The main problem: triboelectrification, which is the threat of static electricity between clouds and the rocket if it were launched. Winds also presented a danger.
The Ares I-X would have been airborne for only two minutes. NASA hopes to use it to run engineering tests on a possible mission to the Moon involving humans. The price tag is $450 million for the short test - which has raised the ire of lawmakers in Washington. Some doubt a Moon mission is feasible, given the economic situation of the country. NASA has decided to test the Ares anyway, hoping to impress lawmakers with a successful test.
The rocket is 33 stories tall, and nicknamed the "stick," given its slender appearance on the launch pad. As NASA prepared to begin its first countdown, a cover that was being used to shield its tip from inclement weather got stuck. A rope that was supposed to pull it off finally broke off, and NASA was prepared to send the rocket up with the cover still on top.
About an hour into the launch window, a cargo ship entered waters of the Atlantic Ocean that were considered in the "danger zone" for falling debris or the rocket itself if there were a mishap.
But ocean-borne ships were the least of NASA's problems. The story along Florida's Space Coast today, as it usually is, was the ever-changing weather.
NASA has not announced a rescheduled launch date or time. Engineers are securing, or "safing" the Ares I-X in the meantime.