The Mammoth Book of Space Exploration and Disasters

Carpenter replied: “I expended it on – by manual and flyby – wire thruster operation on the dark side, and just approaching sunrise. I think that I can cut down on fuel consumption considerably during the second and third orbits. Over.”

The Zanzibar Capcom took over ground communication. Consulting the same flight plan I had, he reminded me I was supposed to be on fly-by-wire. I thought better of it and said so:

“That is negative. I think that the fact that I’m low on fuel dictates that I stay on auto as long as the fuel consumption on automatic is not excessive. Over.”

The irony is that even the ASCS control mode, ostensibly thrifty with fuel, was now guzzling fuel because of the malfunctioning pitch horizon scanner. “Roger, Aurora 7,” replied Zanzibar Capcom and then congratulated me on my trip so far. “I’m glad everything has gone-” but the rest of this message dropped out. “Thank you very much,” I said, hoping he could still hear me.

After Zanzibar was the Indian Ocean Capcom, stationed aboard a United States picket ship called Coastal Sentry, permanently anchored at the mouth of the Mozambique channel. After the usual preliminaries (“How do you read?” ‘Loud and clear. How me?’), he reminded me to conserve fuel and then inquired: ‘Do you have any comments for the Indian Ocean?’ I replied, but not with a greeting. I was having that old ASCS difficulty:

“That is Roger. I believe we may have some automatic mode difficulty. Let me check fly-by-wire a minute.”

Going to fly-by-wire is the best way to diagnose any problem with the thrusters, the small hydrogen peroxide-spewing jets that control spacecraft attitudes. I checked them again. The thrusters were fine. We didn’t know it at the time, but the thrusters were receiving faulty information, through the autopilot, from the pitch horizon scanner. Worse, the error from the automated navigational tool was intermittent and thus hard to identify. I reported that the gyros, my onboard navigational tools, were not “indicating properly.” This sort of problem requires patient investigation. I told the Indian Ocean Capcom to wait.

Carpenter reported: “The gyros are… okay, but on ASCS standby [the off position]. It may be an orientation problem. I’ll orient visually and see if that will help out the ASCS problem.”

I went off autopilot to fly-by-wire, oriented the capsule visually, and then returned to ASCS autopilot, to see what would happen. My hope was to catch the autopilot misbehaving. It was an angel. Imagine that you own a high-performance car that develops a quirky habit, when on autopilot, of veering off the interstate as you’re speeding along at 80 miles per hour. You take it to the dealer, describe the trouble, and the mechanics can’t duplicate the malfunction when they take it out to the freeway the next day. Imagine this happening in space, with your space car, and you have only two circumnavigations left on the orbital hightway. Imagine further that your precisely timed exit off the orbital highway will be performed using this intermittently malfunctioning autopilot. This is what I was facing, but didn’t know it. No one did.

Technicians, pilots among them, often make erroneous assumptions when troubleshooting a problem. An erroneous assumption early on can invalidate all subsequent efforts to find a solution. Nobody realized that the problem lay in the pitch attitude indicator. From the pilot’s viewpoint, the problem with the ASCS was an anomaly, and the intermittent failure meant little. When your navigational tools disagree with the view out your window and this persists in any great disparity, the instruments are malfunctioning. When the instruments are malfunctioning, you have no recourse but to navigate visually with reliable reference points – the horizon, the position of a known star, geographical landmarks. This is what I did.

The Indian Ocean Capcom waited patiently. Nearly a minute passed while I tried diagnosing the problem. We were working off a tight flight plan, so he reminded me I was “supposed to, if possible, give a blood pressure.” This was a simple matter of pressing a semi-automatic device on my suit, which I did, and felt the blood pressure cuff inflate. “Roger,” I said, “I’ve put blood pressure up on the air already. Over.”

Mercury Control had in the meantime picked up on my earlier transmission about the thrusters. During MA-6, a thruster malfunction had forced John to assume manual control for his final two orbits. Rightly concerned about a repeat of the old problem, Mercury Control pressed the capcom to get me to submit a complete report on the thrusters.

Capcom ordered: “Report to Cape you have checked fly-by-wire, and all thrusters are okay. Is there anything else?”