---
# System prepended metadata

title: NCKU ISP Propulsion Develop Report ENG ver.
tags: [ISP_Propulsion, ENG_Ver, NCKU_ISP]

---

# NCKU ISP Propulsion Develop Report ENG ver.
###### tags:`NCKU_ISP` `ISP_Propulsion` `ENG_Ver`

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## Descripion

UNO Engine is series of C-class solid fuel rocket motor which characterized by its low cost and the convenience of making it.

## 2020/09~10
### UNO Engine ver.1
![](https://i.imgur.com/PcowbZy.jpg)


#### Nozzle
Use the first generation UNO nozzle, made of Bakelite
The disadvantage is that it does not have a divergent section, so the gas outlet velocity is limited to below 1Mach
And the processing fee is quite expensive (about one or two hundred yuan)

#### Fuel
Adopt KNSB

#### Engine Material
Use PVC 3/4" pipe

#### Internal Port
Use bamboo chopsticks

#### Nozzle fixed
Use 3/4" dental plug and thermo silicon to fix

## 2020/11~12
### UNO Engine ver.2
#### Nozzle upgrade
- Developed and put into use the second generation UNO nozzle, made of gypsum
![](https://i.imgur.com/0oDhuRn.png)

The advantage of this nozzle is low cost, and the gradual section has been developed
The disadvantage is that the physical strength is poor, and the overall structure is likely to collapse during the engine propulsion phase.

#### Port configuration calculation
- We are not able to calculate the regression rate with variebles such like pressure and temperature yet. Instead, we use geometric shapes to calculate the combustion surface changes produced by ports of a specific configuration, regardless the changing of the presure and temperature in the combustion chamber.


| Hollow column combustion | End face combustion |
| -------- | -------- |
| ![](https://i.imgur.com/tKy9AWc.png) | ![](https://i.imgur.com/NbaKOWe.png)

- Geometric calculation formula
![](https://i.imgur.com/IZkjZeD.jpg)


| Cross port hole geometric design  | The ratio relationship between the combustion surface and the throat area |
| -------- | -------- |
| ![](https://i.imgur.com/zUfOC6u.png)| ![](https://i.imgur.com/pcMzBCg.png)|



Use 3D printing to print a cross-shaped rod
And began to adopt the cross-shaped port and renamed the engine to UNO+

Disadvantages: PLA material cannot withstand the high temperature when pouring fuel
![](https://i.imgur.com/ICxX0Qz.png)


Try to improve: switch to ABS 3D printing material ~~ or use metal material~~

| Port-STAR Pass Geometric Design  | The Proportional Relationship between the Burning Surface and the Throat Area |
| -------- | -------- |
| ![](https://i.imgur.com/GxdhTKE.png)| ![](https://i.imgur.com/k5puiZ1.png)|


#### KNSB Surfactant Experiment
- Use Sodium lauryl sulfate (SLS)
![](https://i.imgur.com/dsPSPQP.png)
Its physical properties are solid fine powder
More suitable for KNSU




- To be tested: Sodium laureth sulfate (SLS)
![](https://i.imgur.com/2WbO3v9.png)
Its physical properties are liquid viscous liquid
More suitable for KNSB
***No experiment yet***

## 2021/01~02
Developed Electrical Ignition System Front (EIS Front)


## 2021/03~04

### Calculate nozzle ratio
Since I'm not able to understand further thermodynamics and fluidynamics theories yet, I just set the same ratio as other research had done before. 
![](https://i.imgur.com/SWwxiPh.jpg)

### Develop Dual engine
![](https://i.imgur.com/73930Kk.jpg)

#### Need materials
-Quick-drying cement
-M3 self-tapping screws
-1.5' PVC pipe
-1.5' set of copper
-1.5' check valve connector
-PVC glue
-Plastic steel

### Horizontal thrust test platform debug 
![](https://i.imgur.com/hDEv253.jpg)
![](https://i.imgur.com/eNB79ka.png)

Use HX771 strain gauge
maximum loads: 500N
Use arduino development board, and use voltage above 5v

#### Strain gauge code
- Correction:
```arduino
#include "HX711.h"
// HX711 wiring setting
const int DT_PIN = 6;
const int SCK_PIN = 5;
const int sample_weight = 467; //The true weight of the reference item (g)
const int x = 5;

HX711 scale;

void setup() {
  Serial.begin(9600);
  scale.begin(DT_PIN, SCK_PIN);
  scale.set_scale(); // Start getting scale parameters
  scale.tare();
  Serial.println("Nothing on it.");
  Serial.println(scale.get_units(x));
  Serial.println("Please put sapmple object on it..."); //Prompt to put the benchmark item
  
}

void loop() {
  float current_weight=scale.get_units(x); // get the average of 10 times value
  float scale_factor=(current_weight/sample_weight);
  //Serial.print("Scale number: ");
  Serial.println(scale_factor,0); // Display the scale parameter, remember it for use in the formal program
}
```
- Measurement:
```arduino
#include "HX711.h"

// Wiring settings
const int DT_PIN = 6;
const int SCK_PIN = 5;
const int x = 1;
const int scale_factor = 236; //The scale parameter, obtained from the calibration program

HX711 scale;

void setup() {
  Serial.begin(9600);

  scale.begin(DT_PIN, SCK_PIN);

  scale.set_scale(scale_factor); // Set the scale parameter
  scale.tare(); // return to zero
  scale.power_up(); // end sleep mode
}

void loop() {
  float present = scale.get_units(x);
  static float pre_value = present;

  if (abs(present-pre_value)> 1000)
    present = pre_value;
  Serial.println(present, 2);
  //delay(10);
  pre_value = present;
  //scale.power_down(); // enter sleep mode
  //scale.power_up(); // End sleep mode
}
```

- Ladder data problem has been resolved
- Tested on the thrust bench and tested the thrust curve of 12cm UNO+ engine
## Horizontal Thrust Test Results
### April 4 2021
Engine: UNO+12
Nozzle: 5mm plastic steel soil
testing report:
- Peak thrust 7136gw
- Average thrust 3975gw
![](https://i.imgur.com/HTIayTQ.png)
(The horizontal axis is the time unit: second; the vertical axis is the thrust unit: gram weight)

To classify the rocket motor, we must calculate the total impulse by using the following equation:

$$\vec J = \int  \frac {d\vec P}{dt} = \vec F dt $$

We did not insert the impulse code yet, so instead of using proper integration with changing thrust, we use the average thrust multiply the time spent, which is 3.975*1.3 = **5.1675 N * S**

![](https://i.imgur.com/a0g5k2K.jpg)
(Screenshot of test video)

### May 9 2021
> **There seems to be a equipment problem with the contingency strain gauge**

1. Engine No. 1: UNO+12
Nozzle: 5mm plastic steel soil
testing report:
- Peak thrust 5228gw
- Average thrust 3767gw
![](https://i.imgur.com/raxm4cg.png)
(The horizontal axis is the time unit: second; the vertical axis is the thrust unit: gram weight)



2. Engine No. 2: UNO+12
Nozzle: 5mm plastic steel soil
testing report:
- Peak thrust 4283gw
- Average thrust 2602gw
![](https://i.imgur.com/TOQuJTy.png)
(The horizontal axis is the time unit: second; the vertical axis is the thrust unit: gram weight)

## Meeting Records

### 0409 meeting content
Continue to make UNO+12
Please happy trio to develop Dual (but I'm going to buy stuff first
Bohan painting nozzle
Strain gauge + remote transmission system (esp32)
Bohan asked his dad about the nozzle material and manufacturing process

### 0416 meeting content
Continue to make UNO+12 <- He Shufei
Please happy trio to develop Dual (but I'm going to buy stuff first
Bohan paint nozzle -> Use nozzle simulator
Strain gauge + remote transmission system (esp32)
Bohan asked his dad about the nozzle material and manufacturing process
1. Established a metal engine plan
2. Use PPR tube as lining
3. DanNing Yan lock screw
4. Nozzle to make fat
5. Confirm internal pressure -> Confirm monkey mouth area -> Confirm outlet area

### 0423 meeting content
Continue to make UNO+12 <- He ShuFei
Please happy trio to develop Dual (but I'm going to buy stuff)
PoHan Lin do the nozzle 3D model graphing
Remote transmission system (esp32) development pin 5/6 5v/gnd

### 0507 meeting content

#### UNO+12 engine specifications
- Weight: 172.5g
- Length: 15.6cm
- Center of gravity: 9cm from the top
(The above data are all statistical results, subject to actual measurement values)

#### DUAL Engine Dev.
- Check valve connector
- Quick-drying cement
- 1.5' set of copper
- 1.5' tube