The American development and deployment of Fifth-Generation stealth aircraft like the F-35 Lightning is one of the central stories of today’s security zeitgeist. But behind the scenes, several countries are already looking ahead to the design of a Sixth-Generation jet.
The relentless pace of research is arguably driven less by combat experience—of which there is little—and more by a sober assessment that development of a successor will take multiple decades and is better started sooner rather than later.
The Sixth-Generation fighter developers can be divided into two categories: the United States, which has developed and deployed two stealth fighter types, and countries that have skipped or given up on their attempt to build Fifth Generations jets. These latter countries have concluded that doing so is so time-consuming and expensive that it makes more sense to focus on tomorrow's technology than try to catch up with today's.
The latter include France, Germany and the United Kingdom, which are in the preliminary stages of developing sixth-generation FCAS and Tempest fighters; Russia, which has given up on developing its Su-57 stealth fighter for at least a decade , but is talking up a conceptual sixth-generation MiG-41 interceptor; and Japan, which is contemplating a domestic sixth-generation F-3 stealth jet, but may settle for a foreign-inspired fifth generation design.
Currently, the United States has two projects: the Air Force's ‘Penetrating Counter-Air'—a long long-range stealth fighter to escort stealth bombers—and the Navy's FA-XX. So far, Boeing, Lockheed-Martin, and Northrop-Grumman have unveiled sixth-generation concepts.
Furthermore, a third set of countries, notably including India and China, are still refining the technology for the manufacture of fourth and fifth-generation aircraft.
Stealth and Beyond-Visual Range Missiles Are Here to Stay
The various Sixth-Generation concepts mostly feature many of the same technologies. Two critical characteristics of Fifth-Generation fighters will remain centrally important to the Sixth: stealthy airframes and long-range missiles. As cost-effective ground-based air defense systems like the S-400 can now threaten vast swathes of airspace, stealth aircraft need to be capable of penetrating ‘anti-access/area-denial’ bubbles and eliminate air defense from a safe distance. Additionally, stealth jets also steeply out-perform non-stealth aircraft in aerial war games.
Thus, low radar cross-sections and radar-absorbent materials will be a necessary, but not sufficient, feature of sixth-generation fighters. Some theorists argue that stealthy airframes may eventually be rendered obsolete by advanced sensor technology—and stealthy airframes can’t be upgraded as easily as avionics and weapons. Therefore, jamming, electronic warfare, and infrared obscuring defenses will also rise in importance.
Beyond-visual-range missiles will remain a key technology. Extent missiles like the AIM-120D can already hit targets over one hundred miles away, but realistically must be fired much closer to have a good chance of a kill against an agile, fighter-sized target. However, new ramjet-powered high-speed air-to-air missiles like the British Meteor and Chinese PL-15 point to why future air warriors may mostly fight at great distances from their adversaries.
Awesome ‘X-Ray-Vision’ Pilot Helmets
The F-35 has pioneered sophisticated Helmet Mounted Displays that can see ‘through’ the airframe for superior situational awareness, display key instrument data, and target missiles via a Helmet Mounted Sight (although that last technology is decades old ). Though these helmets currently have significant teething issues , they will likely become a standard feature in future fighters, possibly supplanting cockpit instrument panels. Voice-activated command interfaces may also ease the hefty task-load expected of fighter pilots.
Larger Airframes, More Efficient Engines
As airbases and carriers become more vulnerable to missile attacks, warplanes will need to be able to fly longer distances, and carry more weapons while doing so—which is difficult when a stealth jet must rely solely on internal fuel tanks and weapons loads. The natural solution is a larger plane. As air forces expect Within-Visual-Range aerial dogfights to be rare and possibly mutually suicidal, they are showing a greater willingness to tradeoff maneuverability to emphasize high sustainable speeds and a greater payload.
These design imperatives may gel well with the development of advanced adaptive g variable-cycle engines that can alter their configurations mid-flight to perform better at high speeds (like a turbojet) or more fuel-efficiently at low speeds (like a high-bypass turbofan).
For several decades air power theorists have forecast a transition to crewless combat jets which won't have to bear the added weight and risk to life and limb necessitated by a human pilot. However, while drone technology has proliferated by leaps and bounds in that time, navies and air forces have been slow to explore pilotless fighters, both because of the expenses and risks, but also likely for cultural reasons. For example, U.S. Navy pilots successfully lobbied to re-purpose a planned carrier-based stealth attack drone into a tanker to refuel manned aircraft.