Launching High Altitude weather ballon and holding it down to 13,000 feet.

[Sarthak]

Hi guys, I need to launch a weather ballon but hold it at 13,000 feet altitude with a rope and not let it go, we are studying local atmospheric phenomena. The problem i am facing, is that at 12k feet, the wind gusts can go up to 50 knots in certain places and because i am holding the ballon with a tope in a fixed length, it can't get the extra leash  to climb up, i think when i reach 12,000 feet and i get a wind gust of 50 knots, my balloon will just be forced down to 7000 feet or something where there is less wind. I came up with a solution, use a host material, which will occupy 3 of 4000 gram balloons, so i just have brut force, this way maybe it can be more absorbing. What host material should i use for the 3 balloons? has this been done before? 

[James Kerman]

Welcome to the forum @Sarthak, I've moved your question to science and spaceflight.

[mikegarrison]

I have no idea what you are proposing.

It would be much more simple (though maybe difficult to schedule) if you launched the balloon when the winds were blowing less.

 

[Nuke]

i think he needs altitude control for his balloon. probably a ballast system of sorts. or perhaps a small hydrogen/helium tank and release valve to control the volume of lifting gas. problem with those systems is thay require consumables which would limit flight time. another option might be a small heater for the gas bag, get a small amount of buoyancy control. 

Edited January 12, 2020 by Nuke

[Guest]

2 hours ago, mikegarrison said:

It would be much more simple (though maybe difficult to schedule) if you launched the balloon when the winds were blowing less.

It would be impossible. At 13kft there's always wind. And it's usually pretty strong wind, too. 

Does the balloon need to be tethered? A free flying one would fix the problem, but a 50kn gust will give it 50 knots worth of ground speed, so that might not be an option if the phenomenon is very local, not to mention it'd significantly complicate recovery.

[Zeiss Ikon]

Beyond the wind at altitude, there's the weight of 4 km of whatever the tether is.  Most weather balloons can't lift four kilometers of any sort of "rope". 

The tether material has to be strong enough to support four kilometers of its own weight.   The longer it gets, the thicker it needs to be just to hold its own weight.  It's possible some kind of fishing line (one of the synthetics) or kite line (also modern synthetic -- Spidewire or Dyneema, for instance) could manage this without a tapered line.  Based on my experience with kites, there also comes a point where the line is horizontal where it leaves the tether point and forms a catenary curve up to the lifting device (balloon or kite) -- and you can't go out further than that without some means of increasing either the available lift or the tension on the line.  With small Eddy style kites and common nylon kite line (and in manageable wind speeds), this happens before you have as much as seven hundred meters of line out, an the kite will be only two or three hundred meters above ground.

There are good reasons weather balloons aren't normally tethered.  First is that one of the measurements they're routinely used for is measuring wind speed at altitude as they rise at a known rate.  Second is, as noted, wind.  Wind will actually push a tethered balloon down, because of the downward component of the tether tension (you can observe this with a party balloon on a string and a fan).

For lower altitudes (up to a kilometer or so) kites are a better choice for tethered observations.  As noted, once you're up a few hundred meters, wind is very much a given, direction and velocity are the only questions.  Trains of kites have been flown roundly as high as the OP wants to go, but this is complex, depends strongly on a very steady ground wind so each kite in the train can be attached and launched in the same direction the line points, and further, depends on winds aloft agreeing in direction with the ground wind (which is not always the case).

[Reactordrone]

Find a 13,000ft mountain and just hold the balloon while you're up there.

[RCgothic]

The only way to hold a balloon in position is to tether it in multiple directions with the tethers at a reasonable angle to resist the wind and excess buoyancy such that the balloon can resist the tendency of the wind to cause it to dip.

But as has been mentioned the weight of the the cables themselves cause the tethers to hang almost vertical at the balloon, so the restraint is much reduced.

Plus now your tethers are more like 6km long, the excess buoyancy is additional load (e.g. Weight) they have to bear, your balloon needs to support at least 3 of them, and your tether base stations are on a circle 12km in diameter.

Distinctly non trivial.

It would probably be easier to design a drone that actively resists the weather with propulsion, even if you have to land to refuel. If you need constant coverage have more.

Edited January 13, 2020 by RCgothic

[sevenperforce]

How long do you need to maintain altitude to get your observations?