|I painted Astronaut John Young as he stood proudly on the Moon but, for a while it didn't look like he and Charlie Duke would even land there at all. Earlier, as they had been orbiting the Moon in their lunar module preparing for descent, a call came from Ken Mattingly in the command module reporting an unexpected oscillation in the backup steering system for the rocket engine. They all knew that, if this oscillation prevented the backup system from controlling the rocket properly, then all three crew members would have to return to Earth as soon as possible. If the primary and backup systems both failed, there would be no way to steer the rocket engine, and Apollo 16 and her crew would orbit the Moon forever.
Immediately, engineers and technicians at mission control in Houston and at other key locations were alerted. Could they determine if the oscillations would prevent the backup steering system from doing its job? From North American Rockwell in California to the Kennedy Space Center in Florida, records were searched, simulations were run, and tests were conducted. In less than 6 hours the results were in. The oscillations would damp out as rocket thrust built up at engine start. The mission could continue. We all breathed a collective sigh of relief.
As John Young would say later, "It was a cliff-hanger from where we were sitting in the cockpit. But the ground, who were calling in data from all over the country, really came through. With a couple of clutch hits, they put us right back in the ball game. It was a superb performance."