Lockheed's Incredible Stealth Ship: Sea Shadow
Imagine if a plane manufacturer, renowned for the F-117A 'Stealth Fighter', were to build a ship. That's exactly what happened during the Cold War. Lockheed's famous secret projects outfit, the Skunk Works, built a ship designed to be invisible to radar. That unique vessel was the Sea Shadow (IX-529).
The genesis of the project started in 1978 when it became apparent that the angled lines of the F-117A would also reduce a sonar signature. This led to a proposal for a submarine with similar facetted lines, but that idea went nowhere. Instead a new idea emerged, to use the technology to build radar-invisible ships. The Defense Advanced Research Projects Agency (DARPA) contracted Lockheed's Skunk Works to test the effectiveness of stealth shaping and coatings on surface vessels. It was also to test the effects of seawater on the radar-absorbent iron ferrite coating.
The thinking behind the Sea Shadow was based on the then- highly-classified F-117A Nighthawk (left). It shared the faceted sides which were angled to deflect radar waves. Photos: Lockheed
The idea was not only to make the ship invisible to surface radars used by enemy ships, but also radar satellites. The Soviets were fielding the RORS satellite which used X-band radar to track ships at sea and relay their position to commanders. The P310 'Demonstration Platform' as it was initially known, would be invisible to these until-now all-seeing eyes in space.
The hull-form chosen was a SWATH design. Standing for Small Water Area Twin Hull, these can be very fast and also very stable in heavy seas. The twin hulls allowed for an extremely angled upper hull which looked completely unlike any ship before it. The angled lines are actually more subtle than they first appear. If you look closely, the sides and top are actually sloping slightly to the rear.
The vessel was assembled in a floating hangar in San Francisco Bay in 1983-84. The hangar, dubbed the Hughes Mining Barge (HMB-1), was the ideal home of the secret project. Lockheed bought in naval architects from local firms to help undertake the project. This being the 1980s, all the plans were done on paper. The vessel might look futuristic even today, but the technology on the ground would be hard to imagine today.
The Sea Shadow inside the Hughes Mining Barge. The HMB-1 was originally built as part of Project Azorian, a CIA operation to salvage the wreck of the Soviet submarine K-129 (GOLF-II Class SSB, sunk March 8, 1968). US Navy photo.
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Sea Shadow started trials in 1985. It was unarmed, being only a demonstrator and test platform, but there were proposals to fit a large radar to it. This was to be added in the payload bay looking out through a large door. Work on the modification started but the project was cut short. Another proposal was for similar ships to be equipped with Patriot air defense missiles. These could operate in advance of regular surface ships.
The technology behind Sea Shadow had potential and the vessel was used in tests for many years. Eventually in the mid-1990s, after the end of the Cold War, the ship was retired. Ultimately she was the only boat like her, there never was an order for a fleet of fully-stealthy SWATH warships. And sadly, in 2012, she was broken up for scrap. An undignified end to an inspiring ship design which is in a class of its own even 35 years later.
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