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  1. #1
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    M26 rocket for the M270 MLRS (Multiple Launch Rocket System)

    Cutaway model of a M26 rocket as used in the M270 MLRS (Multiple Launch Rocket System).
    In the seventies of the last century the western allies (NATO) came tot he conclusion that the Warschau pact forces had an absolute force majeure when it came to rocket artillery compared to the NATO forces. In case of a conflict this could lead to defeat of the NATO forces simply being overpowered. This Warschau pact rocket artillery was quite inaccurate, however it was fired in massive quantities under the doctrine “if you fire a large enough volume of rockets in the direction of a target, at some point a hit will be scored on the target”. Saturation fire in the true sense of the word. Nato forces did not have this -expensive- luxury and had a doctrine which relied upon cannon artillery shooting at the target with precission. Nato had relatively little rocket artillery compared to the Warschau pact forces, and what was available could be traced back to ww2 or the fifties. Artillery rockets like the Lance and the Sargent were large, single shot, had to be assembled before firing (time consuming) ,and needed a large and well trained crew to be fired. As one will understand these systems were also suscepttible to counter fire.
    Together with the NATO partners one started looking for a new system that could fill the gap, and finally found this in a design by Boeing and Vought Aerospace, where the M269 launching system was placed on a M993 Bradley fighting vehicle chassis. Together this forms the M270 MLRS (Picture 01).
    Some advantages of the New M270 MLRS over the old rocket artilley systems were; A tracked vehicle , an armoured crew cabin, twelve missiles can be fired in 48 seconds, short reloading time of rocket cassetes, aiming is done by the computer, small crew (3), and “shoot and scoot” capabillity. Cassetes with 6 rockest each were stored/ left at predetermined places either delevered by a resupply vehicle.
    The way the MLRS was to be used in case of a conflict was to have multiple MLRS vehicles wait in seperate positions, well hidden. Upon fire request, the vehicles appeared to fire rockets at the target, move to reloading points and reload with new cassetes (2 minutes with board crane) and go into hiding again untill the next fire request. Due to this tactic, the MLRS launchers were hard to detect and hard to destroy by counter battery fire.
    The M26 rockets of the MLRS were not meant to attack groups of tanks, although the M77 bomblet can severely damage a tank. For destroying tanks specially designed weapons like the copperhead were available. The M26 rocket was designed to attack targets at a longer distance behind the fronline like radar and air defence sites, supply and assembly areas, airfields, artillery positions, Infantery in the open field, trenches and/or foxholes, trucks and lightly armoured vehicles.
    The M270 MLRS must not be seen as a replacement for the 155 and 203mm cannon artillery, but more as a supplement to one another. Where cannon artillery will be used for pinpoint accuracy fire, the M26 rocket will sarurate a 200x200 mtrs area with 644 bomblets. The combined fire of cannon artillery and the M270 MLRS has a devastating effect upon targets.
    The M26 rocket is moisture- and airtight packed in the launching tube, six tubes are assembled to a container (Picture 02). This container is designed in such a way that the boardcrane of the M270 can load two containers in te M269 launcher. The containers are also used for storage and transport.

    The first time the M26 rocket was used in wartime was during the 1991 gulf war in operation Desert storm. The MLRS made a great impression on the Iraqi troops whom -after firing with artillery on US troops- got a volley of M26 rockets in return. It was a fast learning curve for the Iraqi troops that it was not a smart descission to fire at US troops with artillery. Iraqi troops surrendering to US troops did not talk about fear of air attacks or -cannon- artillery strikes, but were much affraid of the “black rain”, the nickname Iraqi troops gave to the MLRS.
    The MLRS was also used in the last days of the war between Libanon and Israel in 2006, where Israel fired M26 rockets at the positions of Hezbollah terrorists, releasing 1,2 million M77 bomlets over south Lebanon.
    In the first gulf war, M26 rockets were fired at enemy positions in the desert –with hardly inhabitants- so the risc of people getting hurt by M77 duds was very low. During the 2006 Israel –Lebanon war rockets were fired at residential areas, with houses, olive orchards and high grass. This caused a high number of duds, bomblets hanging in the Olive trees by their stabilisation ribbons, or landing -too soft- in the high grass. At the end of 2007 however 30 people were killed and 196 were injured by M77 duds.
    Due to the design of the fuze and the sensitivety of the fuze a dud M77 bomblet will effectively function as a landmine when touched. A disadvantage of these duds is that they are not allways instantaniously lethal, leaving the victim(s) severely crippled for life.
    According to the manufacturer the number of M77 duds is >1%, in practice this number can rise to 20% or even higher, meaning that per M26 rocket 129 duds can remain as duds. The angle of release (too shallow), Release moment (too late or too low), target underground (wooded area or high grass) and the age of the rocket (overdated stock) are of influence on the number of duds.
    The M26 rocket described here is the oldest MLRS rocket type. It was soon surpassed by rockets with a longer range and precission guided rockets with GPS steering. This however meant that the number of bomblets carried in the rocket decreased. The launchers were also mimproved with new electronics. A further development was the HIMARS (High Mobillity Artillery Rocket System), a wheeled truck with a launching system that can house a single cassete of six rockets only.
    More info about this weapon system can be found here: https://en.wikipedia.org/wiki/M270_M..._Rocket_System

    With the threaty of Dublin of 30 may 2008, ratified by 119 countries, the use of the M26 rocket was forbidden for these countries. However, some countries have not ratified this threaty and still use the M26 rocket -Bahrein, Israel, South Korea, Turkey, USA-, either the improved version of the M26. Some countries that ratified the Dublin threaty still use the M270 MLRS, however with a guided missile with a single (120kg) warhead, changing the MLRS from an area weapon to a precission weapon.

    After aquiring the target, the launcher is aimed on target by means of the targetting computer. The electronic fuze is set, the computer descides how many rockets are needed for the specific target and in what ripple timing. The firing button is hit and the computer takes over. When firing at a moving target, aiming corrections are made by the computer during firing.
    The launching time between rockets is 4 seconds minimal. This means that one M270 is able to saturate a target with 12x644 = 7.728 bomlets in 48 seconds. In the Dutch army, a platoon MLRS consisted of three MLRS vehicles, raining down 23.184 bomblets in 48 seconds over a target, and a batery consisted of 9 MLRS vehicles, raining down 69.552 bomblets over a target!

    The M26 rocket (Picture 03) consists of three main parts:
    -The electronic time fuze M445.
    -The warhead with 644 M77 bomblets.
    -The rocket motor.

    Description and functioning of the electronic time fuze M445 (Picture 04) ;
    The electronic time fuze M445 consists of a cast Zamac body which is secured to the ogive cap by means of three hexagon socket set screws at 120 degrees each. In top of the fuze body the airstream generator is placed. Below the airstream generator the electronic assembly is placed, consisting of three circular trays of electronics.
    Below these trays the mechanical Safety and Arming mechanism is placed. Below that , the booster charge (yellow) for the detonator in the mechanical S&A unit is placed.
    Upon launching of the rocket the airstream flows into the hole in top of the fuze body and starts presurizing the membrane of the generator. As holes in the side of the tube leading tot he membrane have holes, air can escape. This will cause a regular building up and release of pressure, causing the membrane to vibrate. A small pin has been placed in the center of the membrane , connected to a steel disc at the other side of the pin. This steel disc is placed between two magnets. The vibrating of the disc between the two magnets induces a 35 volt current. The air escaping the tube of the airstream generator will leave the fuze body through a ring of holes in a recess on the outside of the fuze body.
    The upper of the three electronic trays controls the power output and serves the pyrotechnic arming devices. The middle tray houses the electronic timer which descides the time lapse before the expulsion charge is ignited. The lower disc serves the rest of the functions like activating the timer and electrically igniting the detonator in the S&A unit.
    A flat “computer cable” runs between the middle tray of the fuze to the fire control computer so the fuze activation time can be set, When launching the rocket, this cable is cut.
    In the base of the fuze the mechanical S&A unit (Picture 05) is placed, which will only function with a certain amount of accaleration when launching the rocket. This consists of a disc with an electrically activated detonator, which is rotated out of line with the electric contacts and the booster charge, which are both placed in the centerline. In rest, the disc is fixated by a hook that prevents it from rotating, This hook is rotated into the release position by an electrically activated explosive piston. A second locking mechanism consists of a spring loaded set back weight that runs down a zig zag path on a small shaft (to slow it down in it’s movement), releasing the disc to rotate the detonator in line with the electric contact and the booster charge. The fuze is now fully armed. If the timer has elapsed, it will ignite the electric detonator in the disc, which ignites the booster charge (yellow), which ignites the expulsion charge in the rubber clad pipe in the centre of te warhead. This will spread the bomblet payload in the warhead.
    Between the fuze and the cargo bay of the warhead a Zamac ogive cap is placed, streamlining the space between the fuze and the warhead.

    The warhead (Picture 06) ;
    The warhead consists of an ogive shaped pressed aluminium pipe with a wallthickness of 3mm. Four 1,5mm deep v-shaped grooves are cut in at 90 degrees each over the full length of warhead; these enshure the warhead will easily split open over these weakenings when the expulsion charge is activated. The lower part of the warhead is connected to the motor with 28 rivets, the top of the warhead is connected to to the Zamac ogive cap by means of rivets. In the warhead eight polyurethane containers (Picture 07) are stacked, housing and fixating the bomblets. These containers house –from top to bottom- 35, 56,42, 105,105,105,105 and 84 = 644 M77 bomblets. An aluminium lock-up plate is placed below the lower container, forming the hard barrier between the warhead and the motor. In the middle of all polyurethane containers a hole is present through which an aluminium pipe runs from the Zamac ogive to the aluminium lock-up plate at the bottom of the warhead. This aluminium pipe has a thick rubber cover over it’s full length. The aluminium pipe is filled with gunpowder over it’s full lenth, with a thin aluminium pipe in the center filled with a mixture of RDX + TiKNo, which is used to instantaniously ignite the gunpowder charge in the aluminium pipe. If the electronic fuze is activated, the booster charge of the fuze ignites the RDX charge which ignites the gun powder charge. This will make the pressure inside the warhead rise untill the warhead splits open over the four weakening grooves, throwing the bomblets outward. The polyurethane containers are pulverized during this process. As the rocket rotates with 10 to 12 revolutions /sec, this will enshure the bomblets are spread out over a wide area.

    Description and functioning of the M77 bomblet (Pictures 08 & 09) ;
    The M77 bomblet conists of a pressed steel body, prefragmented on the inside. On the inside of the of the body a copper cone with a top angle of 60 degrees has been roll crimped in place. In top of the bomblet body, a small aluminium cup filled with hexogen has been placed in the centerline of the bomblet body. This forms the booster charge between the stab detonator in the arming slider –when armed- and the main charge.
    To the top of the bomblet body the pressed sheet aluminium impact fuze M223 is fixated with two rivets. A rectangular slot runs over the width of the fuze body, housing the arming slider with the firing cap. The arming slider is spring loaded and is forced to move outward by the spring –if released-, sliding the firing cap under the firing pin in the centerline of the bomblet. The firing pin is screwed into the inertia weight, and both are placed in top of the fuze housing. A stabilization ribbon is rivetted to the back end of the firing pin, folded over the fuze body when in safe condition. The arming slider has two holes; one housing the firing cap, the second hole houses the firing pin in safe condition, enshuring the bomblet cannot arm before being released from the rocket, hence enshuring the firing cap is out of line with the firing pin and booster charge when not armed. The bomblets are designed in such a way that the fuze with the folded ribbon fits the copper cone of the bomblet above it, allowing for a efficient stacking of the bomblets. Thus, 644 bomblets can be stacked in a relatively small space.
    After being released from the rocket, the bomblets enter the airstream. The stabilization ribbon will be tensioned by the airstream and starts to vibrate by the airstream. This vibration -together with the spin induced by the rocket- causes the ribbon to unscrew the firing pin from the inertia weight, retracting the firing pin from the hole in the arming slider. The spring loaded arming slider is now free tho move, sliding the firing cap under the firing pin. Upon impact, the inertia weight with the firing pin move down the firing pin into the firing cap, initiating the explosive train of firing cap, booster charge and main charge.
    The shaped charge of the M77 bomblet will penetrate 70mm ssteel, the fragmentation of the bomblet body is lethal in a five meter radius.
    The bomblet M77 is nearly identical to the M42 (prefragmented) / M46 (not prefragmented) which is used in artillery shells. However, as the speed of a rocket is considerabely lower than the speed of an artillery shell, the M77 needs a longer and wider ribbon.

    Data M77 bomblet:
    Diameter : ø38,7mm
    Length : 88mm (ribbon folded)
    Weight : 215 gram
    Weight explosive charge : 30,6 gram A5 (Hexoggen with 1,5% wax)

    The rocket motor:
    Description and functioning of the rocket motor:
    The rocket motor consists of a thin walled steel pipe with a dome shaped fore end (Picture 10). In the forward rim 28 holes are drilled over which the warhead is placed, connected to the motor by means of 28 rivets. The inside of the back of the pipe is threaded to receive the venturi (Picture 11) . The venturi consists of an aluminium ring which is threaded on the outside, with the phenol resign venturi (black) cast in this ring (Phenol resign is heat resistant). In the throat of the venturi a plastic spacer is placed, housing the ignition cartridge. This aluminium ignition cartridge is filled with a mixture of magnesium and teflon. In the base of the cartridge two electrically ignited squibs are placed,the wiring of these squibs are appr. 0,5 mtr long and end in an electrical comnnector, which is plugged in the firing circuit of the container. The spacer and the ignition cartridge are blown out of the venturi upon starting the rocket engine.
    The fuel stick is made of Hydroxol Terminated Polybutadiene Composition (HTPB), cast in the pipe of the rocket motor. When looking at the longitudinal section of the fuel stick one can observe an elastic filler piece (Picture 10) in the front end of the motor. This is placed there before casting to prevent the fuel stick from developing cracks due to solidification and hardening of the cast in fuel mass. After hardening of the cast, the support piece on which the elastic filler piece is placed is withdrawn from the motor and a hexagon head screw plug is placed to close the forward end of the motor.
    When looking at the cross section of the motor (Picture 12) at different levels the stick has the shape of a wagon wheel with four spokes, with the spokes becomming more narrow towards the forward end of the motor. The fuel stick is burned up after 5 seconds, the boost phase is 1,6 seconds.
    On the afterward part of the rocket motor, four rotating fins are connected to the outside of the pipe. After launching, the rocket rotates against the clock, forcing the fins open in the air stream. In the launching tube, the fins are locked in closed position by the Fin Restraint Release Device (FRRD) (Picture 13) . This mechanism consists of a Zamac housing with two delay detonators (Picture 14) placed in the length direction. These detonators have a friction ignition fuze, the wire of which is connected to the launching tube. A steel wire with a pull force of 40 kg is placed around the fins and connected to both sides of the zamac housing. This prevents the fins from moving outward when the rocket is still in the launching tube. Upon launching the rocket, the pull fuze is activated, igniting the pyrotechnic delay of the delay detonators. After 0,5 seconds the detonators expolde, splitting the zamac housing in half, releasing the wire from the fins. At that moment the rocket is allredy free from the launching tube.
    Behind the fins four notches are placed. Two are guidance notches, two notches induce spin to the rocket as they are hooked behind the spriral shaped rail in the launching tube. The two spin inducing notches have a longitudal break bolt placed that fixates the rocket to the launching tube. When enough pressure and force is induced, these two bolts will break, releasing the rocket.

    Data M26 rocket :
    Length complete rocket : 3940mm
    Length warhead : 2006mm
    Weight warhead : 158 kg
    Expulsion charge warhead : 0,674 kg
    Length rocket motor : 1977 mm
    Weight motor : 148,04 kg
    Weight rocket fuel : 98,9 kg
    Diameter rocket : ø227mm
    Weight rocket : 310 kg
    Range rocket : 32 km

    De Royal Dutch Army had 23 MLRS sytems in use between 1988 and 2004. These were devided in three platoons of three vehicles with the 109 battery field artilley, and three platoons of three vehicles with the 119 mobilization battery field artillery. Five vehicles were kept as reserve and/or replacement.
    In 2004 twenty two were sold to Finland, the twenty third vehicle is exhibited in front of the National Military Museum in Soesterberg

    Countries using the M270 MLRS are :
    Bahrein, Denmark, France, Germany, Greece, Israël, Italy, Japan, Finland, Netherlands (former user, sold them off to Finland), Norway, South Korea, Turkey, USA.

    Here a factory commercial for the M270 MLRS, where the moment of bomblet release can be clearly observed (1min 28 sec)

    As well as two other you tube movies showing the M270 MLRS in action:

    Regards, DJH.
    Attached Images Attached Images

  2. The Following 14 Users Say Thank You to pzgr40 For This Useful Post:

    AMMOTECHXT (16th August 2019), Bellifortis (9th August 2019), Darren (10th August 2019), Depotman (9th August 2019), greif (15th August 2019), HAZORD (9th August 2019), Lostround (9th August 2019), Nabob (9th August 2019), ordnance (8th August 2019), stecol (8th August 2019), tnor_fr (9th August 2019), wichitaslumlord (17th August 2019), Wlad99 (11th August 2019), Yodamaster (8th August 2019)

  3. #2
    Senior Member
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    Picture 11 to 14.

    Regards, DJH
    Attached Images Attached Images

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  5. #3
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    I made an autopsy of such a fuze...

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  7. #4
    Senior Member
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    Jun 2007
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    Very interesting. Your fuze has the same problem that I had. I had three of these fuzes ....all fired with the inner works pulverized. The force of the mechanical safety device (disc) is presumably so powerfull that it destroys the lower inner works of the fuze completely. Luckily enough I was able to gobtain an inert fuze cutaway model to complete the rocket.

    Interesting to see your other you tube movie with the AA-3 seeker disassembly.
    Thanks for posting.
    Regards, DJH




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