Appendix B 

 OPTIMIZATION OF PROPELLANT CHARGE 



The Naval Ordnance Station (NOS) at Indian Head, Maryland provided 

 NCEL with a launcher system design, propellant selection, and a basic 

 range of propellant charge weights to satisfy a broad range of specifi- 

 cations supplied by NCEL. These specifications included an estimate of 

 the water depths at which the anchor was to operate, a maximum gun bar- 

 rel length, estimates of two projectile weights, required velocities 

 for these projectiles, and a maximum tolerable acceleration. NOS 

 selected a shortened 90mm Army gun tube for the launcher system. Using 

 a maximum operating pressure of 35,000 psi the required projectile 

 stroke to achieve design velocities was 26 inches. Eleven inches were 

 required for a cartridge to house the propellant charges; therefore, 

 the 90mm gun tube length was set at 37 inches. Through analysis of 

 ballistic performance with different types of propellants using the data 

 supplied by NCEL and the 90 mm gun tube, NOS determined that standard 

 Navy pyrotechnic propellant was best at providing acceptable projectile 

 velocities over the range of operable water depths. With the propellant 

 type and characteristics of the gun tube known, NCEL could determine the 

 propellant charge weights needed to optimize performance of the chosen 

 anchor projectiles. 



Defined parameters were now: 



Operable water depths: 100 feet to 20,000 feet 

 Gun barrel: 37 inches long; 



2 6- inch projectile stroke; 

 11-inch cartridge 

 Shot start pressure: 3,000 psi 

 Propellant: Navy pyrotechnic 



Projectile weights: 300 pounds and 490 pounds 



Launch vehicle weight: 1540 pounds 

 Projectile muzzle 



velocities goals: 225 fps, 490-pound projectile 



275 fps, 300-pound projectile 

 Maximum allowable gun 



barrel pressure: 35,000 psi 



With this information an optimization study to select the best combina- 

 tion of charge weight and web thickness (material thickness between 

 perforations in propellant) was performed. The goal was to achieve a 

 balance between performance in shallow and deep water for both projec- 

 tiles using a single web thickness and a minimum of different charge 

 weights. A computer program developed by NOS was used extensively in 

 this optimization. Charge weights ranging from 2.25 to 3.75 pounds in 

 .25-pound increments and web thickness from »06 to .11 inches in .01- 

 inch increments were examined for both projectiles over the entire depth 

 range. Plots were made of projectile velocity versus water depth for 

 each web thickness. 



35 



