A.F. Savvateev

High-speed penetration into sand

Abstract The series of experiments aimed at the exploring high-speed impact of bullet on non-solid target were carried out at IPE RAS. The electro-discharge launcher (EDL) employed in these experiments can reach the projectile velocities of 4 km/s. The following topics were considered: the phenomena related to the high-speed penetration into non-solid targets, the parameters that influence the penetration depth and the projectile design suitable for the deepest penetration into sand. Experimental equipment allows the measurement of the penetration depth of bullet, its path inside the sand and the shock waves caused by the high-speed bullet impact. Experiments had shown the absence of significant deviation from a straight-line trajectory for the any tested bullet shapes at the impact velocity of 1.5–3.0 km/s. The most interesting result is the existence of a critical velocity for this type of interaction. The full bullet wear due to the friction with sand occurs at this velocity. The critical velocity value depends on bullet material and dimensions. Experiments show that exceeding the critical velocity leads to reduce in penetration depth. The influence of bullet material, shape and velocity on its penetration depth into sand was measured. These data allow a determination of the main characteristics of projectile for deep penetration into sand.

Multipulse discharge in the chamber of electric discharge launcher

The investigation results of an electric discharge launchers (EDL) chamber operation at hydrogen initial pressure 20-40 MPa, discharge current 0.5-1.0 MA, current rise rate (0.5-1.0)/spl times/10/sup 10/ A/s and input energy up to 2.2 MJ are presented. The coaxial electrode system consists of cylindrical anode and conic cathode. The discharge is initiated by copper wire in the interelectrode gap of 0.8-2.5 mm. The conditions of multipulse discharge current appearance, at the pulses number 5-15 (in comparison with usual multipulse regime 2-3 pulses), amplitude 0.5-1.0 MA and single pulse duration 50-200 /spl mu/s, are determined. The speeds of arc movement (1.5-3.0 km/s) and arc channel expansion (0.2-0.4 km/s), were measured by means of high-speed camera. The efficiency of energy transfer from the power supply (capacitor storage) to the arc was about 85% and from the arc to gas-90%. Electrodes erosion was found to be 30-40% less compared with usual multipulse regime. Besides the anode and cathode, total erosion was 30-40 mg/C at passed charge up to 800 C. The results estimation of different mechanisms contribution to heat transfer from the arc to surrounding hydrogen are discussed. It was shown that both repeated dissipation of arc plasma internal energy after arc extinction and the shock waves, appearing at the breakdowns of interelectrode gap, increase the efficiency of gas heating. It was proposed that decreasing of electrodes erosion at the multipulse regime is connected both with the growth of electrode spots movement speed and with the decreasing of current amplitude from 1.5-2.0 MA (usual multipulse regime) to 1.0 MA.

Attainment of the Pease-Braginskii current in an ultra-high-pressure discharge

Results are presented from experimental studies of the contraction of the channels of discharges in hydrogen and helium at current amplitudes of 0.5–1.6 MA and initial gas pressures of 5–35 MPa. The observed decrease in the brightness temperature of the discharge channel with increasing deposited energy is caused by the heating of the ambient gas. The channel contraction observed near the maximum of the discharge current is due to the attainment of the Pease-Braginskii critical current. Previously, it was shown that megampere discharges operate in a fully metallic plasma of the eroded electrodes. The theoretical value of the Pease-Braginskii current for discharges in vacuum is ∼100–200 kA. The observed increase in the critical current to ∼1 MA is attributed to the absorption of channel radiation in the dense ambient gas.

An Experimental Stand for Studying a High-Current Discharge in a Dense Gas

Experimental studies performed at the Institute for Electrophysics and Electric Power, Russian Academy of Sciences, that aimed at both the study of physics of a high-current pulsed discharge in a superdense gas and the improvement of various prototypes of pulsed facilities allowed a number of physical phenomena characteristic of these processes to be revealed. The most interesting phenomena are the arc contraction and a considerable increase in the electric-field strength in the arc channel with an increase in the initial particle density over 1022 cm−3. A substantial increase in the sum of the near-electrode voltage drops is observed with a rise of the discharge-current amplitude. A setup is described and the measurement results at an initial particle concentration of up to 1022 cm−3 and a discharge-current amplitude of up to 2 MA are presented.

Features of electric discharge in gas of high density

The two-stage facility for the exploration of powerful electric discharge in gas of the corpuscle concentration n of 10/sup 22/-10/sup 23/ cm/sup -3/ was created and tested. The adiabatic compression of gas is performing by the piston at the first stage of thus facility operation. The discharge of capacitive storage was triggered after the achieving maximum pressure in the chamber. The heated gas exhausts from the discharge chamber through the diaphragm unit. In performed experiments the following parameters were measured and estimated: voltage drop on arc, current, arc resistance, pressure in the chamber and corpuscles concentration. Experiment results permit to define the configuration of electrode system provided the stable arc burning at high pressure of gas. It was found that efficiency of energy transfer from arc to gas is close to 100% at such condition (gas pressure and concentration of corpuscles).

Launch package for multiple-rod hypervelocity impact investigation

Today the electrodischarge light-gas launcher (EDL) is not only the subject of investigation, but may be a suitable tool for different kinds of explorations. Such a hypervelocity accelerator gives the possibility to carry out experiments on impact interaction over a wide range of velocities (up to several kilometers per second) with substantial accelerated body masses. This experiment demands the creation of special impactor which in turn requires the launch package design. This paper considers the development of launch package for multiple rod hypervelocity impact investigation. Distinctive features of multiple rod impact investigation are the requirements to the simultaneity and desired impact geometry of interaction (mutual position of penetrators and approach angle). To meet all mentioned demands penetrators were placed in inseparable holding cartridge. The exact approach angle was ensured by means of aerodynamic stabilization. The holding cartridge has to be made from materials with least possible density to decrease its Influence on interaction process. At the same time the holding cartridge has to be strong enough to withstand the overloads during the in-bore acceleration. In this paper the design and test results of the launch package for the multiple rod hypervelocity impact studying are presented. All experiments were carried out with the (EDL) of 30-mm caliber. Hydrogen under the initial pressure of 40 MPa was used as a working gas. It permits us to use the projectiles with masses up to 150 g and explore the velocity range from 1500 up to 3000 m/s.

Study for the Efficiency of Combined Electro-Discharge Launcher

The experiments with combined launcher joined together the preliminary adiabatic compression of working gas by means of powder charge and its subsequent heating by the electric arc are continuing at the IEE RAS. This operation mode provides the high efficiency of launcher and allows to decrease required temperature and pressure of working gas. The results of combine launcher tests experiments are presented in the paper. It was studied the influence of initial experimental conditions on efficiency of acceleration. The main parameters of the experiments were varying in following range: initial pressure-10-15 MPa, pressure before the discharge -150-300 MPa, initial particle density (1.5- 3.3)times1022 cm-3, maximum pulse pressure - up to 500 MPa, discharge current -300-700 kA, current rise rate dI/dt ~1010 A/s. It was defined that best results achieved when gas mass did not exceed the projectile mass. Obtained experimental data permit to build the dependence of acceleration efficiency on initial gas pressure and inputted electric energy. The optimization of working parameters of launcher from the point of view of energy balance was performed. It was shown that consumption of electric energy consists of 30 - 50 % in compare with classic electrodischarge launcher. In this paper the mass-velocity characteristics of combined launcher for the projectile of 1-16 g weight in velocity range 1.5-5.0 km/s are presented. The best ballistic results: velocity of 2.5 km/s for 7.5-g projectile and velocity of 4.9 km/s for 1.5-g projectile.

Overview of EML research in Russia

This paper presents the most important results obtained at different laboratories in Russia over the last two years since the 11/sup th/ EML symposium. Research efforts have been directed toward studying the physical processes occurring in electrodischarge, electromagnetic, and electrothermal-chemical launchers, designing and searching for new low-erosion materials, and developing new methods for accelerating solid bodies to high velocities.

Investigation of Megaampere Discharge in Superdense Gas Media in Order to Obtain a Forplasma Source for Thermonuclear Research

The investigation results, represented in the paper, have been directed to production of dense hydrogen plasma with concentration of charged particle up to 1021 cm−3 and temperature up to 50 eV. This kind of plasma can be used as forplasma source for thermonuclear researches. It is also a source of ultra‐violet and mild x‐ray with a high‐energy yield. A combined two‐stage unit was developed and created to carry out investigations. The unit allows achieving the initial concentration of particle in the discharge chamber up to 5×1022 cm−3 the expense of preliminary adiabatic compression. Plasma was generated at strong current pulse discharge in super dense hydrogen. The experiments were conducted at currents of 100–500 Ka, energy of storage of 100–500 kJ and discharge time of 100–500 μs. The stable discharge is obtained at the mentioned above conditions. The estimations show that near the current maximum the concentration of charged particle in the discharge column is about 1020 cm−3 and temperature reaches ...

Investigation of Electric Discharge in Gas of Superhigh Density with Preliminary Adiabatic Compression

A powerful electric discharge in high-density hydrogen is investigated in a two-stage facility. The initial experimental conditions are as follows: the energy stored in a capacitive storage, 140–300 kJ; the discharge current, 90–220 kA; the current rise rate dI/dt ∼ 108 A/s; the charging voltage, 4.0–6.0 kV. The maximal concentration of hydrogen molecules n, achieved after adiabatic compression of gas (immediately before the discharge), is 3.3 × 1022 cm–3. The electrical parameters of the discharge and the gas pressure are measured in the experiments. The temperature, the concentration of charged particles, and the discharge channel radius are calculated using the results of these measurements. The estimates reveal that, under the given initial conditions, the arc channel temperature is (1.3–1.8) × 105 K, the concentration of charged particles is (0.7–1.2) × 1020 cm–3, and the channel radius is 0.14–0.20 cm.