For KNSU propellant, with an oxidizer-fuel (O/F) ratio of 65/35, the theoretical combustion equation is as follows:
C12H22O11 + 6.288 KNO3 -> 3.796 CO2 + 5.205 CO + 7.794 H2O + 3.065 H2 + 3.143 N2 + 2.998 K2CO3 + 0.274 KOH
at a pressure of 68 atmospheres, and where the following compounds are symbolized as:
sucrose | solid | C12H22O11 |
potassium nitrate | solid | KNO3 |
carbon dioxide | gas | CO2 |
carbon monoxide | gas | CO |
steam | gas | H2O |
hydrogen | gas | H2 |
nitrogen | gas | N2 |
potassium carbonate | liquid | K2CO3 |
potassium hydroxide | gas | KOH |
The mole numbers for each of the products shown above were determined from PROPEP (Propellant Evaluation Program).
Parameter | Units | Note | ||
Process method | Cast | |||
Isp | Specific Impulse, ideal | 166 | sec. | [1] |
Isp | Specific Impulse, delivered (typical) | 130 | sec. | [2] |
C* | Characteristic exhaust velocity, theoretical | 3106 | ft/s | |
To | Combustion temperature, theoretical @1000 psia | 1447 (1720) | deg Celsius (K) | [3] |
To | Combustion temperature, measured@1000 psia | 1350 | deg Celsius | [4] |
Density, ideal | 1.89 | gram/cu.cm. | ||
Density, as cast (typical) | 1.80 | gram/cu.cm. | [5] | |
X | Mass fraction of condensed-phase products | 0.424 | - | |
k | Ratio of specific heats, 2-phase flow | 1.044 | - | [6] |
k | Ratio of specific heats, static | 1.133 | - | [7] |
M | Effective molecular wt. of exhaust products | 41.98 | g/mole | [8] |
Burn rate behaviour | de St.Robert | |||
n | Burn rate pressure exponent, strand | 0.319 | ||
n | Burn rate pressure exponent, erosive | 0.323 | ||
a | Burnrate constant | 0.0665 | [9] | |
ro | Burn rate @ 1 atm. | 0.156 | in/sec | |
r | Burn rate @ 1000 psia | 0.602 | in/sec | |
Tcr | Auto-ignition temperature | > 300 | deg. C. |
[1] At 1000 psi pressure; exit pressure one atmosphere
[2] Static tests AST-17, AST-18
[3] PROPEP combustion results
[4] Measured with type k thermocouple, static test AST-16
[5] Measured (liquid displacement method), typical grain for B-200 motor
[6] Effective (2-phase), at chamber conditions
[7] Value for exhaust mixture
[8] System mass divided by number of gas moles
[9] Use with pressure units of psi. Resulting burn rate is inches per second
Figure 2 -- This chart shows the variation of combustion temperature and molecular weight of exhaust products with O/F ratio.
Figure3 -- This chart shows the variation of theoretical specific impulse with chamber pressure.