It is no accident that most of these aircraft resemble one another or that all (except the future U.S. Long Range Strike Bomber) are unmanned. No shape other than a tailless flying wing provides the desired stealth, and incorporating a cockpit is difficult except in a large vehicle.
All three classes of stealth air vehicle are likely to be operational in 2030, regardless of the JSF program. Three areas of uncertainty will define the actual make-up of air forces worldwide.
The first concerns the ability of RCS-managed conventional aircraft, as part of a system of systems, to operate against improved threats such as Russia's S-400/500 surface-to-air missile (SAM) systems. Boeing is promoting RCS reductions on the Eagle and Super Hornet, along with improved EW, and the U.S. Navy is funding “significant” classified upgrades. The Navy Hornet/Growler community envisions “rolling back” SAM threats with jamming and standoff weapons, and the service's vision for future anti-surface warfare is based on weapons (initially Tomahawk and Joint Standoff Weapon derivatives) rather than stealthy penetrating platforms. European fighter developers are studying RCS reductions for post-2020 versions of current aircraft.
The second unpredictable factor is the rate at which the use of very stealthy unmanned aircraft expands. Many U.S. commentators and think tanks have pushed for a greater role for survivable UAVs and bombers. Designed to survive by stealth rather than speed or agility, these aircraft offer longer range than tactical fighters, which creates options as the U.S. looks at the military balance in the Western Pacific. The emerging threat of a reconnaissance-strike complex aimed at U.S. aircraft carriers has pushed the Navy to the front of this trend.
The third consideration is the performance of the JSF program and its Russian and Chinese analogs, in cost, timeline and flexibility. The pacing item for the JSF is clearly software integration and testing; the U.S. Air Force has accepted that the aircraft will enter service with a limited weapons.
Not coincidentally, the upgrading of the F-22 Raptor, which has also failed to keep pace with aspirations, is dominated by software rather than hardware changes. These challenges are not going to be easier for developers in China, Russia or South Korea.
This is because a stealthy aircraft intended for a full range of fighter missions presents high hurdles in two inseparable software-dominated areas: sensor fusion and emissions control (Emcon). It is also a problem from the viewpoint of networking.
Sensor fusion is common to modern fighters. In principle, it means displaying data from active and passive radio-frequency (RF) sensors, infrared and optical devices, networks and databases as single targets and tracks. On a stealth aircraft, sensor fusion also supports Emcon, minimizing and managing RF energy to avoid detection.
The “fusion engine”—as the software package is termed on the F-35—is complex and critical. Testing is challenging because even the best ground-based systems-integration laboratory may not address the phenomenology of sensors in a real-world. One engineer describes a sensor-fused air combat avionics system as “having a nervous breakdown” when confronted with dense European air traffic. It is also crucial in preventing blue-on-blue attacks and collateral damage.