A conversation I was having at another forum about the new giant passenger plane, the A380, reminded me of your quest for funky new vehicles, especially military ones... and especially your tendency to want to combine two or more different things into one.
The main limiting factor to keep civilian passenger/cargo jets' sizes down is not the ability to make them fly, but the lack of airports with big enough runways and enough other infrastructure for maintenance/repair, fuelling, loading/unloading, and such. Otherwise, they seem to want to keep making them bigger. That creates a situation similar to one that existed around WWII, when the biggest planes were medium by today's standards but still had rather few places to land and take off from.
Back then, the answer was what they called "flying boats": big heavy planes that landed on water because their hulls were like boat hulls. Landing on the ocean or a large enough lake means there's no worry about landing/takeoff strip length, because the water gives you miles and miles more space than you need. So they could land pretty much anywhere with a body of water that was big enough, which was a lot less limiting than having to land at an airport that's big enough. They fell out of use because airports big enough to handle their wheeled counterparts were eventually built in more places. But that still isn't really the case for today's most gigantic plane, or for the next gigantic one they might want to make after it.
When I first thought of the idea of making the next giant airliner a flying boat (flying ship?), I pictured civilian planes "landing" at coastal airports, because the main use for the biggest planes is on transoceanic routes instead of over the continents anyway. But since then it's occured to me that the military services would be more interested in it than civilians, because such plane has a lot more potential "landing" sites than a wheeled one does, including some areas with no suitably large and "friendly" airports nearby.
Military services already use big heavy planes to move people and cargo around like civilian organizations, but also for some more military-specific purposes. A bomber is essentially a just cargo plane that drops is cargo in flight, and so is a plane that soldiers jump out of with parachutes. At least one type of cargo plane has had guns and missile launchers stuck in its cargo hold, making it a ground-attack plane capable of more narrowly picking its targets than a bomber but delivering more firepower to more targets than a fighter or smaller attack aircraft. Another, called AWACS, houses lots of fancy electronics and a technical crew in its cargo hold for surveillance, coordination of other forces in the area, intelligence gathering, and "electronic warfare". Some cargo planes have been known to fly slow and low to the ground with the rear ramp down, and let large packages slide out the back and onto the ground while the cargo plane went on by, providing remote troops in combat zones with supply loads up to and including trucks and tanks.
Essentially, anything you can do with a conventional cargo plane, you can do with a similar-sized "flying boat", except put it down on solid ground... and the giant A380-sized planes I'm thinking about would be so big that their cargo hold size gets comparable to that of an "amphibious assault ship". An AAS looks a bit like an aircraft carrier, but is too small for naval airplanes. It carries helicopters and hovercraft, and some trucks and other land vehicles, to be moved ashore for an attack to quickly establish a presence of military forces on the ground. It even opens up its internal hold by a ramp in the back like a cargo plane does. Even a very big plane might never be quite as big as a true AAS, but they might be able to carry similar stuff, so that one or two of them carrying the right stuff could do the job in a matter of hours instead of the days that an AAS might take to reach the site.
There are technical challenges, like the drag on the hull during landings and launches, the weight of water while it's in flight, the shape of a ship's hull being different from an ideal aerodynamic one, the potential for corrosion with exposure to salt water... but the basic concept works; it doesn't violate basic principles of physics like some other combo ideas do. So the challenges are essentially little details that can be tweaked with modern design and materials to make a concept that already works work better...
The main limiting factor to keep civilian passenger/cargo jets' sizes down is not the ability to make them fly, but the lack of airports with big enough runways and enough other infrastructure for maintenance/repair, fuelling, loading/unloading, and such. Otherwise, they seem to want to keep making them bigger. That creates a situation similar to one that existed around WWII, when the biggest planes were medium by today's standards but still had rather few places to land and take off from.
Back then, the answer was what they called "flying boats": big heavy planes that landed on water because their hulls were like boat hulls. Landing on the ocean or a large enough lake means there's no worry about landing/takeoff strip length, because the water gives you miles and miles more space than you need. So they could land pretty much anywhere with a body of water that was big enough, which was a lot less limiting than having to land at an airport that's big enough. They fell out of use because airports big enough to handle their wheeled counterparts were eventually built in more places. But that still isn't really the case for today's most gigantic plane, or for the next gigantic one they might want to make after it.
When I first thought of the idea of making the next giant airliner a flying boat (flying ship?), I pictured civilian planes "landing" at coastal airports, because the main use for the biggest planes is on transoceanic routes instead of over the continents anyway. But since then it's occured to me that the military services would be more interested in it than civilians, because such plane has a lot more potential "landing" sites than a wheeled one does, including some areas with no suitably large and "friendly" airports nearby.
Military services already use big heavy planes to move people and cargo around like civilian organizations, but also for some more military-specific purposes. A bomber is essentially a just cargo plane that drops is cargo in flight, and so is a plane that soldiers jump out of with parachutes. At least one type of cargo plane has had guns and missile launchers stuck in its cargo hold, making it a ground-attack plane capable of more narrowly picking its targets than a bomber but delivering more firepower to more targets than a fighter or smaller attack aircraft. Another, called AWACS, houses lots of fancy electronics and a technical crew in its cargo hold for surveillance, coordination of other forces in the area, intelligence gathering, and "electronic warfare". Some cargo planes have been known to fly slow and low to the ground with the rear ramp down, and let large packages slide out the back and onto the ground while the cargo plane went on by, providing remote troops in combat zones with supply loads up to and including trucks and tanks.
Essentially, anything you can do with a conventional cargo plane, you can do with a similar-sized "flying boat", except put it down on solid ground... and the giant A380-sized planes I'm thinking about would be so big that their cargo hold size gets comparable to that of an "amphibious assault ship". An AAS looks a bit like an aircraft carrier, but is too small for naval airplanes. It carries helicopters and hovercraft, and some trucks and other land vehicles, to be moved ashore for an attack to quickly establish a presence of military forces on the ground. It even opens up its internal hold by a ramp in the back like a cargo plane does. Even a very big plane might never be quite as big as a true AAS, but they might be able to carry similar stuff, so that one or two of them carrying the right stuff could do the job in a matter of hours instead of the days that an AAS might take to reach the site.
There are technical challenges, like the drag on the hull during landings and launches, the weight of water while it's in flight, the shape of a ship's hull being different from an ideal aerodynamic one, the potential for corrosion with exposure to salt water... but the basic concept works; it doesn't violate basic principles of physics like some other combo ideas do. So the challenges are essentially little details that can be tweaked with modern design and materials to make a concept that already works work better...
