Let’s talk about the payload. Since we’re keeping our project simplest (and, actually, cheapest) possible we need to minimize the payload to bare minimum. The question is what minimum viable payload for such kind of a project?
First of all we need something that would help us to retrieve the payload. In fact retrieving the payload after landing is the most challenging part of HABbing and what makes the real difference between launching a HAB and letting birthday balloons go.
So to retrieve the payload we need to know where it is and the main approach to this is using a GPS. The fact that the balloon can land miles away from the launch point makes it so difficult to find the remaining of it. It also makes it impossible to use audiovisual means to facilitate the search for the payload.
Once we have the GPS we need to send its output to the ground station somehow and there are many methods for this. We will use APRS transmitter which has a lot of advantages to other methods (I’ll dedicate another post specifically to transmitters in general in APRS in particular).
To power those components we obviously need power source. There are many alternatives for this (NiCad battelies, LiPo rechargeables, solar batteries). For this project for many reasons (again, to be covered in a separate post) we will use two batteries. One will be set of 8 1.5V disposable lithium batteries and another one is a 3.7V rechargeable.
In fact this is it. This payload is enough to record the progress of the balloon and retrieve its payload once it is landed. But what we get in return is just a set of boring numbers. In order to have more fun with the project let’s launch a simple camera to the “orbit” and see what the balloon sees and possibly we will find where all the balloons go.
So our last component will be a cheap camera (<$10) that still provides a relatively high-quality video so we can proudly demonstrate it to friends and say “I was part of this project”.