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Imagine a hawk flying about 15 meters away from you. You can easily see it, but if there’s a bee at the same distance, it’ll be virtually impossible to detect it because the human eye can’t spot such small objects at such a distance.

The hawk at 15 meters is comparable to a conventional aircraft, which appears as a giant dot on the radar screen, whereas a bee at that distance is comparable to a stealth aircraft, which does not appear on the radar screen since the image of the aircraft at that distance cannot be resolved.

Although stealth technology does not completely hide an object, it does delay detection, giving the opponent enough time to cause serious damage.

Stealth technology works on the principle of preventing radar reflections from reaching the source of the radar signal.

What is stealth technology?

Stealth technologies are used in military aviators and aircraft designs to avoid radar detection. The US government announced in 1980 that stealth is a combination of passive low observable (LO) features and active emitters such as low-probability-of-intercept radars, radios, and laser designators. In layman’s terms, there are two methods for achieving invisibility.

  • The airplane can be made up of completely flat surfaces and very sharp edges so that any radar signals it reflects are reflected away from the radar equipment.
  • The airplane can be covered in materials that absorb radar signals.

Famous Infringement case

The single-seat Lockheed F-117A Nighthawk ground-attack fighter, which first flew in 1983 and had the radar signature of a small bird rather than an aeroplane, was the first aircraft to use this technology.

The US Pentagon has been accused of infringing on Zoltek Industries’ patent for the past 20 years. Zoltek possesses US Patent No. RE 34,162, which claims a technique for making carbon-fibre sheets with features beneficial in military applications, such as enhancing aircraft stealth. The patented method involves partially carbonised fibres being processed into sheets for use on military aircraft.

Zoltek filed for the invention in 1984, and it was awarded in 1988, the same year that the F-22 and B-2 bombers were first publicly unveiled.

Under 28 U.S.C. 1498(a), Zoltek sued the Pentagon and Lockheed in the CFC, alleging that “use or manufacture of [a patented] innovation” is “construed as use or production for the United States.” When a patented invention is “used or manufactured by or for the United States without licence of the owner thereof, the owner’s remedy shall be an action against the United States in the [CFC] for the recovery of his reasonable and entire compensation for such use or manufacture,” according to Section 1498(a).

Based on expert testimony, a judgement was made in 2014 that part of Zoltek’s method was already known to scientists in the area at the time, rendering the patent invalid.

In the most recent development in a nearly two-decade-long case, the courts have yet to reach an agreement on a ruling that clarifies the extent to which the government is protected from sharing information about secret defence programmes, and the ruling also overturned a Federal Claims Court judge’s 2014 decision finding the patent invalid.

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