At the end of the article:<p>>> The problem remains that fully solar balloons need sunlight, and it is rare for the sky to remain unclouded for long journeys.<p>Above 6,000 metres, it is rather rare that any cloud blocks the sun in daylight hours. This method of transport has potential for freight.<p>Rather than black, you'd want a transparent skin or layers of skins. Focus sunlight with internal reflectors onto an engine. Usefully, waste heat is not a problem here, but valuable, when captured in the envelope.<p>The engine should use more than just heat energy. Visible light for PV power generation. Maybe ultraviolet can be used to elecrolyse environmental water vapour to hydrogen. To provide both lift and energy storage for night time.
I find these and the low tech magazine articles fascinating, though I sometimes feel that either I'm a) falling victim to an elaborate prank, b) unknowingly supporting the output of someone's mental health issues (though I feel that about some of my best loved musical acts too).<p>Now that's there's two sources, I'm further confused as to whether one is mocking the other, but if they are it's possibly too subtle for me to catch.
I'm no balloon expert, but it seems like they could have absorbed more heat with a translucent top.<p>Then the solar rays would enter the chamber before hitting the black fabric and reflecting back into the chamber.. more frequencies of light, more chances to catch the heat.<p>Like the SHGC effect observed by closing/opening curtains
Sailplanes also do this. “Gliders” get a brief mention as an aside, but it’s somewhat glossed over, but fundamentally the sport of flying depends on the same solar thermal phenomenon except instead of producing black material to absorb sunlight, sailplanes rely on existing low albedo features of the landscape to generate the solar heated air.<p>Sailplanes air often towed to the air by powered aircraft in the US, but higher performance sailplanes usually carry their own motor for self launch (often electric) and in Europe are often winch-launched. Gravity launch (rolling down hill) and auto tow (a car pulls the sailplane into the air, usually with a pulley) are also fairly common, and the former would meet this “low tech” qualification.
Isn’t almost anything that’s not powered by nuclear energy flying only with the heat of the sun with extra steps? If you include the definition of “some sun” then even nuclear energy is the same, just with a multi billion year cycle.
Here's a toy one, good reviews, but fragile (have tape) and prob use once -<p><a href="https://www.amazon.com/TEDCO-Tedcotoys-Activity-50-foot-Balloon/dp/B00LW7WGRK" rel="nofollow">https://www.amazon.com/TEDCO-Tedcotoys-Activity-50-foot-Ball...</a><p>Practically perhaps you could use the principal to manage buoyancy on lighter than air... unlikely though, to much added complexity.
When I was a kid at science camp we demonstrated this effect. They had a very long sausage-shaped black plastic bag that we all rand around filling up and laid out in the sun until it rose. I always assumed this strange bag was designed for such demos. In our case something happened (a person let go, a tether broke; I don't recall), and the "solar sausage" flew away completely until we could no longer see it.