There are and will always be, secrets kept by the military. These secrets could be about anything. I myself have always been fascinated by submarines. I always wondered why we never had a huge submarine that could carry aircraft. Heaven knows they have been proposing one for many years. What makes this even more curios is the fact that the Japanese had submarines in World War II that could store and launch up to three planes. But lets get on with the secrets.

ASDS
Source: US Navy

Artist's Conception of entire ASDS
Source: US Navy

There was a secret US program called "Advanced SEAL Delivery System" or ASDS. The purpose of this program was to develop a delivery system for SEAL commandoes using a small submarine type vehicle. Small being a relative term here. I do not know the actual size of the vehicle but it is said to be the size of a house trailer, so I believe this would be somewhere in the 60 foot long area. It has to be very quiet, as it the term used to define submarine noise. The program fell behind target by over 6 years. This in itself is bad enough, but it was supposed to cost about 525 million dollars for six units but the government states the cost is now over 2.3 billion dollars, but in fairness the contractor says when all the bills are in, it will be a lot less. It always seems that anything that is estimated in the mid hundred millions lands up using the "B" word. Problems don't end here, the batteries that will power the vehicle are not powerful enough, forcing the vehicle to surface too early. The contractor is Northrop Grumman Corporation. Many blame the government for the cost overruns and delays. They say these were caused by the Navy changing requirements and just plane expecting too much. These units can be carried by certain of our existing submarine fleet. The specs on the system were released by the Navy and are as follows:
Range 125 NM
Cruise Speed 8 knots
Crew Size 2
Passenger Amount 8 SEALS with equipment
The Navy took delivery of the units in June of this year (2003).

Kursk
Source: PravdaRU

The Kursk was a Russian Nuclear submarine. It sunk under mysterious circumstances. There are many different stories about the sinking of this boat. At first, there were claims that a foreign sub had somehow sunk the Kursk. It was thought that the two boats collided. The first Russian warship on the scene was the Peter the Great. Several stories persisted that the Peter the Great had launched a cruise missile in a test and it had hit the Kursk, sinking it. But there was a problem with this. The Kursk was not on the surface and the missile cited, can not hit submerged targets. Then there was a takeoff on the cruise missile story which claimed that the Peter the Great was doing missile tests. The story states that the ship launched missiles three times. The first two launches went fine, but the third launch sent a missile into the water with a resulting explosion and mushroom cloud. This story was given out by an unknown source and the full story can be read in the English edition of The Moscow Times. The last story might be the true one, but who knows? It states that the Kursk was testing a new type of torpedo. Supposedly two civilians were aboard to conduct tests. The story goes on further to state that an explosion took place aboard the Kursk, it was a torpedo, and the hull was ripped open. Western sources think the torpedo was an antisubmarine device.

Seawolf
Source: US Navy

Money was requested to update the Seawolf class of US submarines. A new acoustic system is to be installed on several of the subs. This will require the subs to be lengthened. In 1999 the navy received funds to modify one seawolf. This was the Jimmy Carter. The new system will detect noise in four areas:
1 .Demultiplex input data streams and distribute to receiver tasks.
2. Detect broad-band acoustic waveform and generate detection data block.
3. Detect leading tone of FSK waveform and generate detection data block.
4. Detect digital clock pulse and generate detection data block.

Victor III Submarine
Source: PravdaRU

The Chinese navy may be acquiring Russian submarines as a stop gap measure before building their own nuclear submarine the Type 093. The 093 is based on Russian technology and western sources compare it to the Russian Victor III. The Victor III is a deadly submarine indeed. It is very fast and very capable and has 21 inch torpedo tubes. Along with the subs, rocket powered torpedoes are said to have been purchased. These have a velocity of 200 knots, which is about five times faster than a conventional torpedo. As of this moment there is no known 100% reliable defense against them.