REPORT ON STATIC TESTING DONE ON 16TH APRIL 2021

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Prep work

This is a summary of the work done in preparation for the static testing.

These activities were:

  1. Modification of the test stand to accommodate for higher load measurements as well as to accommodate the new size of the motor



Motor Design

1.Propellant

The propellant of choice was Potassium Nitrate(Oxidizer) and Dextrose(Fuel/Binder) as well as Iron (III) oxide as the burn catalyst. An oxidizer to fuel ratio of 65%:35% was used and the catalyst added to 1% of the mass of the oxidizer+fuel. The propellant was cast into two grains namely V8 and V9 to form two motors.

V8 Dimensions

Grain length: 150mm

Grain diameter: 30mm

Core diameter: 14mm


V9 Dimensions

Grain length: 150mm

Grain diameter: 30mm

Core diameter: 13mm



Prior to static testing  a simulation using openMotor was done for a theoretical performance of the motor. 

A link to this data is attached: 

https://github.com/nakujaproject/N1-motor/tree/main/Proposed%20Final%20Spec


A photo of the data is attached:


V8

V9


The theoretical performance data is as tabulated:


Performance

V8 KNDX

V9 KNDX




Designation

F65

F63

Impulse

70.37

72.65

Propellant mass (Kg)

0.15

0.15

Average Pressure (MPa)

1.87

1.83

Peak Pressure (MPa)

2.33

2.31

Core (mm)

14

13

Throat (mm)

9

9

Burn Time (s)

1.05

1.11

Designation

F65

F63


2.Motor Casing

The casing of the motor was made from 40mm x 4.5 mm PN25PVC. The top side(bulk head) as well as the nozzle were to be made from tile cement. 

The nozzle was designed with the following dimensions:

  • Throat diameter - 9 mm

  • Exit diameter - 9 mm

  • Throat length - 30mm

  • Divergence half angle - 90 degrees

  • Convergence half angle - 90 degrees


The design of the casing was as follows:

 

Motor Fabrication

The KNSU propellant was cast as follows:

https://www.youtube.com/watch?v=WRfyVkgOjfY

 

The nozzle and endcap were fabricated using tile cement(grout).

The grout is mixed with water in the ratio 3:1 by weight and poured into the pipe. The cast is left to set overnight. The nozzle is made by drilling the whole with a 9mm drill bit. This resulted in a straight nozzle as designed.

The resultant motor was visualized as:


Static Firing

The static firing was a fail as the fuel failed to ignite.


Results

The fuel failed to ignite so no data was acquired.

The motor was cut open after the failed test and revealed the following:


Failures

The team speculated that the failed ignition was as a result of the ignition system used.



Solutions

The propulsion team met and came up with the following solutions:

  1. Fabricate a longer burning igniter to ensure proper ignition



Conclusion

The KNDX in theory seems like a go to propellant due to its specific impulse but it has its construction demerits. It is up to the team to get the most out of this propellant.

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