RRL meaning in Sports ?

The Rocket Racing League was a racing league that planned to use rocket-powered aircraft to race a closed-circuit air racetrack. Founded in 2005, the league made its first public flights in 2010 and was working to begin regular racing seasons. The "Rocket Racers" were slated to compete in the air and on a virtual racetrack easily viewed by a live audience as well as projected on large screen and handheld electronic displays.

Three prototype canard-style Rocket Racer aircraft were built between 2006 and 2010.

The league had planned to hold its inaugural race season in 2008 with four races, but encountered financial difficulties that delayed fielding of Rocket Racers by the six teams that had been previously announced. With the addition of venture capital funding in mid-2009, technology development continued and one exhibition occurred in 2010, with another round of plans for an inaugural season of races in 2011. The 2011 races were, in the end, never scheduled, and by 2014, the league was defunct.