[piloto_ciego]

I don’t think this is correct… a thousand cubic feet of hydrogen is 68lbs of buoyancy at sea level.

A cylinder that was 20’ long, and 5’ in radius (which is a lot bigger than my minivan - would be about 1570 cubic feet.

That could lift about 100lbs at sea level… at flight level 400… that’s going to have to be a huge balloon to lift 100 lbs or the payload has to be tiny tiny - which is possible but I don’t think something the size of a car is adequate.

[idlewords]

Which do you think is the most likely explanation?

1. A lighter than air craft or drone with a small payload

2. A man-made object that uses unknown physics

3. Aliens

I know everyone wants a cooler answer, but I see way too many people being irrational here.

[nl]

> A cylinder that was 20’ long, and 5’ in radius

Your are dramatically underestimating the size of these things:

The Chinese high-altitude balloon shot down over the Atlantic off the coast of South Carolina over the weekend was 200 feet tall and carried a payload the size of a regional airliner, a U.S. Air Force general said in a briefing on Monday.

The balloon's superstructure and hardware weighed "in excess of a couple thousand pounds," said Gen. Glen VanHerck, commander of North American Aerospace Defense Command and U.S. Northern Command.

https://www.newsweek.com/china-spy-balloon-size-200-ft-jet-a...

Here's a similar sized one NASA put up a few years ago: https://remus.jpl.nasa.gov/balloon.htm