Let's Make Robots!

Unmanned Hot Air Balloon Near Space?

After researching various DIY weather balloon setups, I was less than satisfied with the short flight time due to the balloon always exploding. I then had an idea: Why not use a hot air balloon that runs on electricity and recharges through solar panels/mini "windmills"? After all, electrically heating a balloon through something like a hairdrying coil is a lot more effecient and can go a lot higher than propeller powered uav's. It also could have an indifinite flight time (in theory)! Has anyone done something like this before? Could a prop be added for manual control, or would the wind be too fast for that? If so, how could the balloon be controlled for going to different "waypoints", or is that even possible?

This will most likely be my summer "project"!

Here are the laws I found regarding these near space balloons (subsection D): http://www.ecfr.gov/cgi-bin/text-idx?c=ecfr&sid=ea968eea871ed9ab2380f6d979eaa7a6&rgn=div5&view=text&node=14:

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If there is a hole in the bottom (like a regular hot air ballon), all the air will come out when you start going from sea level pressure to the close-to-zero pressure of the high atmosphere. If you seal the balloon to prevent this, well, you are back to the popping ballon. 

For the record, the popping of the ballon is usually the way you get your electronics back.

Could you use a servo to open/seal the balloon, or stay at an altitude of 60,000 feet to prevent this?

You are right back to the issue of energy density. The number of calories (or watts or BTU's or whatever measurement you want to use) in a bottle of propane is thousands of times greater than what you could get from solar panels. 

You are just not going to get the wattage you need from the panels. At the point you do, the panels will be so extensive that the thing will never get off the ground.

The math is just not there, dude.


Looks like I need a new summer project!

plastic solar panels. They have lower efficiency than the standard home based panels, but, they are much lower mass.

Is there any issue with just making a robot-brain, autonomous hot air balloon? I mean, close to the ground, "normal" altitude and with "normal" heating (petroleum fuel). That would be cool as hell.