Phoenix Logs/UNSC Buildings/Supply Pad
From Halopedia, the Halo wiki
Supply landing zones.
Supply Pads allow the firebase to receive a constant flow of Supplies from the Spirit of Fire. These are vital logistical ports for UNSC combat operations, and the force commander should carefully weigh the cost of delaying their construction. To sustain high-tempo missions the Heavy Supply Pad upgrade is needed, which accelerates Supply generation. Though important to the war effort, too many Supply Pads can impede efficiency if they take the place of unit-creating structures—you can't win a fight with just raw materials!
While some useful assets can be salvaged and tapped on the Ark's surface, the bulk of the UNSC's supplies must still be delivered from the Spirit of Fire. Sustaining combat operations on the Ark would be practically impossible without the use of supply pads to quickly unload cargo from dropships and the on-site direction of logisticians to efficiently redistribute the incoming food, ammunition, spare parts, and power cells.