The Naval Ordnance Test Station, a field station of the Bureau of Naval Weapons, has utilized San Clemente Island since 1949 as a base for development testing and evaluation of underwater ordnance. To meet a steady increase in the demands for the services of the San Clemente Island ranges, the Station has expanded its facilities and arranged for other island services and support as they have been needed. This development of the underwater ranges was under the direction of the Bureau of Ordnance and with the co-operation of Commander, Amphibious Force, Pacific, who exercised management control of the island until April 1959, and Commander, Naval Air Station, North Island, who assumed control at that date.
San Clemente Island, located 55 miles off the southern California coast, is about twenty miles long and from one to four miles wide. At the northern end is the auxiliary landing facility used for training flights and for flying in personnel and light equipment. Wilson Cove, the only housing area on the island, is on the northeast coast. Along the east coast extending south from Wilson Cove is a missile range developed by the Naval Ordnance Test Station, with shore and underwater launchers. The south end of the island, particularly Pyramid Cove, is used as a Navy bombardment area. On the hill above the east end of Pyramid Cove is the Observation Post used by the Gunfire Support School teams from Coronado to spot targets in conjunction with bombardment exercises. On the southeast corner of the island is an area used for training exercises by the Underwater Demolition Team from San Diego.
San Clemente Island was discovered by Cabrillo, a Portuguese explorer in the service of Spain, in 1542 and was given its present name by Viscaino nearly a hundred years later. There was a sizable Indian population in those days, a people with a fine physique and a culture superior to that of the aborigines on the mainland. The dissolution of this race began with the coming of the white man, and no one knows when the last natives left the island. But San Clemente is still teeming with life, though it is not strictly indigenous. At least 2,000 wild goats roam the ridges and canyons and hide in the caves formed by the cooling lava in prehistoric ages. A few grey fox and wild boar may be found; and wild cats, descendants of the house tabbies brought by the early sheep ranchers, are periodically hunted in order to protect the quail. But for an extremely interesting coverage of the island’s history since the discovery by Cabrillo and of the animal, bird, marine, and botanical life, the reader is referred to an excellent article in the October 1942 Proceedings.
In the Wilson Cove area are many of the NOTS buildings. The operations building, on the waterfront near the main pier, is a 40-by- 100-foot structure containing a torpedo shop, an instrument- repair and check-out room, a photographic darkroom, and a small machine shop. Just south of the operations building is a large building used as a garage, shared by the Air Force and NOTS.
In the housing area overlooking Wilson Cove are four buildings used by NOTS, one converted BOQ which houses approximately 95 men, two forty-man barracks, and a mess hall. The central communications for the NOTS activities on San Clemente Island are presently located in the BOQ. The remainder of the buildings house the administrative and maintenance groups for NAS, North Island, and personnel from the 670th A.C. & W. Squadron from Norton Air Force Base, who man a radar station on the island.
The Wilson Cove pier and the ramp adjacent to the pier are used to off-load supplies and serve as the logistic key to the island. The bay in front of the pier is used as a landing area for the amphibian planes that carry NOTS personnel to the island.
Just south of Wilson Cove on the east shore is the missile launcher that was used for the RAT program and is currently being used for new weapons development firings. Complete facilities for missile assembly, checkout, and ready storage have been constructed adjacent to the launcher. South from the launching pad on the tops of the high cliffs are located more than 25 stations for photographic and electronic instrumentation of test flights. These stations extend to the southeastern tip of the island. The high cliffs with deep water close to shore provide a unique test area.
In a cove just south of the missile launcher, a concrete pad has been placed on the ocean floor. About this pad has been assembled the Polaris Pop-Up test facility. The Pop-Up program consists of experimental subsurface launchings of the Polaris missile. A launching tube simulating the Polaris submarine launcher has been installed in a buoyant launch vessel. During test operations the checked-out missile is loaded into the launching vessel, the tube is prepared and checked-out, and the launcher vessel is then lowered to the underwater pad by cable through sheaves on the pad to a winch on shore. Buoyancy tanks in the side of the launcher are flooded to stabilize the launcher during lowering and while resting on the pad. Fallback nets are then placed above the launcher to catch the missile as it falls back into the water and protects the launcher for impact by the missile. The fall-back system consists of two slightly overlapping harbor defense nets buoyed in a horizontal position in the water. Prior to time of launch the inner edges of the two nets are pulled apart, providing a path for missile ejection. As the missile passes through the net in its upward trajectory, the nets are released to provide a closed system for catching the missile upon its return to the water.
For certain underwater ejection tests of the Polaris missile the fail-back to the water and into the nets is undesirable due to the high loads experienced at impact. For these tests a special crane, dubbed Fishhook, has been constructed to catch the missile at the apogee of its unpowered flight. This crane supports the proper rigging and take-up mechanism to reel in a cable attached to the missile at the same speed as the missile’s upward travel. When the missile reaches its high point the cable reel stops and the missile is suspended at that point with no downward trajectory. Fishhook has been used in many tests with satisfactory results.
A YFN barge has been converted for use as an instrumentation and monitor barge. More than ninety channels of internal instrumentation are recorded within the missile, and 150 channels of external missile and launcher information are cabled to the monitor barge. Three underwater television cameras, with monitor screens on board the barge, are used to observe the lowering of the launcher and the checking of the instrumentation and firing lines by divers. Underwater cameras as well as underwater television record the firing of the missiles from the launcher and the initial underwater trajectory. Cameras are installed on shore and are operated to record water-exit angle, acceleration, and initial air trajectory of each round. A Navy net tender (USS Butternut, AN-9), stands by to handle the launcher and assist with recovery of the missile. The net tender is also available to place and care for the fall-back net, and an LCM driving barge is located at San Clemente Island during firing periods to handle equipment for the divers. Other small craft are available to clear the area of unauthorized.
A staging vessel fabricated from two YFM barges to form a catamaran-type hull structure is used as a missile final checkout and loading area. This vessel has a fifty-ton crane to handle the missile, and supports to hold the 200-ton launcher in place during checkout and loading. Approximately eighty men are stationed on the island to operate the equipment during the firing periods.
On the hill overlooking both the shore and underwater launch sites is a telemetry ground station and a radar plotting station.
A second underwater launching system in use at San Clemente has a ship-suspended platform. This facility consists of an LCU which has been modified to include a large well through the main deck, an instrumented platform to be lowered through the well, and the necessary hoists and cabling to support the platform. A Mk-8 gyro compass and a vertical gyro mounted in the platform provide orientation information. A torpedo tube for launching experimental missiles can be mounted on the platform. The platform may be lowered to great depths, the data and fire control instrumentation being transmitted to the LCU via multi-conductor cables stored on large reels. This facility may be moved to any test site under its own power. For underwater launchings, this vessel is moored in the waters just south of the Pop-Up site, so that full advantage may be taken of the shore-based instrumentation. Acoustic transducers are often attached to a three-axis mount on the suspended platform for underwater acoustics research programs and torpedo guidance panel development.
Certain non-buoyant items of underwater ordnance require recovery of the water entry payload during full scale development tests. To provide an area to test these weapons in their proper environment, but yet provide for recovery, a range was developed along the northwest coast of San Clemente Island. This range, known as the Eel Point Range, provides suitable underwater areas, between fifteen and thirty fathoms, where divers may recover the expended payloads.
The Bureau of Ordnance has required that an area be established where warshot torpedoes may be fired to check the functioning of the exploder and the warhead under full explosive conditions. A test range was developed by NOTS to test captive torpedoes in warshot condition so that the unit will impact on every firing. The range consists of a barge moored off shore with a cable running to a shore anchor. A steel target plate is attached to the cable near the shore end. The torpedo, suspended on the cable, runs along it to impact the target. This sets off the exploder which in turn fires the warhead. This operation is photographed by cameras from shore. The program requires that divers be on hand to re-rig the cableway after each firing (since the warhead demolishes the plate and breaks the cables) and to recover the torpedo in case of a dud firing. The torpedoes are prepared in the operations building at Wilson Cove and the explosive warheads are stored on the island.
The aircraft-torpedo development programs require an area where full-scale air drops of torpedoes may be made under controlled conditions. San Clemente Island has been used for such tests since 1950. The combination of shore-based cameras and a portable hydrophone range provides pertinent information on the functioning of aircraft torpedoes when delivered from fixed-wing, jet, or helicopter aircraft.
The torpedo workshop in the operations building at Wilson Cove is used for a post-run check of the torpedoes after they have been recovered at the end of their runs. Small boats recover the torpedoes and act as a general security patrol to clear the area before the drops.
Some of the weapons tested during their development at San Clemente Island are the Torpedoes Mk 13, Mk 32, and Mk 43 Mod 1, the weapons ABLE, RAT, and Polaris.