The Acidalium is a spaceship in the manga series Gundam SEED C.E. 73 Δ Astray.
Though Mars remains neutral in the Earth Sphere's conflicts, the Acidalium is equipped with multiple weapons, all of which are concealed behind sliding hatches. Its primary armament is a Positron Blaster Cannon in the bow. The ship also carries twelve sets of 3-tube missile launchers just aft of the main cannon, and twelve 5-barrel CIWS rotary cannons in wing-mounted pods.
Interplanetary Sailing Unit
As the ship's mission requires it to travel long distances with no opportunity to replenish its supplies, it is equipped with a large "interplanetary sailing unit". This unit, connected to the Acidalium's rear, is roughly two and a half times longer than the ship itself, and contains three large quadruple thermonuclear pulse thruster arrays and a large fuel supply. When operating near Earth or Mars, the sailing unit is detached at an appropriate docking facility.
The Acidalium is an interplanetary transport that was built at the Mars colony Australialis, for the purpose of interplanetary travel between Mars and Earth. The ship has a very small crew, and its captain is Ergnes Brahe, a hot-headed Coordinator who also pilots the GSF-YAM01 Δ Astray. His second in command, Nahe Herschel, pilots the transformable GSF-YAM02 Guardshell.
When the Acidalium arrives in the Earth Sphere in CE 73, the Acidalium docks at the PLANT capital, Aprilius One. Ergnes meets with PLANT Supreme Council Chairman Gilbert Durandal, who discusses the possibility of cooperation between PLANT and Mars. Shortly after the meeting, the Earth Alliance launches a massive offensive against PLANT, and Ergnes impulsively launches in his Δ Astray to assist in the defense of PLANT.
After the battle, Durandal assigns TMF/A-802W2 Kerberos BuCUE Hound pilot Isaac Mau to the Acidalium as an observer, while Ergnes leaves for Earth to investigate the Earth Alliance forces. This results in a confrontation with elements of the elite Phantom Pain militia, with an inconclusive duel between the Δ Astray and Phantom Pain's GAT-X105E+AQM/E-X09S Strike Noir Gundam being broken up when the Acidalium itself intervenes, destroying several GAT-01A2R 105 Slaughter Daggers with a blast from its positron cannon.
The ship's next stop is Orb, where Ergnes meets Chief Representative Cagalli Yula Athha and attends her wedding to Yuna Roma Seiran. When the wedding is interrupted by Cagalli's brother, Kira Yamato, who uses the ZGMF-X10A Freedom Gundam to "abduct" his sister. Not knowing the true nature of these events, Ergnes attempts to pursue in the Δ Astray, but is blocked by Rondo Mina Sahaku in her MBF-P01-Re2AMATU Gundam Astray Gold Frame Amatsu Mina. After a brief battle, the Orb noblewoman convinces Ergnes that "rescuing" Cagalli would not be the best interest of either the Chief Representative or Orb itself.
After the Acidalium departs from Orb, Phantom Pain Lieutenant Sven Cal Bayang takes command a team of five Orb pilots, with the mission of capturing the Acidalium. As the alliance between the Atlantic Federation and Orb was not yet finalized, the Orb pilots are assigned Phantom Pain's Slaughter Daggers, allowing Orb to deny participation in the mission if necessary. In the ensuing battle, three of the Orb pilots are killed and Sven's Strike Noir has its Noir Striker destroyed. However, Sven utilizes the IWSP of one of the surviving Slaughter Daggers and is able to severely cripple the Δ Astray. In the aftermath of this battle, the Acidalium flees at Isaac's suggestion to Lagash, ZAFT's secret underwater supply base, for emergency repairs. Just as the ship leaves, the new Martian mobile suit MMF-JG73L ∇ descends from space, piloted by Ergnes' older (technically) sister Setona Winters.
The Acidalium is named for the Mare Acidalium on Mars.