CLOSE IS NEAR ENOUGH

[Music] Oh [Music] [Music] [Music] 47 major shifts 52 submarines countless human lives this was the toll exacta drum the united states navy during world war two by underwater weapon the war introduced sophisticated weapons and delivery systems powerful torpedoes depth charges ingeniously sensitive minds all these can sink ships the natick discovered an even more disturbing factor in this war a ship does not have to sink to be put out of action direct exposure of the hull to a near contact explosion and cause hall rupture and immediate flooding or even relatively distant designation and severely damages you underwater explosion can shake loose vital equipment including propulsion systems it can produce damaging vibrations in delicate electronic systems it can make weapons completely inoperable a direct hit therefore is not necessary to produce significant damage close is near enough with this reason the Navy established the underwater explosions research division in 1946 you erd was chartered to develop technology that would allow chip designers to strengthen the hulls of ships and submarines and to harden shipboard installations the division also was to provide guidance to weapon designers on how to improve underwater weapon performance ships from the Navy's growing mothball fleet were subjected to underwater explosions simulating actual weapon attacks early research was concerned with improving the underwater explosion resistance of the whole structure while advancing knowledge of the basic phenomena and target response systems to be evaluated were installed on the ship's instrument and subjected to explosions on the basis of these studies effective structural systems were developed to protect aircraft carriers from torpedo attack what happened during another water exposure how do these forces affect the surroundings an explosion under water produces a highly compressed gas bubble the bubble generates an initial shock wave followed by secondary pressure waves as the bubble pulsing on the surface the shockwave causes the formation of a relatively low spray goal the pulsating bubble then produces a series of clues [Music] the gas bubble is attracted to solid objects under the water once drawn to a target it pulses on the structure causing severe local pressure the initial shock wave can damage your ship the pulsating gas bubble following close behind strikes the weakened hull causing even greater damage explosions beneath the ship pose additional hazards they can lift the ship on the first post forming a void beneath the hall as the ship begins to drop forcibly into this void the second pulse erupts with disastrous effects experiments with a complete shift serve a dual purpose they provide actual measurements of weapon effects and they allow designers to identify weaknesses so that more effective protection can be included in future designs from such trials you erd engineers can measure the shock variations throughout the ship they can observe how men react to severe detonations what occurs in engine rooms to piping and propulsion systems they see the reactions of electronics gear and the response of the structure itself the success of these experiments depends on the realistic simulation of a combat environment and on the ability of sensors to measure target response an underwater explosion takes only seconds and much too fast for scientists to observe the phenomenon without special equipment they could not isolate vulnerable areas but would see only the resulting damage reliable instrumentation therefore is vital since this is the only way to reconstruct events leading to equipment and hull failure high-speed photography can slow the action with a camera set at 2400 frames per second time can be expanded substantially this produces a clear visual record for study [Music] other measurements are made with velocity meters strain gauges pressure gauges and accelerometers all are monitored by high-speed recording equipment these devices must be sensitive enough to measure high-frequency oscillations but cannot be damaged by severe shock motions much of the instrumentation used in these experiments was developed or adapted by u er D electronic engineers after targets are instrumented cables are deployed to record measurements in some cases a watertight instrumentation box is installed on the target stir explosive cable cutters can disengage it remotely to the target sink too soon [Music] the Box serves as a terminal four gauge wires from the target to the underwater explosions research bars the recording center for all instrumentation the barge operated and maintained by you er D is the focal point for experiment rather than the Norfolk Naval Shipyard or far out at sea although it has no propulsion system and must be towed to experiment sites the barge can support research parties in remote areas for up to 30 days it has hotel facilities workshops and equipment to handle models explosive charges and other heavy gear required for its fellow the recording centers aboard receive information from instrumentation installed on the target the center's are isolated from severe shock motion by an elaborate suspension system gauge response is reported on magnetic tape [Music] the recordings are transferred to clots which can be digitized or placed on punch cards these time histories then are plotted by computers two scales suitable for detailed analysis from this data engineers make recommendations to ship and weapon designer their experimental studies provide the much-needed verification of new design techniques due to the serious consequences of hull fracture or machinery phasers the explosion resistance of modern submarines is even more important initially the explosion resistance of existing hall designs was studied by using large scale models or complete submarines that have been declared surplus in this case the explosion resistance of a deeper diving hall design was investigated a section of the new design was inserted in an existing hall at the same time engineers studied the ruggedness of internal installation [Music] research of this nature as enable designers to propose equipment that is more shock resistant today you erd engineers use the submarine shock simulation vehicle to evaluate the strength of submarine installation the vehicle consists of a full-scale compartment of a modern submarine with fore and aft ballast tanks the usefulness of this approach was demonstrated successfully in 1970 when selected machinery installations and piping were given a comprehensive shock evaluation complete systems can be installed in the compartment components are instrumented to record their response [Music] pages are wired into recording equipment vehicle is submerged remotely from the bar vehicle was subjected to a full range of shock severity equipment interactions were realistic most significant the ruggedness of systems as a whole was certified in future trials the submarine shock simulation vehicle will be used to investigate the shock resistance of delicate weapon delivery and electronics due to the inherent difference between responsive a submarine and a surface to underwater explosions a different type of platform for surface ship equipment is required [Music] gas turbines diesel engines electronic and weapon equipment are realistically mounted on floating shock platform after instrumentation and connection to the barge the platforms are subjected to a series of underwater explosion the shock platforms can be used repeatedly they provide an economical class way to certify systems for surface ships at times full-scale trials with large ships are necessary usually to satisfy requirements from weapons designers [Music] such targets are taken from the mothball late and prepared for sinking instrumentation is placed at specified areas throughout the ship an instrumentation box is installed on the stirrer [Music] engineers make plans for the experiment at sea they require coordination of many support units leaked hugs observation helicopters and numerous military installation experiments like this in a realistic environment are necessary for the development of new efficient warheads a particular concern is the minimum amount of explosive and the best location under the hull for defamation [Music] such a combination can lead to immediate sinking or severe weakening of the hull juror leaving the ship unable to perform her mission this ship sank a few minutes after the explosion she became part of an artificial reef to benefit the fishing industry the fracture toughness of new high-strength steel is probed with large scale models at both shallow and deep submergence since our submarines must dive deeper in the future such examinations must be conducted before using the material in full scale construction submarine hull penetrations vital to the integrity of the watertight envelope are verified in full-scale submarine section enclosures of the submarine portion which is very difficult to analyze it must possess the same explosive resistance as the rest of the structure models of enclosures like these small-scale hemispheres provide much valuable information the models are fabricated then mounted on special devices on the bar they are subjected to explosions at various depths in addition to such research the division responds to fleet requirements it investigated the explosion resistance of the mark 105 a helicopter towed hydrofoil used as a minesweeping device before the mark 105 could be used in shallow waters the Navy wanted to know how resistant it would be to exploding mine the hydrofoil was assembled on the barge and placed in the shipyard basin simulated mines were set off it ever decreasing distances [Music] although the mark 105 was tested to near destruction Engineers concluded that it would meet the demands for a high-speed minesweeper in shallow waters it was used extensively in Vietnam at the close of the war fast new ships and platforms are presenting even more challenges to you er D and the high intrinsic value of these multi-mission craft will demand special protection explosions resistance can be engineered into conventional ships and submarines but new pract like surface effect ships and hydrofoils present problems of a different nature possibly more sensitive to the plume than the underwater shockwave chip designers must keep pace with the development of sophisticated homing influenced underwater weapons and as long as such weapons are you research like that provided by the underwater explosions research division will be required to cover this minute only through such investigations and we defend ourselves against the underwater threat and