The Xtreme Gravity Series is a charitable race founded by Don MacAllister of America Works for Kids.According to the race rules, the competing cars must weigh a maximum of 88 pounds, can be up to eight feet long and up to 36 inches tall and wide. Volvo, for example, participated in this race in 2004 with a car that was constructed of water-jet-cut high-strength aluminum, carbon fiber composite, and fiberglass.

The Silbervogel has a load-bearing carbon structure and slim rims, making it a very light car. The driver can enter the car via its detachable top. It is constructed of a transparent lower shell, a silvery top part, and a glass band that runs from the car’s nose to the back.

"Each detail has been optimized for lowest resistance. This also applies to the main body shape. Polished aerodynamics is important, especially for gravitation race-cars. That's why the Silbervogel is fully encased.", explains Hirzel.

TFOT has covered various concept cars, including Morgan Motor's "LifeCar", which was designed to be an aesthetic, high performance, hydrogen fuel cell vehicle with zero emissions, a new concept car called "sQuba", which is the world's first 'green' diving car,and the Jeep Renegade, designed by Chrsyler to be the ultimate 'green' outdoor vehicle. TFOT also reported on the newly renamed Progressive Automotive X PRIZE International Competition, designed to bring about radical breakthroughs by encouraging the design and creation of a new generation of viable, super fuel-efficient vehicles.

More information about the Silbervogel can be found at Jakob Hirzel's website.