To a layperson like me, could you explain how these balloons will be cleaned up / collected after their life? What material are they made up of?
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).
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?
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.
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.
At least, that's how I understand hot air balloons "steer".
Congratulations for a great non-saas market and product!