Implosions were used to raise the pressure and temperature of a driver gas to extreme values. Strong planar shock waves were thereby generated. A theoretical and experimental study was conducted on the performance of a 2.54-cm-diam shock tube driven by a 20-cm-diam hemispherical implosion driver. The analytical performance of the shock tube was predicted by numerically solving the set of governing nonlinear partial differential equations including appropriate loss mechanisms in the different regimes of the flow. The actual performance of the shock tube was determined experimentally by monitoring the shock velocity, flow uniformity, and test time for different driver conditions. These included stoichiometric hydrogen-oxygen mixtures with and without a PETN explosive liner. Planar shock waves were produced up to 11 km/sec without PETN and up to 19 km/sec with the addition of only 113 g of PETN explosive. Uniform test times of about 2-1 / sec were available at a distance of 33 m from the diaphragm (where the shock velocities were now 9 and 14 km/sec).

Strong Planar Shock Waves Generated by Explosively-Driven Spherical Implosions

Review of some exploratory test results for an electrical discharge driver with a conical-shaped arc chamber. The characteristics of the discharge cycle in the conical chamber and the shock tube performance are described, and the obtained results are compared with those reported by Menard (1971).

A conical arc driver for high-energy test facilities.

The use of hydrogen-neon gas mixtures for experimental simulation of inviscid hypersonic ionizing blunt body flows in hydrogen-helium atmospheres is considered. An existing approximate theory of blunt body similarity is employed, and it is found that the ionizing relaxation of hydrogen can be accommodated in that theory if the effect of ionisation along streamlines is correlated by a binary reaction variable involving the hydrogen partial pressure. The correlation is identical for helium and neon, and is not influenced by the fraction of diluent. Thus blunt body flows of hydrogen-heli um mixtures can be simulated with hydrogen-neon mixtures of a different diluent fraction. The simulation is demonstrated by using experiments with a 60% hydrogen 40% neon mixture in a free piston non-reflected shock tunnel to obtain the shock shape on a hemispherically blunted cone entering the atmosphere of Uranus or Neptune. NOMENCLATURE nose radius hydrogen ionization energy diluent ionization energy Boltzmann's constant forward rate constant typical body dimension particle mass particle number density

Hypersonic Blunt-Body Flows in Hydrogen-Neon Mixtures

This is the first part of a two-part paper describing the operating characteristics of the electric arc-driven shock-tube facility at NASA Ames Research Center. In this part, the operating envelope of the facility and the technology of the arc driver are presented. Specifically, the question as to how well the behavior of the arc driver is understood and controlled is addressed. A plasma kinetics model of the exploding wire is developed to describe the arc behavior in the driver. Using this model, the performance parameters for the arc driver, and thereby the performance of the facility, can be predicted approximately.

Operating Characteristics of a 60- and 10-cm Electric Arc-Driven Shock Tube—Part I: The Driver

An investigation is made to establish predictable electric arcs along triggered paths for research purposes, the intended application being the heating of the driver gas of a 1 MJ electrically driven shock tube. Trigger conductors consisting of wires, open tubes, and tubes pressurized with different gases were investigated either on the axis of the arc chamber or spiraled along the chamber walls. Design criteria are presented for successful arc initiation with reproducible voltage-current characteristics. Results are compared with other facilities and several application areas are discussed.

Arc Driver Operation for Either Efficient Energy Transfer or High-Current Generation

High performance electric arc driven shock tube for shock velocities to 45 km/sec and test times over 4 microseconds, using 80/20 helium-hydrogen mixture

Wesley A. Menard

Papers

A higher performance electric-arc-driven shock tube