Electrostatic rockets

If the propellant is to be accelerated by electric body forces a primary requirement is that the propellant be a charged particle. While interest has centered on positively charged atomic ions, the use of both negatively and positively charged colloids has been considered. 

A simple model of an electrostatic accelerator allows equating the kinetic energy of the ejected propellant with the electrical energy emended, to produce the ejection velocity  

The most attractive approach to reducing the specific impulse of electrostatic accelerators and thereby to maintain reasonable electrical power system requirements is to choose a propellant with a small charge to mass ratio. In direct contrast to electrothermal rockets, electrostatic rockets require propellants with large molecular weights for efficient operation. 

An attendant requirement is, of course, that the ionized specie be readily produced. Species with low ionization potentials are therefore required. Of the atomic species, cesium with an atomic mass of 133 AMU and an ionization potential of only 3.89 ev has been the favored propellant. Colloidal species can be either solids or liquids. The criterion of selection of the colloidal material is based on the facility with which colloids of uniform mass and charge can be produced. 

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A large part of the interest in electrostatic atomization has arisen from two fields of interest combustion of fuel oils and ion propulsion of rockets in space. Work in the latter area has been concerned primarily with atomization at high vacuum (10-8 atm) as in the work of Cohen (C5), Hogan (HI2, 13), Hendricks (H6), Schultz and Branson (S2), and Schultz and Wiech (S3). Graf (G8), Matthews and Mason (M3), Peskin and Raco (P3), Randall, Marshall, and Tschernitz (Rl), and Vonnegut and Neubauer (V4) have been concerned primarily with atomization at atmospheric pressure. Most of the... 

Diamino-2,2, 4,4 6,6 -hexanitrodiphenyl (DIPAM) [Structure (2.30)] is extremely insensitive to electrostatic discharge, requiring more than 32 kj for initiation. In addition, it has good thermal stability (m.p. ca. 304 °C) and has been used to achieve stage separation in space rockets and for seismic experiments on the moon in a manner similar to HNS [74]. 

Hazard Properties. It must be verified that the propellant is sufficiently insensitive to shock, electrostatic discharge, friction, thermal decomposition, or self-heating (in larger quantities) that it does not represent an unwarranted hazard in its intended use. Rocket propellants are energetic compositions and must be formulated so that chance stimulus will not initiate violent reaction. 

MAJOR PRODUCT APPLICATIONS personal computers, aircraft, rockets, satellites, automation equipment, electrical and electronics parts, mechanical parts, medical instruments, fishing rods, golf clubs, tennis rackets, brake pads, composites, mufflers, surface preparation for electrostatic painting... 

The characteristics of several QCM instruments for aerosol measurement have been reviewed (ll). Particles are collected by impaction, electrostatic precipitation or both. The mass sensitivity is reported to be affected by the location of deposited particles on the crystal, the size of the particles, and the type of coating. In addition, the sensitivity changes as the crystal becomes loaded. Despite some limitations, most of the studies Indicated that QCMs can be successfully used for aerosol measurement with good correlation coefficient with the reference filtration method. Applications included measurement of aerosol in ambient air, particulate emission from automobiles and diesel engines, smoke plume from a coal-fired power plant, solid fueled rocket plvune, and particulate matter in the effluents in combustion sources. 

Electrospray (Fig. 8.4) is a process where a high potential is applied onto a liquid to generate a fine aerosol. Electrospray or electrostatic spraying has been applied to electrostatic painting, rocket propulsion, or fuel atomization. The phenomenon of electrospray was observed and investigated long before it was practical to the analysis of gas-phase ions transferred from solution into a mass spectrometer. One of the earliest reports of the effect of an electrical tension applied to a liquid was made in 1600 by William Gilbert. He observed that a... 

G. Maise and A. J. Sabadell, Electrostatic Probe Measurements in Solid Propellant Rocket Exhausts, AIAA J. 8, 895-901 (1970). 

In contrast to gas thrusters, ion thrusters accelerate charged particles with an electrostatic field. This approach leads to the highest /gp but typically very low thrust levels. Thrusters can be used in either continuous or pulsed operation, according to the application. Miniature rocket launchers and micro air vehicles require a continuous thrust and are best served by a unique thruster or engine with a continuous feed of propellant. Alternatively, digital micro-propulsion refers to an array of single-use thrusters that provide a small impulse (short burst of thrust) to accurately orient a small spacecraft or correct a vehicle s trajectory. 

There are three basic types of electric propulsion systems electrothermal, electrostatic, and electromagnetic. In electrothermal propulsion, the propellant is heated either by an electric arc or a resistance heater. The hot propellant is then exhausted through a conventional rocket nozzle to produce thrust. Electrostatic propulsion uses electric fields to accelerate charged particles through a nozzle. In electromagnetic propulsion, an ionized plasma is accelerated by magnetic fields. In all three types, electricity from a nuclear source, such as a fission reactor, is used to power the propulsion device (Allen et ak, 2000 Bennett et al., 1994). The power flow for a typical nuclear-electric propulsion scheme is shown in Figure 1. 

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