Need help with DIY high alt glider

Hello againI'm trying to make a UAV that will go to about 30Km high with the aid of a weather/sounding balloon. After the balloon pops/ gets relised I want the UAV to parachute down taking pictures as it goes then at around 20,000 feet for ether a glider to open out on top, or a ram parachute to open up to help fly the UAV back. The only problem is that I have found very little help on the net on which is better or how to make them for a UAV that weights about 1.5kgAny help with ether how to make a powered parachute or powered glider would be very much appreciated.Thanks for all the help with the tracking of it by the way.I've decided to chance to a fixed wing aircraft (powered glider maybe?) due to the high speed at which it will be traveling. Dose anyone have any ideas on what materials are a good choice for the wings as during the descent they will experience high g-force. I was thinking about foam maybe but not to sure as I don’t have any experience at designing and building foam models. I am planning on doing a lot of testing between now and Christmas with different airframes if I can build a strong yet light enough model. (Less then 1.5kg.)Dose anyone know if it would be possible to get ardupilot to relies itself from the balloon at between 60,000 to 80,000 feet and follow waypoints back to base camp. And is it possible to use an xbee-pro with ardupilot to control the UAV whiles in flight? Or can you update ardupilots waypoints using xbee while the UAV is in flight?
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  • Since you speak about parachutes: where do I purchase parachutes? I need one for my UAV project, and find it hard to find serious suppliers. Need: Approx 3m diameter or maybe even larger. I plan to recover by parachute instead of by landing the small UAV normally.

  • This is what I use for a staged recovery: RDAS - For example it detects apogee to deploy a small drogue or release it from the baloon. Especially help full if you use several baloons for a heavier payload as they want pop at the same time. Then at a set altitude it deploys / releases the main parachute.

    I have set myself the same challange using a ram parachute but not using a baloon but a rocket to get up to great heights. I'm only taking small steps at a time. First of all I want to get an easystar up and running (almost there) as this is a proven concept. After that I will try to adjust it to a paraglider. - under the projects page, work in progress
  • I don't think you will have any luck with trying to fly a parafoil at 100,000ft, because of a phenomenon called 'Added Mass' - when calculating the CoG and thus stability of a parafoil, which is usually somewhere in the rigging between the foil and the payload, you also include the mass of the air that is being accelerated by the parafoil at that time. At 100,000ft, there is barely any air mass to be accelerated, so the CoG shifts right back down towards the payload, greatly reducing the Moments of Inertia in the axes you care about, and leading to instability and collapsing parafoils. As others have said, if you want a parafoil, open it low.

    You have a big project here, with a lot of material to cover. Parafoils are harder to control that fixed-wing aeroplanes because the flight control surfaces are not rigidly coupled to the payload, where you inertial/attitude sensors are - so your feedback does not represent the true state of the system. You have a bunch of annoying n'th order relationships between the two, and nothing linearises particularly well. The are some simple-ish tricks though to help you, like making turning stability control a function of bank angle rather than turn rate.

    1.5kg is certainly possible. I would start by getting an off the shelf kit, as ernani reis has done, and get that under control. Then maybe try a dumb weather balloon experiment - a payload in a box with a pre-deployed parachute (check my homepage) will teach you a lot.

    Best of luck with this, and keep us posted.

  • I think they have a CAA weight limit. Is it for the Vulture thing? I suggest that you wait as much as possible to open the parachute, paragliders are very slow, and you can drift out of control with a light wind, let alone a 20.000ft wind. I have had a good experience with the sail, is very maneuverable, but very slow (they all are slow, the is particularly maneuverable). should handle your 1,5kg (I would redo the strings, though). My gondola with ardupilot, receiver, battery, motor, power supplies and logger weight about 600g. I am still working on a passable control law, mine is barely under control right now - nothing I would send 7.000m high and out of sight.
  • You could connect more than one balloon together to increase lift. I would use a servo operated release mechanism other than counting on all three balloons bursting at the same time (which is unlikely to happen).

    You could use baloons designed for radiosondes and helium. That can be readily purchased on the net.

    The electronics and power sources need to be thermally insulated. Any battery taken to flight level 200 will have to be severely derated in terms of available capacity.

    However, before you attempt to launch something like this, I would strongly advice you to get approval from the air traffic control center that is responsible for your area. In addition a NOTAM (notice to airmen) needs to be issued in advance. You also need to file an expected flight trajectory.

    Good luck. Post any progress!

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