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PVC Motor Specs for Sucrose Propellant

The dimensions chosen for these motors are only a sample of the infinite combination of possible dimensions.  These have only been tested to date through the 3/4" size.  The nozzle throat diameters were chosen to correspond to standard 1/64" drill sizes and the grain bore sizes are in 1/8" increments to fit the most standard available steel rod sizes for the coring rods. 

The grain bore sizes are all the same for any one motor size for standardization and simplicity.  A person could make smaller bores at the top and larger bores closer to the nozzle and gain a little more propellant in a given motor.  The difference probably isn't worth the effort, however.

 Most of these motors are actually erosive burning motors because the bore diameter is less than twice the nozzle throat diameter.  Non-erosive buring sucrose propellant motors would have to have bores too large.  There would not be much propellant left.  The effect of erosive burning is that the pressure will be a little higher and the burn time a little shorter than the information given.  That effect is not much outside the range of variability of these motors anyway.

Ignition time was set to 0.  In reality, there will be a slight ramp up to pressure.

The performance specifications here have been determined using CP Technologies FPRED - V3.3.

The performance values in these tables are calculated theoretical values.  Actual values will vary due to a variety of factors.  My experience in testing is that the actual values were quite close to those predicted here.

The items all motors have in common are:

• 15 degree half-angle (centerline to cone wall) exit (diverging) cone on the nozzle

• Converging nozzle cone was either none or 45 degree half-angle.  The difference is negligible.

• Propellant formula is:  KNO₃ 65%, Sucrose 35%

• Propellant was mixed by dissolving in water and then the water driven off in the heating process

• PVC pipe casing is schedule 40

• Target chamber pressures are around 300 psi

• When testing was done, it was done without an ejection charge and with Rockite as the nozzle and header material

• Nozzle retention method was either circumferential holes or I.D. retaining ring (see casings, nozzles & headers)

• Nozzles and headers are the same thickness (length) as the I.D. of the casing

• Washers are used in the nozzle to keep the throat from eroding.  Without washers, the pressures and thrust would be slightly less.

• Nozzle Coefficient (C*) = 3106

• Burn rate equation exponent (n) = 0.319

• Burn rate equation coeficient ( c) = 0.0665

• Theoretical Max Isp = 166 sec, Actual at these pressures are around 100 sec.

• Density (ρ)= .068 lb/cu in

• Gamma (k) (ratio of specific heats) = 1.044

• Overall Efficiency used for calculation = 75%

• Exit Cone Efficiency used for calculation = 90%

• Erosive Burn = None

• Ignition Time = 0

• Throat Erosion used for calculation = 0

• Ambient Pressure (psia) = 14.7

• Grains are BATES grains with OD inhibited & cylindrical bore

 

Motor Designations by Case Size & Number of Grains   Number of Grains Case Size 1 2 3 4 5 6 1/2" C14 D28 E42 E55 E74   3/4" D23 E46 F71 F107 G135 G164 1" E37 F82 G119 G160 G229 H268 1-1/4" G73 H147 H218 I291 I388 I435 1-1/2" G87 H174 I267 I356 I453

 

1/2" Motors -- 1/4" Bore Nominal PVC Size 1/2" Grain O.D. .59" Grain Length 1.00 Bore Dia .25" Grain Weight .015 lb Burn time .43 sec.
Motor Designation C14 Number of Grains 1 Case Length 2.25" Nozzle Throat Dia. .109" (7/64") Nozzle Exit Cone Dia. .22" Max. Chamber Pressure 281 psi Max Thrust 3.32 lbs Average Thrust 3.14 lbs Impulse 6.63 NSecs	Motor Designation D28 Number of Grains 2 Case Length 3.25" Nozzle Throat Dia. .156" (5/32") Nozzle Exit Cone Dia. .30" Max. Chamber Pressure 272 psi Max Thrust 6.55 lbs Average Thrust 6.18 lbs Impulse 13.29 NSecs
Motor Designation E42 Number of Grains 3 Case Length 4.25" Nozzle Throat Dia. .188" (3/16") Nozzle Exit Cone Dia. .37" Max. Chamber Pressure 290psi Max Thrust 10.10 lbs Average Thrust 9.54 lbs Impulse 20.2 NSecs	Motor Designation E55 Number of Grains 4 Case Length 5.25" Nozzle Throat Dia. .219" (7/32") Nozzle Exit Cone Dia. .22" Max. Chamber Pressure 281 psi Max Thrust 13.28 lbs Average Thrust 12.55 lbs Impulse 26.5 NSecs
Motor Designation E74 Number of Grains 5 Case Length 6.25" Nozzle Throat Dia. .188" (3/16") Nozzle Exit Cone Dia. .47" Max. Chamber Pressure 318 psi Max Thrust 17.5 lbs Average Thrust 16.6 lbs Impulse 34.5 NSecs
3/4" Motors -- 1/4" Bore Nominal PVC Size 3/4" Grain O.D. .78" Grain Length 1.38" Bore Dia .25" Grain Weight .039 lb Burn time .68sec.
Motor Designation D23 Number of Grains 1 Case Length 3.00" Nozzle Throat Dia. .142" (9/64") Nozzle Exit Cone Dia. .28" Max. Chamber Pressure 288psi Max Thrust 5.75 lbs Average Thrust 5.27 lbs Impulse 17.5 NSecs	Motor Designation E46 Number of Grains 2 Case Length 4.38" Nozzle Throat Dia. .203" (13/64") Nozzle Exit Cone Dia. .39" Max. Chamber Pressure 279 psi Max Thrust 11.33 lbs Average Thrust 10.40 lbs Impulse 34.4 NSecs
Motor Designation F71 Number of Grains 3 Case Length 5.75" Nozzle Throat Dia. .250" (1/4") Nozzle Exit Cone Dia. .48" Max. Chamber Pressure 274 psi Max Thrust 16.9 lbs Average Thrust 15.5 lbs Impulse 51.8 NSecs
3/4" Motors -- 3/8" Grain Bore Nominal PVC Size 3/4" Grain O.D. .80" Grain Length 1.38" Bore Dia 3/8" Grain Weight .0352 lb Burn time .53sec.
Motor Designation F107 Number of Grains 4 Case Length 7.13" Nozzle Throat Dia. .297" (19/64") Nozzle Exit Cone Dia. .58" Max. Chamber Pressure 288 psi Max Thrust 25.2 lbs Average Thrust 24.1 lbs Impulse 61.3 NSecs	Motor Designation G135 Number of Grains 5 Case Length 8.5" Nozzle Throat Dia. .328" (21/64") Nozzle Exit Cone Dia. .66" Max. Chamber Pressure 299 psi Max Thrust 32.0 lbs Average Thrust 30.6 lbs Impulse 76.8 NSecs
Motor Designation G164 Number of Grains 6 Case Length 6.25" Nozzle Throat Dia. .359" (23/64") Nozzle Exit Cone Dia. .72" Max. Chamber Pressure 299 psi Max Thrust 38.4 lbs Average Thrust 36.8 lbs Impulse 92 NSecs
1" Motors -- 3/8" Bore Nominal PVC Size 1" Grain O.D. .97" Grain Length 1.75" Bore Dia 3/8" Grain Weight .071 lb Burn time .76 sec.
Motor Designation E37 Number of Grains 1 Case Length 3.75" Nozzle Throat Dia. .188" (3/16") Nozzle Exit Cone Dia. .35" Max. Chamber Pressure 264 psi Max Thrust 9.08 lbs Average Thrust 8.50 lbs Impulse 32.0 NSecs	Motor Designation F82 Number of Grains 2 Case Length 5.50" Nozzle Throat Dia. .250" (23/64") Nozzle Exit Cone Dia. .50" Max. Chamber Pressure 313 psi Max Thrust 19.6 lbs Average Thrust 18.38 lbs Impulse 66.8 NSecs
Motor Designation G119 Number of Grains 3 Case Length 7.25" Nozzle Throat Dia. .313" (5/16") Nozzle Exit Cone Dia. .61" Max. Chamber Pressure 295 psi Max Thrust 28.7 lbs Average Thrust 26.8 lbs Impulse 99.4 NSecs	Motor Designation G160 Number of Grains 4 Case Length 9.00" Nozzle Throat Dia. .3594" (23/64") Nozzle Exit Cone Dia. .71" Max. Chamber Pressure 299 psi Max Thrust 38.4 lbs Average Thrust 36.0 lbs Impulse 132 NSecs
1" Motors -- 1/2" Grain Bore Nominal PVC Size 1" Grain O.D. .97" Grain Length 1.75" Bore Dia 1/2" Grain Weight .0610 lb Burn time .57sec.
Motor Designation G229 Number of Grains 5 Case Length 10.75" Nozzle Throat Dia. .406" (13/32") Nozzle Exit Cone Dia. .83" Max. Chamber Pressure 321 psi Max Thrust 53.3 lbs Average Thrust 51.4 lbs Impulse 149 NSecs	Motor Designation H268 Number of Grains 6 Case Length 12.5" Nozzle Throat Dia. .3594" (23/64") Nozzle Exit Cone Dia. .91" Max. Chamber Pressure 305 psi Max Thrust 62.5 lbs Average Thrust 60.3 lbs Impulse 177 NSecs
1-1/4" Motors -- 1/2 Bore Nominal PVC Size 1-1/4" Grain O.D. 1.35" Grain Length 2.25" Bore Dia 1/2" Grain Weight .181 lb Burn time 1.05 sec.
Motor Designation G73 Number of Grains 1 Case Length 5.00" Nozzle Throat Dia. .234" (15/64") Nozzle Exit Cone Dia. .47" Max. Chamber Pressure 318 psi Max Thrust 17.5 lbs Average Thrust 16.34 lbs Impulse 84.0 NSecs	Motor Designation H147 Number of Grains 2 Case Length 7.25" Nozzle Throat Dia. .328" (21/64") Nozzle Exit Cone Dia. .67" Max. Chamber Pressure 328 psi Max Thrust 35.6 lbs Average Thrust 33.1 lbs Impulse 169 NSecs
Motor Designation H218 Number of Grains 3 Case Length 9.5" Nozzle Throat Dia. .406" (13/32") Nozzle Exit Cone Dia. .82" Max. Chamber Pressure 317 psi Max Thrust 52.6 lbs Average Thrust 49.0 lbs Impulse 252 NSecs	Motor Designation I291 Number of Grains 4 Case Length 11.75" Nozzle Throat Dia. .469" (15/32") Nozzle Exit Cone Dia. .94" Max. Chamber Pressure 318 psi Max Thrust 70.2 lbs Average Thrust 65.4 lbs Impulse 336 NSecs
1-1/4" Motors -- 5/8" Grain Bore Nominal PVC Size 1-1/4" Grain O.D. 1.35" Grain Length 2.25" Bore Dia 5/8" Grain Weight .165 lb Burn time 1.05 sec.
Motor Designation I388 Number of Grains 5 Case Length 14.0" Nozzle Throat Dia. .5625" (9/16") Nozzle Exit Cone Dia. 1.09" Max. Chamber Pressure 279 psi Max Thrust 83.0 lbs Average Thrust 87.2 lbs Impulse 378 NSecs	Motor Designation I435 Number of Grains 6 Case Length 16.25" Nozzle Throat Dia. .625" (5/8") Nozzle Exit Cone Dia. 1.19" Max. Chamber Pressure 268 psi Max Thrust 103 lbs Average Thrust 97.8 lbs Impulse 448 NSecs
1-1/2" Motors -- 1/2" Bore Nominal PVC Size 1-1/2" Grain O.D. 1.55" Grain Length 2.5" Bore Dia 1/2" Grain Weight .281 lb Burn time 1.31 sec.
Motor Designation G87 Number of Grains 1 Case Length 5.50" Nozzle Throat Dia. .266" (17/64") Nozzle Exit Cone Dia. .52" Max. Chamber Pressure 304 psi Max Thrust 21.37 lbs Average Thrust 19.57 lbs Impulse 125 NSecs	Motor Designation H174 Number of Grains 2 Case Length 8.00" Nozzle Throat Dia. .375" (3/8") Nozzle Exit Cone Dia. .74" Max. Chamber Pressure 305 psi Max Thrust 42.8 lbs Average Thrust 39.2 lbs Impulse 251 NSecs
Motor Designation I267 Number of Grains 31 Case Length 10.5" Nozzle Throat Dia. .453" (29/64") Nozzle Exit Cone Dia. .91" Max. Chamber Pressure 317 psi Max Thrust 65.4 lbs Average Thrust 59.9 lbs Impulse 378 NSecs
1-1/2" Motors -- 5/8" Grain Bore Nominal PVC Size 1-1/5" Grain O.D. 1.55" Grain Length 2.5" Bore Dia 5/8" Grain Weight .263 lb Burn time 1.05 sec.
Motor Designation I356 Number of Grains 4 Case Length 13.00" Nozzle Throat Dia. .562" (9/16) Nozzle Exit Cone Dia. 1.07" Max. Chamber Pressure 279 psi Max Thrust 85.6 lbs Average Thrust 80.1 lbs Impulse 465 NSecs	Motor Designation I453 Number of Grains 5 Case Length 15.50" Nozzle Throat Dia. .625 (9/16) Nozzle Exit Cone Dia. 1.07" Max. Chamber Pressure 280 psi Max Thrust 109 lbs Average Thrust 102 lbs Impulse 590 NSecs

PVC pipe tables have been moved to the Misc. Tables page.

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