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Weather Woes: Storm Forces Liftoff Delay

July 22, 1999 ::

Satellite Radar for KSC Weather.
Photo: NASA

Once again, the launch of STS-93 has been postponed, this time due to lightning.

According to NASA officials at a press conference which just ended, the procedures followed tonight for lightning protocols were ones which have been in development only in this last year. The new rules require that a storm cell generating lightning be more than 10 nautical miles from the launch site before a shuttle is cleared for launch. A storm cell developed at T-20 minutes on the countdown clock within 8 nautical miles

Chandra & Shuttle Columbia wait patiently on Launch Pad 39B at KSC.
Photo: NASA

south of the launch site. In an effort to wait out the storm, the clock was stopped at T-5 minutes. The launch window of 46 minutes was reevaluated. The storm remained in the danger zone and also increased its cell size, and the mission experts calculated that the launch window could be extended 6 additional minutes. The storm continued to increase in size and did not move. The launch window was then extended 4 more minutes for a T0 of 1:24 am. Lightning struck 8 miles away shortly before 1:19 am when the GO for launch and restart of the countdown clock was to happen, and so the launch had to be scrubbed.

There is a 24 hour turnaround for the STS-93 launch, now scheduled for 12:24 am July 23. There is a 10% chance of scrub due to possible weather interference during re-tanking, since meteorologists predict SW winds and possible lightning in the afternoon within 5 nautical miles. There is also a 20% chance of scrub due to possible debris clouds and wind from this storm system during the launch sequence. Shuttle managers announced early this afternoon that the window for a July 23rd launch will extend from 12:24 a.m. until 2:20 a.m.

We'll try this all again tonight. See you then!

Lightning is a giant spark, a big charge of electricity. A single flash of lightning reaches a temperature approaching 50,000 degrees Fahrenheit in a split second. The extreme heating causes the air to expand at an explosive rate, which in turn causes thunder. At any given moment, nearly 1,800 thunderstorms are in progress over the surface of the Earth.
Photo: Windows to the universe
Copyright 1998, Regents of the Univ. of Michigan

-T. Ruiz

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