Posted by John Keller

The Lockheed Martin Sea Shadow, an experimental surface vessel that helped design modern warships with low radar cross sections, is heading for the scrap yard after nearly 30 years of surface. The black dual-hull ship, built in the 1980s under a shroud of secrecy, has served its purpose and will be auctioned for scrap this week.

Despite its undignified end, however, the Sea Shadow, which tests showed was nearly invisible to radar during sea tests, has led to radar-evading design technologies that have gone into the Navy's newest Littoral Combat Ship (LCS), as well as into new models of the Navy's Arleigh Burke-class destroyers.

The notion of radar-evading stealth technology perhaps reach its zenith in the 1980s before the close of the Cold War. Lockheed Martin had designed the super-secret F-117 stealth attack jet, and then company experts turned their attention to developing surface warships that might likewise be nearly invisible to radar signals.

The result was the Sea Shadow, a spaceship-like test vessel that primarily was taken to sea for testing at night, and was built and stored in a secret submersible barge near San Francisco, which cloaked the vessel from orbiting spy satellites.

The Sacramento Bee ran a terrific story last weekend by Matt Weiser entitled Scrap heap may be last stop for secret slice of Navy history, which gives a detailed account of the Sea Shadow's development and testing.

Take a look at the photos that accompany stories about the Sea Shadow and then compare it to versions of the Navy LCS. See all those funny angles in the ship hulls and superstructures? That's key to the design's ability to evade radar signals.

Radar detects targets by bouncing radio waves off the targets and measuring the reflected return of the radio energy. The best radar returns come from right angles. Notice that the LCS designs don't have too many of these. The angles of the LCS vessels, as well as radar-evading aircraft such as the F-35 Joint Strike Fighter are designed to scatter radar energy, rather than provide clear returns. It's not fool-proof, but it can be quite effective.

The Sea Shadow test vessel reportedly was able to sneak up on Navy warships at night without being detected until very late in the game. It this had been an armed enemy ship, U.S. aircraft carriers might have been in serious trouble.

Now the testing is all over. It's a pity the Sea Shadow couldn't become part of some museum's collection, but so far it is not to be. Its legacy will live on, however, in the designs of modern warships.