[Benclaman]

These are awesome questions! Here's a couple answers:

1) We're building our full size airship to fly at 60 mph, which increases the usability in inclement weather.

2) Joe answered this in another comment, but our airships use pretty small quantities of helium compared to the bigger ones, so it's not a major operational cost.

3) For sure this is an issue, but the bigger the blimp is, the more bullet holes you'd have to fill it with to prevent it from reaching its final destination. The german zeppelins of world war I were really hard to shoot down. See 5:47 of the below video.

https://www.youtube.com/watch?v=nlQgprSGpNI

[ManBlanket]

I just attended a 7 year old girl's birthday party who was gifted a bb gun by her domestic-swilling uncle. We confirmed the temptation to shoot balloons is real. That said it seems like the other points you mentioned are working in your favor. The chances of hitting a small moving aircraft at a relatively high altitude is much lower than a 747 loaded onto a passing train. Plus I would like to imagine the temptation to shoot at something would diminish significantly as our hill billy wouldn't necessarily know it is unmanned. Not to mention anyone who has listened to a firearm safety talk is well-versed in how gravity affects projectiles. I wouldn't anticipate this being a significant problem, but it was a fun thought to entertain nonetheless.

And hey I'm just spit-balling here but isn't wind a much less of an issue at dusk, night, and dawn? Would this not be a significant factor in when you would operate? I would imagine most people shooting 747s on passing trains aren't getting out of bed to do that, after all.

[datameta]

In my experience around sunset and sunrise there is a period of varying wind characteristics, at least this seems to be the case in a city by water.

[Cthulhu_]

I mean for 3, it's called 'vandalism' but it should be considered assault, attempted murder or even domestic terrorism. I'd put a security system on there (using e.g. high speed cameras) so that hopefully you can pin down where the shots come from, then sick the authorities on them. I have no tolerance for people using guns irresponsibly.

[Mountain_Skies]

They're unmanned though there could be a danger to people on the ground if there was enough damage done that it couldn't land under control.

[squarefoot]

Also if the idiots know they're unmanned and used to deliver goods, they could be even more motivated to attempt to shoot them down to steal the cargo. I also would consider putting cameras and the necessary technology to help identifying anyone attempting to shoot them down.

Or maybe paint them as sharks, then add some powerful lasers on their back:)