The Mammoth Book of Space Exploration and Disasters

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.”

Carpenter described: