Space History I Didn't Know.

The capsule escape rockets for the Mercury and Apollo capsules worked in one unmanned test in each program when the booster rocket failed.

Here's silent footage from the Mercury-Atlas 3 test.

For Apollo, the booster was a Little Joe. The flight was one of a series to test the escape rocket system, but the booster itself came apart, resulting in a "no shit" firing of the escape system.