Designing a space balloon is not such a simple thing. Ideally I would like a simple, cheap and reusable system.
Using off the shelf components and subsystems is by far the easiest and fastest way to build it. But like everything, you don’t necessarily have it for a good price, with all the cool features and options.
I spent some time studying what would the payload need this weekend and I ended up with more questions than answers.
Where The Hell is My Balloon?!
The top priority is to retrieve the payload after its launch. To do so, I need to :
- Log the balloon location (latitude, longitude, altitude)
- Send this information to the recovery team on the ground on a regular basis
Problem#1: Location
The best way to track the balloon is to use a GPS. But most GPS receivers seem to have hard limits at 60,000 feet ASL (18km). DoD regulations prohibit standard consumer GPS receivers from functioning above 60,000 feet and 999mph. It would be considered as a ballistic missile.
I would like to reach 100.000 ft ASL so I need to find a GPS that work above that threshold. Multiple lists of GPS working above 60K ASL are available on Internet and specialized forums. However almost all of them are single devices that need to be integrated with electronic boards. Yes you can tell that I really don’t know anything about all this…
But what does that mean Not Working Above 60K ft?
Does that mean that the GPS literally stops functioning? Or does that mean that it just doesn’t calculate the altitude? A potential workaround would be to use a barometric altimeter but it tends to not be accurate at high altitude. How inaccurate are we talking about? 1000 ft or 10.0000 ft ? Am I wrong or is the formula just more complex at high altitude?
So basically,
- I need to find a GPS working above 60.000 ft ASL
- I need to find a way to determine the max altitude reached
Problem#2: Communication
GSM can work up to 10 miles high for old phones (about 50.000 ft), newer phones work about up to about 6 miles (31.000 ft). So tracking a balloon using GSM communications implies losing contact during the ascent and hopefully getting it back during the descent. The main consequence is that the recovery team may end up very far from the balloon or worse, lose contact and never find the payload.
I tried to deny it and find another solution but apparently the only way to track the balloon during the whole flight is using ham radio (amateur radio). A radio transceiver needs be connected with the GPS to send the location on a regular basis to a receiver on the ground. Unfortunately I haven’t found any out of the box solution yet and I don’t know enough about ham radio and electronics to build it myself.
So it all comes down to compromises:
- Either spending some time building my own tracking system
Pros: It will do what I want and it’s not very expensive
Cons: It will take forever to build it and test it
- Either using a GSM phone but risking losing the payload
Pros: It’s super easy to put in place and is the cheapest solution
Cons: The payload may land 250 miles away from us or we may never find it
- Or finding the appropriate turnkey solution
Pros: It will do exactly what I am looking for
Cons: Usually very expensive
So I have a couple of options that I need to study in greater details. I just wanted to give you a brief overview of my main questions.