* The "sparks" are igniters meant to burn off excess hydrogen gas during engine start but before mainstage (full power) operation. Without these, a large cloud of explosive hydrogen and air could form under the Shuttle. If it exploded, it could damage the Shuttle structure or knock off tiles. These sparks DO NOT "ignite" the rocket engines. Engine ignition is accomplished by an internal "blowtorch" of fuel and oxidizer in each engine, which is ignited with sparkplugs!
j lzrd / swift idiot - 2008-08-23 LIFTED IN DEFIANCE OF GRAVITY or however that quote goes around here.