Multiple Point Ignition in Harp Guns

Abstract

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 "I 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 has been used in the 119-foct long 16-inch gun at Yuma Proving Ground, Arizona with very good results. ýA' 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 propellant accelerated the HARP projectile to 5900 feet per second and an apogee of 414,000 feet was #pUhve4. Even better performance can be achieved with multiple point ignition. A WM/M propellant with 0.220 web (920 pounds) allows the HARP projectile to reach 6800 feet per second and an altitude of 540,000 feet Swhilp a n2?25 M8M propellant yields a muzzle velocity of 7000 feet per seronfd and a 590,000-foot apogee.

Solventless Extruded Double-Base (Edb) Propellant Charges—a Review of the Properties, Technology, and Applications

“…Although Groundwater describes successful static testing of such grains when gun fired at 7900 g and 1500 m/s, there were problems with grain failures. Subsequent to Groundwater's report, Bull and Murphy (1991) have described how the grain collapse was avoided by filling the star cavity (of a 159-mm diameter gun-fired motor) with a zinc-barium solution matching the density of the EDB propellant.…”

A Brief Journey Through the History of Gun Propulsion

“…While small payloads (31.5 g) are reported to have been launched to velocities in excess of 3.5 km/s from a 40-mm barrel and a C/M of 25 (31), substantial masses too have been launched to hypervelocities using truly conventional propulsion. Over 30 years ago, in a follow-on program to the joint US/Canadian High Altitude Research Program (HARP) program, a 60-kg projectile was launched to a velocity of over 3 km/s from what was essentially a triple travel 16-in Naval gun (32). More recently, this author and others conducted hypervelocity firings at more modest C/M levels, still achieving velocities in the 2.5-3km/s range, but with detailed interior ballistic measurements that showed excellent agreement with multiphase flow calculations for downbore pressures throughout the firing cycle (33,34).…”

“…The Wilhelmgeschutze (or Paris Gun), shown in figure 15, dates back to WWI and launched 106-kg projectiles to 126 km, but with muzzle velocities of under 1700 m/s (34). Some half a century later, the 16.4-in HARP gun ( figure 16) launched a variety of high velocity projectiles, including 160-kg research vehicles at muzzle velocities of nearly 2200 m/s and achieving an apogee of 180 km (32). These latter firings were conducted at a C/M of about 2.4 and employed a unique distributed ignition system to achieve satisfactory flamespreading and prevent the formation of pressure waves.…”