It still looks insanely heavy for what it is. I am no engineer, but my grandfather was chief aerodynamicist at BAE and he impressed upon me the need for flying machines to be light. There is a reason early airplanes were built out of thread and canvas, and modern aircraft are made out of expensive aluminum rather than cheaper steel. Lighter-than-air machines function because the lifting mechanism - the balloon filled with the lighter-than-air gas (either hot air or helium etc.) is very, very large in comparison to the thing being lifted.
Here is some bad math (TM); that balloon has a volume of about 700 cubic feet (based on it being about a 13ft sphere, which is based on an estimation it is four 40mm bases long and two 40 mm high, average of three 40mm bases in diameter if it were a sphere, 28mm=6ft in scale, which means 120mm = about 26ft).
This link
http://science.howstuffworks.com/helium2.htm breaks a lot of this down for you. Key detail is here;
One cubic foot of helium will lift about 28.2 grams, so multiply the volume of the balloon by 28.2.
Actual figure is 707 cu ft - so that is slightly less than 20kg lifting capacity if it is filled with helium.
Helium is a noble gas, difficult to generate. Hydrogen is surprisingly easy (acids reacting with bases) so is more likely.
Based on the information on that site, hydrogen is 0.089888 g / liter while air is 1.25 g / liter.
Our balloon is 20020 liters - so that much air would weigh 25.025kg, and that much hydrogen would weigh 1.8kg. A lifting capacity of 23.225kg . . .
I understand this is fantasy - one isn't expecting some realistically-scaled balloon; exaggeration is fine. But the armored nature of it looks just too much and too heavy. It needs to be a light wicker basket, or a canvas box, or something. Not a hulking great open-topped-tank.
