For the past 4 years, I've been doing a spelljammer/planescape combo in my games. Planar mercantile consortiums, the Elven Imperial Armada aiding in the war against Iuz...all sorts of stuff.
Anyway, planejamming has become a big thing. So far, four different styles of planar helms have been encountered.
Here's a list, along with general prices, and other odd gear:
Twist Drive: 150,000gp - Shrinks the vessel, and it's entire contents, down to man-size so they may pass through a pre-existing portal/gate. Only smaller vessels can mount this, as the larger ones are too big to shrink to a usable size.
Minor Gate Drive: 400,000gp - Combines a Twist Drive with a Gate generator. Opens an ordinary sized gate to the destination, and shrinks the ship to fit through. Same size limitiation as the twist drive. Advantage is not needing pre-existing portal.
Major Gate Drive: 1,000,000gp - Opens a HUGE gate for the vessel to pass through, along with other smaller ships in vescinity. No shrinking necessary. Think White Stars from bab5. Note: Device is big, and only 100+ Ton ships have room.
Phase Drive: 3,000,000gp - Plane-shifts entire vessel to destination, with accuracy of a gate spell. Mainly seen on military vessels, as Major Gate Drives are more cost-effective unless you need the element of suprise.
Nav suite: 500,000gp - Appears as a yard-diameter crystal ball. When activated, projects an holographic map of requested area out into room. Automatically continually updates star/plane/system maps with automatic scrying. Also combines with a portal detection system to show permanent portals on the map.
Sidewalls: Tonnage^2x10 gp cost for generator + Tonnage^2 gp/point of DR- Raises barrier field around ship to protect against attacks. Gives ship DR X/-, where X is the power of the sidewalls. Gives 1/2 X as deflection bonus to AC. Operates for up to 1 hour per day.
