form of a slide rule. The charts show exactly what star should be in the center of the window at any point in the orbit – by keeping that star at the very center of your window you know you’re maintaining zero yaw. But there are troubles even here, for the pilot requires good “dark adaption” (or a dark-adapted eye) to see the stars, and dark adaption was difficult during the early flights because of the many light leaks in the cabin. The backup measures (“backup” here meaning human) were absolutely critical to have in place at retrofire – in the event of attitude instrument failure.
Deke and I discussed suit temperature, which like the cabin was hotter than I liked. He suggested a different setting, which I tried. Then Woomera capcom hailed me, and I replied: “Hello, Woomera capcom, Aurora 7. Do you read?” while still in voice contact with Deke, at Muchea. “Roger, this is Woomera,” came the capcom’s voice. “Reading you loud and clear. How me?” Deke was confused. He couldn’t hear Woomera and thought to correct me.
Between Muchea and Woomera, I was trying to see the ground flares, a check for visibility. Deke gave me the attitudes to view the first flare, which involved a whopping, plus-80 degrees yaw maneuver and a pitch attitude of minus 80 degrees. But the cloud cover was too dense. “No joy on your flares,” I told Woomera and then went to drifting flight, where I found that just by rocking my arms back and forth, like attempting a full twist on the trampoline, I could get the capsule to respond in all three axes, pitch, roll, and yaw.
The Cape advised me to keep the suit setting where it was, because the temperature was coming down. I continued in drifting flight, and at capsule elapsed 01 02 41.5, over Canton, we checked attitude readings with telemetry. The Canton Capcom told me my body temperature was registering 102 degrees Fahrenheit, clearly a false reading.
Carpenter reported: “No, I don’t believe that’s correct. My visor was open; it is now closed. I can’t imagine I’m that hot. I’m quite comfortable, but sweating some.”
A food experiment had left crumbs floating in the cabin. I remarked on them, and reported the dutiful downing of “four swallows” of water. At his prompting, however, I could not confirm that the flight plan was on schedule. But I reported what I could: “At sunset I was unable to see a separate haze layer – the same height above the horizon that John reported. I’ll watch closely at sunrise and see if I can pick it up.”
Canton Capcom wished me “good luck,” and then LOS – loss of signal.
Everyone on the ground had had an eye on the fuel levels since the end of the first orbit. Gordo Cooper, capcom at Guaymas, had told me to conserve fuel, which was then at 69 percent capacity for the manual supplies, and 69 percent for the automatic. By the time I returned for my second pass over Kano, they had dropped to 51 and 69, respectively.
Carpenter reported: “The only thing to report is that fuel levels are lower than expected. My control mode now is ASCS.”
I explained to the Kano Capcom: “I expended my extra fuel in trying to orient after the night side. I think this is due to conflicting requirements of the flight plan.”
Live and learn. I spoke to the flight recorder, although Kano Capcom still had voice contact.
I should have taken time to orient and then work with other items. I think that by remaining in automatic I can keep – stop this excessive fuel consumption.
When I went to fly-by-wire aboard Aurora 7, very slight movements of the control stick in any axis activated one-pound thrusters and changed the attitude very slowly. Larger stick movements would activate the twenty- four-pound thrusters, which would change the attitude much more quickly but use twenty-four times as much fuel. If the manual proportional control mode were chosen, the change capsule attitude would be proportional to stick movement, just as an airplane. (Move the stick a little, get a little bit of thrust; move it halfway, get half thrust; move it all the way, get full thrust.) Each increment of movement had attendant increases in fuel expenditure. If, however, both control modes were chosen concurrently – and this happened twice during MA-7 as a result of pilot error – then control authority is excessive and fuel expenditure exorbitant.
For my flight the twenty-four-pound thrusters came on with just a wrist flick, that I then corrected with a wrist flick in the other direction. This countermovement often activated the twenty-four-pound thrusters yet again, all for maneuvering power not required during orbital flight. The high thrusters weren’t needed, really, until retrofire, when the powerful retrorockets might jockey the capsule out of alignment. The design problem with the three-axis control stick as of May 1962 meant the pilot had no way of disabling, or locking out, these high-power thrusters. Because of my difficulties and consequent postflight recommendations, follow-on-Mercury flights had an on-off switch that would do just that, allowing Wally Schirra and Gordo Cooper to disable the twenty-four-pound thrusters. Gemini astronauts had a totally different reaction control system.
But I understood the problem and resolved to limit my use of fuel. Consulting my index cards, I saw that I still had voice reports to make on several experiments – the behavior of the balloon, still tethered to the spacecraft; a night-adaption experiment; and the ingestion of some more solid food. Holding the bag, however, I could feel the crumbled food. If I opened it, food bits would be floating through my work space. I made a mental note: “Future flights will have transparent food bags.” See-through bags would make crumb strategy easier during these zero-G food deployments. I was beginning to regret my lack of training time.
Before loss of signal, Kano Capcom asked me to repeat my fuel-consumption critique.
Capcom asked: “Would you repeat in a few words why you thought the fuel usage was great? Over.”
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
“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,
