But that's merely a measurement. Thetheaterpart is how it opens -- rising in a gullwing fashion, but more specifically, like a two-piece articulated gullwing, which, when done, the Model X winds up looking like a perched pterodactyl. In a vast shopping mall parking lot, this will be noticed. Tesla calls them falcon-wing doors, the word falcon being a popular one on the premises of the Tesla design studio. Where we were standing is adjacent to Tesla CEO Elon Musk's other rather big endeavor, the Space X rocket factory in Hawthorne, Calif., which builds the Falcon 9 rocket ship.

The prototype's doors are interesting. Unlike 'ordinary' gullwings, the Model X's powered articulation allows them to stay close to the car's flanks as they rise, making ingress and egress in tight parking spots a snap. You just step into the vehicle and sit down; no ducking and squirming necessary. Musk, a father of five boys, made a point of demonstrating how much easier this will make installing child seats. The opening's unusually long length also helps accessing the Model X's twin, third-row seats (there's seven seats, all told). Frankly, the whole thing is an intriguing -- but complicated solution -- and it'll be interesting to see how all this works out in the real world (think, rain storms; kids getting their razor scooters caught in the hinges). And speaking of hinges, in a roll-over scenario, the hinges between lower door halves the upper and will free, letting you climb out (no explosive bolts ala the gullwing door Mercedes-Benz SLS).

While the Model X we examined was a prototype with plenty of details that'll undoubtedly change (for instance, I wouldn't bet on the side mirror-replacing video cameras making it -- though they'd reduce drag by a useful 5 percent), what'll stay includes the Model S's magnificent, 17-inch hi-res, multi-touch display, as well as that car's fascinating overall architecture.

Transferred straight from the Model S will be its pancake-flat, under-floor battery packs but in two sizes (60 and 85 kW-hrs) unlike the S trio of packs (the small, 40 kW-hr size being deleted). Given the Model X's greater CdxA, it'll have between 10 to 12 percent less driving range, meaning between about 214 to 267 miles, depending on the battery you've got. Recharge times are unchanged at about four hours for the big battery (at a colossal 20-Watt rate; by contrast, our longterm Chevrolet Volt with a 16 kW-hr battery needs 3.5 hours). Wow.

Simply extending the Model X's extruded structure between the front and rear cast aluminum subframes has allowed the wheelbase to grow by about four inches. The resulting interior volume is astounding, but the clever bit is that, with the low, flat battery, and the small-size and low-positioning of the electric motors, there's room galore. There's a generous rear cargo hold even with the third-row seat erected, plus a decent front trunk as well. With no tall gasoline engine in front, there's plenty of crush space, and dynamically, its handling promises to be unusually good despite the Model X's height, what with all the weighty stuff being so low (this, being somewhat mitigated by the door-supporting roof structure). Depending on speed and circumstances, the Model X's air suspension will allow it to vary its ride height by about an inch. Musk estimated the X to weigh between 10-15 percent more than the Model S, or about 4700 lbs.

You might have noticed me mentioning 'electric motors' earlier. A second, front motor with about half the rear's estimated 300 horsepower will be optional, offering a lot of interesting dynamic possibilities as you can redirect the powerinstantlybetween the front and rear (lateral distribution being via individual brake application). There's greater regen braking available, and even its handling balance might be actively controlled via the fore-aft distribution of power ... or regen-caused drag). Our brief ride around the parking lot suggests the Model X will be quick -- Musk claims 4.4 seconds to 60 mph quick (from, presumably a sport edition). Pricing is expected to about the same as the Model S (starting at $49,900 after the Federal tax credit) with production starting late next year and volume delivery happening in 2014.

As Musk quipped "I don't think a car company should be a one-trick pony." The Model X gives Tesla a couple of tricks up its sleeve. And moreover reinforces a brand-new EV proposition in the marketplace that the Nissan Leaf and Mitsubishi i don't provide -- the long-range battery-electric car that isn't limited to neighborhoods or stratospherically priced. With deliveries of the Model S slated for no later than July, we'll soon see if the market is ready for that proposition.