Space: Tune In Next Leak

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Less than an hour after engineers began pumping 385,000 gal. of highly explosive liquid hydrogen into the fuel tank of the space shuttle Columbia, the countdown was halted and the flight scrubbed -- for the third time in just over three months. "We do not consider that the vehicle is safe to fly," declared shuttle director Robert Crippen, who earlier this summer grounded the entire fleet when leaks turned up in the shuttle Atlantis as well. NASA has not been able to get a shuttle off the ground since April, when it launched the now crippled Hubble telescope. Though shuttle engineers once talked of 24 flights a year, so far NASA has managed only three in 1990.

Engineers have tried to fix the plumbing between the shuttle and its huge external tank, but the leaks keep turning up in different places. "My first reaction was frustration," said shuttle scientist Ed Weiler, "but my next thought was 'My God, I'm glad they stopped; some of my friends are aboard.' "