The HMS Sojourner was an experimental airship from some years back. A huge Suspendium crystal had been found in a deep mine, and the kingdom's best scientists had examined it and found it to be flawless. A crystal of this size, powered up, could lift a ship to unprecedented heights.
The Sojourner was built around the crystal, carefully cradling it in a giant frame of shock absorbers. Huge boilers and generators provided the power to energise the crystal. A team of experienced engineers tended to the engines. The captain was a steadfast veteran.