Pressure of RDX

In discussing Eq. (1) in the earlier papers of this series, it was emphasized several times that despite some serious questions which had been raised regarding the accuracy or appropriateness of the computer codes input information, our temporary intent was to devise a simple calculational method which might best reproduce ruby results. It was also mentioned that the Kistiakowsky-Wilson equation of state7,8 parameters used in ruby6 were chosen by Mader5 so as to best accommodate five experimental measurements the detonation pressure of RDX at 1.80 g/cc, the detonation velocities of RDX at 1.00 and 1.80 g/cc, and the detonation velocities of TNT at 1.00 and 1.64 g/cc. 

The temperature developed on explosion is 3380°C. There are two grades specified for RDX types A and type B. Type A contains no HMX and type B has a constant impurity of from 8 to 12 percent HMX. Types A and B are produced by different manufacturing processes. Type A RDX melts between 202°C and 203 C type B RDX melts between 192°C and 193°C. The vapor pressure of RDX is given by the equation ... 

A linear relationship between Chapman-Jouguet pressure and density was confirmed for Cyclotol and Octol (Ref 28). Despite the near-equal performance of RDX and HMX at equal densities there appears to be no economical way of making the density of RDX equal to the cast density of HMX. Dinitrobenzene (DNB) has been evaluated as an economical or emergency substitute for TNT but charges prepared with DNB gave somewhat poorer performance than... 

The penetrating power of a shaped charge is approximately proportional to the cube of its diameter, but also very dependent on maintenance of exact axial symmetry during construction. It is also proportional to the detonation pressure of the explosive used, so that suitable fillings are cast Pentolite or RDX/TNT. Well-known applications of shaped charges are in the British PIAT and American bazooka. 

When some portion of the AP particles contained within an AP composite propellant is replaced with nitramine particles, an AP-nitramine composite propellan-tis formulated. However, the specific impulse is reduced because there is an insufficient supply of oxidizer to the fuel components, i. e., the composition becomes fuel-rich. The adiabatic flame temperature is also reduced as the mass fraction of nitramine is increased. Fig. 7.49 shows the results of theoretical calculations of and Tf for AP-RDX composite propellants as a function of Irdx- Th propellants are composed of jjxpb(0-13) and the chamber pressure is 7.0 MPa with an optimum expansion to 0.1 MPa. Both I p and T)-decrease with increasing Irdx- The molecular mass of the combustion products also decreases with increasing Irdx due to the production of Hj by the decomposition of RDX. It is evident that no excess oxidizer fragments are available to oxidize this H2. 

Fig. 13.21 shows another example of oscillatory burning of an RDX-AP composite propellant containing 0.40% A1 particles. The combustion pressure chosen for the burning was 4.5 MPa. The DC component trace indicates that the onset of the instability is 0.31 s after ignition, and that the instability lasts for 0.67 s. The pressure instability then suddenly ceases and the pressure returns to the designed pressure of 4.5 MPa. Close examination of the anomalous bandpass-filtered pressure traces reveals that the excited frequencies in the circular port are between 10 kHz and 30 kHz. The AC components below 10 kHz and above 30 kHz are not excited, as shown in Fig. 13.21. The frequency spectrum of the observed combustion instability is shown in Fig. 13.22. Here, the calculated frequency of the standing waves in the rocket motor is shown as a function of the inner diameter of the port and frequency. The sonic speed is assumed to be 1000 m s and I = 0.25 m. The most excited frequency is 25 kHz, followed by 18 kHz and 32 kHz. When the observed frequencies are compared with the calculated acoustic frequencies shown in Fig. 13.23, the dominant frequency is seen to be that of the first radial mode, with possible inclusion of the second and third tangential modes. The increased DC pressure between 0.31 s and 0.67 s is considered to be caused by a velocity-coupled oscillatory combustion. Such a velocity-coupled oscillation tends to induce erosive burning along the port surface. The maximum amplitude of the AC component pressure is 3.67 MPa between 20 kHz and 30 kHz. - ...

Sampling is difficult because the vapor pressures for most explosives are very low. For example, the room temperature equilibrium headspace concentration of RDX in air is about 10 pptv (parts per trillion by volume). Collection of vapor is further compounded for explosives that are bound in matrices and wrappers and/or are concealed in wrappings or baggage. The prospects for trace detection of explosives are considered to be better when sampling objects for explosives contamination in the form of particles and residue. 

The spectra in Figure 11.4 were recorded from headspace vapor either at room temperature (TNT, PETN) or elevated temperature (about 50°C for RDX). For TNT this corresponds to a saturated headspace vapor pressure of less than 10 ppb. At these levels strong signal is observed with relatively weak signal from room air. Explosives compounds that have been detected by the MS detector with high sensitivity include TNT, ADNT, DNT, NT, TNB, DNB, DMNB, RDX, HMX, EGDN, NG, PETN, and TATP. (see Explosive Definitions, page 329). 

Dremin Shvedov (Ref 3) measured by an electromagnet method the CJ pressure time of reaction in detonation waves of RDX, TNT, PETN, Tetryl, DINA, and of some of their mixts. The results obtd were significantly different from previous data. An attempt was made to explain this difference Refs 1) W.E. Deal, "Measurement of Chapman-Jouguet Pressure for Explosives", JChemPhys 27, 796-800(1957) 2) N.L. 

Dremin et al (Ref 12) gives values for the following parameters of RDX TNT D=detonation velocity, Uj = velocity of detonation products at the detonation-wave front, and P = Chapman-Jouguet-plane pressure at various densities... 

Detonation, Water Plexiglos Induced Shock Wove Velocity in. Cook et al (Ref 2) applied the "aquarium technique in the exptl detn of the equation of state for water Lucire. The results for water are compared with similar results by other methods. Measurements of the peak pressures in the deton wave are presented for RDX, RDX/salt, TNT HBX-1. Peak pressures were found to be the CJ or deton pressures of the thermohydro-dynamic theory. There was no evidence whatever for the "spike of the Zel dovich-von Neumann model even though conditions were such that this spike would have been detected by the method employed if it were present, at lease in the large diam, nonideal expls of max reaction zone length Refs.T) C. Fauquignon, CR 251, 38 (I960) 2) M, A. Cook et al, JAppl... 

Cyclonite is a very important explosive. The outstanding properties of RDX as an explosive are high chemical stability, not much lower than aromatic nitro compounds and high explosive power which considerably surpasses that of aromatic nitro compounds such as TNT and picric acid. RDX has a detonation velocity of8600 ms"1 and a detonation pressure of 33.8 GPa at a density of 1.77 gem"3. RDX is used in mixtures with TNT (Hexotols, Cyclotols, Compn. B) wax (Composition A) aluminum (Hexals) aluminum and TNT (HBX, Hexotonal, Torpex) etc. 

Duxita B. An Italian expl consisting of RDX 94.5, K nitrate 3-0 castor oil 2.5% white, odorless pdr, d 1.74g/cc, mp ca 225°(dec) very sol in acet, si sol in ale Abel s Test at 80° — 30 mins. Impact Test with 5kg wt 55 to 85cm suitable for pressure-loading shells and bombs... 

The volume of gas produced during an explosion will provide information on the amount of work done by the explosive. In order to measure the volume of gas generated standard conditions must be established, because the volume of gas will vary according to the temperature at which the measurement is taken. These standard conditions also enable comparisons to be made between one explosive and another. The standard conditions set the temperature at 0 °C or 273 K, and the pressure at 1 atm. These conditions are known as standard, temperature and pressure , stp . Under these standard conditions one mole of gas will occupy 22.4 dm3, which is known as the molar gas volume. The volume of gas V produced from an explosive during detonation can be calculated from its equation of decomposition, where information can be obtained on the amount of gaseous products liberated. Examples for the calculation of V during detonation of RDX and TNT are given below. 

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