"challenger" flew normally for almost a minute. at the 59 second mark, though, the aluminium seal broke. this allowed the burning rocket fuel to escape through the broken part of the o-ring. a visible plume of fire came out of the right srb, burning both the external fuel tank and the piece of metal keeping the two connected. this plume burned through the bottom of the fuel tank, where the liquid hydrogen fuel was stored. at 68 seconds after liftoff, the engines increased power to produce the highest thrust possible (known as throttling up). the flight controllers informed the shuttle crew that their flight status was "go" at the throttle-up stage. the flight commander, dick scobee, responded with ""roger, go at throttle up."