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Weyland-Yutani/USCM M577A3 variant

The M577 evolved from the Marine 70 battlefield deployment strategy, which proposed a requirement for a low-cost lightweight APC capable of being transported into combat aboard a dropship. Designed as a multi-role vehicle within a lightly-equipped rapid-reaction force, the M577 is mobile and well armed. However, the rigid design restrictions and compromises imposed by the need to be drop-transportable have resulted in a lighter, less capable vehicle than other APCs currently in US service.
Because of the USCM requirement that the vehicle's combat weight be kept below 15,000 kg, the M577's components were designed to be as lightweight as possible. The chassis chosen for the prototype was based on that of the M570 family of wheeled vehicles which, in the late sixties, was being developed for use in a variety of roles, mainly as a prime mover and mortar platform. The APC is built around a 4 x 4 wheeled layout, powered by a 286 kW multi-fuel gas turbine engine which generates a power-to-weight ratio in the region of 19.7 kW/kN. Although the wheeled configuration does not give as rugged a cross country performance as a tracked vehicle, it does offer considerable savings in terms of weight penalties and reliability. Each of the massive 159 cm diameter wheels receives power independently from the engine via a fully automatic, electronically-controlled transmission system. The tires are armoured against small-arms and splinter, and their pressure is controlled by a central regulation system. This allows the driver to reduce the vehicle's ground pressure over soft terrain by deflating the tires, whilst still being able to re-inflate them for road travel. The M577 has a top speed of approximately 150 km/h.
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The M577's chasis is made of bonded titanium and incorporates a 5 cm foam-packed floor cavity to protect against forged-fragmentation mines. Ground clearance is normally only 22 cm, but the vehicle employs a hydro-pneumatic, fully active suspension to allow a clean ride over rough terrain. The suspension is capable of boosting clearance by a full 30 cm and allows the M577 to comfortably tackle vertical obstacles up to 0.5 m. The hull is made from welded light alloys and is latched and bonded (rather than welded) to the chassis in order to prevent fatigue and failure from piezo-electric effects associated with an alloy-titanium interface. The inside of the hull is lined with boron carbide ceramic tiles, each of which has been coated with a polymer resin to prevent cracks or shattering during normal travel; this resin is 2 mm thick on the outward-facing surface of the tile and is said to provide limited ablative protection against pulsed lasers. The tiles are backed with a thick layer of woven fire resistant polymer armour to limit spalling in the event of a hull penetration. Because of weight restrictions, the armour is very light. It is capable of defeating fragmentation, small arms rounds and low-velocity armour penetrating ammunition such as rifle grenades; however its ability to stop dedicated tank-killing weaponry is light.

Crew and Passengers:


The M577 is operated by two crew (the driver and section commander) and allows thirteen positions for passengers, all equipped with yoke harness restraints for orbital combat drop. Entry is made via the main starboard sliding door or port side drivers hatch. The interior is spacious, allowing for plenty of room for weapons and supply stowage. The Marine 70 requirement called for the ability to carry sufficient ammunition and supplies for up to three days of fighting; in practice this is possible, though the interior of the vehicle becomes somewhat cramped. In tactical areas where re-supply is frequent, no more than two days of supplies and ammunition are usually carried. The mid section of the APC houses the Tactical Operations Centre; from here the section commander can maintain contact with the vehicle's infantry compliment via video and audio linkup, and monitor the battle in real-time via the battle management displays. As well as allow video and audio communications to the outside world, within a radius of 100 miles.



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A platoon disembarking their M577 APC.



Sensors:
The driver's view is limited to a forward window of quartz armoured crystal, though this is supplemented by periscope ports providing vision to the sides and forward quarters. Multi-function screens by the driver's and section commander's positions present a sensor-fusion display of the tactical zone around the APC. The sensors can be activated by the driver, or from the Tactical Operations Centre by the section commander. A sensor cluster is mounted with the main searchlight and can be played across a 270 degree zone in front of and around the APC. The cluster comprises a turreted thermal imager, TV optics with magnification from x4 to x20, a UV detector and an ultrasonic motion tracker. Millimeter-wave targeting radars mounted in the forward gun cupola and the main turret can track targets acquired by the main sensors, or may alternatively use their own ground-mapping and search functions to acquire targets. The effective tracking range of these radars against man-sized targets is approximately 3000 metres in open terrain. The sensors are supplemented by a forward mounted white-light and infrared searchlight for the active illumination of targets.

Stealth and Defensive Systems:
The slab-sided shape of the APC hull provides for a high radar cross-section on the battlefield. An attempt has been made to reduce this by incorporating radar absorbent materials into the hull skinning, with only partial success. Hull paints are laser absorbent to protect against lidar, and the M577 boasts an infrared camouflage feature in which cooling elements are arranged in patches and stripes beneath the skin to break up the IR signature of the vehicle.

Active defenses for the APC consists of a chaff/ flare decoy dispenser mounted to the rear of the vehicle, and a fire control jammer capable of spoofing millimeter-wave tracking radars (available power for this system is limited). The decoy dispenser, which is supplied by a multi-cartridge rotar feed is capable of releasing particulate smoke as a barrier against ranging or pulsed lasers. These defenses are automatically deployed if activated by the driver or section commander.

Weapon Systems:
The M577 carries a formidable array of weaponry in support of its infantry complement. It can either carry one of two front weapon alternatives both housed in a hull mounted cupola covering the APC's forward area. The first alternative are twin synchronized Republic Electric RE700 20mm Gatling Cannons. The Republic Electric RE700 20mm gattling cannon is supplied by a 1700 round multi-feed ammunition dispenser which offers a selection of High Explosive Armour Piercing and 'Beehive' type Anti-personnel Fletchette (APF) rounds at the flick of a switch. These caseless rounds carry no propellant and are fed mechanically into the revolving chambers which are then sprayed with hydrogolic binary propellants which ignite and launch the round . Binary propellant systems are rare at this calibre (the only other such system in Colonial Marine service is the 25mm GAU/113 aboard the UD-4 dropship), but aboard the M577 this system offers substantial weight, rate-of-fire and reliability advantages over a standard caseless weapon and provides effective anti-personnel support for the APC. The only drawback of the weapon is that it is mounted to cover only the vehicle's forward arc, traversing between 60 degrees left and right of axis, and cannot be fired from a hull-down position. The second weapon option mounts a twin Lase Cannon, which has a very high rate of fire and is an extremely effective anti-personnel weapon.
The M577 also houses an Automatic Light Mortar, which is mounted on the roof of the vehicle and is generally used against opponents in good defensive positions. There are 32 rounds for the weapon stored in the APC.
The M577's main weapon system is turret mounted (see below for different weapon variations), allowing the APC to fire from the safety of a hull-down position. The turret assembly is fully traversable, self contained (including ammunition and power supply) and is carried on a rail track which runs down the rear of the vehicle. Geared electric motors run the turret along the track and allow it to be depressed to the APC's rear, reducing the vehicle's headroom so that it may be carried inside a shuttle or dropship payload bay. The weapons are stabilized within the turret for firing while on the move and can be elevated and depressed between +85 and -7 degrees. Hydraulic rams on either side of the turret can tilt it up to 15 degrees in all axis to provide additional elevation or maintain a level firing platform for the weapons. Target acquisition and weapons control are controlled by the section commander from the Tactical Operations Centre; however, independent targeting automation systems (or manual targeting control) can handle these functions so reducing the commander's workload. Additional armament stored in the M577 includes 7 cannisters of CN-20 Nerve Gas, 4 x M20 Claymore mines (two per M8 bandoleer), 2 x M41A Pulse Rifles, 2 x M240 Flame Units & 4 x UA 571-C Sentry Guns.


There are three different main weapons currently in service (The weapon variation used in the film was the M577A3):

M577A1

The initial production M577A1 mounts two Light Disrupters. The power source is a 6 mW hydrogen fuel cell drives a homopolar fast-discharge generator which stores power until it has sufficient energy to pulse the disrupters. When the laser is fired, it creates an ionized trail in the atmosphere which is charged by the gun's electromagnetic coil to form a solenoid magnetic tunnel. The ammunition - Cadium Telluride pellets of five grams mass - is fed mechanically into the tunnel, where it is vaprized by the laser beam into superheated plasma, which is accelerated by the magnetic coil to velocities in the region of 5000 m/s. The plasma travels the tunnel until it impacts the target at a focussed point, using its considerable kinetic and thermal energy for maximum effect penetration. Because of the power useage, both guns fire in sequence rather than simultaneously; thus, cyclic rate of fire (allowing for adequate cooling between shots) is 40 rpm. Each gun carries up to 1000 rounds of ammunition. Maximum effective range is dependent upon the ambient atmospherics, but in ideal conditions can be up to 4000 metres. Also included in this turret are two Light Missile Launchers, which can fire Sprint and Dogleg missiles. The missiles are carried on in the top racks of the APC, 8 of each warhead giving a maximum of 16.


M577A2

The variant M577A2 mounts two Republic Dynamics M2025 40 mW free-electron lasers in the 2.0 - 3.0 micron range, which are effective against both ground and air targets. Beam power is supplied by a 10 mW hydrogen fuel cell driving a homopola fast-discharge generator. The beam is propagated, without the need for lasants, by the interaction of a particle-accelerated electron beam with a static electric field. The advantage of a free-electron laser in Colonial Marine service is its ability to be tuned to wavelengths that would minimize beam degradation by the local atmosphere. In addition, a reactive tune facility, cued by laser returns from the beam, is incorporated to allow rapid retuning in the event that countermeasures (such as smoke or steam) are deployed to block the beam. The lasers can be used in two modes. In 'dazzle' mode, the beam is used to burn enemy optical/ infrared sensors or blind infantry men and pilots, has a low output (20 kW - 50 kW). It is in this mode that the beam is at its most efficient, playing continuously across a target without need for pulsing or the associated effects on beam propagation from thermal blooming, ionization or dielectric breakdown. In 'pulse' mode, a beam is pulsed at full at full power at the target. Damage is caused by the mechanical impulse of the beam as it superheats the target area, and in the case of the M2025 is capable of penetrating infantry personal armour or the skin of a missile or aerospace craft. Range and effectiveness in pulse mode is entirely dependent on the ambient atmospheric conditions, but in ideal conditions, the weapon has an effective range against aerospace craft of up to 3000 metres.


M577A3

The most recent variant of the M577, the M577A3, mounts two 20 MeV turbo-alternator powered charged particle beam cannon, The deployment of these weapons has been made possible due to the introduction of a Martin-Continental micro magnetohyodgynamic tubine capable of generating 20 mW of electrical power to run the big particle accelerator guns. Sufficient turbine fuel exists to power the guns for 50 seconds firing and there is some 300 kg of deuterium tankage to provide particle beam mass. The effective range of the weapons against light armoured targets is approximately 3000 metres though at longer ranges the beams are capable of disrupting unshielded electronics.


M579 Armoured Personnel Carrier


Identical to the M577 except for its weapons. The M579 is a 20mm quad system mounted on an M570-series armoured chasis. Controlled by a highly accurate multi-spectrum sensor, the M579 can track and defeat even hypervelocity threats up to 1500 metres away by filling the sky around them with high explosive and armour-penetrating shells. In place of the M577's forward gun cupola, the M579 is armed with a quad vertical launch-bin installation for the SIM-118 Hornet missile.


M572 Armoured Mortar Carrier


This vehicle is used as a mobile platform for the M402 Multiple Launcher, the main difference between the weapon encountered on these being that it can autoload a new magazine in under 6 seconds and has room for 200 rounds of ammunition. There is room for a crew of 4 (a driver, commander and two loaders).