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Methods used to determine structural damage caused by fragments from accidental explosions are outlined. Structures considered include launch facilities for liquid propellant rockets and metal plates and sheets. Penetrating and nonpenetrating fragments were considered.
A kinetic model is developed for a plasma generated by fission fragments and the results are employed to study helium plasma generated in a tube coated with fissionable material. Because both the heavy particles and electrons play important roles in creating the plasma, their effects are considered simultaneously. The calculations are carried out for a range of neutron fluxes and pressures. In general, the predictions of the theory are in good agreement with available intensity measurements. Moreover, the theory predicts the experimentally measured inversions. However, the calculated gain coefficients are such that lasing is not expected to take place in a helium plasma generated by fission fragments. The effects of an externally applied electric field are also considered.
A hypothesis is proposed which interprets the relative motion of two fragments of a split comet in terms of a slight difference between their effective solar attraction rather than in terms of the impulse imparted to them at separation. A quantitative version of this hypothesis is formulated by assuming that the difference in effective solar attraction varies with heliocentric distance in direct proportion to the actual solar attraction so that the ratio of the two forces is constant and equal to a measure of the relative effect between the two fragments under consideration. Results obtained using this formulation are compared with observational evidence on the split comets P/Biela, Liais 1860 I, 1882 II, P/Brooks 2 1889 V, Swift 1899 I, Kopff 1905 IV, Mellish 1915 II, Taylor 1916 I, 1947 XII, Wirtanen 1957 VI, Ikeya-Seki 1965 VIII, Kohoutek 1970 III, and West 1975n. The hypothesis is found to fail only in the case of comet Wirtanen 1957 VI. Some unusual phenomena associated with split comets are examined.
Results are presented for measurements of total fragmentation cross sections of relativistic O-16 ions in CsI crystals, which were performed using a monochromatic bevatron ion beam at energies of 0.5 and 2.1 GeV/nucleon. The total fragmentation cross section at each energy is determined on the basis of detected changes in the charge of the incident ions, and the values obtained at both energies are found to be the same to within the experimental errors. Values of the O-16 nucleon radius and overlap parameter are derived simultaneously from the measured cross sections.
Key airworthiness design criteria considerations for fragment protection as found in various FAA requirements in FAR Parts 25 and 33, and in interpretive 8110 orders are reviewed. The impact of providing aircraft armor in lieu of engine armor for typical three- and four-engine wide bodied transports for protection within the length of the engine case as well as from fragments exiting ahead of the enlet engine inlet flange is assessed. For protection within the length of the engine case, armor weight penalties, plus fuel burned and dollar cost of carrying the armor protection are defined. Immediately ahead of the inlet flange, direct tangential impacts are predominant, but further forward, rebound impacts predominate. Armor thickness requirements and fuel cost impact of protection are given.
Empirical guidelines for the design of minimum weight turbine rotor disk fragment containment rings made from a monolithic metal were generated by experimentally establishing the relationship between a variable that provides a measure of containment ring capability and several other variables that both characterized the configurational aspects of the rotor fragments and containment ring, and had been found from exploratory testing to have had significant influence on the containment process. Test methodology and data analysis techniques are described. Results are presented in graphs and tables.
Petrological and geochemical analysis of lithic fragments separated from the Apollo 15 deep-drill core showed these fragments to fall into the essentially the same range of rock types as observed in surface soil samples and large rock samples. Three particles are singled out as being of special interest. One sample is a mare basalt containing extremely evolved phases. The particle may represent small-scale imperfect crystal/liquid separation in a lava flow. A green glass particle is not the ultramafic emerald green glass described from the Apollo 15 site, but rather an ANT-like light green color, and has a quite different chemical composition from the ultramafic variety. One mare basalt displays a positive Eu anomaly and is enriched in plagioclase relative to olivine plus pyroxene.
Fragmentation characteristics for four artificial meteoroids of high density and high tensile strength with varying size, velocity, and material are investigated. The meteoroids analyzed were lifted to natural meteor altitude by a rocket vehicle system. The meteoroids were then accelerated back into the Earth's atmosphere at natural meteor velocities. Anomalous deceleration of high density meteors was studied. It is shown that anomalies in the deceleration are due to progressive fragmentation of the meteoroids. These anomalies in the deceleration of high density meteoroids are similar to the anomalies that occur in the deceleration of natural meteors, which are generally assumed to be porous and of weak structure.
The role played by fission fragments and electron distribution functions in nuclear pumped lasers is considered and procedures for their calculations are outlined. The calculations are illustrated for a He-3/Xe mixture where fission is provided by the He-3(n,p)H-3 reaction. Because the dominant ion in the system depends on the Xe fraction, the distribution functions cannot be determined without the simultaneous consideration of a detailed kinetic model. As is the case for wall sources of fission fragments, the resulting plasmas are essentially thermal but the electron distribution functions are non-Maxwellian.
A study of basaltic fragments from the Apollo 11 bulk sample using instrumental neutron activation analysis, the petrographic microscope, and the electron microprobe is presented. The fragments include Group A, B2, and B3 basalts, of which two of the Group A samples are vitrophyres with bulk compositions similar to the crystalline high-K rocks which crystallized under different physical conditions and represent a second high-K cooling unit. The B2 samples relate to each other through ilmenite fractionation, and the B3 samples relate through olivine fractionation; it is concluded that the B2 samples have an anomalously high La/K ratio and may have generated in the same source region as the Group D basalts.
Nuclear-pumped lasing of Ar-Xe and He-Xe has been demonstrated using (U-235)F6 fission-fragment excitation. Fission fragments were created by absorption of thermal neutrons in a combination of gaseous (U-235)F6 and laser-tube wall coatings formed from UF6 chemical reaction products. At a pressure of 600 torr Ar-(3%)Xe, lasing occurred at 2.65 microns in Xe. Up to 3 torr of gaseous (U-235)F6 was added to 600 torr Ar-Xe before serious laser quenching occurred. With 3 torr of (U-235)F6 added, 38% of the energy deposition came from gaseous UF6 and the remainder from the uranium wall coating. The neutron flux at lasing threshold was found to be 4 x 10 to the 15th n/sq cm sec.
Numerical calculations of the collapse of adiabatic clouds from uniform density and rotation initial conditions show that when restricted to axisymmetry, the clouds form either near-equilibrium spheroids or rings. Rings form in the collapse of low thermal energy clouds and have a ratio of rotational kinetic energy to the absolute value of gravitational potential energy greater than approximately 0.43. When the axisymmetric constraint is removed and an initial m = 2 density variation is introduced, clouds either collapse to form near-equilibrium ellipsoids or else fragment into binary systems through a bar phase. Ellipsoids form in the collapse of high thermal energy clouds and have a rotational kinetic energy/absolute value of gravitational potential energy ratio less than approximately 0.27. The results are consistent with the critical values of the rotational kinetic energy/absolute value of gravitational potential energy ratio for instabilities in Maclaurin spheroids, and suggest that protostellar clouds may undergo a dynamic fragmentation in the nonisothermal collapse regime.
Using the combined data from 1976 and 1977 balloon flights the isotopic composition of cosmic ray Fe and fragmentation nuclei with Z equals 17-25 have been determined. The telescope used in these studies contains two Cerenkov counters and four total energy counters with an overall mass resolution sigma equals 0.35-0.40 amu. For Fe, approximately 320 nuclei with C/C(max) less than 0.5 are mass analyzed with the result extrapolated to the cosmic ray source, Fe-56 equals 0.952, Fe-54 equals 0.048 plus or minus 0.030 and Fe-58 less than 0.030 of all Fe. Two other isotopes are found to have a significant source abundance, A-36 with an abundance of 0.048 plus or minus 0.013 x Fe and Ca-40 equals 0.088 plus or minus 0.016 x Fe at the source. The source abundance of all other isotopes is less than 0.015 x Fe at the 1 sigma level. Of these fragmentation isotopes there is evidence that most of the Cl-36 has decayed as well as possibly some Mn-54.
The fragmentation of Fe nuclei in carbon and CH2 targets at energies of 650, 800, and 950 MeV/nuc has been studied. Direct measurements of the interaction between Fe nuclei and the carbon and CH2 targets were carried out. The Fe to H charge changing cross sections derived for selected nuclei showed a clear energy dependence, consistent with the results of Westfall et al. (1979). Values for the total inelastic cross section Fe to H charge changing were obtained by two methods: the first method involved subtracting the total CH2 and C cross sections (values of 703 plus or minus 9 mb and 65 plus or minus 10 mb at 950 MeV/nuc and 650 MeV/nuc, respectively were obtained). The same cross sections were obtained by adding the individual charge changing cross sections. A cross section for Fe to fragment into lower mass Fe isotopes of 65 plus or minus 5 mb was also observed, giving total inelastic mass changing cross sections of 768 plus or minus 11 mb and 716 plus or minus 12 mb, respectively. In addition, the individual isotopic cross sections for Z equals 16-25 are reported.
Aspects of the current theory of molecular-cloud (MC) evolution and star formation are reviewed, with consideration of recent star and MC observations. The problem of MC collapse is discussed in terms of fragmentation in spherically symmetric collapse, the role of magnetic fields and density fluctuations, anisotropic collapse, and nonlinear interactions between fragments. Protostellar winds are identified as the source of the energy supporting MC against collapse, sweeping shells of mass into MC to produce low-mass stars continuously, and sustaining the production of massive stars once it is triggered by the collision of MCs, as in the spiral density-wave peaks. The clumping and coagulation processes are considered for the case of the MC in Orion. The protostellar-wind mass input required to inhibit systematic MC-core collapse is estimated at 10 to the -6th solar mass/cu pc year.
The collapse of a very low thermal energy, rotating cloud results in fragmentation to a binary protostellar system even in the nonisothermal regime. The solar system therefore probably did not form from a fragmentation hierarchy involving ejection of the presolar nebula from a multiple system.
The mechanism of particle evaporation was used to examine ablation effects in the fragmentation of 2.1 GeV/nucleon oxygen nuclei by lead targets. Following the initial abrasion process, the excited projectile prefragment is assumed to statistically decay in a manner analogous to that of a compound nucleus. The decay probabilities for the various particle emission channels are calculated by using the EVAP-4 Monte Carlo computer program. The input excitation energy spectrum for the prefragment is estimated from the geometric ""clean cut'' abrasion-ablation model. Isotope production cross sections are calculated and compared with experimental data and with the predictions from the standard geometric abrasion-ablation fragmentation model.
A general approach is required for describing matter of behavior when the failure is likely to involve growth and coalescence of a large number of fractures. Failures of this kind appear frequently in rapid dynamic processes, particularly in the formation of spall fragments. An approach to formulating constitutive relations that accounts for the opening, shear and growth of an ensemble of cracks is discussed. The approach accounts for plastic flow accompanying fragmentation. The resulting constitutive relations were incorporated into a Lagrangian computer program. A theoretical approach to coalescence is described. The simplest formulation uses a linear Liouville equation, with crack growth limited by the mean free path of cracks, assumed constant. This approach allows for an anisotropic distribution of cracks. An alternative approach in which the decrease of the mean free path with increasing crack size is accounted for, but the crack distribution is assumed isotropic is described. A reduction of the governing Liouville equation to an ordinary differential equation of third order is possible, and the result can be used to determine how mean free path decreases with increasing crack size.