Zephyr: A High Altitude Long Endurance Unmanned Air Vehicle ...

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Chapter 3My Projects3.1 RadiosondeCurrently a program has been created that allows the user to enter the altitude theywant the aircraft to fly at and it automatically calculates the power needed to achievethis height. The program takes into account the air temperature, pressure, air speedand density amongst other things in order to calculate the power. While the otherthree variables are being measured on the aircraft continuously, the density values thatare used are from the International Standard Atmosphere (ISA) model which showshow a number of variables, including density, change over a range of altitudes. Thishowever is a general model and in reality the density varies depending on yourlocation, the air pressure and temperature, and the weather systems present.While on trial, NASA transmits radiosonde data to the team which gives accurate dataabout the weather conditions in the area at that time. A radiosonde is a type ofweather balloon that is radio controlled, which measures and transmits currentweather data. By comparing the standard data to the actual data it was possible for meto calculate the difference between the two. Knowing this information allows an errorto be incorporated into the program in order to give a more accurate density andtherefore a more accurate power estimate. Eventually the density will also bemeasured on the aircraft along with the other variables and there will not be a need forthe radiosonde data.28
Graph 4 shows radiosonde density data collected daily between 22nd July 2007 and31st July 2007 in White Sands, New Mexico as well as the standard density predictedby the ISA model.Graph 4 showing the variation between radiosonde and ISA density dataAs you can see, the densities from the radiosondes are all almost identical to eachother (there is some variation near ground level but as <strong>Zephyr</strong> will not be flying at thisaltitude during a mission it does not matter). It is also clear to see that the ISA datadiffers from the radiosonde data quite significantly. At the altitudes where <strong>Zephyr</strong> islikely to fly (between 45,000ft and 65,000ft), the difference between the real andpredicted densities is the greatest; about 50g/m 3 at 50,000ft, with an average of about20g/m 3 .29
Page 1 and 2: Zephyr:A High Altitude Long Enduran
Page 3 and 4: AcknowledgementsI’d like to thank
Page 5 and 6: ContentsChapter 1 - Introduction an
Page 7 and 8: Chapter 1Introduction and Backgroun
Page 9 and 10: 1.1 History of ZephyrZephyr is a li
Page 11 and 12: The Zephyr 5 project continued with
Page 13 and 14: airframe, with the main aim to impr
Page 15 and 16: 1.2 Environmental IssuesDuring the
Page 17 and 18: order to function, they may not thu
Page 19 and 20: 1.2.3 Cosmic RaysCosmic rays are en
Page 21 and 22: wind speeds. This is to ensure that
Page 23 and 24: crystalline silicon cells and can b
Page 25 and 26: which are then insulated. In order
Page 27 and 28: motion of the aircraft including ro
Page 29 and 30: Within the portable cabins the crew
Page 31 and 32: Simple payloads instructions withou
Page 33: In the event that the wing does not
Page 37 and 38: 3.2 NIOSH Lifting EquationThe hand
Page 39 and 40: Variable Description MultiplierD (c
Page 41 and 42: Using the given values, the corresp
Page 43 and 44: 3.3 Airspeed SensorThe current airs
Page 45: 12VSensorPCBZenerDiodeFigure 8. Dia
Page 48 and 49: 3.4 PayloadThe payload is the carry
Page 50 and 51: where λ is the wavelength, c is th
Page 52 and 53: 3.5 Angle of Attack SensorThe angle
Page 54 and 55: The magnetic sensor seemed much mor
Page 56 and 57: Chapter 4Angle of Attack Experiment
Page 58 and 59: The sensor was powered using an ext
Page 60 and 61: It has to be noted however, that on
Page 62 and 63: experience the atmospheric conditio
Page 65 and 66: 5.2.1 Aerial PhotographyThe most co
Page 67 and 68: meaning that these cameras can be u
Page 69 and 70: Infoterra have a project called Far
Page 71 and 72: it out for long endurance missions.
Page 73 and 74: Figure 18. QinetiQ’s Zephyr5.4 Co
Page 75 and 76: where it is needed rather than havi
Page 77 and 78: Appendix 3Schematic diagram of the
Page 79 and 80: Appendix 5The results table for the
Page 81 and 82: BibliographyQinetiQ Documents[1] St
Page 83: [19] Encyclopedia Britannica, 2004.

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