Volume 50, Number 2 (February, 2007) of Sea Power discusses the Navy's new project to develop a super-fast submersible. Information on exactly how this is to be done is scant, because the research project is in its initial stage. Essentially, the project is to determine the feasibility of using supercavitation to dramatically increase the speed of submersible vessels.

The Navy has awarded Electric Boat with 5.7 million dollars and Northrup Gruman with 5.4 million dollars to investigate the properties of underwater propulsion using supercavitation as a means to dramatically reduce friction and hydraulic drag. There are some staggering engineering problems, yet the Russian Navy reportedly has overcome most of them to produce a torpedo that attains speeds in excess of about two hundred knots.

The term supercavitation refers to the underwater vessel's capability to emit air bubbles at the bow of the vessel in such quantity to produce an air envelope in which the vessel travels. Research with models has indicated that the air pocket can be achieved either by artificially blowing air through a bow diffuser or developing a blunt-nosed craft that would naturally generate the cavitation. Obviously, both of these possibilities seem far-fetched to the practical minded submariner, however, if the Russians can do it, the Navy should do some of its own basic research.

If one ponders the four hundred knot submarine many questions leap to mind that seem staggering. A few of them include:

1. What is the drag effect of expelling air under great pressure through the vessel's bow? Is this not like a jet engine's reversers which have the effect of stopping the aircraft?
2. What shape would a hull take to produce cavitation in the required huge volume?
3. What happens to the emitted air? Does it not surface and leave a giant wake?
4. If the vessel's speed exceeds the rise rate of the bubbles the vessel's stern will also be wrapped in air. In this case would not either a propulsor or standard screw be biting into air rather than water?
5. The same concern is applied to control surfaces. How does one control the super fast vessel?
6. What hydraulic vibrations are to be anticipated at such speeds?
7. Since sea water pressure is inversely proportional to cavitation rate, what depth restrictions would such a vessel have?

These are the obvious engineering concerns, but if one wants to be creative, consider the "blind flying" aspect of having no sonar. Even if sonar could be developed to overcome the commensurate noise, how does one avoid obstacles as such speeds? Of course a periscope would be useless, so how does one navigate?

These are a few of the obvious questions that pop into one's mind at the most casual level, but let us remember that the research project is limited to small vehicles, about the size of a bread box. The Navy's need is to propel a small craft into littoral water where SEAL teams can do their work. The current research does not envision a full size submarine plowing through the water at such fantastic speeds. However, if submarines of the future will be built with such capability, most of us will reflect favorably on the "good old days" of diesel power.