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.
The maiden flight of the Sojourner: A gaggle of naturalists brought nets and sketchbooks to capture the inhabitants of the far skies. A cadre of natural philosophers brought their instruments and theories. A priest lobbied, successfully, to be permitted on board. All were clad in wool and leather to ward off the wind and the cold.
The fires were stoked, the boilers hot, the generators turning. A few smaller Suspendium chambers brought the ship to a comfortable hovering position a dozen metres off the ground. Observers were stationed on a nearby hill. The big switch was thrown. There was a loud bang, a rush of air, and the Sojourner was gone.
The Sojourner project was quickly closed down, insistently forgotten. Conventional wisdom assumes that the big crystal had burst, vaporising the ship in the process. Perhaps it was flawed after all, or perhaps it was simply not safe to energise something that large. Although there was the matter, a few weeks later, of a hastily-suppressed report by the Royal Institute of Astronomy...