The Scorpion’s rugged, adaptable design has changed little from its origins at the dawn of human interstellar colonization. This vehicles has remained in service due a combination of affordability, simplicity, and versatility that is difficult to match by other – supposedly superior – designs. The Scorpion’s functional uses are numerous and varied, though the UNSC uses it predominantly for direct assault, localized defense, and anti-armor operations.
The Scorpion’s design has become the template for all contemporary UNSC main battle tanks. Its heavy automation and reliable autoloader allows the tank to be operated by one individual, though the most common variants seat a secondary gunner to operate a pintle-mounted machine gun. The flat, broad-armored body is inset within four independently articulated bogies fitted with adaptive track segments. The track plates feature makeshift hard points that allow infantry to climb aboard the side of the tank and use it for transportation, though this is not recommended for use in combat zones.
The M820 Scorpion is just as heavily armored and mobile as its predecessors, and represents a new weapon platform without decades of deferred technology revisions and historical compromises.Most notably, the tanks M990 electrothermal-chemical (ETC) 150mm smoothbore cannon breaks legacy ammo compatibility with the M808 in order to accomodate both planned cannon-launched guided munitions and future advances in energetic propellants.
M808C: Still in service with armored units throughout the UNSC Army and Marine Corps, the previous "mainline" iteration of the M808 features a M512 90mm smoothbore cannon for anti-tank and anti-fortification use, and a pintle-mounted M247T 7.62mm medium machine gun. It is substantially heavier than the M820, massing 66 tons (59.9 tonnes) when fully loaded.
M808B: This older variant does not have the M247 pintle mount, but adds a coaxial M231 medium machine gun to the main turret, controlled by the operator. This versatle chassis saw a law number of locally-produced variants and field upgrades over its nearly two centuries of use. The UNSC Army made periodic attempts to codify these modifications, with little success. Recorded examples include the UE8-14 and 12-9FS, both of which had thinner armor augmented by ceramic appliqué plates to make the tank easier to air transport.
M808B2: The “Sun Devil” variant replaces the 90mm cannon with two twin-linked 40mm autocannons. Ostensibly an anti-aircraft vehicle, the Sun Devil was used in an anti-personnel role throughout the insurrection years.
M808B3: Used for heavy fire support roles, the “Tarantula” variant with its two mounted pods on either side of the turret can fire clusters of hypervelocity Scimitar rockets. Its ineffectiveness against Covenant forces meant that most B3s were converted back to standard B models.
M808: The first M808 model entered service in 2218.