From Halopedia, the Halo wiki
In 2554, a recolonization fleet was sent to the glassed world Alluvion, only to find that the Sundark Sea had been split asunder by formerly dormant Forerunner shield pylons. A new, exotic source of energy was discovered. It was thought capable of replacing deuterium for human spaceships. In 2556, the UNSC contracted Liang-Dortmund to establish the Alluvion Research Center. The corporation started developing the Nordica V, a prototype of vessel to test the fuel source. Six ships were built at the ARC, and some launched successfully. Only a year into the project, the mining efforts triggered the withdrawal of the shield pylons, and the sea collapsed, destroying the site and presumably the remaining ships with it.
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