Three launch pad video cameras show the lightning strike Tuesday. Photo: NASA TV/Spaceflight Now

A bolt of lightning blasted from a thunderstorm cloud Tuesday night and struck the launch pad where space shuttle Atlantis is being prepped for its liftoff Friday. The $2 billion spaceplane was not damaged.

The strike hit the towering lightning mast atop pad 39B at 5:56:52 p.m. EDT (2156:52 GMT). Lightning in Florida is a frequent occurrence and strikes at the shuttle launch pads are not uncommon.

The specially-designed Lightning Protection System, used at both seaside shuttle launch pads, did its job in shielding the spaceship. Wires running down to the ground from the mast directed the lightning away from the pad structure.

"Fortunately, our lightning protection saved us and it doesn't look like it affected any vehicle systems or flight hardware," NASA test director Steve Altemus said.

Instrumentation at the pad recorded the strike. Officials said only a minor surge was noted on the liquid oxygen vent arm.

The severe storms did hold up routine pre-launch work Tuesday but the time was expected to be made up as the countdown continues to Friday's scheduled launch.

In a more dramatic lightning strike 17 years ago, pad 39A was hit while Challenger sat fully fueled and five astronauts were strapped aboard just hours before the eighth shuttle launch.