Something had fouled up. But at first the cause wasn’t clear; all Donnelly got was a rash of symptoms, monitored by his controllers.

“We’ve got more than a problem.” That was EECOM, in charge of electrical and environmental systems: life support in Apollo-N. He was shouting. “I have CSM EPS high density. Listen up, you guys. Fuel cell 1 and 2 pressure has gone away.” Controller jargon, for fallen to zero. “And I’m losing oxygen tank 1 pressure and temperature.”

Natalie York was talking to the crew. “This is Houston. Repeat that, please.”

“…We’ve got a problem,” Jones said over the air-to-ground. “The NERVA is out, and we’re seeing a Main Bus A undervolt.”

“Roger. Main Bus A. Stand by, Apollo-N; we’re looking at it.”

Guidance said, “We’ve had a hardware restart. We don’t know what it was.”

A hardware restart meant some unusual event had caused the computer to shut itself down and reboot. Donnelly called for confirmation from another controller.

The crew kept reporting the Bus A undervolt.

The electrical power for Apollo-N came from three fuel cells in the Service Module. The current from the cells flowed through the A and B Buses, conduits which fed the rest of the spacecraft’s components. An undervolt alarm meant the spacecraft was losing its electrical power.

Donnelly tried to get confirmation of the problem from EECOM. “You see a Bus undervolt, EECOM?”

“…Negative, Flight.”

But EECOM had hesitated.

He knows more than he’s telling me. He’s still trying to figure it through. What the hell was happening? The mission seemed to be falling apart before his eyes.

Donnelly pressed EECOM again; he needed more data. “The crew is still reporting the undervolt, EECOM.”

“Okay, Flight. I have some instrumentation problems. Let me add them up.”

Instrumentation problems. EECOM sees the undervolt, all right. But he doesn’t believe what the instruments are telling him. He’s looking at a lot of ratty data, he thinks some kind of major telemetry failure is under way. He wants to be sure before he reports it to me.

Donnelly said, “I assume you’ve called in your backup EECOM to see if we can get more intelligence applied here.”

“We have him here.”

“Roger.”

Then INCO, the instrumentation and communications controller, called in. “Flight, INCO. The high-gain antenna has switched to high beam.”

What in hell did that mean? “INCO, can you confirm the time when that change occurred?” If he could, it might be a clue in pinning down what was happening…

Before INCO could reply there was another call. “Flight, Guidance. We have attitude changes.”

“What do you mean, attitude changes?”

“The RCS valves appear to be closed. They should be open.”

Reaction control problems. Antenna problems. Problems with the oxygen tanks, and the fuel cells.