NC-NG-GAP propellant

Table 4.10 shows a comparison of the theoretical combustion properties of NC-NG-DEP and NC-NG-GAP propellants at 10 MPa. Though the molecular mass of the combustion products. Mg, remains relatively unchanged by the replacement of DEP with GAP, the adiabatic flame temperature is increased from 2557 K to 2964 K when 12.5 % DEP is replaced with 12.5 % GAP. Thus, the specific impulse is increased from 237s to 253s. The density of a propellant, p, is also an important parameter in evaluating its thermodynamic performance. The density is increased from 1530 kg m to 1590 kg m" by the replacement of DEP with GAP. Since GAP is also compatible with DEP, double-base propellants composed of four major ingredients, NG, NG, DEP, and GAP, are also formulated. 

Table 4.10 Chemical compositions and thermochemical properties of NC-NG-DEP and NC-NG-GAP propellants (10 MPa).

The combustion wave of an NC-NG-GAP propellant consists of successive two-stage reaction zones.0 1 The first gas-phase reaction occurs at the burning surface and the temperature increases rapidly in the fizz zone. The second zone is the dark zone, which separates the luminous flame zone from the burning surface. Thus, the luminous flame stands some distance above the burning surface. This structure... 

Fig. 6.19 Burning rates of a nitro-azide (NC-NG-GAP) propellant at different initial propellant temperatures, showing high temperature sensitivity.

Though both propellants contain equal amounts of NC and NG, the burning rate of NC-NG-GAP is approximately 70% higher than that of NC-NG-DEP at Tq = 293 K. The pressure exponent of burning rate remains relatively unchanged at = 0.7 by the replacement of DEP with GAP. However, the temperature sensitivity of burning rate defined in Eq. (3.73) is increased significantly from 0.0038 K" to 0.0083 K- ... 

The gas-generating propellants are (1) ammonium perchlorate-polybutadiene (AP-PB) composite propellants, (2) nitrocellulose-nitroglycerin (NC-NG) doublebase propellants, and (3) glycidyl azide polymer (GAP) propellants. 

The burning rates of a nitro-azide propellant composed of NC, NG, and GAP are shown in Fig. 6.19. For comparison, the burning rates of a double-base propellant composed of NC, NG, and DEP are shown in Fig. 6.20. The chemical compositions of both propellants are shown in Table 6.6. The adiabatic flame temperature is increased from 2560 K to 2960 K and the specific impulse is increased from 237 s to 253 s when 12.5% of DEP is replaced with the same amount of GAP. 

The burning rate of nitro-azide propellants composed of NC, NG, and GAP is shown in Fig. 6-18. As a comparison, the burning rate of double-base propellants... 

Typical gas-generating propellants are (1) AP-PB composite propellant composed of 50% AP and 50% HTPB that is cured with isophorone diisocyanate (IPDI), (2) NC-NG double-base propellant composed of 70% NC and 30% NG that is plasticized with diethyl phthalate (DEP), and (3) GAP propellant composed of GAP copolymer that is cured with 12.0% hexamethylene diisocyanate (HMDI) and cross-linked with 3.2 % trimethylolpropane (TM P). 

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