Question: What is the Kappa Platform? What is the Kappa Architecture?
Answer: [summary compiled from various articles and discussions over the last two years]
The Kappa Platform, or architecture, is a new vehicle architecture developed by General Motors to enable the Pontiac Solstice to become reality as a production car.
A vehicle architecture or platform is the basic underlying, load-bearing structure in a vehicle. Analogous to the framing of a building, it also is the majority of expense in production, design, and validation of a new car. A typical strategy for an automotive company is to develop a new architecture or platform rarely - and use that platform for producing variants or improving successive generations of vehicles.
Regarding the Kappa Platform:
In 2002, the Pontiac Solstice Concept was shown, in two forms: a driveable roadster convertible, and a design study of a fastback coupe.
The Pontiac Solstice was recieved very well at the 2002 NAIAS. The driveable roadster concept car shown had been cobbled together from many different components, using a cobbled portion of the "Delta" architecture (a Front-Wheel-Drive small car architecture that supports the Saturn ION and the Chevy Cobalt). The thinking was that this architecture might be heavily modified and used to produce the Solstice.
We have speculated that when General Motors decided to try to produce the Solstice as a highly-styled, low-cost, low-volume niche vehicle for enthusiasts, it became apparent that there were no existing platforms that could be used to achieve the needs of a modern roadster.
Therefore, the Kappa Platform was developed to provide the necessary structure for a two-seat, Rear Wheel Drive convertible. It features hydroformed rails and a tunnel structure similar to the Corvette architecture, and is designed for a short-long-arm suspension for the front and rear. It features rear wheel drive, longitudinal-mounted transmission and front-mid engine.
At this time it appears the platform has only been designed to accomodate a single engine - the four-cylinder Ecotec family. It also appears this platform was only designed to be "left-hand drive".
Since the Solstice, GM has designed another roadster that looks radically different, but shares the same underlying Kappa Platform: The Saturn Sky. The Saturn Sky was styled after the pattern of the Vauxhall VX Lightning design (see below). It also appears that there will be a European version built off the same platform, the details of which have not been released at this time.
Three other concept vehicles were built off the initial Kappa Platform, and shown at the 2004 NAIAS: The Vauxhall VX Lightning, The Saturn Curve and Chevy Nomad. All three cars were recieved reasonably well, but were not nearly as embraced as the original Solstice Concept.
The Vauxhall VX Lightning is the same size as the original Solstice Concept, and pieced together in the same manner as the 2002 Solstice Concept, and had been shown in Europe several months earlier, before the "Kappa Platform" had apparently been finalized. The Vauxhall VX Lightning is the styling pattern after which the appearance of the Saturn Sky is based.
The Saturn Curve and the Chevy Nomad Concept Cars were built on "modified" versions of the Kappa Platform, and exhibited 12" longer wheelbases, and 2+2 seating.
See also
A Look at GM's Kappa RWD Architecture