Answer the question from the given passage. Your answer should be directly extracted from the passage, and it should be a single entity, name, or number, not a sentence.
Q: Passage: Grissom, White, and Chaffee decided to name their flight Apollo 1 as a motivational focus on the first manned flight. They trained and conducted tests of their spacecraft at North American, and in the altitude chamber at the Kennedy Space Center. A 'plugs-out' test was planned for January, which would simulate a launch countdown on LC-34 with the spacecraft transferring from pad-supplied to internal power. If successful, this would be followed by a more rigorous countdown simulation test closer to the February 21 launch, with both spacecraft and launch vehicle fueled. Question: What was a plugs-out test done to simulate on the LC-34?
A:
launch countdown