Friendship 7: A Real Fireball — an interactive Space Academy mission

On February 20, 1962, John H. Glenn Jr. became the first American to orbit the Earth aboard the Mercury capsule he named Friendship 7. The flight came at a tense moment in the space race: the Soviet Union had already flown two cosmonauts around the planet, while the United States had managed only brief suborbital hops. Lifting off from Launch Complex 14 at Cape Canaveral atop an Atlas rocket — a booster that had failed and exploded in earlier tests — Glenn was flung into a 100-by-162-statute-mile orbit at roughly 17,500 mph, circling the globe once every 88 minutes and 29 seconds. "Oh, that view is tremendous!" he radioed, describing a sunrise or sunset every 45 minutes and the mysterious luminous "fireflies" drifting past his window that later proved to be frost flaking off the capsule.

Near the end of the first orbit a yaw attitude-control jet clogged, causing the automatic system to drift the nose off-heading and then jerk it back, wasting precious hydrogen-peroxide fuel needed to hold the capsule steady for retrofire. Glenn took over by hand, flying the remaining two orbits largely in manual fly-by-wire mode. In doing so he helped demonstrate that a human pilot — not merely an autopilot — could reliably control a spacecraft, a finding that reshaped how NASA valued its astronauts. But the drama that gripped the nation came from the ground. Flight controllers saw an anomalous reading from "Segment 51," a sensor suggesting the landing bag had deployed early, which would mean the heat shield was unlatched and held on only by the straps of the spent retrorocket package.

If the shield was truly loose, the intense re-entry heating would burn straight through the capsule and kill Glenn. Standard procedure called for jettisoning the retropack before re-entry, but Mission Control made the bold decision to keep it strapped on, reasoning that its straps would help hold the heat shield in place through the worst of the heating. As Friendship 7 plunged back into the atmosphere, the retropack tore apart in the fire; flaming chunks streaked past the window, and Glenn — unable to tell whether it was the pack or his own shield disintegrating — reported, "This is Friendship 7. A real fireball outside." After a few minutes of ionization blackout, his voice returned. The shield had held; the Segment 51 warning had been a faulty sensor switch, the heat shield secure all along. Friendship 7 splashed into the Atlantic after 4 hours, 55 minutes, and 23 seconds aloft, and the destroyer USS Noa had the capsule aboard about 21 minutes after landing. Glenn returned a national hero, restoring American confidence and momentum in the race to the Moon.