High-altitude object’ shot down by military over Alaska, White House confirms

[Kamaji]

I believe, could be wrong, that the metallic coating of mylar makes it less porous so that it doesn't leak the helium as quickly. It also reduces the solar heating reducing the pressure changes from day to night and back again.

Metallized films:  https://en.wikipedia.org/wiki/Metallised_film#:~:text=The%20coating%20also%20reduces%20the,cost%20than%20an%20aluminium%20foil.

[DB]

Metallized films:  https://en.wikipedia.org/wiki/Metallised_film#:~:text=The%20coating%20also%20reduces%20the,cost%20than%20an%20aluminium%20foil.

So it sounds like I got it right. Thanks for the link.

[mountaineer]

 2019:

Published August 2, 2019 12:33pm EDT
Pentagon testing mass surveillance balloons across the US
By Christopher Carbone | Fox News

The U.S. military is conducting mass surveillance tests across six Midwest states using experimental high-altitude balloons, according to documents filed with the Federal Communications Commission.

According to The Guardian, which first reported the tests, up to 25 unmanned solar-powered balloons are being launched from rural South Dakota and drifting 250 miles through an area that spans portions of Minnesota, Iowa, Wisconsin and Missouri, before wrapping up in Illinois.

The balloons are carrying high-tech radar designed to track vehicles at any time of the day, during any type of weather, while moving at altitudes of up to 65,000 feet. They are also intended to "provide a persistent surveillance system to locate and deter narcotic trafficking and homeland security threats," the British news site reports. ...

ranger posted the story here: https://www.gopbriefingroom.com/index.php/topic,370754.msg2024346.html#msg2024346