I rationalized the size of the balloons and how slowly the ships fall as well as why the hull takes continuous damage when touching anything and how we survive hwacha blasts by assuming that the balloons are not what actually keep most of the ship's weight afloat. The balloon is more like a fish's air bladder, and the ship itself is kept almost neutrally buoyant by the same technology that kept both the Juggernauts AND the naval warships (we will get to those) in the air .
The devices themselves are build into the hull, and any metal they are integrated into is given a gravity repulsion field. This makes the ships themselves weigh almost nothing, and requires very little helium to keep them in the air. If the balloon is broken, the ships fall slowly to the ground, like a balloon filled with air.
Why does touching the ground cause damage, though? Well, if the ship's hull comes into close proximity to a large mass, it interferes with the field the device emits. This causes torsion in the field, thus twisting anything effected by it. In other words, your armor and hull. So, it is not the impact itself that causes the damage for the most part, but the gravity repulsion field gone haywire. One of these devices is contained in the 'hull' repair point on your ship.
But, the hwachas! Yes, of course the hwachas. Again, with a bit of hand waving, we can blame the field created by the device. Nothing larger than dust particles can enter or leave the generated field. The bullets are not actually hitting the ship. They are impacting the field. The force they create is transferred into the field itself, disrupting its flow. The 'armor' going down is actually the device getting its field scrambled. 'Fixing' the armor is actually realigning those fields. After a certain point, armor 'break', the impacts to the field transfer the energy directly to the device itself, and begin damage its physical connection to the hull. When it is fully detached, it sends out a torsion wave that blows your ship apart.
Why can't you fall to the ground? Given the little understood quantum physics nature of the device, anything falling off the ship falls onto the deck near the device. Or, maybe you do fall to your death, and a
quantum double is created. No one has been brave enough to check.
Boarding does not work and is not attempted for obvious reasons.
Now, what about those naval ships in the middle of the desert? The devices would have been invented when navel ships were still in use. Having discovered the nature of the the gravity repulsion field, the Juggernauts were soon constructed. This sudden appearance of a new super-weapon destabilized the delicate balance of power, and war erupted soon after. There were few Juggernauts constructed, but still many naval warships. A new plan was put into place to quickly move naval warships around. They would be floated through the air. Given their mass, they were equipped with thousands of the devices, and tethered to hundreds of weather balloons until neutrally buoyant. Once lifted into the air, the massive warships could be easily towed over landmasses to new waters, where they would be lowered and the devices shut down. Sometimes, they would even be towed to waterless areas, such as deserts, where they were 'parked'. From there, they would fire their massive guns into previously safe cites (nod to Labyrinth).
Eventually, some of the Juggernauts were brought down, along with the navel ships they had in tow. Other naval ships were lost in storms as their tethers broke, and set adrift with their crews unable to leave what became a floating prison. Some of these ships have even been found high in mountains, or dashed amongst jungle temples far from safe waters.
Knowledge of how the devices were made was lost as the tide of battle turned to their city of manufacture in a surprise attack. Facing certain defeat and capture of the facility, the officers in charge triggered the fail-safe, destroying the massive complex. The scientists responsible for the discovery were never found. No one else really understood what they had even created.
War raged on and on, spreading and twisting as once allies turned on each other on rumors that they were working on their own devices. Whether this was true or not never came to light. The result was worldwide devastation, along with famine and disease that reduced the greatness of human kind to groups of scavengers.
Eventually, after generations, tinkers and inventors discovered ways to get salvaged devices working again, though without knowledge of their making or actual mechanics. They also could not figure out how to construct ships with more than one device without said ship instantly exploding once the devices were activated. This severely limited the size of the new ships, but still set off a mad scramble to scavenge any still working device from the aged wreckage. Hundreds of navel warships remain unaccounted for, as well as several Juggernauts. The prospect of countless devices still waiting to be found created the equivalent of a gold rush. Men and women spent their fortunes on just one device so that they may soar the skies in search of this new treasure. Others found it more easy to prey on the treasure hunters. Kill the ship, and the device often remains unharmed.
Due to the devices' nature interacting with the gravity of the planet, the gravitational repulsion field has an upper height limit to its abilities. Much like one magnet hovering over another, once that height is reached, it can go no higher. There are rumors that one ship tried, using extra balloons and downward-facing propellers. The rumors each tell of different lands, captains, and names, but they all end the same. A ship tried to fly too close to the sun, and rained back to the earth.
Thus became born the days of Icrarus....
At least that is how I rationalize it.
