A Patriot battery missed a Scud because it had been on for 100 hours

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This missile defence failed because it was on too long. Its clock was off by a third of a second. That was enough.

The Patriot predicts where a Scud will be next. Then looks only there. That needs the time. The clock counts tenths of a second. Converting it in 24-bit registers loses a little precision. And that error grows every hour the system stays on.

A Scud flies at about Mach 5. Tiny time errors become big distances. After 8 hours, the gate is off by 55 metres. Around 20 hours, the target falls outside the gate. After 100 hours? About 687 metres.

The Patriot was built to move often. A few hours per site. In the Gulf, batteries sat still. Alpha Battery ran over 100 hours.

11 February. Israeli data shows a 20 percent shift after 8 hours. 16 February. The Army releases fixed software. 25 February. A Scud hits a barracks. 28 Americans are killed. 26 February. The fix reaches Dhahran. One day late.

But here's the catch. A warning did go out. It said very long run times could shift the gate. It never said how long. A reboot takes 60 to 90 seconds. It resets the clock to zero.

Some bugs grow just by staying on. Drift, leaks, counters. Know how long your system can safely run. As a number.

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