German automotive industrialist who took part, with Max Valier and Friedrich Wilhelm Sander, in experiments with rocket propulsion for automobiles and aircraft.

He was a grandson of Adam Opel, who in 1862 had founded at Rüsselsheim a firm bearing his name that manufactured bicycles, sewing machines, refrigerators, air compressors, and (from 1898) automobiles. The world's first rocket-propelled car, the Opel-Rak 1, was initially tested on March 15, 1928. Opel himself test-drove an improved version, the Opel-Rak 2, on May 23 of that year. On Sept. 30, 1929, Opel piloted the second rocket airplane to fly, a Hatry glider fitted with 16 solid-fuel rockets.