Fourth Bridge
| Fourth Bridge | |
|---|---|
| |
| Type | Airship |
| Creators | Alethi |
| Captain | Navani Kholin |
| World of Origin | Roshar |
| Universe | cosmere |
“She is an odd ship, to be sure, but majestic in her own way. ”
The Fourth Bridge is Roshar's first airship. It was built in the Shattered Plains, and named after Bridge Four.[1]
Design
“Hundreds of laborers in Urithiru turning winches to raise and lower the ship. Dozens of chulls used to move it laterally. Thousands of fabrials to facilitate both—all needing to be perpetually reinfused. Careful synchronization via a half dozen spanreeds to coordinate maneuvers. ”
The Fourth Bridge is a rectangular, wooden box; a hundred feet long, sixty feet wide, and about forty feet high, with three decks within. Fans are built into the back to increase speed, though for now, the speed difference they provide is minimal.[1]
The back half of the upper deck is covered by a semi-round roof, while the front half is open to the air, and surrounded by a railing. Bridge Four's original bridge is embedded into the floor; the Windrunners have a habit of kneeling down and touching it before taking off. A command station, composed of several tables, is typiacally placed in the sheltered part, though in some cases, it might be moved to the front. The furniture is bolted down.[1][3]
![[3]](#cite_note-Navani.27s_Notebook_-_The_Fourth_Bridge.jpg-3){kind=link}
The lower decks serve as the hold. It has wide door that open, allowing large amounts of people to come in and out. It functions akin to a drawbridge; normally, it is part of the wall, and can be lowered and raised by ropes to open and close it. While sparsely-furnished, the holds can accomodate several hundred people.[1] There are numbers painted on the walls, dividing the hold into a number of sections.[2][3]
Mechanics
The airship doesn't so much fly as it floats. There are hundreds of gemstones forming a lattice of masive Cojoiner fabrials embedded into the ship. They are connected to a pair of "dummy ships". One of the dummies is hanging off the side of the Urithiru plateau; the other is built on the Shattered Plains.[4][5] The airship is steered from those two lattices; the Fourth Bridge communicates its needs to them through spanreeds. As they cannot be used for long periods of time due to movement, the scribes use them by turning them on and off, creating a code of blinks.[1]
The cojoiner fabrials are isolated using aluminum so that only certain planes of movement are transferred between the paired gem halves. The Urithiru structure can only convey vertical motion; the Shattered Plains lattice can only transfer horizontal motion.[5][1] To allow the ship to continue moving when the space for the lattices runs out, an additional aluminum mechanism is used to reverse the motion while the gemstones are temporarily unhooked.[1]
The entire structure requires significant manpower to function properly. In Urithiru, hundreds of people operate the winches that raise and lower the vertical lattice; on the Plains, squads of chulls are used to move the ship horizontally. The entire structure requires hundreds of gemstones to be perpetually infused with Stormlight.[1] Fans have been installed to ease the load on the horizontal fabrials, but as of right now, they are barely functioning. There are also weight concerns, as adding too much mass to the existing structure might cause the gemstones to crack.[2]