Floating risk?

[gianluca belgrado]

In a few weeks, I should be launching the weather balloon. Currently, I am planning to have the balloon ascend at 4 m/s, with a payload of 750 g, with a 1600 g balloon. According to the calculator from Random Engineering, it should burst at an altitude of 40.4 km. With this amount of gas, is there a possibility that the balloon won't burst? I would like to reach an altitude higher than 40,000 meters. 

[Mark Jessop]

The last flight I did which went over 40km had pretty similar parameters to what you are proposing, and we did go into a float for maybe 15 min at a bit over 40km before the balloon finally burst. 

It was a scary moment, as the balloon was heading interstate at maybe 150 kph at the time. I was very close to triggering our remote cutdown system, but the balloon burst before I was able to trigger it.

So I'd say that yes - you do run a risk of floating your balloon. 

73

Mark VK5QI

On Sun, May 26, 2024 at 2:30 PM gianluca belgrado <belg...@gmail.com> wrote:

In a few weeks, I should be launching the weather balloon. Currently, I am planning to have the balloon ascend at 4 m/s, with a payload of 750 g, with a 1600 g balloon. According to the calculator from Random Engineering, it should burst at an altitude of 40.4 km. With this amount of gas, is there a possibility that the balloon won't burst? I would like to reach an altitude higher than 40,000 meters. 

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[gianluca belgrado]

Thank Mark. Do you remember the neck lift value you used for the balloon and the weight of the payload?

[Steve]

In my experience at 4m/sec that will almost certainly float for a while (and not reach burst height).  Steer clear of 4.5m/sec or less especially with the larger Hwoyee balloons. I'd aim for a minimum of 5m/sec with a 1600 Hwoyee.

The old CUSF balloon burst calculator includes a float warning:

    https://sondehub.org/calc/

To go higher loose some payload mass .

    Steve

On 26/05/2024 06:00, gianluca belgrado wrote:

In a few weeks, I should be launching the weather balloon. Currently, I am planning to have the balloon ascend at 4 m/s, with a payload of 750 g, with a 1600 g balloon. According to the calculator from Random Engineering, it should burst at an altitude of 40.4 km. With this amount of gas, is there a possibility that the balloon won't burst? I would like to reach an altitude higher than 40,000 meters. 

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[Mark Jessop]

I had about 630g of payload mass. I don't remember the neck lift. 

The flight data is still in the SondeHub-Amateur database here: https://grafana.v2.sondehub.org/d/HJgOZLq7k/basic?orgId=1&var-Payload=HORUS-V2&time=1716681600000&time.window=21600000&from=1651883477091&to=1651897327439

It looks like I achieved about 4m/s ascent rate.

73

Mark VK5QI

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[gianluca belgrado]

5 m/s is enough, right?