In advance of the Space-X launch tomorrow there was a “hold-down” test at Launch Pad 39A. The “hold-down” test is a rehearsal for the launch to ensure the fueling and countdown procedures are all set before the actual launch.
The Falcon 9 rocket assembly consisting of nine Merlin 1D engines was fired for more than three seconds. After the test fire crews were called to the scene and the four-acre fire was quelled by numerous helicopter water dumps.
The test is customary and apparently all is ready for the launch which you can seehere tomorrow. Launch time is 21:55 UTC / 17:55 ET.