February 15, 2012:
Australian submarines are being fitted with a new and improved radar absorbent material (RAM). The new, locally developed RAM is more easily attached to the sub, especially odd shaped structures like masts. The new RAM is also more robust. The new Australian RAM means that subs using it will spend less time sidelined for RAM repairs because RAM gets beaten up and damaged by time at sea.
RAM has been around since 1943 (World War II) and is essential for diesel-electric boats (like the Australian Collins class subs) which spend a lot of time on the surface, or just below surface, using their noisy diesel engines via a snorkel device that breaks the surface to take in air and get rid of the engine exhaust. Snorkels can be spotted by modern maritime patrol aircraft radar and many nations are getting more search planes. The noise of the diesel engines can easily be picked up by other subs. Moreover, using a snorkel is often uncomfortable for the crew as the air intakes automatically close if the weather is rough on the surface and waves get close to the air intakes. Using RAM on the snorkel device also makes it difficult for aircraft radar to spot the sub. But if the sub is in an apparently safe area it's preferable to run on the surface.
Diesel-electric subs are increasingly being equipped with AIP (air independent propulsion) systems. This enables the sub to stay under deeper and longer, thus making the sub harder to find. AIP allows the sub to travel under water for more than a week at low speed (5-10 kilometers an hour). But even with AIP, the subs will still spend some time on the surface and they still need RAM.