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Potassium Nitrate-Dextrose (KNDX) Propellant Chemistry and Performance Characteristics

Standard Composition (65/35 O/F)

For the KNDX propellant, with an oxidizer-fuel (O/F) ratio of 65/35, the theoretical combustion equation is as follows:

C6H12O6 + 3.31 KNO3 -> 2.116 CO2 + 2.300 CO + 4.512 H2O + 1.424 H2 + 1.655 N2 + 1.585 K2CO3 + 0.133 KOH

at a pressure of 68 atmospheres (1000 psi), and where the following compounds are symbolized as:

dextrose (anhydrous)solidC6H12O6
potassium nitratesolid KNO3
carbon dioxidegasCO2
carbon monoxidegasCO
steam gas H2O
hydrogengas H2
nitrogen gas N2
potassium carbonateliquidK2CO3
potassium hydroxidegasKOH

The mole numbers for each of the products shown above were determined from PROPEP (Propellant Evaluation Program).

Characteristics of the KN-Dextrose Propellant (65/35 ratio)
Process methodCast
IspSpecific Impulse, ideal152.6sec.[1]
IspSpecific Impulse, measured130sec.[6]
C*Characteristic exhaust velocity, theoretical2992 (912)ft/s (m/s)
C*Characteristic exhaust velocity, measured2922 (891)ft/s (m/s)[7]
ToCombustion temperature, theoretical @1000 psia1437 (1710)deg Celsius (K)[2]
ToCombustion temperature, measured@1000 psiaTBDdeg Celsius
Density, ideal1.879gram/
Density, as cast1.859gram/[3]
XMass fraction of condensed-phase products0.426-
kRatio of specific heats1.131-[4]
MEffective molecular wt. of exhaust products42.42g/mole[5]
Burn rate behaviourplateau
roBurn rate @ 1 atm.0.084in/sec
rBurn rate @ 1000 psia0.509in/sec
TcrAuto-ignition temperature> 300deg. C.

[1] At 1000 psi pressure; exit pressure one atmosphere
[2] PROPEP combustion results
[3] Measured, typical
[4] Mixture (2-phase flow), at chamber conditions.
[5] System mass /number of gas moles
[6] Typical
[7] Typical

Data chart

Figure 1 -- This chart shows the variation of theoretical specific impulse with O/F (oxidizer/fuel) ratio.

Data chart

Figure 2 -- This chart shows the variation of combustion temperature and molecular weight of exhaust products with O/F ratio.

Data chart

Figure3 -- This chart shows the variation of theoretical specific impulse with chamber pressure.

Last updated

Originally posted December 10, 2000

Last updated March 15, 2023

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