When Friendship 7 nearly killed John Glenn

Credit: Rocky Mountain News (Feb 21, 1962)

After weather delays, fuel tank problems and scrubbed launches, John Glenn finally made it into orbit on Tuesday, February 20, 1962.

The flight was more than an accomplishment for the former Marine pilot. It was a significant coup for the nation. With this first orbital flight, America had finally caught up to the Soviet Union's Yuri Gagarin. Few involved in NASA's Mercury program could deny spaceflight was dangerous, especially when racing against the Russians. But when Glenn lifted off 39 seconds after 9:47 that morning, no one thought this first orbital flight could turn out to be the agency's first fatality in space.

Glenn's Atlas rocket carried his Friendship 7 capsule into orbit through clear skies, and the astronaut was greenlit for "at least seven orbits."

The mission quickly curtailed when problems arose with one of the capsule's yaw thrusters. The capsule's automatic stability system wasn't working, forcing Glenn to manually maintain its attitude. Yet another, more serious problem was brewing inside the small spacecraft. Stations monitoring Glenn's flight on the ground noted a "Segment 51" sensor warning. It was an indication that the landing bag on Friendship 7 had deployed.

Precious Cargo

The landing bag was part of the Mercury landing system designed to soften the impact of splashdown. But its placement made the Segment 51 warning a real problem: the landing bag was folded like an accordion and stored between the heat shield and the capsule's body. So, if the landing bag was deployed, it meant the heat shield that protected the astronaut from the fiery heat of reentry had separated from the capsule as a result. That meant Glenn's chances of making it back to Earth alive were non-existent.

As the gravity of the situation sunk in, tensions rose in mission control. Losing an astronaut in space so early in NASA's history would be devastating to the nascent agency, but losing Glenn was potentially worse. The Mercury astronauts were all public figures, but Glenn was something of a national hero.

On July 16, 1957, he broke the trans-America speed record in a Vought F8U Crusader jet aircraft, which Glenn can be seen sitting in above. He flew from Los Alamitos Naval Air Station in California to Floyd Bennett Field in New York in 3 hours and 23 minutes (and 8.4 seconds), at an average speed of 725.55 miles per hour. It was a landmark flight that landed him in newspapers across the nation. Three months later, he found himself in the spotlight again with an appearance alongside child star Eddie Hodges on "Name That Tune." When he was presented as an astronaut, he added an outstanding set of values about family, country and God to this public image. The media — and the nation — loved it.

To bring its hero home, NASA needed a quick fix to this potentially deadly problem.

Dwindling Options

What the engineers on the ground really needed was a visual: for Glenn to hop outside his craft and tell them what he saw. But the hatch on the Mercury spacecraft couldn't be opened in orbit, and even if it could the Mercury flightsuits weren't EVA-ready. Since a visual check wasn't an option, NASA's ground team had to get creative with a solution that would fix a potential problem without hindering a normal reentry, just in case the warning light turned out to be erroneous.

The solution lay in the straps that attached the retropack to the capsule. The retropack — the cluster of three rockets designed to reverse the capsule's direction in orbit and slow it for reentry — was held in place over the heat shield by three straps. It was designed to be jettisoned before reentry, but engineers suspected that the retropack's straps might keep the heat shield in place.

The idea worked in theory, but no one was really sure what the retropack would do to the capsule during reentry. It could affect the capsule's balance, for example. If the capsule tumbled end over end, it would burn up in the atmosphere, heat shield or no. Luckily, one engineer anticipated the possibility of a Mercury capsule reentering the atmosphere with its retropack attached: Max Faget of NASA's Langley research center, who designed the blunt Mercury capsule.

During the early days of dreaming up America's first spacecraft, Faget had to consider all possible scenarios to build the best possible capsule. One scenario was a failure of the retropack to jettison. To see what reentry with the retropack in place would do to the capsule, he ran a simple test at NASA's Ames research center's entry heating simulator. Two aluminum, small scale Mercury capsules were put in a wind tunnel, both with phenolic resin and glass fiber heat shields but only one with a mini retropack in place. The simulated friction and heat of reentry charred both capsules equally, suggesting that it was perfectly safe, if not ideal, to leave the rockets in place during reentry. Faget told mission control that his data supported their decision.

The Ride Home

For Glenn in obit, the news came slowly. Two hours and 47 minutes into the flight, the Canton Islands capsule communicator — capcom — asked Glenn over the radio whether he'd heard any loud flapping noises as he was pitching around in orbit. If he had, it would be an indication that the landing bag had deployed and the error was real.

He hadn't, and it wasn't until he reached the end of his third and final orbit, four hours and 22 minutes after launch, that Glenn's capcom in Hawaii told the astronaut about the Segment 51 reading on the ground. Hawaii said it was likely an erroneous warning and probably nothing to worry about. When he passed over California, he got the order to keep his retrorockets attached during reentry. Glenn had just over 20 minutes to contemplate the dangerous reentry he was facing before he entered the ionization blackout, the period of radio silence before splashdown.

It was a nervewracking reentry; Glenn watched pieces of flaming debris flying past his window. He thought it was his heat shield burning into pieces, but it was the retrorocket straps. They burned away in just 24 seconds. At 30,000 feet, the small stabilizing drogue parachute deployed, and as he passed through 11,000 feet the main parachute deployed. Friendship 7 splashed down in the Atlantic Ocean where the Navy destroyer USS Noa was on hand to recover Glenn.

The Segment 51 warning turned out to be erroneous solved by simple rewiring. The landing bag anomaly never surfaced on another Mercury mission. But in the wake of Glenn's flight, the landing bag mishap paled in comparison to the euphoria felt nationwide over finally matching the Soviets' orbital feat.

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