I heard it on the radio at 9:08 in the evening. I had just sat down after dinner. The announcer came on with a bulletin: something had happened on Apollo 13. An explosion. The spacecraft was damaged. Mission Control was assessing.

I turned up the radio and stayed there.

The details came out slowly, the way they always do in a real emergency when nobody knows exactly what happened yet. What I could piece together: at 55 hours and 54 minutes into the mission — about 200,000 miles from Earth — an oxygen tank in the Service Module exploded. The explosion damaged the Service Module, venting oxygen into space. Two of the three fuel cells — which power the Command Module by combining hydrogen and oxygen — were dead, their supply of oxygen gone with the tank. The remaining oxygen was venting as well.

Jim Lovell looked out his window and said later: “We are venting something out into space.” It was oxygen. The spacecraft’s life support was bleeding away into the vacuum.

His first transmission to Mission Control was the sentence that everyone will remember: “Houston, we’ve had a problem here.” Past tense. They’ve had a problem. He said it calmly and precisely, the way you describe something after it happened, not while it’s still happening. Except it was absolutely still happening. The problem was ongoing and worsening and nobody yet knew how bad it would get.

I am writing this at midnight. The radio is on next to me. Betty asked me to come to bed. I told her I couldn’t. She understood. She went to bed. I’m in the kitchen with the radio, and every fifteen minutes or so there’s a new update, and each update tells me something a little more specific about how bad the situation is.

Three men are 200,000 miles from Earth in a spacecraft that has lost most of its power and oxygen supply. The Command Module has perhaps 15 minutes of power remaining in the batteries if they run everything at full. The Moon landing is obviously cancelled. The question — the only question that matters right now — is whether they can get home.

Mission Control is working on it. They’re always working on something — that’s what they do. But this is different from a thruster problem or a navigation update. This is the kind of problem where if they get it wrong, Jim Lovell and Jack Swigert and Fred Haise don’t come home.

The radio announcer is saying that Mission Control is considering having the crew move into the Lunar Module — using it as a lifeboat. The LM has its own oxygen, its own power. It was designed for two men for two days. There are three men and they need four days to get home. The math is hard. But it might be the only option.

I put down my coffee and looked at my hands for a while. Then I got up and stood in the kitchen window and looked at the night sky. Clear tonight. The Moon is up.

Somewhere out there, past the Moon, three men are figuring out if they can survive in a spacecraft that just blew up underneath them.

I’m going to stay by the radio tonight.