. Secondly I would like to thank Guy Benson for his explanations of how the numerical model of conventional arcjets that I inherited worked, and of why things were done in the code the way that they were. I would also like to especially thank Folusho Oyerokun for his insights into how the addition of cesium changed the behaviour of an arcjet, and together with Prof. Manuel Martinez-Sanchez, as to what were the important questions to be answered in the research. Even though I never spoke to him in person I'd also like to thank Scott Miller, who's code I inherited and who's thesis was an invaluable resource. I am very grateful to the Engineering and Physical Sciences Research Council (EPSRC) for providing me with the studentship that has enabled me to come and study at MIT. I would also like to thank Essex University, and Brett Giddings in particular for allowing me to use their computers last summer when I was back in England so I could continue my research. Next I would like to thank everyone in the Space Systems Lab, especially the secretaries Peggy Edwards and SharonLeah Brown, and my colleagues Salma Qarnain, James Szabo, Tatsuo Onishi, Paulo Lozano, and Rob Bayt. Thinking back a little I'd also like to thank Leicester University, especially my advisor Bob Warwick, and also Glenn Orton at JPL for the wonderful opportunities he gave me to work there as part of Caltech's summer research fellowships. I don't think I can get away without thanking all my friends here especially April Smith and her Mum, Dad and sister Sabrina, Rebecca Rogers who was kind enough to proof read my thesis for me, Becca Tatem, Christian Stetson, Mary Greenfield, Nat Stahl, Lenny Rosenfeld and Andy Webb. Lastly and perhaps most importantly I'd like to thank my Mum, Valerie and Dad, Peter and my brother Ian for their endless support and encouragement. "Oook." The Librarian, Unseen University. "Two Parts Science, One Part Insanity" STP engineers testing the limits of performance:

Power Electronics for a Miniaturized Arcjet

Abstract: A 0.3 kW Power Processing Unit (PPU) was designed, tested on resistive loads, and then integrated with a miniaturized arcjet. The main goal of the design was to minimize size and mass while maintaining reasonable efficiency. In order to obtain the desired reductions in mass, simple topologies and control methods were considered. The PPU design incorporates a 50 kHz, current-mode-control, pulse-width-modulated (PWM), push-pull topology. An input voltage of 28 +/- 4V was chosen for compatibility with typical unregulated low voltage busses anticipated for smallsats. An efficiency of 0.90 under nominal operating conditions was obtained. The component mass of the PPU was 0.475 kg and could be improved by optimization of the output filter design. The estimated mass for a flight PPU based on this design is less than a kilogram.

Material Spraying Using Electromagnetically Accelerated Plasma Jet

Abstract: In magneto-plasma-dynamic (MPD) arcjet generators, plasma is accelerated by electromagnetic body forces. The MPD arcjet generator can produce higher-velocity, higher-temperature, higher-density and larger-area plasmas than those of conventional thermal plasma torches. Two types of MPD arcjet generator were developed for applications to mullite, zirconia and titanium-nitride spraycoatings. The MPD spray process could successfully form dense, uniform and hard ceramic coatings. In titanium nitride reactive spraying, plasma diagnostic measurement and flowfield analysis were also carried out. A large amount of N and N+ was expected to be exhausted with a high velocity from the MPD generator. Both the electron temperature and the electron number density were kept high at a substrate position compared with those for conventional low-pressure thermal sprayings. A chemically active plasma with excited particles of N+, Ti, Ti+ and Ti2+ was considered to contribute to better titanium nitride coatings. All coating characteristics showed that the MPD arcjet generators had high potentials for ceramic spray coatings.