Remote Environmental Data Analysis Using Sounding Rocket

In this study a low-cost environmental data monitoring system for sounding rocket is developed based on Internet of Things (IoT) and several sensors. Rocket sounding can investigate the physical and chemical properties of the atmosphere. We propose to build rocket operated by Raspberry Pi with low cost monitoring sensors that can provide real-time altitude, pressure, humidity and temperature with 0.1 second time interval. Temporal resolution of the low-cost gas sensors is one second, therefore, can only be used to monitor the surrounding environment before and during the flight operation. Experimental and simulated values are analyzed and compared to understand the atmospheric dynamics. This study will help space physics community to develop high altitude sounding rocket. Keyword: Internet of Things, Rocket Sounding, Raspberry Pi

. PVC material is ideal for pressure resistor and thermal insulator. 6 mm nozzle were created using the 7/32" drill bit. The rocket engine is attached with 1-meter-long and 0.5 cm thin wooden rod at the launch platform ( Fig. 1). Finally, battery-operated remote-control ignition is attached at the end of the nozzle to launch the rocket safely from the platform.   Fig. 2 (upper terminal) is the typical model rocket design [14]. Fig. 2 (lower terminal) is the simulated rocket design [26] based on our model rocket. In this experiment, rocket fuel, recovery system, nose cone, payload, fins for balance purpose are used. Inside the payload, several sensors and Raspberry Pi are inserted. PVC is used as a thermal insulator to separate the fuel and the payload. Details of the sensors are also discussed in section 4.

III. PARAMETERS TO MEASURE
To measure a set of parameters during the flight interval is the most challenging part of the study. Without the precise time rest of the data cannot be adequately analysed. In this project, Raspberry Pi internal clock ensures accuracy of time in 100 ns interval [17]. The expected temporal resolution of the sensors is 0.1 second. Therefore, data is collected 0.1 second interval. Though, horizontal position (latitude and longitude) is one of the fundamental parameters it is not measured directly from the sensors. Usually the range of the flight not exceed 50 meters from the launch site. However, based on the initial and final position of the rocket using normal ruler and Global Positioning System (GPS), the range of the trajectory can be calculated. Altitude is another important measurement for the sounding rocket project. BMP 180 sensor is ideal to measure altitude with an accuracy of 8 cm spatial resolution and 20 ms temporal resolution. Linear velocity and acceleration is always an important factor. With the positional (latitudinal and longitudinal) data three-dimensional velocity and acceleration can be recovered. In most of the sounding rocket project, attitude (orientation of a rigid body) is measured using magnetometer and accelerometer [18]. In this project, the attitude was not measured as magnetometer was not readily available. Normal pressure and sea level pressure is collected from DHT 11 sensor. Horizontal wind speed is one of the important parameters during the operation period. Wind speed can be measured using simple cup anemometer [19] consisting of three or four cups, conical or hemispherical in shape, mounted symmetrically about a vertical spindle. LiDAR/SoDAR is a sophisticated device to measure wind speed. In this study, the wind velocity and directions were obtained from Bangladesh Meteorological Department (BMD) [13], NOAA [20] and windy [21].
IV. PAYLOAD Inside the rocket, Raspberry Pi microprocessor, micro SD card, WiMAX and battery are inserted covered by bubble wrap.

A. Microprocessor
The microprocessor is the brain of the payload. Rest of the components in the payload are connected to it. In this project, RPi 0 W model is used as a microprocessor (Fig. 3). RPi 0W is a lightweight and powerful single board computer, running with an operating system Raspbian, a Debian-based Linux operating system, which is free and developed for the RPi. The RPi has a built-in wireless LAN, Bluetooth 4.1, 1.0 GHz single core CPU, 512 MB RAM, mini HDMI and USB On-The-Go ports, micro USB power port and 40 General Purpose Input/output (GPIO) pins which helps to keep fairly fast computing and processing power. The RPi continuously reads parameter data from various sensors based on the corresponding connection pins. The RPi also upload the monitored data to the cloud through the Wi-Fi module, and the cloud stores the data.

B. Data Recording and Remote Communication
For our current design, perception of small, light and availability, the most obvious solution is a micro SD card. There is a micro SD card slot in our RPi. 32 GB micro SD card is inserted in RPi 0W to store data. Besides, Teletalk WiMAX is used (Fig. 3) to collect the real time data. Using the teletalk internet connection, the real time data is transferred into the firebase console. Firebase projects are backed by Google cloud platform which is free for the user. The data is stored in json format and can be plotted to analyse the flight mission. Fig. 4 shows the basic operation of the RPi which is popularly known as Internet of Raspberry Things (IoRT). BMP 180 and DHT 11 sensors provides temperature, altitude, atmospheric pressure and sea level pressure data. Real time data is monitored by the user as well as the data is stored in the micro SD card.

VII. LAUNCH PROCEDURE
Before launching the rocket with fuel, the model rocket need to be tested by dropping from the altitude similar to apogee calculated from the simulation. The model rocket requires to be airborne. At first, object having equal weight of the model rocket is dropped attached with parachute ( Fig. 7 (a), Fig. 8 (a)). Simulation is performed using Open Rocket Simulation Software to ensure the safe landing. Data from the simulation indicates that decent landing velocity of the payload should be less than 7m/s. This ensures the rocket falling from certain altitude with the parachute will remain safe. A second drop is then made with the instruments and monitor the data ( Fig. 7 (b), Fig. 8 (a)).  Finally, flight test with the fuel is performed using trial error method. Table 3 shows the summary of the flight test. E40 fuel without the payload and parachute were tested for five times (Flight No. 1-5 in the column 1). Four tests (flight No. 6-9) were performed with the prototype rocket without payload and parachute. Final test (test no. 10) was performed with the payload and parachute.

Rocket Arrangement Flight Status and Flight Path Comments
1 Rocket Fuel only ( Fig. 9 (a)) Fuel comes out comes out, Failed Inappropriate ratio of the white mixture 2 Rocket Fuel only ( Fig. 9 (b) Rocket Fuel only ( Fig. 9 (c)) Failed Selection of clay 6 Rocket Fuel only (Fig: 10 (a)) 2 m apogee, 50 0 inclination 20 cm stick stuck between fuel and launch platform 7 Rocket Fuel only (Fig: 10 (b), (c)) Clockwise wobble with 10 0 inclination from vertical axis 8 Rocket Fuel and dummy rocket (without payload and parachute) (Fig. 11 (a)) Helicoidal path (Fig. 11 (c)) Asymmetric shape (Fig. 11 (a)) 9 Rocket Fuel and prototype rocket (Fig. 12) 1.5 m apogee. (Fig. 12) Stuck with the launch platform ( Fig. 12 (a)) 10 Rocket Fuel with payload and parachute 30 m apogee. Almost straight path with 10 0 inclination from vertical axis ( Fig. 9(a) As shown in the Table 3, first five tests were failed. The possible reasons are the ratio of the white mixture, the width of the fuel pipe, selection of clay, position of nozzle and ignition. Result obtained from the flight 9 as shown in fig. 12 indicates the test rocket fuel and the stick was stuck with the launch platform. Care should be taken on selecting the 1 meter long stick on launch pad. Data collected from the flight no. 9 was averaged to 0.2 sec as shown in the table 4. Fig. 12 shows the path details of the flight no.  In the final test (test no. 10) all the problems were overcome. The test was performed with the parachute and payload. At 0.1 sec, the rocket titled to 10 o from the vertical axis ( Fig. 13 (a)). At 1 sec, the rocket reaches 26 meters from the ground and the rocket path started to bend. It was found that the stick attached with the fuel was not straight. Therefore, due to the kinetic inertia and the bend of the stick, the path of the flight was bended ( Fig.  13 (b) and (c)). The 30 m apogee was recorded at 1.75 sec (Fig. 13).  Fig. 14 shows the flight duration and altitude of the experimental rocket and simulated rocket. Apogee and duration of the experimental rocket is lower than the result obtained from simulation. Environmental data was also monitored 75 s before the rocket started to detach from the launch platform (Fig.  12). Since Potassium nitrate, sugar and clay produces CO, smoke and LPG, MQ-02 gas sensor is used to monitor the gases (measured in ppm). The data are collected 0.5 s interval period operated by Arduino UNO which can only store in a micro SD card. The data indicates that the density of the CO, smoke and LPG went high from 5 s to 14 s, 40 s to 58 s and 70 s to 75 s. This indicates that the burning occurs in three stages before deploying.  Table 5 shows the price of the equipment used for rocket mission. The rocket fuel (Potassium Nitrate, Sugar, PVC pipe and wire) 400 BDT. As on 28 October 2019, 1 dollar is equivalent to 84.67 BDT. Therefore, the rocket without the sensor costs $ 4 only. The total cost with the RPi, sensors and related materials to monitor the flight and environment takes 6520 BDT or $ 77.04. Typical high-altitude balloon with 8 m diameter with sensors costs $206 or 17,500 BDT. A meteorological drone with the sensor costs at least $ 354.46 or 30,000 BDT. Therefore, this study indicates the sounding rocket is cost effective as well.  [29]. On 11 May, 2018 Space-X successfully launched Bangabandhu Satellite-1 at Kennedy Space Center in Florida, USA. However, Bangladesh space agencies did not initiate to launch sounding rocket. Launching rocket is one of the challenging parts of the research as it involves high cost, cutting edge technology and precise calculation. This work will help the government agencies to initiate the sounding rocket project in Bangladesh. In near future, Bangladesh will be able to launch sounding rocket and low altitude spacecraft. Synthetic Aperture Radar (SAR) can be deployed as a payload in the sounding rocket to monitor flood, deforestation, landslides [30].