first lets take a moment here and recognize something, there is not one Sixth generation Program but four. two are black under Darpa, two are White under there services, two are for the navy two are for the USAF. Between today and 2025 The USN and USAF could merge them into a Joint White program but today there are four.
the White Folders for the USN and USAF are empty, With only a Cover sheet outlying wants. the Air force's Next Generation Tactical Aircraft and the USN's Next Generation Air Dominance.
the Two Black Folders are Darpa X plane Demonstrators And in those folders are hundreds of subprograms for specialized systems and subsystems that will form the two fighters some are common between the two demonstrators some unique the contents of these folders may become the contents of the white folders but that's down the line.
So If there is not one program we need to then recognize that the two services may not share the same vision or definition of a sixth generation fighter.
The Navy's NGAD aims for a 40,000 lb (18,000 kg) weight class fighter well the USAF seems to be aiming heavier.
with this is mind I think We should then Take our list of desired wants and break them down by individual service wants.
FA/XX
1. Spectrum dominance
Navy fighters cannot be specialists. There have been Some Navy fighters that have been specialists in the past sure but the limitations of number of available aircraft vs space vs crew capacity of a ship always force multi role. Every "superiority" or "Dominance" in the Navy has to be a predator of both air and sea. If it's not capable of strike it will be looked to be made as capable of ground strike. the Navy needs this. it cannot afford to waste the airframes.
2. Advance propulsion
Critical questions remain but one of the driving forces behind the program is range. not speed. the Official Combat Radius of a F35C is about 600 NM. that is the distance a F35C can fly patrol there for a set amount of time and return to base with minimal fuel left, this is now a problem because of the potential of systems like the DF21D. ( please let's not debate that system or implications or there are threads for that. I am using it as a point of example) The Df21D represents a class of weapon the Antiship Ballistic missile. This Class of Weapon is designed to force Carriers back over a thousand nautical miles. to push the carrier so that it's aircraft is not in a position to be a threat. right now the PRC and Russia have the capability to deploy such systems in the next decade. That forces the USN to question the relevance of it's Carriers. It may not be as dead as a Battle ship, but why invest multi billion dollars and thousands of lives on Ford class Carriers if they can't be placed in position to launch strikes without risk of being sunk with no chances of defence.
This is part of the argument for ADVENT.
Imagine if you will a traditional fighter jet engine the F135 is the Bugatti Veyron it's high powered, it's sexy with reclining leather seats, that goes really fast, and gets really ______ gas mileage!
Now Imagine a traditional Jet liner engine as a Audi S8 it's got nowhere near the speed or horse power but alot of the same tech and it's got fuel economy that allows it to go far beyond what the F135 could ever dream of in terms of range. It sips fuel, That gives it legs. for the same amount of fuel it will get you twice maybe three times as far but it will take longer.
This is Where the ADVENT comes in. this is where the YF120 would have been but it was not deemed needed. It's a platform that bridges the gap. in our car analogy it's the Shadowhawk STV it's a car powered by an engine that gets the same horse power and speed as the Veyron but with a MPG closer to that of the S8.
YF120 used a variable cycle engine, but the USAF aired conservatively and moved to a conventional engine. now with the push of ASBM's pushing Carriers back the Navy is really forced to find a way to keep in the fight and ADaptive Versatile ENgine Technology could do that if it could double or triple the range of a fighter from the F35's 600NM to 1,200 NM or 1,800NM Allowing the Carrier to operate from a standoff but with most if not all it's capacity.
3. Autonomous sensor and payload integration
As the range increases and stealth proliferates Navy fighters are going to have to hunt smarter. Smaller more sophisticated targets with less sensor help from the carrier group. this is going to drive sensors and weapons. lots of sensors and weapons it needs to see more and target more.
Now the Navy has less flexibility of weight vs other trade offs then the Air Force. If the Air force builds a larger( read Heavier) fighter they can just use more runway, The only real issue for that is the size of the Airbase and a Airbase dwarfs the size of any Aircraft carrier unless it's on a atoll there is no real limitation for the Air Force other then financial. so the Navy is more willing to trade on Stealth but don't think this means that it's not going to include stealth in the design it's just more willing to shed some stealth for other things. more frontal stealth then all aspect.
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