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Floatplane jets are a lovely concept, but there are so many problems they are never going to be feasable.
The Convair Sea Dart was not a floatplane. It floated on its integral fuselage/delta wing, and used hydroplanes--basically water-skiis--to stand out of the water to achieve takeoff speeds and initially on landing.
It had problems all right. For one thing, the engines it was designed for were not available and it tested with markedly inferior engines. For another, it like many other planes meant to be supersonic in its generation suffered from the lack of area-ruling. Convair by the way was developing landplane delta-wing fighters in parallel--the F-102, which like the Sea Dart failed to break the sound barrier as designed. They went back and redesigned its fuselage with the "Coke-bottle" waisting at the junction of the wing's leading edge with the fuselage, in accordance with Whitcomb's area rule, and then it performed OK. Had something like this been done with the Sea Dart and had it been equipped with engines of the designed thrust, I am sure it would have performed as designed in the air.
The hydroplanes were another problem. As the plane accelerated toward takeoff speed, the waves gave them a good hard pounding. They had shock absorbers but it was still pretty bad.
My own notion is, to use hydro
foils, fully submerged surfaces generating lift in a manner exactly analogous to how wings get it in air. I think if Convair had tried this they could have demonstrated that the concept of an airplane that lifts its hull clear of the water at a relatively low speed and accelerates on foil lift to takeoff speed is perfectly viable.
Seaplanes could be made by modifying standard landplanes, moving their engines as necessary to avoid spray ingestion (and there would be less spray due to a far smaller segment of the craft cutting the surface--just the streamlined struts holding the foils below the water and the rest of the plane above it would penetrate). Making the lower surface of the plane watertight and strong enough to resist dynamic water pressure at speeds up to the speed the foils can lift the hull clear would be the other major modification, other than the foils themselves which I believe could retract flush to wing or fuselage exactly like wheel landing gear. In fact such a plane could be equipped with both wheels and foils, and thus be amphibious.
There would be weight penalties, mainly from strengthening the body of the plane, and moderately from the foils themselves. But there need not be much in the way of streamlining penalty.
This is the sort of waterborne jet fighter (and bomber, and transport) I am thinking of. I'd think that if Convair ever got the Sea Dart right (as I am sure they could with enough of a commitment to the concept from the Navy) it would wind up looking like a modified F-102, with air intakes higher up and farther back to shield them from spray, and a sealed bottom and some provision of a lower lip on the exhaust to keep water from freely seeping or spraying in. Also, the Navy wanted twin engines in case of engine failure while the F-106/F-106 used a single engine. Otherwise there were a lot of similarities of design, since they came from the same designers at about the same time to perform similar missions.
Meanwhile the basic design of fast subsonic big jets like the Boeing family of bombers and transports lends itself to the concept too, if we can switch the engine pods to above and behind the wing instead of below and ahead--at least one small commercial passenger jet, designed by VFW in Germany, did this in the 1970s. Then it is a matter of making the wings strong enough to serve as sponsons during low-speed taxiing while floating on the water.
So in addition to fighters, we could have medium to big bombers, and transports as big as you like--C-5 sized, 747-sized--shuttling to and from the vicinity of a fleet at sea and fixed bases, ready to accompany fighters and other attack planes part of the way or to resupply the fleet units with urgently needed supplies. Even if such planes don't replace carrier planes, they certainly would allow smaller vessels to serve as detached units and still have their own air cover and airborne resources.
I have also been toying with the idea of small aircraft carriers that use hydrofoils or hovercushions to achieve speeds like 120-150 knots in surges; if a surface vessel can reach such speeds they can launch and retrieve airplanes much as the airships Akron and Macon (ZRS-4 & -5) did. The latter would simply fly at 60 knots or so, and the biplane Sparrowhawk fighter/scouts, which could stay airborne at that speed, would hook on to a trapeze hung below. A hydrofoil or hovercraft carrier would be stationary relative to a low-flying jet, which could be caught with guiding hooks and set down on a platform. Haven't yet finished estimating what sort of engine power that would take--clearly it depends on how big the "carrier" has to be.
I'm thinking 500 tons or so, a frigate or very small destroyer, capable of carrying maybe five 25-ton fighter or attack planes. Major maintenance would be done on a dedicated fast armored and armed tender ship, but again small task forces could be detached for specific missions.
Another thing to consider about these alternatives is the vulnerability of a big carrier and the utter dependence its planes have on their being a carrier deck (or some kind of airfield) for them to land on. An accident on a carrier deck can take that ship's flight deck out of commission for weeks; this is why carriers are assigned to task forces at least in pairs. Even so it would be easy for both to be damaged enough that any planes airborne would have no choice but to ditch. If instead the task force were made up of seaplane tenders carrying an equivalent number of planes that could land on water (takeoff can be via catapult, JATO rockets, and the like) then even if all surface units dedicated to serving the planes were sunk, the planes could still land and presumably be towed or hauled aboard any ships that did survive.
High-performance seaplanes might even be based on a submarine, though it would have to be small planes and a big sub, and the planes' takeoffs and landings would tend to give away the sub's position.
Or if they relied on fast hydrofoil/hovercraft "decks," there would be many of them and presumably at least one or two would survive and be able to land planes.
Big carriers have worked out well for the USN post-WWII largely because no one dares to try and sink one; such an attack is of course tantamount to declaring war on the USA. If an all-out war does break out, obviously a carrier has some ability to defend itself via its planes which will protect it. But the enemy will try hard to get through as just a little damage can take a carrier out of commission for a long time, and both theory and WWII experience show that it need not take much to destroy one permanently. Even a nuclear-powered flattop that needs no flammable fuel to propel itself or power its operations still carries a lot of the stuff anyway for its planes, along with lots of ordinance. Something nasty getting through the defenses is particularly likely to do major damage to a carrier as opposed to other sorts of ship, armored deck or no.
It seems only smart to have some alternatives handy to fall back on.