Hi @MINENAZ16,
the foto of firing is a very nice one. Thank you. It's incredible that such a rather bulbous shape, flies straight. The rocket seems to have been too fast for the camerasetting. The motor seems just to have ignited and I'm not shure if, more like shadow, one can discern 4 fins that just open. The more detailed foto of the rocket does no show any collapsible fins.
regards,
Bellifortis.
The firing picture comes from the October 2015 issue of the Marine Corps Gazette. The firing taking place Camp Lejeune, North Carolina.
The smoke seen in the image is just what's left in the motor chamber leaking out, or what's blown out of the front of the launching tube after the projectile has exited, this as the propellant (should) burn out completely within the launching tube. The rocket motor section, the MK 115 MOD 0, is based on that used by the Israeli B-300 rounds. It contains approximately 425 g of Type II M7 minimal-smoke double-base stick propellant. The rocket motor gives the practice (or live HEDP round) a muzzle velocity of about 217 m/s (712 ft/s).
The bulbose nose of the practice rocket is the same shape as the MK 1 MOD 0 High Explosive Dual Purpose (HEDP) rocket, this so it can emulate its flight accurately. It differs in that the warhead body is blue coloured and inert, the MK 4 MOD 0 practice round having a metal body, the MK 7 MOD 0 is supposed to be plastic. The HEDP rocket itself is comprised of the MK 118 MOD 0 warhead section and aforementioned MK 115 MOD 0 motor section. The HEDP rocket when housed in its transport casing, along with six MK 217 MOD 0 spotting rifle rounds, is designated as the MK 3 MOD 0 HEDP round.
The warhead of the HEDP rocket is essentially a HESH (High Explosive Squash Head)/HEP (High Explosive Plastic) design, but with s dual-mode (DM) fuze, the MK 420 MOD 0. The fuze has a short or a long delay that is dependant on the type of target it strikes, respectively hard of 'soft'. The warhead contains 1.08 kg (2.38 lbs) of aluminised Composition A3 or 1.18 kg (2.60 lbs) of PBXN-18.
The projectile has eight, not four fins. These are attached to the motor's convergent/divergent (de Larva) nozzle. The fins are backwards folding, spring-loaded, knife-like and canted to induce spin.
The MK 1 MOD 0 HEDP rocket is also launched from the M141 BDM (Bunker Defeat Munition), also known as the SMAW-D (D = disposable).