The Lightning featured a conformal ventral store to house either a fuel tank or a rocket engine. The Napier Double Scorpion engine also contained a reserve of of high-test peroxide (HTP) to drive the rocket's turbopump and act as an oxidiser; fuel was drawn from the aircraft internal tankage. The rocket engine was intended at an early stage in the Lightning's development to boost performance should non-afterburning (reheated) engines be fitted. The basic performance with reheated Avons was deemed sufficient, and the rocket engine option was cancelled in 1958. The ventral store was routinely used as an extra fuel tank, holding of usable fuel. On later variants of the Lightning, a ventral weapons pack could be installed to equip the aircraft alternatively with different armaments, including missiles, rockets, and cannons.