Underwater Supersonic Objects

dailymail |  As swimmers know, moving cleanly through the water can be a problem due o the huge amounts of drag created - and for submarines, this is even more of a problem.

However, US Navy funded researchers say they have a simple solution - a bubble.

Researchers at Penn State Applied Research Laboratory are developing a new system using a technique called supercavitation.

The new idea is based on Soviet technology developed during the cold war.

Called supercavitation, it envelopes a submerged vessel inside an air bubble to avoid problems caused by water drag.

A Soviet supercavitation torpedo called Shakval was able to reach a speed of 370km/h or more - much faster than any other conventional torpedoes.

In theory, a supercavitating vessel could reach the speed of sound underwater, or about 5,800km/h.

This would reduce the journey time for a transatlantic underwater cruise to less than an hour, and for a transpacific journey to about 100 minutes, according to a report by California Institute of Technology in 2001.

However, the technique also results in a bumpy ride - something the new team has solved. 

'Basically supercavitation is used to significantly reduce drag and increase the speed of bodies in water,' said Grant M. Skidmore, recent Penn State Ph.D. recipient in aerospace engineering.

'However, sometimes these bodies can get locked into a pulsating mode.'

Creating a supercavitation bubble and getting it to pulsate in order to stop the pulsations inside a rigid-walled water tunnel tube had not been done.

'Eventually we ramped up the gas really high and then way down to get pulsation,' said Jules W. Lindau, senior research associate at ARL and associate professor of aerospace engineering.

They found that once they had supercavitation with pulsation, they could moderate the air flow and, in some cases, stop pulsation.

'Supercavitation technology might eventually allow high speed underwater supercavitation transportation,' said Moeney.  

China is also developing a'supersonic' submarine that could travel from Shanghai to San Francisco in less than two hours.

Researchers say their new craft uses a radical new technique to create a 'bubble' to surround itself, cutting down drag dramatically. 

In theory, the researchers say, a supercavitating vessel could reach the speed of sound underwater, or about 5,800km/h. 

The technology was developed by a team of scientists at Harbin Institute of Technology's Complex Flow and Heat Transfer Lab. 

Li Fengchen, professor of fluid machinery and engineering, told the South China Morning Post he was 'very excited by its potential'. 

The new sub is based on Soviet technology developed during the cold war.