主题：【原创】八一献礼：《善隐者，上隐于九天——热点战机 -- 中华暖风

In an article published by the U.S. Naval Institute this month (July 2012), Greenert writes that a rapid expansion in computing power combined with changes to sensor technology have made it increasingly easy to sidestep the stealth capabilities of ships and aircraft.

The Limits of Stealth

The rapid expansion of computing power also ushers in new sensors and methods that will make stealth and its advantages increasingly difficult to maintain above and below the water. First, though, military sensors will start to circumvent stealth of surface ships and aircraft through two main mechanisms:

Operating at lower electromagnetic frequencies than stealth technologies are designed to negate, and

Detecting the stealth platform from angles or aspects at which the platform has a higher signature.

U.S. forces can take advantage of those developments by employing long-range sensor, weapon, and unmanned-vehicle payloads instead of using only stealth platforms and shorter-range systems to reach targets.

Stealth ships and aircraft are designed to have a small radar or infrared electromagnetic signature at specific frequencies. The frequency ranges at which stealth is designed to be most effective are those most commonly used by active radar or passive infrared detection systems. At lower frequencies detections do not normally provide the resolution or precision necessary for accurate targeting. Using more powerful information-processing, however, military forces will be able to develop target-quality data from these lower-frequency passive infrared signals or active-radar returns. 5

The aspects at which stealth platforms are designed to have their smallest signature are those from which detection is most likely. For example, an aircraft or ship is designed to have a small signature or radar return when it is approaching a threat sensor—or has a “nose-on” aspect. Improved computer processing will produce new techniques that can detect stealth platforms at target aspects from which they have higher radar returns. Multiple active radars, for instance, can combine their returns through a battle-management computer so radar detections from a stealth platform’s less-stealthy side, underside, or rear aspect can be shared and correlated to allow the stealth platform to be detected and attacked. Similarly, passive radar receivers can capture the electromagnetic energy that comes from transmitters of opportunity—such as cell-phone or TV towers—and bounces off a stealth platform at a variety of angles. With better processing in the future, those weak, fragmented signals can be combined to create actionable target information. 6

Those developments do not herald the end of stealth, but they do show the limits of stealth design in getting platforms close enough to use short-range weapons. Maintaining stealth in the face of new and diverse counterdetection methods would require significantly higher fiscal investments in our next generation of platforms. It is time to consider shifting our focus from platforms that rely solely on stealth to also include concepts for operating farther from adversaries using standoff weapons and unmanned systems—or employing electronic-warfare payloads to confuse or jam threat sensors rather than trying to hide from them.