Melvin A. Cook

Mechanism of Cratering in Ultra‐High Velocity Impact

The equations of the hydrodynamic theory of penetration of targets by shaped charge jets are presented first in general form. These equations are then expressed in the ideal form and examined by experimental observations. Then a nonideal theory is presented that takes into account heat losses by compression, shock heating, and radiated shock waves. The conditions for impact explosions of targets are then discussed and a theory extended to cover the entire velocity range of impact from the plastic deformation threshold vσ to well above the impact explosion threshold vc. Some experimental evidence relating to this more general theory is also presented.

Measurement of Detonation Velocity by Doppler Effect at Three‐Centimeter Wavelength

This article describes the application of the Doppler principle to the measurement of detonation velocity with three‐centimeter electromagnetic radiation. The method makes use of the ionized wave front in detonation as a moving reflecting surface for electromagnetic waves. Detonation velocities for four different solid explosives were calculated from the observed Doppler frequencies and the indices of refraction, which were measured by a microwave interferometer. Complexities in the observed Doppler patterns come about because the cylindrical charges act as multimode dielectric wave guides.

Hydrophobicity control of surfaces by hydrolytic adsorption

Abstract The surface activity of free acids and bases with hydrophobic groups is considered in comparison with corresponding anionic, cationic, and ion-pair surface activity. The hydrlytic adsorption model of froth flotation is reviewed from the points of view of “contact bubble” vs. pH curves, collector-depressant competition curves, surface hydrolysis constants, contact angle-concentration curves, and infrared spectroscopy. Methods are considered for distinguishing hydrolytic adsorption, ion-pair adsorption, and other types of adsorption processes that may conceivably yield hydrophobic surfaces by adsorption from aqueous solutions.

Impact Cratering in Granular Materials

Craters produced by projectile impact in granular materials were studied for a wide range of energies and projectile types. Crater sizes were shown to depend on projectile size and shape and on the particle size of the target material. The volume of the impact crater was related to the kinetic energy of the projectile and to the measurable cohesive strength of the target material. Excellent agreement was found between the experimental results and a hydrodynamic theory of cratering slightly modified from earlier studies.

Detonation Wave Fronts in Ideal and Nonideal Detonation

Extensive wave shape data are presented for various (effectively) unconfined explosives over wide ranges of diameter d, length L, density ρ1, and physical conditions. Observed wave fronts were invariably spherical segments with radii of curvature R increasing at first directly with L(R=L), but eventually becoming steady at a constant value Rm/d between 0.5 and 4 depending on the charge diameter primarily through the ratio a0/d (a0=reaction zone length). At the critical diameter of propagation (large a0/d) Rm/d approached 0.5, and at large diameter (small a0/d) it approached or leveled off at the upper limit of about four. The upper limit (Rm/d∼4) is apparently a restriction imposed by the fundamental nature of detonation of solid explosives with free boundaries.

Instrumented Card‐Gap or SPHF‐Plate Test

The deflagration to detonation transition, or DDT, was studied by means of the shock‐pass‐heat‐filter (SPHF) method using Composition B donors in all cases and Composition B, HBX, and Baratol receptors. The SPHF plates were glass, steel, brass, and aluminum. The influence of donor charge diameter and length, and the receptor diameter on the sensitiveness limit, the curves of S1 vs τ′, and S2 vs τ′ were established for these conditions. A striking result is that S2/τ′ proved to be constant equal to the (effectively sonic) velocity of the initial (relatively) unreactive shock wave in the receptor prior to the DDT; it was independent of donor and receptor charge size, the SPHF plate thickness and type. Based on observation with nitromethane, Dithekite, and liquid TNT by the University of Utah and U. S. Naval Ordnance Test Station groups the phenomenon that eventually initiates the DDT forms on the receptor surface of the SPHF plate as a luminous spot that then flashes effecting the DDT at the instant it coll...

Deflagration to Detonation Transition in Solid and Liquid Explosives

An explosive deflagration lasting a period r (s), and then suddenly undergoing transition to normal detonation may be achieved by interrupting the detonation wave in a primer charge by an inert, solid medium of thickness S1 less than a critical value Sc, and causing the reaction to commence as a deflagration in a receptor charge on the opposite side of the plate.

Rare gas adsorption on solids of the lunar regolith

Abstract This article analyzes the composition and concentration data on rare gases in the lunar solids taken in the Apollo 11 and 12 missions. The results indicate, among others, the following striking facts: 1. 1. Rare gas retention by the lunar materials is primarily by adsorption rather than absorption. 2. 2. The origin of the rare gases is primarily solar wind rather than indigenous or radiogenic. 3. 3. The accommodation coefficient of the lunar regolith for rare gases seems amazingly high. This is indicated by almost negligible fractionation; the composition of rare gases in the breccia, soil, and type A crystalline rocks is astonishingly close to that in solar wind. 4. 4. “Structural adsorption” potentials of rare gases on lunar solids appear amazingly high on the basis of the adsorption concentrations and a tenuous lunar “atmosphere.” Intense surface activation of the lunar materials is thus indicated.

Propagation Characteristics of Detonation‐Generated Plasmas

Studies are presented showing the electrical properties of the highly ionized, detonation‐generated plasmas ejected into various gaseous media at the bare surfaces of high explosives. These external plasmas are shown to originate from chemionization in the reactions of high explosive at free surfaces and are not produced by thermal ionization in the shock wave propagated in the surrounding gaseous medium. The initial external‐plasma length Lp* was found to be directly proportional to the length a0 of the reaction zone of the high explosive‐generating source. Conduction measurements in plasmas propagating in chlorine, oxygen, argon, nitrogen, helium, and air showed that the electron affinity of the gaseous medium is important in determining the rate of decay of the plasma and its ultimate disintegration. The lifetime of external plasmas are substantial in media of low electron affinity, exceeding appreciably 250 μsec in such media as argon, helium, and nitrogen. Free electrons contribute practically the en...