Zvi Kaplan

Electrothermally augmentation of a solid propellant launcher

The augmentation of a ballistic process based on solid propellant burning by an electrothermal energy source is the subject of an experimental and theoretical investigation to obtain improved launching techniques. The plasma jet formation method, the internal ballistics modeling approach, and the experimental testbed are described. Experimental results show the enhanced burning rate of a solid propellant ignited and augmented by the injection of plasma jets. Preliminary experimental evidence of the improved performance of the proposed method over that of conventional ballistics using solid propellant alone is presented. >

A field study of a hypervelocity solid propellant electrothermal 105 mm launcher

The operation of a Solid Propellant Electrothermal Chemical (SPETC) launcher was tested extensively in support of the US Army Space and Strategic Defence Command (USA SSDC) requirement for integrated field tests for a propsed Hypervelocity Weapon System (HVWS). Efforts were undertaken to translate ballistic results obtained earlier with a 105 mm SPETC launcher at Soreq NRC Israel for field use. A 105 mm firing fixture was used in the study. Forty-nine field firings were carried out in the 105 mm launcher without a single failure of the electrothermal fixture. Controlled pressure vs time profiles and velocities in the range of 1800-2030 m/s were obtained at pressures of the order of 450-550 MPa and accelerations of up to 64 kgee. This was achieved using projectile masses from 3.8-5.2 kg and various power pulses up to 1.8 MJ. An ensemble of 14 firing experiments indicates that the SPETC process is highly repeatable. The interior ballistic process is smooth and applicable to high gee sabot separation tests. The SPETC launcher was found to be very reliable, robust and flexible with a high potential for future weaponization. >

Confined high pressure discharge experiments

Plasma jets created by a discharge of current density in the range of 20-200 kA/cm/sup 2/ were studied experimentally. Time-of-flight, spectroscopy, and X-ray imaging techniques were used to measure the velocity, temperature and the density of the plasma jet. These techniques were applied to the plasma of a free jet both in air and in vacuum, resulting in reliable and interrelated values that coincide and confirm each other. The results are pertinent to the use of high-pressure discharges to generate plasma jets for electrothermal launchers. >

Experimental demonstration and simulation of a dual-stage solid propellant gun concept

A novel method for the acceleration of projectiles to hypervelocity is presented. The method utilizes two solid grain propellant charges which are operated in tandem in a dual-stage mode. The second charge is encapsulated into a massive case which is placed adjacent to the projectile. This stage is ignited at a time delay, after the first charge. Experiments done on a 13-mm barrel demonstrate the feasibility of this acceleration scheme. Zerodimensional simulations predict significant improvement over single-stage gun, using the same maximal pressure as imposed by conventional barrels. A specific calculation of a 0.48-kg projectile accelerated in a 4.4-m-long, 60-nim barrel predicts velocities over 2500 m/s. Nomenclature A = barrel cross-sectional area C,, C2 = mass of main charge and moving charge I = y2 ~ y.i, the distance between ra2 and ra, m{, m2 = masses of the dynamic breech and the projectile, respectively Pair = air pressure in front of the projectile PI-PI = measured pressures in successive locations along the barrel, PI = at the breech P,, P2 = average pressures in the two gas media, 1 = main, 2 = moving charge PII>-> ?2b behind the dynamic breech and at the

Visualization of plasma-fluid mixing through X-ray shadowgraphy

Changes induced by the impact of a hot plasma jet on a fluid have been recorded using X-ray shadowgraphy. The process is of particular importance in the operation of electrothermal acceleration devices. Sets of frames taken every 40 mu s reveal details of the interaction. Fluid erosion is observed to occur only at the fluid extremity directly hit by the plasma. The erosion rate has been evaluated for the initial collision stages when the volume accessible to the fluid remains constant; the measured values range between 100 m/s and 200 m/s. >