The land testing provided a severe test of the anchor's structural 

 design. Upon firing, the launch vehicle would recoil upward through 

 the wood support beam, rising as high as 200 feet (60 m) in the air 

 before dropping to the ground. Although the accelerations during firing 

 on land are similar to those attained underwater, the impact of the 

 launch vehicle as it lands after its recoil is much more severe on land 

 than in the water. No failures of major components occurred, and the 

 minor damage that was sustained was entirely due to the launch vehicle 

 impact, not to the actual firing accelerations. This problem is elim- 

 inated when the anchor is used underwater. 



The ballistics performance indicated an under estimation of gun 

 barrel pressures for each charge weight. Subsequent tests of the par- 

 ticular lot of propellant used indicated considerably different burn 

 rate characteristics than are normally expected for M6 propellant. 

 Rerunning the computer simulation with the new values accurately pro- 

 filed the test pressures. Predicted and actual pressures are plotted 

 in Figure 9. The pressure-time curves for the tests indicated a very 

 smooth pressure buildup and release as is desirable. Examples of the 

 pressure-time curve are given in Figure 10. 



The new burn rate values do not seriously affect anchor performance 

 above 10,000 feet (3,100 m) of water depth. However, below that depth, 

 the propellant is completely burned before the piston leaves the gun 

 barrel. No additional propulsion is available to drive the piston from 

 the gun barrel; thus, as the depth increases, the ambient water pressure 

 reduces the net propulsive force. The result is the decrease in projectile 

 velocities below 10,000 feet (3,100 m) apparent in Figures 6 and 7. For 

 anchoring below this depth a slower burning propellant must be used. 



It was unnecessary to reduce the high-speed film to obtain velocity 

 and acceleration data, because the agreement between predicted and actual 

 results for the propellant system was good. 



Sea Tests 



The first sea tests of the 10K anchor were recently completed 

 at the MILS cable installation at Midway Island. The anchors were to 

 be used only for testing purposes, but a YTB scheduled to install heavier 

 20K anchors was withdrawn; therefore, the 10K anchor had to be used 

 to provide a temporary four-point mooring for the ARS Bet-iver . The sea- 

 floor was coral, and very little was known about its strength charac- 

 teristics. Only four sediment flukes were available; therefore, they 

 were slightly modified on site to accept the downhaul cable directly 

 into the fluke. 



The anchors were installed from a 35 -foot (10.7 m) workboat. The 

 anchors were transported to the site slung from a small A-frame off 

 the bow (Figures 11 and 12). A 6-ton (5.45 metric-ton) salvage winch 

 was placed in the well deck, and it was used to control-lower the anchor to 

 the seafloor. Each anchor was installed with 1.45 pounds (657 gm) of 

 M6 propellant. A 1 x 2-foot (31 x 61 -cm) fluke was used for the first 



11 



