RDX composite propellant

Fig. 7.34 Flame photographs of an AP composite propellant (a) and an RDX composite propellant (b) showing that the luminous flame front of the RDX composite propellant is distended from the burning surface ...

The combustion wave structure of RDX composite propellants is homogeneous and the temperature in the solid phase and in the gas phase increases relatively smoothly as compared with AP composite propellants. The temperature increases rapidly on and just above the burning surface (in the dark zone near the burning surface) and so the temperature gradient at the burning surface is high. The temperature in the dark zone increases slowly. However, the temperature increases rapidly once more at the luminous flame front. The combustion wave structure of RDX and HMX composite propellants composed of nitramines and hydrocarbon polymers is thus very similar to that of double-base propellants composed of nitrate esters.[1 1... 

Fig. 7.35 Scanning electron microphotographs of an RDX composite propellant surface before combustion (a) and after quenching (b) by rapid pressure decay from burning at 2 MPa.

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. 

The burning rates of AP-RDX composite propellants are dependent on the physicochemical properhes of the AP, RDX, and fuel used, such as particle size, as well as on mixture raho and the type of binder. The results of burning rate measurements are reported in AlAA Paper No. 81-1582.125] Various combinahons of AP and RDX parhcles are used to formulate AP-RDX composite propellants, as shown in Table 7.6.125] pjjg particles incorporated into the propellants have bimodal combinations of sizes, where large RDX particles (RDX-I), small RDX particles (RDX-S), large AP particles (AP-I), and small AP particles (AP-S) are designated by d, d, dj, and da, respectively. HTPB binder is used in all of the propellants shown in Table 7.6. 

Fig. 7.52 Burning rate characteristics of RDX composite propellants composed of coarse RDX and fine RDX particles.

Fig. 7.55 Effects of particle size and mixture ratio of AP and RDX on the burning rates of AP, RDX, and AP-RDX composite propellants.

Fig. 7.57 Effect of binder on the burning rate characteristics of RDX composite propellants (HTPB and HTPE).

Fig. 7.58 Burning rate characteristics of AP, AP-RDX, and RDX composite propellants (HTPE).

The addition of aluminum powder to AP-nitramine composite propellants increases the specific impulse, as in the case of AP composite propellants. Fig. 7.50 shows the theoretical fp and 7 -values for AP-RDX composite propellants containing as a function of The propellants are composed of... 

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