13 MORE Things That Saved Apollo 13, part 11: The Caution and Warning System

By Nancy Atkinson May 4, 2015
13 MORE Things That Saved Apollo 13, part 11: The Caution and Warning System

Jim Lovell: Houston, we've had a problem. We've had a MAIN B BUS undervolt. Capcom: Roger. MAIN B undervolt. Okay, stand by, 13. We're looking at it. Fred Haise: Okay. Right now, Houston, the voltage is – is looking good. And we had a pretty large bang associated with the Caution and Warning there.

“Critical conditions of most spacecraft systems are monitored by a caution and warning system. A malfunction or out-of-tolerance condition results in illumination of a status light that identifies the abnormality. It also activates the master alarm circuit, which illuminates two master alarm lights on the MDS and one in the lower equipment bay and sends an alarm tone to the astronauts’ headsets. The master alarm light and tone continue until a crewman resets the master alarm circuit. This can be done before the crewmen deal with the problem indicated. The caution and warning system also contains equipment to sense its own malfunctions.”

Nancy Atkinson

Nancy Atkinson

Nancy Atkinson is a space journalist and author with a passion for telling the stories of people involved in space exploration and astronomy. She is currently retired from daily writing, but worked at Universe Today for 20 years as a writer and editor. She also contributed articles to The Planetary Society, Ad Astra (National Space Society), New Scientist and many other online outlets.

Her 2019 book, "Eight Years to the Moon: The History of the Apollo Missions,” shares the untold stories of engineers and scientists who worked behind the scenes to make the Apollo program so successful, despite the daunting odds against it. Her first book “Incredible Stories From Space: A Behind-the-Scenes Look at the Missions Changing Our View of the Cosmos” (2016) tells the stories of 37 scientists and engineers that work on several current NASA robotic missions to explore the solar system and beyond.

Nancy is also a NASA/JPL Solar System Ambassador, and through this program, she has the opportunity to share her passion of space and astronomy with children and adults through presentations and programs. Nancy's personal website is nancyatkinson.com