I can't say what the rationale was for the Andy Collins mini-game in Dungeon about two or three years ago, but in the original, it was called a spelljamming helm. Greater and lesser jamming helms were powered by the magical capabilities of their users for the day; only spellcasters could use them, and their tactical speed was related to one-half or one-third the caster's level, depending on if it was a minor or major 'jamming helm.
Non-spellcasters had other means, which worked the same way, but they were powered by different things; forges destroyed magic items to power them, lifejammer helms sucked living creatures dry of life to power them, series helms were used by creature with spell-like abilities (like mindflayers) to power them, and the dwarves used pure creative force - yep, they MADE STUFF to power their helms.
In all cases, there were two speeds for helms - tactical and full speed. All helms powered craft at the same full speed - something like 50,000,000 miles per hour. Only the tactical speed different by its user.