Self-Propelled Heavy Artillery
The Self-Propelled Heavy Artillery (SPHA) walker, also referred to as the Mobile Assault Cannon (MAC), functioned as a versatile heavy artillery platform. It was deployed by the Grand Army of the Republic throughout the Clone Wars, and later by the Galactic Empire. This unit shared visual similarities with the smaller RX-200 Falchion, which was another Republic asset during the Clone Wars. Depending on its specific configuration, the walker was designated differently: SPHA-T (turbolaser), SPHA-I (ion cannon), SPHA-V (anti-vehicle laser), SPHA-C (concussion missile launcher), SPHA-M (mass-driver cannon) and SPHA-F (thermobaric cannon).
Description
The SPHA, or Self-Propelled Artillery Walker, utilized a dozen legs to achieve mobility and stability. Unlike smaller walker variants, such as the AT-TE, the SPHA's considerable size and weight prevented its deployment via LAAT/c gunships. Instead, these artillery platforms were directly unloaded from Acclamator-class assault ships, with each ship capable of transporting 36 SPHAs.
During combat operations, SPHA walkers typically received commands from ground-based posts. These command centers provided a broader, more comprehensive view of the battlefield compared to the elevated perspective from within the walkers themselves. Furthermore, each SPHA unit included a complement of 30 clone troopers. These troops could rapidly deploy through a dorsal hatch, securing the immediate vicinity of the walker in a matter of seconds. This provided protection against enemy infantry and lighter combat vehicles.
Main weapons
The SPHA walker's basic frame served as the foundation for various weapon systems, with the turbolaser (SPHA-T) configuration being the most well-known. This particular variant was armed with a heavy turbolaser cannon, which could inflict massive direct damage on large or slow-moving targets. The turbolaser offered exceptional range and the capability to penetrate deflector shields.
However, this formidable weapon suffered from a key limitation: it could not provide indirect fire support to targets outside of its line of sight. This deficiency was addressed in other SPHA models. Another drawback was the weapon's limited charge capacity; after firing a certain number of shots, the depleted guns needed replacement with charged guns brought from the rear.
Other SPHA variants deployed during the Clone Wars included the ion cannon (SPHA-I), anti-vehicle laser (SPHA-V), concussion missile (SPHA-C), thermobaric burst (SPHA-F), and mass-driver (SPHA-M) versions. Some of these variants were equipped with 12 retractable antipersonnel blasters, which required an additional 10 gunners to supplement the standard 15-member command crew.
History
Development
Rothana Heavy Engineering was responsible for the development of the SPHA walker.
The immense power requirements of the turbolaser cannon in the SPHA-T version significantly influenced the design of the walker's other components.
Instead of a sophisticated turret system, designers opted for a simpler approach: the entire walker would reposition itself to adjust to different firing coordinates. Similar to other walkers, the articulated legs of the SPHA provided immunity to anti-repulsorlift weaponry, but this came at the expense of some maneuverability.
Later, the Galactic Empire engineered a more streamlined variant known as the SPMA. Advances in weight-reduction technology allowed the SPMA to be more mobile and compact.
Usage
The SPHA, particularly the SPHA-T model, made its debut during the First Battle of Geonosis. There, it played a crucial role in destroying several Lucrehulk-class core ships and Hardcell-class interstellar transports.
Throughout the Clone Wars, SPHA units saw widespread use in ground engagements, including the Battle of Cato Neimoidia, the Battle of Muunilinst—where many were lost to the fast-moving IG lancer combat droids—, the Battle of Rhen Var, and the Second Battle of Tatooine.
Following a suggestion from Anakin Skywalker, numerous Venator-class Star Destroyers belonging to the Open Circle Fleet were retrofitted with SPHA-T turbolaser cannons inside their ventral hangar bays. These proved highly effective during the Battle of Coruscant, particularly against enemy Munificent-class star frigates.
The SPHA series of walkers remained in service during the initial years of the Galactic Empire. Eventually, they were superseded by the SPMA series, which offered superior speed and maneuverability compared to the more cumbersome SPHA-Ts.
Behind the scenes
Erik Tiemens, the Concept Design Supervisor, created the initial concept art for the SPHA-T. His original design featured a tracked vehicle, but George Lucas requested a walker instead. During production, the SPHA was internally referred to as "Clone Tank A".
Both Star Wars: Attack of the Clones: The Visual Dictionary and Star Wars: The Complete Visual Dictionary incorrectly identify the SPHA-T's turbolaser as a troop hatch. Additionally, The New Essential Guide to Vehicles and Vessels mistakenly describes the SPHA-T as being propelled by multiple treads. In reality, it is a walker that moves using twelve legs.
The vehicle's size is somewhat inconsistent. The length of 140 meters, as stated in The Official Star Wars Fact File 71, does not align with its perceived size in Star Wars: Episode II Attack of the Clones, or the dimensions presented in The New Essential Guide to Vehicles and Vessels.