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Measurement of Speed of Sound Profile Using Laaces Balloon

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Measurement of Speed of Sound Profile Using Laaces Balloon Abstract Measuring and Calculating the Speed of Sound Profile Results The goal of this mission was to test the speed of sound at different The environmental data measured in the launch at NASA CSBF on May altitudes and ultimately at a maximum height of 100,000 feet during 16 agree reasonably well with the data measured by Dallas weather a total solar eclipse. In conjunction with this testing, environmental during a Total Solar Eclipse using LaACES Balloon station which is about 122 miles north from the CSBF. The sonar parameters including temperature, pressure, and humidity are stopped working at temperatures lower than -40 °C (readings are all measured and used to calculate the speed of sound to compare to zeros). In addition, the acquired speed of sound data are quite noisy. the measured results. The first balloon launch of payload Dorothy Adam Chase, William Dever, Matthew Foltz, Tyler Morgan, Brett was conducted in NASA CSBF on May 16, 2017. The improved payload “Dorothy 2” was launched successfully in Carbondale, IL. on Schaefer, Brian Schaefer, and Zhuang Li Aug. 21, 2017. Data are analyzed and further improvement plan is discussed. McNeese State University, Lake Charles, LA Background The measurements of speed Pressure and humidity data from May 16th launch of sound profiles were conducted 6 Volt Battery Pack in the 1960’s when measurements were conducted in New York Temperature 5-V Voltage 3-V Voltage Pressure City, New York, both in the Sensor Regulator Regulator Sensor Summer and Winter seasons, as show in the figure to the Humidity right [1]. The measurements Sensor Arduino Due Sound Speed were in a much wider range Microcontroller Sensor (0 to 120 km). For the altitude range of 0 to 30 km, it can be 3 Volt DC heating seen in the figure that the Battery pad Temperature data and speed of sound plotted as measured and calculated th speed of sound dec reases as it from May 16 launch Overall layout of electronic components Power supply layout reaches 10 km and then 352 370 y = 45.463x - 435.59 350 y = 24.302x - 70.782 inc reases again as it reac hes The Arduino Due allows for a lower power consumption and better compatibility with existing hardware to make the 350 R² = 0.80208 348 330 the 30 km altitude. 346 integration seamless. 310 344 (m/ s ) 290 342 270 The speed of sound can be calculated using measured temperature, speed of sound 340 A 6-V battery pack supplies power for the microcontroller and sensors. Most of the devices run off 3.3 V line while the 250 15 15. 5 16 16. 5 17 17. 5 speed of sound (m/s) 338 humidity, and pressure data from an empirical formula studied by E.A. sonar runs off the 5 V line supplied by the board. Most of the hardware connections are actually done through the 16. 95 17 17. 05 17. 1 17. 15 17. 2 17. 25 17. 3 Dean 330 325 (1) coding of the Arduino Due, which lightens the payload while also makes it easier to test and prepare the module before 320 cT= 20.06 s 320 flight. To ensure the sonar sensor still func tions at low temperatures, a heading pad is used. The heading pad, 310 300 315 where Ts is c alled absolute sonic temperature that inc ludes the effec ts 290 constructed using a mesh of polyester filament and micro metal conductive Fiber, is powered by a stand-alone 3-V 310 280 of humidity and pressure [2]. The speed of sound on a normal day is 270 battery. y = 23.517x - 73.347 305 y = 23.269x - 71.261 260 speed of sound (m/s) roughly 340 m/s under one standard atmospheric pressure on the 250 speed of sound (m/s) 300 Mechanical Design 15. 75 15. 8 15. 85 15. 9 15. 95 16 16. 05 16. 1 16. 15 16. 2 16. 45 16. 5 16. 55 16. 6 16. 65 16. 7 surface of the earth. kelvin kelvin The external structure is composed of two layers of 1/2 inch thick polystyrene. The dimensions of the container form a square root of temperature square root of temperature th The physical measurement of the speed of sound can be done by box with sides 7.5 inches wide, 8.8 inches long, and 4.69 inches tall (19.05 cm x 22.38 cm x 11.91 cm). The thickness of Sonar data from May 16 launch timing how long a sound wave reaches a target of a fixed distance. In the box serves as thermal insulation and shock absorption. Econokote, a heat shrinking skin, was ironed on to the In the second launch, the sonar was functioning over the entire flight. the balloon payload Dorothy, the speed of sound is measured by outside of the box for extra structural and thermal support. There are 5 holes in the box. Two holes are 16 cm apart at Data are much less noisy. It means the heater worked as expected. timing a ultrasonic sonar pulse reflecting off a purely reflective mirror. opposite corners of the box on top and bottom for the strings, with another one on top for external temperature However, the recorded ping times at altitudes higher than 5 km are In the meantime, temperature, pressure, and humidity are measured sensor, pressure sensor, and sonar. The circuit boards were glued to the bottom of the box with hot glue using a piece signific antly less than reasonable values. Further investigations exc luded and applied to the empirical formula (1) to calculate the speed of of foam as a spacer. The housing was built to be compact to save weight and to heat components and batteries more the wind or vacuum influences. Similar behavior was repeated in freezer sound. The measured and calculated results are compared. efficiently. Small PVC pipes, which are stronger than ordinary soda straws, were used to help guide the rope and make tests as frost was observed on the transmitter/receiver. So a defrosting it easier to open and c lose the module. The parts for holding the mirror and sonar are 3D printed using PL A plastic , mechanism will be implemented in the next revision. Payload Design known for it’s durability and ease of use. All parts are glued using Gorilla brand glues due to their high strength. 30 350 25 Electrical Design meas ured 340 20 calculated 15 330 10 The payload needs to be able to conduct all environmental testing as 320 y = 32.723x - 227.13 Altitude (km)5 well as measuring the time from the ultrasonic sonar module. To do speed of sound (m/s) 0 310 this without losing resolution in the data and not receiving false 280 300 320 340 360 16.5 17 17.5 18 speed of sound (m/s) readouts from the sonar module itself, an Arduino Due is used. Such a square root of temperature kelvin microcontroller has a clock speed of 87 MHz which can read the timing Sonar data from Aug. 21 stlaunch during solar e clipse of the sonar down to the microsecond level and can read the data from all available components in a timely manner or around 3.14 Conclusion sec onds a reading. The results from the Aug. 21st were as expected for the conditions that had taken place during the eclipse. Environmental readings showed Completed build of Dorothy 2 module Wind Tunnel testing of Dorothy 2 improved reliability in its data c ompared to the first launc h. The sonar experienced icing on the transmitter/receiver causing the data to give false readings. Overall, the launch was a success and the data can be Software Design used to in conjunction with future launches. The software runs off a main loop that runs infinitely. An interrupt was designed to allow for safe system initiation and shutoff and also safe data acquisition in the form of an SD card. The program records the data from all sensors within References 3.14 seconds. Another loop within the main loop takes about 10 readings from the sonar in around 3 seconds to give an 1. Yang, X.R. Atmospheric Acoustics, D e Gruyter (2016) average reading in the post flight analysis. The program also has an initial startup check sequence and LED notification 2. Dean, E.A. Atmospheric Effects on the Speed of Sound, U. S. Army loc ated on the Arduino shield for visible notific ation to the operator. Report ASL-CR-79-1011-4 (1979) .
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