Finally, at a little after seven forty-five, the great Atlas engine were fired, sending out billows of steam, flames, dust, smoke, fumes and heat. At this signal, all four Carpenter children abandoned their posts in front of the television, where all three networks were covering the launch live, and dashed out to the beach. Already the pale morning sky was streaked with contrails, and in the distance they could see the Atlas lifting off. Against the low slant of the sun, Rene saw the Atlas streak into the sky and then disappear.
Just before liftoff, Scott had been thinking about his grandfather, Vic Noxon. “At last I’ll know the great secret,” the old man had told Dr Gilbert on a golden Sunday morning on the Front Range. He was dying. He knew he was dying. He wasn’t afraid. Scott was confident that May morning, like his Grandpa Noxon, that everything was going to be all right – that this experience so long anticipated had finally arrived. As the rocket engines began to rumble and vibrate beneath him, he became preternaturally alert to the many sounds and sensations of liftoff.
There was surprisingly little vibration, although the engines made a big racket and he felt the rocket swaying as it rose. The ride was gentler than he expected. He looked out his window, placed directly overhead, to see the escape tower streaking away like a scalded cat. One especially odd thing, for one accustomed to level flight after the required climb, was to see the altimeter reach seventy, eighty, then ninety thousand feet and yet know that he was still going straight up.
No one noticed at the time – there was no dial to measure its functioning – but the capsule’s pitch horizon scanner (PHS) had already started malfunctioning. The Mercury capsule was chockfull of automatic navigational instruments, among them the PHS, which does just what the name implies: it scans the horizon for the purposes of maintaining, automatically, the pitch attitude of the capsule. For MA-7, however, the PHS immediately began feeding erroneous data into the Automatic Stabilization and Control System (ASCS), or autopilot. When this erroneous data was fed into the ASCS, the autopilot responded, as designed, to fire the pitch thruster to correct the perceived error. This in turn caused the spacecraft to spew precious fuel from the automatic tanks. Fuel was a finite commodity.
Forty seconds after tower separation, the pitch horizon scanner was already 18 degrees in error. It was indicating a nose-up attitude, or angle, of plus-17 degrees while the gyro on the Atlas showed pitch to have been minus 0.5. By the time of spacecraft separation, the pitch gyro aboard the capsule had “slaved” to the malfunctioning pitch-scanner output and was in error by about 20 degrees. NASA later found that the error would persist, intermittently, to greater and lesser degrees, throughout the three-orbit flight, with near-calamitous effect as MA-7 readied for reentry less than five hours later.
At the moment, Scott was focused on the gravitational forces, which peaked at a relatively gentle 8 Gs. He marvelled at the intense silence, but then experienced an even greater sensation of weightlessness. At five minutes, nine seconds into the flight, he reported to Gus listening as Capcom at Cape Canaveral: “I am weightless! – and starting the fly-by-wire turnaround.”
The sensation was so exhilarating, his report to the ground was more of a spontaneous and joyful exclamation than the routine report he had expected to make. The fly-by-wire manual controls were exquisitely responsive and quickly placed the Mercury capsule into a backward-flying position for the beginning of Scott’s first circumnavigation of the earth. John had accomplished this maneuver on autopilot, as specified by his flight plan, causing the system to expend more than four pounds of fuel in the process. In the fly-by-wire control mode, it could be done using only 1.6 pounds.
The three-axis control stick (or hand controller) designed for Mercury was a nifty device that allowed the pilot to fly the capsule in either the “manual proportional” or “fly-by-wire” (“wire” here meaning electrical) systems. The manual proportional system required minute adjustments of the control stick – of perhaps 2 or 3 degrees – to activate the one-pound thrusters. Fore and aft movements controlled pitch, which is the up or down angle of the spacecraft, side-to-side movements controlled roll. The pilot could control or change the direction left or right, by twisting the control stick – a hand control that replaced the old rudder pedals used in airplanes The MA-7 flight plan specified only limited use of the ASCS.
Gus Grissom, as Capcom, gave Carpenter the good news: “We have a Go, with a seven-orbit capability.” Carpenter replied: “Roger. Sweet words.”
Sweet words indeed. With the completion of the turnaround maneuver, I pitched the capsule nose down, 34 degrees, to retroattitude, and reported what to me was an astounding sight. From earth-orbit altitude I had the moon in the center of my window, a spent booster tumbling slowly away, and looming beneath me the African continent. But the flight plan was lurking, so from underneath the instrument panel I pulled out my crib sheets for the flight plan written out on three 3 x 5 index cards, and Velcroed for easy viewing. I could just slap them up on a nearby surface, in this case the hatch, covered with corresponding swaths of Velcro. Each card provided a crucial minute-by-minute schedule of in-flight activities for each orbit. They gave times over ground stations and continents, when and how long to use what type of control systems, when to begin and end spacecraft maneuvers, what observations and reports to make on which experiments. In short, they told me, and the capcoms, who had copies, what I was supposed to be doing every second of the flight – every detail of which had been worked out, timed, and approved before liftoff. A brief investigation of these cards is enough to suggest constant pilot activity. But to get the best appreciation of just how busy we all were during those early flights, read the voice communication reports between the capcoms and the astronaut.
It was time to open the ditty bag. Stowed on my right, it contained the equipment and the space food for the flight. First out was the camera, for I needed to catch the sunlight on the slowly tumbling booster still following the capsule. The camera had a large patch of Velcro on its side. I could slap it on the capsule wall when it wasn’t in use. Velcro was the great zero-gravity tamer. Without it, the equipment would have been a welter of tether lines – my idea, incidentally, and not a very good one, for John’s flight. He had ended up in a virtual spaghetti bowl full of tether lines and equipment floating through his small cabin.
Also in the ditty bag were the air-glow filter, for measuring the frequency of light emitted by the air-glow layer, star navigation cards, the world orbital and weather charts-adjuncts to the earth path indicator (EPI) globe mounted on the instrument panel. The EPI was mechanically driven at the orbital rate so that it always showed the approximate spacecraft position over the earth. There were also bags of solid food I was to eat (a space first), and the densitometer.
But the most important items at this point in the flight were probably the flight plan cards. I had been tracking the booster since separation, maneuvering the capsule with the very good fly-by-wire system: “I have the booster in the center of the window now,” I reported, “tumbling very slowly.” It was still visible ten minutes later, when I acquired voice contact with Canary capcom.
Carpenter: “I have, west of your station, many whirls and vortices of cloud patterns. [Taking] pictures at this time – 2, 3, 4, 5. Control mode is automatic. I have the booster directly beneath me.”
The brilliance of the horizon to the west made the stars too dim to see in the black sky. But I could see the moon and, below me, beautiful weather patterns. But something was wrong. The spacecraft had a scribe line etched on the window, showing where the horizon should be in retro-attitude. But it was now above the actual horizon I checked my gyros and told Canary capcom my pitch attitude was faulty.
Carpenter reported: “I think my attitude is not in agreement with the instruments.”
Then I added an explanation – it was “probably because of that gyro-free period” – and dismissed it. There were too many other things to do.
John had also had problems with his gyro reference system. Kraft described it in an MA-6 postflight paper, where he wrote that the astronaut “had no trouble in maintaining the proper [pitch] attitude” when he so desired “by using the visual reference.” All pilots do this – revert to what their eyes tell them when their on-board tools fail. But future flights, he said, would be free of such “spurious attitude outputs” because astronauts would be able to “disconnect the horizon scanner slaving system,” called “caging the gyros” in these future flights. Because my flight plan for the follow-on mission called for so many large deviations from normal orbital attitude (minus-34- degree pitch, 0-degree roll, 0-degree yaw), I was often caging the gyros when they weren’t needed for attitude
