Stealth Ships - Can a Ship Become Invisible?

The basic ethos is this: If a navy warship is detectable, it can be sunk. The harder it is to detect it, the tougher it is to attack it. Of course, a big advantage in any shootout is this: if your stealth ship is undetected while it can still ‘see’ the enemy, you have a huge advantage.

A country’s navy has always been the main means of projection of the nation’s power thousands of miles away from home. Colonial powers used their navies for conquest, logistical support and plunder. In modern warfare where technology and weapon systems are universally available, the ability of a ship to remain undetected to the enemy is vital- and so the vital importance of stealth ships.

Ships can be detected by the following means

• Visually - with the naked eye or by satellites or spotter aircraft. Some aircraft, like the Orion or the AWACS, use very advanced technology.
• Radar – A WWII invention, useful at sea over a few hundred miles at most.
• Sonar – essentially for submarines.
• Infra-red – especially for missiles, some of which zero in on sources of heat.

Stealth technology uses design, material and advanced technology to ensure that a warship avoids detection by electronic systems. This is a constantly evolving process, as anti stealth systems are being simultaneously developed across the world.

A stealth ship, therefore, aims at becoming invisible to Radar, Sonar and Infrared systems. Radar detection is one of the hardest to counter; the aim of stealth technology being to reduce the cross section of the radar echo received by the enemy (RCS, or Radar Cross Section) so that the echo tends to merge with the clutter (background ‘noise’) on a Radar screen. Radar absorbing material, honeycomb or ‘tumblehome’ designs and modifications in aerodynamic construction help towards a ship becoming more ‘invisible’ to an enemy’s radar systems.

Stealth technology as it applies to SONAR consists primarily of reducing a vessel’s acoustic signature. Although submarines have been doing this since the days of the Cold War, recent design improvements have significantly reduced acoustic signatures to an extent where a submarine can be absolutely ‘silent’ to an enemy seeking to ‘ping’ it by Sonar.

Infra red systems are countered in stealth technology by masking the sources of heat on the vessel, the main source being the machinery space or the Engine Room.

Ever since around 2004, the Swedish Visby Corvette has been ahead of its competitors in technology and design, and, by extension, is arguably the most invisible naval ship around. Constructed with carbon fibre, it has an angular design to reduce the RCS considerably. Designers claim that the RCS can be reduced further (to about 99%), effectively reducing its detection range considerably) with the use of retractable weapon systems, although they are understandably tight lipped about revealing too much.

Engineers know that avoiding right angles during construction reduces RCS hugely, as these angles reflect radar beams to a much larger extent. So they avoid right angles as far as possible to reduce radar signatures. Many use ‘secret angles’ to minimise RCS, the whole idea being, as one designer told the BBC, “ to make it look like it is not a big ship.”

The Visby claims to be undetectable by electronic means eight miles away in a rough sea. It does 35 knots, and is designed for mainly coastal patrolling and warfare.

Besides the Swedes with their Visby class (an acknowledged leader in the field), other countries which have stealth or ‘invisible’ ships include the US, British, Dutch, Finnish, Singaporeans, Norwegians, Indians, French, Chinese and the Germans.

All photographs from http://news.bbc.co.uk/2/hi/in_pictures/3770969.stm

Diagram of the Visby from http://www.naval-technology.com/projects/visby/images/visby4.jpg