The Thousand~Year Peace is not yet here. As we await its coming the wealthier nations prepare for war. No one knows how or when the ex~Soviet Union, Iran and other nations plan to employ the submarines they are acquiring. These are not leftovers from the 1940s. They are modern long range submarines equipped with advanced propulsion, electronics and weapons. It behooves the United States to proceed with the development of a true submersible capable of combatting these foreign submarines from beneath the surface.
SSN-X4 Principal Features
SSN~X4 is a hypothetical nuclear powered submarine of moderate size-about 1 ,200 tons. Her primary target is an enemy deep diving submarine. Her design incorporates a number of major features provided by advanced technology. These give her the ability to close targets while fully submerged, and attack with rockets from beneath them. Principal features are:
- An electro-optical system equipped with optical sensors to allow the attack party to observe and attack targets from the depths.
- Two batteries of solid propellant underwater rockets capable of blowing holes in the bottoms of submarines and surface ships
- Computerized automated tracking, maneuver and optical tire-control systems to give her the ability to safely approach and attack while fully submerged
- The internal arrangement shown in Figure 1 places the control room in the bow. As shown in Figure 2, the proximity of all members of the attack party permits easy viewing of underwater imagery on large screen displays, other tactical displays, and improved intercommunications.
- A very accurate inertial navigation system
- Modem sonar equipment for long range target detection and classification, and blu~green laser equipment for aerospace communications.
Attack from the Depths
The experimental SSN-X4 completed scheduled engineering tests in August 1999 and then began system tests to demonstrate her effectiveness as an ultra modern, anti-submarine submarine.
Surface Ship Attack. Upon completion of high speed and deep submergence runs, SSN-X4’s Commanding Officer sets course for the test area south of San Clemente Island. The target group was already on station. It was composed of an unmanned target (an old destroyer taken out of the back channel), an escorting destroyer, and a cruiser. The target was rigged for remote radio control of speed and steering by the escorting destroyer. The cruiser provided accommodations for upward of 50 observers from both shore and sea commands. Shortly before noon the 000 of the submarine raised the non-penetrating electro-optical periscope for a sweep around the horizon and detected the tops of the target group about eight miles to the east-southeast. The CO ordered “battle stations, rocket”, and instructed his Exec to set up the target group on the tracking system console. As prescribed in the test plan, the Exec set target group speed as 15 knots and course 27fJJ. He also entered the estimated range to the target as 16,000 yards.
Initial Agproach Phase. The target led the group. Her controlling escort was a mile astern on her starboard quarter and the cruiser a mile north of her on her starboard beam. SSN-X4’s tracking system maintained an independent track of each ship. As soon as the Exec announced that the problem had been set up, the CO cut in the track display on his own console. He advanced the ship movements in time and determined that at 15 knots he would cross ahead of the cruiser in about 15 minutes. He then selected point ahead of the cruiser and about a mile north of her project-ed track as the terminal point for the initial phase of the approach. Readjusting the display to real-time..to display the current situa-tion, he specified depth 300 feet, speed 15 knots, and turned the problem over to the automatic control system’ for execution of a completely submerged approach.
Track displays on the consoles of the CO, Exec, Tracking and Weapons Officers showed miniature profiles of SSN-X4 and ships of the target group, together with their generated tracks, bearing lines and distances from the submarine to the ships of the target group. This displayed data allowed the attack party to easily follow the approach as it developed. Some minutes later sonar detected the escort destroyer’s echo ranging, and sonar bearings permitted a minor adjustment to be made to the target setup.
The Attack. The automatic control system completed the run to the initial terminal point as specified. At that time the CO reduced speed to five knots. Shortly thereafter, sonar bearings confirmed that the submarine had passed ahead of the cruiser at a generated distance of about 6,000 yards. Six minutes later a blurred image of the target’s underwater hull was picked up by the port side optical sensor at a range of 3,200 yards. Optical bearings were then fed into the tracking system. Image sharpness increased as the target drew nearer, and a range of 1,500 yards was obtained with the blue-green laser range finder. The optical system was then put into the automatic tracking mode to allow target azimuth and elevation angles to be directly entered into the fire control system to generate data for aiming the rocket battery.
The Captain directed the Weapons Officer to arm four rockets of the after battery, and to fire on automatic when the submarine arrived at a pre-planned position directly beneath the target. The automatic control system maintained the submarine’s attitude, course and depth precisely as the moment for rocket launching neared. A slight jar was felt when the rockets fired. The Weapons Officer reported, “four rockets launched”, and the Captain ordered “ahead full” to clear the area beneath the damaged ship. View of the target was temporarily obscured by rocket exhaust gasses. However, the roar of the rockets’ exhaust as they sped to the target could be clearly heard throughout the submarine, as well as from sonar speakers. Within two seconds the warhead charges were heard to explode as they hit the hull.
Observers on the cruiser and escort destroyer saw the forward half of the target fold back against the stem in a hairpin like bend. Then the bow rolled onto its sides and both halves sank. The submarine attack party also witnessed the hulk sink into the depths on their large screen displays.
Anti-Submarine Attack. An aged diesel submarine had been selected as target for this attack. The target was trimmed for near neutral buoyancy and suspended from large buoys at bow and stem. This allowed it to drift with the current at a depth of 200 feet. Antennas on the buoys provided a means for radio control of a high pressure air bank within the hull so that ballast tanks could be blown if necessary to resurface the submarine.
A P-3 ASW aircraft equipped to communicate with the submerged submarine by blue-green laser link initiated the exercise by transmitting an “Execute”. The sky was clear and the sun was high. Starting at a range of 6,000 yards from the buoys, SSN-X4 approached the target from its beam at speed 10 knots, depth 300 feet. Speed was reduced to five knots and depth increased to 450 feet when the electro-optical system detected the target at a range of 3,000 yards. The attack was conducted in a manner similar to that made on the surface ship, except that only three rockets were launched when beneath the target. The implosion caused by high pressure sea water rushing into the fractured hull caused it to break into a few large pieces which quickly sank.
Underwater rockets are not new. During World War II the Germans began development of a submarine launched underwater rocket with the code named URSEL. It was designed as a U-boat weapon of last resort. Four rockets mounted on rail launchers were affixed to a trainable base located in the U-boat’s superstruc-ture. The rockets could be launched at depths up to at least 50 meters (164 feet), and possibly up to 100 meters (328 feet). Rocket speed was 60 meters (190 feet) per second, enabling one to hit its target a second or two after launch. The proposed tactic was to fire the rockets simultaneously as the attacker approached within range. The rockets were ignited electrically from inside the U-boat when a tilted topside hydrophone indicated a favorable angle for firing. Rockets that missed the target were designed to self destruct after broaching the surface. Rockets launched from a depth of 50 meters showed approximately 50 percent hits on a square four by four meter target. Samples of URSEL and a smaller underwater rocket were taken from German development sites for further examination after the war.
In the United States in the early 1950s, a group led by the noted hydrodynamicist Calvin Gangwer of Aerojet Azusa con-ducted limited tests of underwater rockets. As I recall, 5″ HVARs were fitted with fins to provide spin stabilization. Rockets launched in a horizontal trajectory from a platform at a target off San Clemente Island showed good accuracy and considerable promise. However, the project was soon cancelled.
All animals, including human beings, are able to see when light energy from all, or portions of, the electromagnetic specturm impacts on light sensitive receptors in the eye. In this discussion, vision refers to that portion of the spectrum extending from infra-red to ultra-violet. This is not to say that radiation from other portions of the spectrum cannot be observed. Although light energy suffers very little attenuation in air and space, attenuation increases greatly when it travels through sea water. Thus, the unaided ability of the human eye to see in that medium is quite limited.
Except for Jacques Cousteau, Auguste and Jacques Piccard, Robert S. Dietz, Nils Jerlov, a few other scientists, plus scuba divers, and salvage experts, there has been little interest in seeing far beneath the surface of the sea. Most submariners probably consider the range of vision too limited to be tactically useful because they are unaware of the great advances that have been made in electro-optic technology which now greatly extends the range of underwater vision.
Some Facts About Underwater Visjon Capabmty. Four major factors determine our ability to see objects through sea water. The first is the amount of light emanating from the body we want to see. Th second is the ability of light to penetrate the water separating us from that object. The third is our ability to capture and utilize the light emanating from the object, and the fourth is the clarity of the water.
Objects are visible when light is emitted by, or reflected from them. In general, underwater hulls of ships will be seen when light from the sky is reflected from their hulls. Sunlight on the water is the major source of this light. The sun is also the source of light reflected from the moon and stars, and indirectly the source of chemical and biological light produced by animal and plant life in the sea.
Major factors determining the degree to which objects are illuminated by light from the sky include the position of the earth in its orbit about the sun (season of the year); the altitude of the suo or moon; the latitude of the object to be viewed; and the degree of cloud cover, haze, fog and overcast. Aside from light reflected from a ship’s hull, the glow of bioluminescence resulting from the passage of ships can sometimes be seen. In both cases we are concerned with the penetrability of this light through ocean water to a light collector.
Approximately 60 percent of the attenuation of light energy as it travels through sea water is due to scattering and 40 percent to absorption. Water has only one important frequency window in which attenuation is minimum. It lies in a narrow band of blue-green light near 480 mu (0.480 microns or millionths of a meter}. At what depth can the unaided human eye detect light? It appears from the observations of William Beebe in the 1930s and Jacques Piccard in the ‘5os and ’60s that on a bright sunny day in clear water, light grows dim at about 500 feet. (See references 2 and 3.) Figure 3 is a copy of a photograph of a school of tuna taken under natural light conditions at a depth of 200 meters (656 feet) during the Gulf Stream drift-cruise of the mesoscaphe Ben Franklin., Light fades to a faint hint of death gray at about 1,500 feet, and total darkness sets in at about 2,400 feet. In the open ocean, water clarity does not seem to be a serious problem. The above observations have been made through portholes in underwa-ter vehicles, and do not reflect what can be accomplished by using light amplifiers, large light collectors, and computer aided image enhancement.
The Sub-Surface Attack System Design
Underwater Rocket Weapon System. The primary target is an enemy deep diving submarine. Rocket range should be about 1,000 feet, and the payload must consist of a conventional shaped charge with adequate power to fracture the hull of such a subma-rine upon contact. The rocket battery should be capable of launching at least four rockets singly, and in salvo. The launcher must be controllable in train and elevation, and retractable within the envelope of the streamlined hull or superstructure. Launcher reload capability is highly desirable.
The ElectrOptica) System. In view of the severe attenuation of light in sea water, an electro-optical system must be employed to replace the human Mark I eyeball. Without trying to design the electro-optical system in detail, it must function in the blue-green portion of the spectrum and should generally consist of one or more of each of the following: a controllable large aperture light collector (camera}; a light sensitive element to convert light energy to electrical signals; fiber-optic cabling for the transmission of electrical signals; a light amplifier (photomultiplier}; and a receiver with imagery display capability. The system should Relatively simple cameras are used in underwater photography and remote underwater television. Similarly, light amplifiers, filters, fiber optic cables, and computer controlled color displays are available. These represent the basic technology that must be employed in developing equipment for our special application. Considerations for design are:
- Light Collection. The ability of a camera to collect light energy is largely dependent upon the area of the collector lens. The area of a 10 inch diameter lens can collect 100 times more light energy than a 1 inch diameter lends. Periscopes are generally poor light collectors. Our under-water cameras need large collector lenses.
- Image Display. A computer controlled color display should be employed to allow the user to select the best presentation for the intended use. Imagery should be displayed in a manner to show the angular direction and movement of the line-of-sight in orthagonal reference planes. The display should allow the operator to make angular measurements for target tracking, fire control and other purposes.
- Fire Control Considerations. The very short wave length of blue-green light can provide accurate bearing data. The system should provide for automatic target tracking based on optical bearings. A blue-green laser range finder should be provided for precise range measurements. A simple lead-sight type of aiming device should be adequate because of the short time of flight of the underwater rocket (about 1 to 3 seconds), the expected slow speed of ship and submarine targets (20 to 50 feet/second), and their great inertia.
- Potentially hostile nations are acquiring modem long range submarines.
- Technology exists to support development of an experimental submersible equipped with the advanced electrooptical/rocket attack system described above.
- Our Navy should immediately begin this development in order to improve U.S. ASW capability. Secondary development objectives are training of personnel in the maintenance and usage of these new types of equipment, and the development of tactics.