my guess is that when it's rocket powered it's shielding the (blocked?) intakes of the scram jet. when it ejects the rocket booster and switches to the scramje

my guess is that when it's rocket powered it's shielding the (blocked?) intakes of the scram jet. when it ejects the rocket booster and switches to the scramjet it changes attitude (and the "waverider" details at wikipedia are quite interesting - http://en.wikipedia.org/wiki/Waverider http://en.wikipedia.org/wiki/Waverider)