# SAC Project Overview
###### tags: `System`
[toc]
## 目標

- 開傘系統
- 降落傘
- 航電系統
- 酬載
- 控制系統
- 發動機
- 箭體

## 2.7.2.1 摘要 Abstract
本發射載具的任務是驗證彈射酬載裝置的可行性，載具上的特殊設計是採用了減滾系統，以降低火箭本身滾轉對酬載的穩定性影響。酬載內將會搭載GPS,壓力計及陀螺儀，用來測量酬載自發射載具彈出後的相關姿態數據，以量化酬載的穩定性。對於更高級別的任務，本任務可以提供彈射酬載裝置的基礎模型及數據，來進行後續的開發及驗證。
The mission of the launch vehicle is to evaluate the feasibility of a payload ejection device. The special design applied on this vehicle is the de-spin system. The purpose of the de-spin system is to reduce the rolling effect on the payload stability from the rocket. GPS modules, pressure meters and gyro sensors will be installed on the payload to determine the attitude data after the payload is being ejected from the rocket and quantify the stablity of the payload. For high-class missions, this mission provides the basic model and data of a payload ejection device and proceed the further development and evaluation of this device.
## 2.7.2.2 介紹 Introduction
我們是來自台灣國立成功大學的NCKU ISP團隊，團隊內部分為結構組，航電組，推進組及行政組，由校內航太系的教授擔任團隊導師。我們管理團隊的策略是定期召開小組會議，並制定技術的開發驗證時間軸。結構組主要開發玻璃纖維箭體及火藥開傘。航電組開發自製航電電路板。推進組主要研發金屬艙壁的固推發動機。而行政組則是規畫專案整體時程及財務管理，並引導各組別如期完成技術開發。我們團隊定義了本次SAC比賽任務是驗證彈射酬載裝置的可行性，而酬載將會是搭載了GPS,壓力計及陀螺儀的測量儀器。團隊的經費主要由國立成功大學及相關協力廠商贊助。
We are NCKU ISP team from National Cheng Kung University in Taiwan. Our team is divided into four divisions: structure ,avionic,propulsion and execution. The structure division is developing the fiberglass body tube and powder parachute deployment system. The avionic division is developing the self-made avionic circuit board. The propulsion division is developing the metal shell solid rocket motor. The execution division is planning the overall schedual and financial management of this project, and provide guidence to each divison to complete their development on time. Our team has defined the mission of SAC 2023 competition is to evaluate the feasibility of a payload ejection device. The payload will be an instrument with GPS modules, pressure meters and gyro sensors on it. The funds of our team are mainly from NCKU and other supporting companies.
## 2.7.2.3 系統工程總覽 System architecture overview

## 2.7.2.4 任務概念總覽 Mission concept of operations overview
### 發射流程
- Phase1 : Ignition
- "Fire" Signal send to the ignitor
- Motor start running
- Rocket leaves the lauch-pad
- Phase2 : Propellant burns out & de-spin
- Motor runs out of propellant
- When the angular acceleration is below the setting value, de-spin system will deploy, and the rocket stops spinning
- Phase3 : Payload deployment
- Using payload ejection system to eject the payload
- Phase4 : Rocket & Payload parachute deployment
- Payload deploy its parachute
- Rocket itself will seperate a small segment which is the outside shell of the payload, under it is the rocket parachute, and the rocket parachute deploy
- Phase5 : Rocket & Payload touch down
- Both rocket and payload fall back to the ground

## 次系統技術重點
### Propulsion subsystem
- type:solid motor
- propellant：KNSB
- properties
- level: M class
- total impulse; 6819 N-s
- max. thrust: 2400 N
- avg. thrust: 1554 N
- burning time: 4.38 s
- specific impulse: 248 s
- empty mass: 5.5 kg
- material: Aluminum、Stainless Steel
- nozzel: Graphite
- nozzle expansion ratio: 8
- length: 757mm
- diameter: 87mm
- propellant mass: 5.33 kg

### Aero-structures subsystem
- Supersonic flight
- 於launch後2~5.2s為超音速飛行，期間上升高度為1.3km，故選用Ogive形狀之鼻錐以減少超音速飛行階段之阻力
- The launch vehicle will turn into the supersonic flight in 2 sec after launch. In this stage, the launch vehicle will travel 1.36 km.So, we determine to use the "Ogive" nosecone to reduce the shock drag.
- 離架速度為41.4m/s且穩定度為1.4，可抵擋14.2m/s的風
- The velocity off rod is 41.4 m/s, and the static margin will be 1.4. So the launch vehicle can withstand the wind upto 14.2 m/s.
### Recovery subsystem
流程：在完成酬載彈射後，引爆爆炸螺栓使裝有降落傘段的箭體分離，再引爆內部的黑火藥氣囊，使降落傘可以彈出。為確保降落傘在彈出後可有效且快速開啟，使用引曳傘幫助主傘可以順利拖出並展開。為確保降落傘彈出後開啟時不會產生太大的減速度進而損傷其他部分，傘繩會以繞成多個迴圈，並以膠帶黏住迴圈交點，使其達到緩衝效果。
Process: After the payload ejection, the subsystem detonates explosive bolts and separate a body tube session which contains the parachute. Later, detonates the black powder canister to eject the parachute. To ensure the parachute is being deployed quickly and effectly after the ejection. A drogue parachute will be used to assist the main parachute being pulled out and fully expanded. To ensure the parachute will not produced too much deacceleration effect and harmed other subsystem after being deployed. The paracords will wind into several loops and their intersections will be tapped, these designs will provide a buffer effect.
- 降落傘：使用半橢圓形降落傘及引曳傘(drogue parachute)
- 開傘機構：使用爆炸螺栓及黑火藥控制
- 傘繩：高強度耐高溫尼龍傘繩

### Payload subsystem
流程：在達到最高點時，脫開鼻錐上的機械鎖使酬載可以順利由彈簧彈出。而酬載外殼所連接的滑軌可以使其在彈出時大大減少阻力。酬載外型為 3U 的立方衛星，雖然是假酬載(dummy payload)，但因為需要彈出，所以為了方便尋找，酬載本身包含通訊系統及 GPS 。在酬載從火箭彈出後，酬載內部的回收系統會彈出降落傘，使其可以安全的著陸。而開傘系統則是同樣引爆黑火藥氣囊來推出降落傘。
Process: After the rocket reachs its apogee, the subsystem unlocks the mechanical lock on the nose cone. Allowing the payload being ejected successfully from a spring. The rails attached to the payload shell can reduce the drag force effectly. The shape of the payload will be a 3U cubesat shape. Although it is a dummy payload, it still requires an ejection process. For the purpose of searching needs, the payload itself contains a communication system and a GPS module. The recovering subsystem on the payload will eject a parachute to provide a safety landing after the payload is being ejected from the rocket. The payload parachute deploying subsystem will detonate the black powder canister to push the parachute out.

- 酬載：假酬載包含通訊系統及定位系統
- 酬載回收系統：酬載內包含降落傘及其彈射系統
- 彈射系統：使用機械鎖固定，並用彈簧將酬載彈出
- 固定架：酬載彈射系統以滑軌固定

### Avionics subsystem
The avionics system is the brain of the rocket. It uses the barometric sensor, Pitot tube, IMU and GPS to identify the rocket itself pose, position, speed, acceleration, heading and so on. It is a state machine to run the task during the launch sequence. It desides when to initiate reaction wheel spinning and yo-yo de-spin system. It will also trigger the paylaod and parachute deployment by identifying the attitude and altitude of the rocket. And it also transmit the data of the rocket throught communication system. In order to prevent the failure of main board, the identical redundent board is necessary to take over the control to make sure of the success of the mission.
- Main board
- Redundent board
- Barometric sensor
- Pitot tube
- Inertial measurement unit
- Global Positioning System
- Lora communication system

### De-spin subsystem
The De-spin system contains two phases. The first one is using the yo-yo de-spin mechanism to rapidly slow down the spin of rocket. The second one is using the reaction wheel to eliminate the spin. Because we try to build the platform that can provide rides for all kinds of payload. The stabalization of the deploy process is vital. Therefore, after launching the rocket, the rocket will start spining and it will stop accelerating angularly eventually. The first phase of de-spin deployed, then the second phase slow to spin to 0. After that the rocekt reaches apogee and it deploys the paload without any rotation.
- yo-yo de-spin mechanism
- reaction wheel

## 時間流程

## 相關驗證系統
- 推力測試台
- 發射架
- 地面站