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 employed by the Grand Army of the Republic during the Clone Wars, and subsequently by the Galactic Empire. Its design shared similarities with the smaller RX-200 Falchion tank, which was also a Republic asset during the Clone Wars. Depending on the specific loadout, the walker was designated with different suffixes: SPHA-T (turbolaser equipped), SPHA-I (ion cannon equipped), SPHA-V (anti-vehicle laser equipped), SPHA-C (concussion missile launcher equipped), SPHA-M (mass-driver cannon equipped) and SPHA-F (thermobaric cannon equipped).
Description
The Self-Propelled Artillery Walker (SPHA) utilized twelve legs as its mobile foundation. Unlike smaller walkers, such as the AT-TE, the sheer size and mass of SPHA units prevented their transport via LAAT/c gunships. Instead, they were directly deployed from landed Acclamator-class assault ships, with each ship capable of carrying 36 of these artillery platforms.
During combat scenarios, SPHA walkers typically received instructions from ground-based command centers. These centers provided a broader and more connected 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, who could rapidly deploy through a dorsal hatch. These soldiers could quickly exit the vehicle to secure the immediate vicinity of the walker, offering protection against enemy infantry and lighter vehicles.
Main weapons
The SPHA walker's basic structure was adapted to support a variety of weapon systems, with the turbolaser (SPHA-T) configuration being the most documented. The primary armament of this variant was a heavy turbolaser cannon, designed to inflict substantial direct-fire damage on large or slow-moving targets. This turbolaser possessed exceptional range and the ability to penetrate deflector shields.
A key limitation of this potent weapon was its inability to deliver indirect fire support to targets beyond line of sight, a deficiency addressed in other SPHA models. Another drawback was the weapon's limited charge capacity; after firing fully charged shots, they needed replacement with pre-charged guns from support lines.
Other SPHA variants deployed during the Clone Wars included those equipped with an ion cannon (SPHA-I), anti-vehicle laser (SPHA-V), concussion missile launcher (SPHA-C), thermobaric burst weapon (SPHA-F), and mass-driver cannon (SPHA-M). Certain model variations incorporated 12 retractable antipersonnel blasters, requiring 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 demands of the turbolaser cannon in the SPHA-T version heavily influenced the design of the vehicle's other components.
Designers opted against a complex turret system, instead choosing to rely on the entire walker repositioning itself to adjust for different firing coordinates. As with other walkers, the use of articulated legs made the SPHA resistant to anti-repulsorlift weaponry, but at the expense of some maneuverability.
Later, the Galactic Empire engineered a more streamlined variant, the SPMA. This version was more mobile and compact, thanks to advances in weight-reduction technology.
Usage
The SPHA, especially the SPHA-T model, made its debut during the First Battle of Geonosis. 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 surface engagements, including the Battle of Cato Neimoidia, the Battle of Muunilinst—where many were lost to the agile 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 installed within their ventral hangar bays. These proved particularly effective during the Battle of Coruscant, especially against enemy Munificent-class star frigates.
The SPHA series of walkers remained in service during the early period of the Galactic Empire, until the development of the SPMA-line. The SPMA vehicles offered enhanced speed and maneuverability compared to the more cumbersome SPHA-Ts.
Behind the scenes
Concept art for the SPHA-T was created by Concept Design Supervisor Erik Tiemens. Initially, he envisioned a vehicle with treads, but George Lucas requested a walker design. The SPHA's original production name was "Clone Tank A".
Star Wars: Attack of the Clones: The Visual Dictionary and Star Wars: The Complete Visual Dictionary both incorrectly identify the SPHA-T's turbolaser as a troop hatch. Additionally, The New Essential Guide to Vehicles and Vessels erroneously describes the SPHA-T as being driven by multiple treads. It is, in fact, a walker propelled by twelve legs.
The vehicle's precise size remains somewhat ambiguous. The length of 140 meters cited in The Official Star Wars Fact File 71 appears inconsistent with its depiction in Star Wars: Episode II Attack of the Clones, as well as the dimensions presented in The New Essential Guide to Vehicles and Vessels.