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| ▲ | rogerrogerr a day ago | parent | next [-] |
| As a bugsmasher pilot, I’d be most worried about 40k ft of fishing line wrapping itself around the spinny bits on the front. What’s the tensile strength on that stuff? Doubt it’d cause an immediate issue, but doesn’t sound very fun to remove. |
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| ▲ | firesteelrain a day ago | parent | next [-] | | 3-6 newtons or about 0.7-1.3 pounds-force Also it’s not 40k ft of wire. Altitude is 40k ft The wire is about 16 ft for one leg of the dipole. That is the taught part. The other just floats in mid air underneath the payload The community is very small and doubtful the sky will be filled with them The balloons follow the jetstream from where they are launched. I have seen them fly over the Artic Circle, for example | | |
| ▲ | timeinput a day ago | parent | next [-] | | I think there was confusion about whether it was tethered / what the tensile strength of the tether was. Reads like it wasn't tethered. How did you communicate with it? Amateur bands? LoRa? | | |
| ▲ | LeifCarrotson 21 hours ago | parent | next [-] | | These and other high-altitude balloons are almost never tethered nor recovered - they're not a kite, that would be completely impractical. You're nearing the altitudes at which the tensile strength of even supermaterials like Dyneema fibers are unable to lift the weight of their own tail, much less hold up against the tension of the jet stream. You'd need some kind of reverse rocket equation pyramid, where the topmost thousand meters have to lift the entire line, and are therefore made from line 0.6mm in diameter, and the next thousand meters are made of a slightly thinner, slightly less strong, slightly lighter fiber (because they don't have to lift the top thousand meters of line), and so on for the next 50-100km, depending on how much sag you expect the line to have. "Oops, the balloon popped, excuse me while I do an ultramarathon across town spooling up my thousand-dollar tether from everyone's backyards...please don't cut it or trip over it or drive over it..." No, it merely trails a 5 meter length of wire that acts as an antenna. You can receive the signals from hundreds of amateur receivers set up across the globe, often receiving transmissions at very long ranges. When the balloon eventually falls, yes, it's litter, but it's only a couple grams - go to your local park and pick up some trash, you can atone for a lifetime of HAB hobby sins with a single black bag full of alcohol bottles, fast food wrappers, and cigarette buts. | | |
| ▲ | dylan604 20 hours ago | parent [-] | | > almost never tethered yet you can't say never, hence the question. balloons are launched for different purposes. if you're trying to keep a balloon on station to gather local data, it's gotta be tethered. maybe not typical of a 40k' altitude, but they definitely use tethered balloons. | | |
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| ▲ | firesteelrain a day ago | parent | prev [-] | | Yes, it is not tethered to the ground. The balloon is at the top, then 36awg wire, then solar panels and raspberry pi, then wire hanging down for lower half of dipole Both top and lower part of dipoles are soldered to Raspberry Pi It uses WSPR. Some of them use APRS but it is less common |
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| ▲ | rogerrogerr 21 hours ago | parent | prev [-] | | Got it. Really cool project. |
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| ▲ | dylan604 21 hours ago | parent | prev [-] | | if you're not familiar, 36AWG wire is thin. very thin. according to [0], it is 0.1270mm. seems to me that it might melt free from friction thin. [0] https://size-charts.com/topics/house-size-chart/wire-size-ch... | | |
| ▲ | rogerrogerr 20 hours ago | parent [-] | | I’m familiar; I thought this was tethered to the ground. But it’s self contained within a few meters at 40k ft - not a problem. I do suspect if you encountered small gauge fishing line being used as a tether, you’d find at least some of it wrapped tightly around your spinner on the ground. Probably not much friction at play. |
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| ▲ | bonyt 20 hours ago | parent | prev | next [-] |
| I think you can file a NOTAM for a weather balloon even if you don't need clearance. Might depend on the size and payload, though, like if it's closer to a party balloon than a real weather balloon, and how high it's going. |
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| ▲ | firesteelrain 19 hours ago | parent [-] | | 14 CFR Part 101, Subpart D – Unmanned Free Balloons excludes PicoBalloons due to their size and form | | |
| ▲ | dylan604 18 hours ago | parent [-] | | That would explain the difference in experiences. My balloon was 8' diameter at launch and expanded to ~40' when it burst at ~90k'. Mine needed the radar reflector and blinky lights. They were supposed to blink at a certain rate, but we cheated and had lights blinking faster as that's all we could find for our budget/schedule. | | |
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| ▲ | dylan604 21 hours ago | parent | prev | next [-] |
| No radar reflectors or blinking lights of any sort? The little flights up to 90k' with a parachute return required those for night flights. Maybe most people just ignore that?? |
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| ▲ | firesteelrain 21 hours ago | parent [-] | | It’s not required at all. These are so small that they are not covered by like FAA type regulations |
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| ▲ | gtoubassi 17 hours ago | parent | prev | next [-] |
| If you have any details written up on your kit (in partic what solar you used) I'd appreciate a link. I'm looking to do similar |
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| ▲ | 5d41402abc4b 11 hours ago | parent | prev [-] |
| What happens if there are heavy winds? |
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