A 2.2-kton nuclear explosive was detonated underground at one end of a 122-m long, 1-m i.d. horizontal tunnel at the Nevada Test Site. The purpose of the experiment was to study the hydrodynamic flow of energy down a tunnel from a nuclear explosive. This report describes the experimentation utilized to record luminosity of the shock front for the first 15 μsec and time of arrival of the shock front at specific positions along the tunnel. The observed temperature, determined from shock-luminosity data and the blackbody radiation assumption, dropped from 11.8 to 2.3 eV at times of 3.2 and 18 μsec respectively after the peak energy output of the nuclear explosion. The shock wave traversed the 122 m in approximately 4 msec, with a velocity ranging from about 13 cm/μsec near the shot point to approximately 1 cm/μsec at the far end.
A shock-tube experiment was performed with 5.5 kg of high explosives to generate and to drive an air shock down a steel pipe 7.8-cm i.d. and ∼25-m length. Fiber optics and pressure transducers were installed at specific locations to record optical and pressure time of arrival of the air shock and pressure histories in the pipe. The initial∼Mach 30 air shock attenuated to∼Mach 6 at the end of the pipe. A numerical simulation of this experiment was performed. This paper presents the experimental arrangement and results, and briefly describes the numerical models used. The calculation results are compared with the data. During the interval of approximately 8 msec required for the shock to travel the length of the 25-m pipe, the calculations indicated that the predominant factors in attenuating the time of arrival of the shock were heat transfer and friction, respectively.
Marvel, a nuclear‐driven shock‐tube experiment, consisted of a 2.2‐kT nuclear explosive detonated 176 meters underground at one end of a 122‐meter long, 1‐meter diameter horizontal tunnel. Vaporization of material in the immediate vicinity of the explosive provided the source of high‐energy driven gas. The driven gas was the ambient atmospheric air in the tunnel. Marvel was conducted as an experimental and calculational study of the time‐dependent flow of energy in the tunnel and surrounding alluvium. This paper describes (1) the design of Marvel, (2) the dynamic and postshot experimental results, and (3) a numerical simulation of the experiment. Experimental and calculational results indicate the following. The high‐energy air shock traveled down the tunnel nearly 50 times faster than the shock in the surrounding alluvium. Over the first 30 meters of the tunnel, the shock had a velocity of approximately Mach 380; during its 4‐msec transit of the 122‐meter tunnel, it attenuated to approximately Mach 30. Significant ablation of material from the tunnel walls had the primary effect in attenuating the air shock. The source energy was preferentially channeled down the tunnel, and a cone‐shaped cavity resulted.
A gas-jet experiment was conducted using a Voitenko compressor to deposit approximately 7×1013 erg of energy into 27.5 g of air. This high-energy gas or plasma jetted down a 2-cm-i.d. 350-cm-long steel exit pipe containing air initially at a pressure of 20 μ of mercury. The jet structure was composed of a 5.5-cm/μsec low-density (<5×10−5 g/cm3) peak followed by a ∼4-cm/μsec higher-density (∼3×10−3 g/cm3) peak. Both peaks appear to attenuate to a terminal or steady-state velocity of 2.4 cm/μsec near the end of the pipe. Brightness temperature and pressure profiles are obtained at specific locations over the first 100 cm. To correlate the pressure-temperature results, a two-dimensional jet configuration is suggested. A maximum brightness temperature of 93 000°K was measured for the plasma jet as it started down the exit pipe.
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