The state of the art relative to the measurement of shock and detonation pressures of the magnitude generaled by condensed high explosives is reviewed. Carbon resistors have been shown to provide a relatively inexpensive and direct method for such measurements, provided adequate calibration data are available. The gauge is fabricated by heat‐sealing the carbon resistor (470 Ω, 0.125 W) into a suitable plastic material such as polystyrene; when subjected to a strong shock wave, the gauge undergoes compression and the conductivity increases in proprtion to the magnitude of the pressure. The present investigation was concerned with the experimental derivation of calibration equations relating the pressure (in gigapascal) as a function of the conductivity change ΔG (in siemens). The point of inflaction occurring at approximately 2.36 GPa, corresponding to 0.02082 S, is in agreement with previous observations in the literature. Additional experiments are being planned to resolve a problem concerning oscillatory ringing in the gauge voltage records.

The use of modified forms of the Rosenthal electrothermal equation to aid in the design of a capacitor discharge firing circuit for a specific detonator is described. The electrothermal parameters Cp and γ, representing the heat capacity of the bridge and the heat loss factor, respectively, were calculated from previously obtained firing data for the detonator. These calculations provided input to the design of a firing circuit utilizing electrolytic capacitors, which have a large value of electrical capacity but also a non‐negligible internal resistance. Calculations were performed which (1) revealed the degrading effect on detonator initiation caused by too large a value of internal resistance, and (2) permitted selection of a particular capacitor that would allow reliable functioning of the detonator with initiation times of about 230 μs. The circuit was designed utilizing this capacitor, and in the experimental evaluation of the circuit the measured initiation times were compared with the calculated values. Good agreement between the two was documented, and the conclusion was reached that the detonator functioned reliably. The merits of the electrothermal analysis and the assumptions utilized therein relative to a vigorous heat transfer/reaction kinetics modeling of the flow of energy from the bridge into the explosive flash charge are discussed in detail.

An estimate of the detonation pressure of carbohydrate‐metal composite explosives has been obtained experimentally by use of carbon resistor pressure gauges mounted in the wall of the confining tubes. The composite explosives were formulated from a pharmaceutical mixture of 10/90 nitroglyccrin/ß‐lactose by weight, and was rendered detonable by inclusion of flaked aluminum and both flaked aluminum and ammonium perchlorate. The detonation pressure of the nitroglyccrin/ß‐lactose mixture with 10 percent aluminum by weight was approximatcly 1.1 GPa. The incorporation of 30 percent ball‐milled ammonium perchlorate to this formnlation increased the detonation pressure to 12.2 GPa. These pressures must be considered as estimates of the true detonation pressure, because of (a) the suspected non‐ideality of the detonation state of these explosives, (b) the statistical nature of the response of the gauges, and (c) possible inconsistencies in the interpreatation of the gauge records. It is recommended that a number of gauges be used in a given experiment, and the results be averaged as one means of cireumventing the above difficulties.

For many years, carbon resistors have formed the basis for measurement of shock and detonation pressures associated with condensed explosives. The gauge is fabricated by heat‐sealing the resistor into a plastic material such as polystyrene. When subjected to a strong shock wave, the resistance decreases, and the resulting increase in conductance is a function of the magnitude of the pressure. The present investigation was concerned with the experimental derivation of revised calibration equations, which was necessitated by the need to incorporate a terminating resistor into the gauge circuitry. The use of this resistor decreased the effect of standing waves and eliminated oscillatory ringing in the recorded signal. Typical records over a wide range of pressures are presented. An error analysis of the recorded data showed that the uncertainty in the measured pressure was of the same order of magnitude as the uncertainty in the interpretation of the recorded voltage from which the conductance was computed. An extensive discussion of the relevancy of the experimental data is presented, and the need for additional calibration experiments is stressed.

An experimental program is described in which the capacitor‐discharge initiation characteristics of a detonator containing a vacuum‐deposited thin‐film chromium bridge were studied. The objective of the effort was to define the conditions that would result in overall function times of 10 μs or less. The threshold initiation energy of the detonator was in the range of 11.5 mJ–20.0 mJ. Consistent performance was obtained from a firing energy of 54 mJ, which was achieved by a 5‐μF capacitor charged to 147 V. Under these conditions, the average overall function time was 4.2 μs, with a standard deviation of 0.2 μs. Other tests showed that at higher capacitances and lower voltages the function time increased substantially and became more nonreproducible, even though the stored energy was considerably above the threshold value.