Posted by mo fakahany on November 19, 2009 at 12:40pm
Good day to all, Im new here in this great forum, been reading the previous posts, blogs and articles for a while now, and they are extremely useful for a UAV Newbie like me.Im currently doing a project at college, and I need your help.First things first; the aim of the project is to collect weather data from high altitude and retrieve the instruments/data back to launching point safely. This will be done via an UAV attached to a weather balloon that will descend up to a certain altitude and cut itself free and glide back to Launching position. Data collected will be via temperature sensors and camera taking picture of the horizon (hopefully)After surfing the internet I found only one similar project (done from 7 years ago):http://www.members.shaw.ca/sonde/index.htmAs design and aerodynamics is not exactly my field, I need your help in designing the high altitude glider/plane.More details:1.Equipment Loaded:•Receiver, servos, battery, all Ardupilot stuff and Xbee.(didn’t buy them yet so you tell me how much they weigh??)•Servos(super sub-micro 6g each)2.Payload(on plane):•Parachute (~170 g)•Digital Camera(~500g)•Sensors(~100 g)3.Balloon Payload: the total weight of the whole setup shouldn’t be more than 3kg, preferably <2.7kg.4.Range and altitude:•Range: most probably it will travel +/-10km horizontally.•How high: targeting 10-15km above sea level.5.Speed: Doesn’t matter for me as long as it is stable.6.Launching area/terrain: a Soccer Field or desert7.Launching technique/method:•Using a silicon rubber bungee cord or Hand launching (for the testing phase).•Attach it to a Helium Balloon and let go of balloon at certain altitude.8.Control system: RC (on takeoff and landing) and Ardupilot, but I will discus that on the Ardupilot forum as I have some questions about it.9.Engine: I don’t want to use an engine (more weight; engine and battery) but will I need it any ways? Maybe while testing!10.Rescue system: Parachute opens at a certain altitude; for smooth landing (max landing speed: 5m/s)11.Material available for construction:•Balsa wood•Foam(dense and normal)•High strength unidirectional Carbon Fiber (density=1.78g/cm^3, thickness=0.12mm).12.What I think might be a good design:•(I think) I want to build something made up from balsa wood/foam and carbon fiber, to be light and endure the high vibration and flexing of the wings at high altitudes.•Is something like this is good? (Enough space for everything, but way too heavy).http://hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=8344&Product_Name=DG-1000_Fibreglass_Glider_2.63M__(102in)_ARFhttp://royal-model.sweb.cz/b4.htmhttp://www.rebelflyingclub.com/photos/RFC/gliders/2003-08-00/jasons_applause.jpg•Should I go with a T shaped or a V shaped tail?•Should I go with a Rudder, flaps and Ailerons•Looking for previous designs, plans and advice.Waiting for you repliesRegardsFakahany,
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Hi, I think that this similar project you referenced provides quite a lot of valuable information. I would assume that main concern is cold (below -40 degrees/celsius) and very high winds up there, so you may want to look into airframe design that flies very fast and may even be more similar to jet than to glider. If you go with glider design, then it may be good to seriously clip its wings at least. If you land with parachute, then high landing speed is not an issue.
The release altitudes you are talking about make this a non-trivial project. I an not an aerodynamics expert, but there are airframe issues to be addressed at 15000 meters. Suffice it to say that the air is very thin up there and there are aerodynamic issues when indicated airspeed (airspeed adjusted for reduced density) and true airspeed diverge.
Also it is very cold up there, and your instrument package and autopilot and control system will need to be capable of functioning at very low temperatures.
Finally, the two gliders you provide links for have good gliding performance. You may want to rethink that. If the glider has a low sink rate (ie. is a good glider) it will take a very long time to come down from 15000 meters (assuming it didn't break up due to aerodynamic issues).
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Also it is very cold up there, and your instrument package and autopilot and control system will need to be capable of functioning at very low temperatures.
Finally, the two gliders you provide links for have good gliding performance. You may want to rethink that. If the glider has a low sink rate (ie. is a good glider) it will take a very long time to come down from 15000 meters (assuming it didn't break up due to aerodynamic issues).