COLORADO SPRINGS, CO -- The Air Force's top space official wants the service to pursue the production of a fully domestic, next-generation rocket engine. "This is my personal opinion, I would love to see us produce an engine," Air Force Space Command chief Gen. William Shelton told reporters on May 20 during the National Space Symposium. "If you look at our history, when's the last time we produced an engine? The industrial base has kind of withered away. There is...