MULTIPLE POINT IGNITION IN HARP GUNS
ARMY BALLISTIC RESEARCH LAB ABERDEEN PROVING GROUND MD
Pagination or Media Count:
The usual powder charge in the 16-inch HARP gun can be as long as 12 feet in an even longer chamber. If the charge length is more than 2 feet shorter than the available chamber, the pressure time curve can be significantly improved by dividing this interval into 2 to 4 sub-intervals by use of wooden spacers. An even more dramatic improvement can be achieved by igniting this column of powder at several points. Recently, five point ignition with two squibs in each location was used in the 119-foot long 16-inch gun with very good results. The service charge for a 16-inch gun is 660 pounds of standard 16-inch gun propellant. This charge will launch a 3000-pound projectile at 2800 feet per second, but is too slow burning to launch the standard HARP projectile plus sabot weight of 410 pounds at this velocity. With multiple point ignition, 1275 pounds of this old propellant accelerated the HARP projectile to 5900 feet per second, and an apogee of 414,000 feet was achieved. Even better performance can be achieved with multiple point ignition. A WMM propellant with 0.220 web, 920 pounds, allows the HARP projectile to reach 6800 feet per second and an altitude of 540,000 feet while a 0.225 M8M propellant yields a muzzle velocity of 7000 feet per second and 590,000 feet apogee.
- Atmospheric Physics