[tndl]

Sure thing! They're made of about 300 grams of polyethylene. Towards the end of their lifespan, we can steer them to an area that's easy for us to drive out and pick them up. The payload has a GPS, which lets us track where they are both in the sky and on the ground.

Right now, most weather balloons fall back to Earth and stay where they land unless someone happens across them (since they can't be controlled and only last a couple of hours).

[mariushn]

How do you control the altitude? I would imagine 'heat/cool the air inside the baloon', but this would be too energy intensive?

Congratulations for a great non-saas market and product!

[DAlperin]

> we can steer them to an area that's easy for us to drive out and pick them up.

What does this look like in practice? As you mentioned I know you don't really have any lateral control, but I imagine you can wait for it to overfly somewhere convenient to descend?

[shagie]

I believe it is along the line of...

Pull up https://www.pivotalweather.com/model.php?m=nam&p=sfct-mean-i... and pick some point (note the 'click for point sounding'). You can see the wind direction at that location as a function of altitude.

Using this as a vector field, you can do "the balloon is here now, 30 minutes from now it will be there, if it is at altitude Z at that time, it will be follow the wind in this direction" which in turn allows you to predict where it will be in 30 minutes and take the forecast for that location at that time and determine what altitude you want to be at.

Saying I want it to be at X,Y at some time is solving this backwards. Which isn't necessarily easy, but it's computable.

[tndl]

Pretty much this. We add the data the balloons themselves are collecting to make things more precise as well

[shagie]

Digging into it a little bit more...

The Balloon Learning Environment https://research.google/blog/the-balloon-learning-environmen... (https://news.ycombinator.com/item?id=31155137 - 73 points | 10 comments)

(2016) Station-keeping of a high-altitude balloon with electric propulsion and wireless power transmission: A concept study https://www.sciencedirect.com/science/article/abs/pii/S00945...

(2022) Station-keeping for high-altitude balloon with reinforcement learning - https://www.sciencedirect.com/science/article/abs/pii/S02731...

(2023) Resource-Constrained Station-Keeping for Helium Balloons using Reinforcement Learning - https://arxiv.org/abs/2303.01173

Chasing the citations from those papers to previous works can provide a fairly deep rabbit hole of things to read.

[ImPostingOnHN]

Due to the rotation of the earth, wind current direction rotates based on altitude. If you want to go in a particular direction, you ascend or descend to a altitude that has winds blowing in that direction.

At least, that's how I understand hot air balloons "steer".