Classifications

• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
  • C06B23/00—Compositions characterised by non-explosive or non-thermic constituents
  • C06B23/04—Compositions characterised by non-explosive or non-thermic constituents for cooling the explosion gases including antifouling and flash suppressing agents

Definitions

• muzzle flash has long been of concern to propellant formulators and systems engineers.
• The, important, undesirable aspects of muzzle flash such as signature, temporary loss of night vision by gun crews, significantly increased muzzle blast and reduced gun performance are well known.
• More recently muzzle flash has been implicated in loss of aircraft due to compressor stall and flame-out .
• gun muzzle flash usually consists of three components: a weak "primary” flash due to visible emission from hot product gas molecules; a strong but brief “intermediate” flash cause by recompression of the product gases on passing through the shock front; a strong and long-lived
• Secondary flash corresponding to rapid combustion of fuel-rich muzzle gases in the atmosphere. Secondary flash is the most important and it is the suppression of this phenomenon that is one of the objects of this invention.
• alkali metal salt flash suppressants A problem with alkali metal salt flash suppressants is that they usually reduce the impetus of the propellant, cause smoke and, when used in aircraft cannon, are the prime cause of aircraft skin erosion and fouling.
• the alkali metal salts can also foul, corrode or otherwise degrade the performance of aircraft engines.
• the object of this invention is to provide a method of and means of flash suppression which can be readily applied and will not give rise to significant skin erosion or fouling, will not materially reduce propulsion and which produces minimal smoke.
• the flash suppressants were added to the charge in several ways. All suppressant salts were analytical reagent grade and powdered in a mortar and pestle then dried before being used. Suppressant salt discs were 6mm in diameter and contained either 100 or 200 milligram of material. The discs were pressed in a Manesty Pelleting Press under sufficient pressure to form hard pellets. They were stored in a dessicator until ready for loading. They were placed on top of the propellant charge prior to crimping. Suppressant salt grains were formed by mixing 1:1 w/w salt and hydroxyethyl cellulose (Hoechst TYLOSE H4000) with sufficient water to form a thick gelatinous paste.
• Hoechst TYLOSE H4000 hydroxyethyl cellulose
• the paste was then extruded through a glass hyperdermic syringe with the needle removed.
• the resulting strands were dried and cut to length with a mechanical propellant cutter.
• the dried, finished grains had nominal diameters of 1.0mm and a length of 1.5mm, comparable dimensions to those of propellant grains.
• These flash suppressant salt grains were loaded on top of the propellant charge. It was not possible to process ammonium sulphate or potassium carbonate by this method as these salts appeared to be incompatible with the hydroxyethyl cellulose.
• the suppressant salts were also used in powder form similar to the way salts were incorporated in the experiments of Bracuti et al referred to earlier herein. In this case the appropriate weight of each salt was wrapped in a small piece of polymer film and loaded on top of the propellant charge.
• the experiments were carried out in four sessions, the results of which are summarized in Tables 1 - 4 which form part of this specification.
• the first session was primarily to assess the secondary flash produced by the unsuppressed single-base propellant.
• Three propellant batches were produced, one deterrent coated in the same way as standard AR 2206 and two others processed as uncoated base grains.
• the base grain batches were of differing web sizes produced by dies having diameters of 0.050" and 0.055".
• Table 1 shows the coated propellant and the smaller web base grain flashed consistently at all charge weights. The larger web base grain did not flash because it was found that the propellant grains did not burn completely.
• the coated propellant was used in the remaining two experiments as the "base-line" propellant for which flash was to be suppressed.
• the final experiment investigated the efficacy of ammonium chloride and ammonium nitrate salts when mixed into the propellant at processing stage in the proportion of 6% weight for weight (W/W). As table 4 indicates, both compounds were very effective at eliminating muzzle flash.
• the ammonium nitrate was found to be superior to ammonium chloride in propellant compatibility and ballistic performance. No attempt was made to incorporate ammonium carbonate or bicarbonate salts into this particular propellant due to extreme incompatibility.
• ammonium salts in a proportion not exceeding 12% W/W, excepting the carbonate and bicarbonate salts, either incorporated directly into a granular gun propellant used for any gun, or in the form of inert grains containing the salts which are added to the propellant charge, the percentage limitation ensuring that the ammonium salt does not materially effect the propellant charge but acts simply as a flash suppressant.

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• 1985
  • 1985-08-30 EP EP19850904401 patent/EP0195027A4/de not_active Withdrawn
  • 1985-08-30 WO PCT/AU1985/000207 patent/WO1986001796A1/en not_active Application Discontinuation

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