The Balloon

[Deesse23]

Let’s be honest,  no balloon the size of a small car can possibly carry any substantial intelligence package.   A balloon’s carrying capacity must necessarily be less than the weight of a volume of air at the balloon’s operating altitude equal to the size of the balloon itself

A balloon the size of a small car, say 10 cubic meters, would therefore have a carrying capacity at 40k feet of 4 lbs minus the weight of balloon itself.

I'm not an electronics engineer, but it seems that you could pack a fair bit of microminiaturization into a four lb (or slightly smaller) payload.

Boru

As an electronics engineer i agree. You can put a LOT of transistors into a 4lb ECU.
Batteries for a potential transmitter however..i mean, everyone could intercept and read your data (and thus know what you are interested in)...but maybe you wanna store your data on even more small transistors and read it out back home....IF your intention is to get the thing back home.....but how to get a balloon back home...