Droplet vaporization in supercritical pressure environments

For most liquid-fueled combustion systems the behavior of the fuel as it is introduced to the combustion zone, often by spray injection, will have a significant impact on combustion. The subsequent combustion may be affected to a considerable degree by the initial spread of the liquid, break-up of larger fuel sheets and droplets into droplets of various sizes, droplet vaporization, and diffusion of gaseous fuel. Among the many factors which affect spray break-up and droplet vaporization are the environmental conditions into which the spray is introduced. For both diesel engines and rockets the environment pressure and temperature may be above the critical pressure and temperature of the injected fuel. In a compression-ignition internal combustion engine, the environment consists primarily of air, at pressures from 20 to 100 atmospheres and temperatures ranging from 900 to 1500 K. Even higher pressures are encountered in turbocharged diesels. A typical diesel reference fuel, dodecane, has a thermodynamic critical pressure of about 17 atmospheres, and a critical temperature of 600 K. Fuel is injected into a diesel engine environment in which ambient pressures exceed the critical pressure. While droplet temperatures are subcritical at first, they may rise to the critical temperature or higher.This paper will survey current understanding of supercritical pressure droplet vaporization. Specifically, the topics covered will include: liquid phase behavior; vapor phase behavior; thermodynamic and transport properties; droplet distribution and break-up; micro-explosions; and effects of microgravity.     

Expressions in Closed Form for the Angular Accuracy of a Scanning Radar

Closed-form expressions are given for the standard deviation of the error in estimating angle (usually azimuth) in a scanning radar. The formulas apply to Swerling's lower bound and to the error using a pulse-to-pulse two-pole filter. They apply to non-fluctuating and Swerling II targets and hold for all signal-to-noise ratios. Comparison with graphical results in the literature shows that the average deviation obtained using the formulas is less than 4 percent.     

Genetic response of bacterial spores to very heavy ions.

Using spores of two Bacillus subtilis strains differing in repair capacity, we have studied repair and mutation induction in the spores after irradiation with very heavy ions up to uranium with specific particle energies up to 18.6 MeV/u. The results indicate that repair and mutation induction after heavy ion irradiation are closely related to each other and that both phenomena strongly depend on the atomic number and specific energy of the ions. The effects are discussed in comparison with results obtained after X-irradiation.     

Comparative neutral composition instrumentation and new results

Composition and gas density measurement at all altitudes in the atmospheres of earth and other planets are made by mass spectrometers. Because of the impartiality and large dynamic range they are particularly favored for exploratory missions. Measurements of trace constituents, inert gases and height profiles, especially below clouds, are objectives where mass spectrometry is most useful. Significant advances have been made in recent years in development of light weight automated instruments. Experiments conducted in rarified atmospheres have been more successful or results were less controversial than in attempts to analyze high pressure atmospheres. Gas sampling and conditioning techniques are highly specific because of measurement environments and engineering constraints on the mission, and are usually the most critical elements in the experiment. Chemical sample enrichment and scrubbing for noble gas enhancement are additional sample conditioning techniques now employed. Dynamic range of more than 10⁸ is achievable. Reliable measurements of complex organic or chemically active trace constituents with mixing ratios of less than 10^?9 still require significant instrument development particularly where weight, power and sampling time are severely restricted. Adaptation of familiar and proven laboratory techniques for flight instruments is usually not straightforward and practical.     

Radar Performance Review in Clear and Jamming Environments

The performance of electronically scanned radar systems is evaluated for clear and barrage jamming environments. Radar figures of merit in jamming are derived for search and track modes and are directly related to antenna pattern relative sidelobe levels. A random sidelobe model is analyzed with various numbers of independent jammers. Probability distributions of detection probability are derived to determine detection performance versus average jamming level and number of jammers.     

Effects due to an artificial earth satellite in rapid motion through the ionosphere or the interplanetary medium

Conclusion In this paper we have been concerned with the results of theoretical calculations of the interaction between a fast moving body and a tenuous plasma. Particular attention was paid to the case where the velocity of the body is much smaller than the velocity of neutral particles and ions, while the dimensions of the body are sufficiently large in comparison with the Debye radius. Such conditions are realized during the motion of artificial satellites or space rockets through the ionosphere, or through the interplanetary medium in the immediate neighborhood of the earth. Although this case has, on the whole, been investigated quite extensively, there are still a number of problems which require further analysis. Firstly, it is necessary to take into account the effect of the electric field on the motion of ions in the near zone at the rear of the body. Another important problem is that of magnetic disturbances. In the case of scattering of radio waves by the trail of the body, it would be interesting indeed to know the increase in the effective cross-section in the resonance region in which 0. A number of other research problems which arise in the analysis of phenomena in the neighborhood of a moving body have been noted in the Introduction.In the lower layers of the ionosphere it is important to allow for the fact that the dimensions of the body are comparable with the mean free path. Under these conditions there is the further interesting problem of the heating and additional ionization of the plasma, the disintegration of the surface, and the emission of waves. At large distances from the surface of the earth, the dimensions of the body may become comparable with the Debye radius, and the velocity of the body in the given region may become smaller than the thermal velocity of the particles. The character of the various disturbances introduced by the body under these conditions will also require a special investigation.Thus, the interaction of a moving body with plasma leads to special and exceptionally varied effects. Disturbances due to the body are very considerable, so that the physical state of the region surrounding the body is very different from the state of the undisturbed medium.The above results indicate that the phenomena in the neighborhood of satellites and space rockets in the ionosphere, or the interplanetary medium, must be taken into account, in the processing of experimental data when it is required to deduce information about the state of the undisturbed medium. This is particularly important in the analysis of the results of measurements obtained with various types of probes. Considerable errors may be introduced if these effects are not allowed for.Further extensive experimental and theoretical studies of the structure of the disturbed region in the neighborhood of moving bodies in plasma are clearly necessary. Such investigations will, in particular, lead to the development of the most effective methods of studying the properties of the media through which satellites and space rockets travel.Translated from the Russian: Ob effektah vyzyvaemyh iskusstvennym sputnikom bystro dviimsja v ionosfere ili meplanetnoj srede (Uspehi fizieskih nauk 79, 23–80) by Express Translation Service.     

Wide angle X-ray optics for use in astronomy

Recently there was a suggestion in the literature to apply the principle of the lobster-eye to X-ray astronomy imaging (J.R.P. Angel, Ap. J. 233, 364, 1979). Our own suggestion for a wide angle X-ray telescope made earlier (W.K.H. Schmidt, Nucl. Instr. Meth.127, 285, 1975) is very similar to the above one. It consists of one or two sets of plane mirrors used in a grazing incidence configuration. The advantages of this type of X-ray optics over other systems for particular astronomical observations will be discussed.     

Radiation protection problems for the space station and approaches to their mitigation.

With the advent of a permanent manned space station the longstanding problems of radiation protection in manned spaceflight have acquired an immediacy. This paper endeavors to emphasize the gaps of our knowledge which must be closed for effective radiation protection. The information that is required includes the accurate determination of the exposure inside the space station to the various components of tile ionizing radiation, the evaluation of the biological importance of the different radiation qualities and the depth dose distribution of the less penetrating component. There is also the possibility of an interaction with weightlessness. It is necessary to establish adequate radiation protection standards and a system of dosimetric surveillance. There is a need for studies of possible methods of hardening selective shielding of the space station. Spaceflight experiments, which might contribute to the solution of some of these problems are discussed.     

Significance of fluid dynamics aspects for material science experiments

Fluid dynamics aspects for material science experiments may be treated with respect to purely space experiments and preparatory experiments on the ground. Preparatory experiments are necessary because little experience of material science experiments in space is available. Preparatory experiments on earth are needed in the field of surface tension and viscosity, surface layers, forming and positioning of liquids. Concerning space experiments the following subjects may be treated: convection phenomena, capillarity and kinetics of liquids. Convection phenomena (Marangoni convection) can be studied without disturbance by gravitation which has a considerable technological relevance. Under space conditions the kinetics of fluids may be studied in large model structures with changing capillarity and wetting properties.     

Analysis of the Switched Self-Balancing Comparsion Radiometer

Analysis of the switched self-balancing comparison radiometer with coupling between the channels is given. The comparison source is a stationary, zero-mean white noise generator of known spectral density. An expression for the power spectrum at the output of the radiometer is derived. It is shown that measurement errors due to interchannel coupling can be corrected by phase switching. Radiometer sensitivity is also calculated. The switched version of the radiometer has been simulated at low frequencies and is under construction at X-band.