Springhill-class mining ship
From Halopedia, the Halo wiki
These mining ships were already considered ancient by the beginning of the Human-Covenant War, these vessels which was originally used for mining gaseous materials from nearby gas clouds or gas giants by skimming the planet's surface for processing. 
However, by the time of the Human-Covenant War, resource constraints and/or desperation has forced some, like the CAA Heavy Burden into being repurposed as a construction and ordnance transport ship; housing the HRUNTING/YGGDRASIL Mark II (D) armor system in the process.
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