Self - Propelled Heavy Artillery The Self - Propelled Heavy Artillery ( SPHA ) walker was a modular heavy artillery unit used by the Grand Army of the Republic during the Clone Wars , and by the Galactic Empire afterward . It bore a resemblance to the smaller Republic stun tank also utilized during the Clone Wars . Description . A Self - Propelled Artillery Walker ( SPHA ) had twelve legs that served as mobile support structures . Unlike smaller walkers , such as the AT - TE , SPHA units were unable to be carried into battle by LAAT / c gunships because of their large size and weight . Instead , they were deployed directly from landed " Acclamator " - class assault ships , which could carry 36 of the artillery platforms . In battle , SPHA walkers usually received orders from ground - based command posts , which provided a less isolated and more in - touch view of the battlefield than the towering walkers . In addition , SPHA units had a complement of 30 clone troopers , which could be deployed rapidly via a dorsal hatch . In seconds , the soldiers could disembark the vehicle and secure the area immediately around the walker , providing protection from enemy infantry and other light units . Main weapons . The SPHA walker chassis served as the basis for a number of different weapons platforms , though the best chronicled version was the turbolaser ( SPHA - T ) configuration . This variant ' s main weapon was a heavy turbolaser cannon , capable of causing extreme direct fire damage to large or slow - moving targets . The turbolaser boasted tremendous range and was capable of penetrating deflector shields . The primary disadvantage of this powerful weapon was that it was incapable of providing indirect fire support to out of sight locations , a problem remedied in other models . Another disadvantage was that the weapon could only be charged to a certain level — upon firing such shots , they had to be replaced with charged guns from the rear lines . Some of these other variants deployed during the Clone Wars include the ion cannon ( SPHA - I ) , anti - vehicle laser ( SPHA - V ) , concussion missile ( SPHA - C ) , and mass - driver ( SPHA - M ) . Also , these units had the disadvantage of ammunition , as it would run out if not managed properly . Some of these model variations included 12 retractable antipersonnel blasters , necessitating an additional 10 gunners to the command crew of 15 . History . Development . Developed by Rothana Heavy Engineering , a covert subsidiary of Kuat Drive Yards , the SPHA walker was designed to fulfill the role of mobile ground - based long - range artillery support . It complemented the two other key components of Republic military strategy — the AT - TE walker and the LAAT / i gunship . In a typical attack , the AT - TEs and LAATs would spearhead the assault , establishing a forward base and allowing heavier support forces ( such as SPHA walkers ) to consolidate gains and provide reinforcements . The power usage of the turbolaser cannon in the SPHA - T variant dictated the design of the other parts of the vehicle . Designers rejected a complex turret mechanism , instead relying on the entire walker to reposition in order to adjust for different firing coordinates . Because of the fixed weapon positioning , as well as the slow firing speed of the turbolaser , the SPHA was unable to track rapidly moving targets , such as speeders or small atmospheric craft . Like other walkers , the use of articulated legs prevented the SPHA from being vulnerable to anti - repulsorlift weapons , at the cost of some mobility . The result of this development process was a walker that possessed a very capable capital ship - class weapon , but was hampered by its low mobility . This low mobility was exacerbated by the fact that SPHA walkers were equipped with heavy armor , especially in the frontal area of the vehicle around and just below the command deck . This armor was necessary to protect the vehicle ' s reactor core from enemy fire , as any meltdown , and subsequent explosions , would cause tremendous collateral damage . The Galactic Empire later developed a more compact version , the SPMA , which was more mobile and compact , thanks to weight - reducing advancements in technology . Usage . The SPHA , particularly the SPHA - T , first appeared in the First Battle of Geonosis where it was instrumental in bringing down several " Lucrehulk " - class core ships and " Hardcell " - class interstellar transports . SPHA units were used throughout the Clone Wars , seeing action in surface battles such as the Battle of Cato Neimoidia , the Battle of Muunilinst — where many were destroyed by the nimble IG lancer combat droid s — , the Second Battle of Rhen Var , and the Second Battle of Tatooine . At the suggestion of Anakin Skywalker , many " Venator " - class Star Destroyers of the Open Circle Fleet had SPHA - T turbolaser cannons installed inside their ventral hangar bays , where they were used effectively during the Battle of Coruscant , especially against enemy " Munificent " - class star frigates . The SPHA - line walkers continued in service in the early years of the Galactic Empire , until the SPMA - line was developed , with the SPMA vehicles being faster and more maneuverable than the cumbersome SPHA - Ts . Behind the scenes . Concept art of the SPHA - T was drawn by Concept Design Supervisor Erik Tiemens . He initially imagined a treaded vehicle , but George Lucas changed it to a walker . The SPHA ' s production name was " Clone Tank A " . In both " " and " " , the SPHA - T ' s turbolaser is incorrectly labeled as a troop hatch . Also , in " The New Essential Guide to Vehicles and Vessels " , the SPHA - T is incorrectly said to be driven by multiple . It is in fact a walker , driven by twelve legs .