The Myth of John Glenn’s Seven-Orbit Mission

First American to Orbit the Earth

John Glenn was the first American to orbit the Earth on his historic spaceflight on February 20, 1962.  It’s good to remember what exactly he accomplished. 

Glenn was actually the fifth person to go to space. NASA astronauts Alan Shepard and Virgil “Gus” Grissom each made fifteen-minute suborbital trips to over 100 miles (160 km) in altitude in mid-1961. Grissom's short flight ended when his Mercury capsule Liberty Bell 7 sank to the bottom of the Atlantic. They were two dangerous and pioneering missions, but not the first people in space. 

Soviet cosmonaut Yuri Gagarin became the first person to travel to space. Gagarin was the first person to orbit the Earth on April 12, 1961. Cosmonaut Gherman Titov then spent a full day in space a few weeks after Grissom’s short flight. 

In the Space Race during the Cold War, the United States led in a few areas, but the Soviets kept grabbing the spectacular firsts. This made America look technologically backward. When Glenn splashed down at the end of his planned three-orbit mission, he became a national hero because he was the first astronaut to surpass at least what Gagarin had done.

Was Glenn Really Supposed to Orbit the Earth Seven Times? (No.)

Glenn’s heroic flight ended with a scary reentry. Flight controllers thought that the heatshield on his Friendship 7 capsule might be loose. (Ultimately this was caused by a faulty sensor.) But contrary to the urban legend, Mercury Control did not end his mission early because of that scare. 

Glenn's flight was always supposed to be three orbits. The mission plan was inscribed into the map at the control center at Cape Canaveral, Florida, the predecessor to Mission Control in Houston, Texas.

Three orbits by a human was in fact the primary objective of NASA’s Project Mercury. The logic of that number can be seen in the map. After three circuits it is still possible to land in the Atlantic recovery area near the Cape launch site. After that, the rotation of the Earth makes the fourth and further orbits less convenient. If a spacecraft landed long, it might end up in the mountains or jungles of South America.

The Origin of the Myth

Two major Hollywood movies, The Right Stuff and Hidden Figures, appear to have originated and then perpetuated the seven-orbit myth. The Right Stuff is a dramatization of Tom Wolfe’s great book of the same name and was released in 1983. Wolfe’s narrative arc about test pilots stretches from Chuck Yeager breaking the sound barrier in 1947 to the flights of the Mercury astronauts. The narratives is an entertaining mix of cinematic fact and fantasy. 

Two debunkers of the seven-orbit myth, historians Dwayne Day and Rick Booth, point to The Right Stuff movie as the likely culprit. The seven-orbit story is not in Wolfe’s book, nor is there evidence of it earlier. When Glenn returned to space on board the Space Shuttle Discovery in 1998, major media repeated the legend that his first space mission was forced down early. 

Much more recently, another entertaining and popular film, Hidden Figures, gave the legend another lease on life. The film tells the story of Black women mathematicians in the early space program. The seven-orbit myth was one of several major violations of historical accuracy in an otherwise inspiring movie. When screenwriters feel that history isn’t dramatic enough for the audience, so they have to embellish it.

Why seven orbits? 

It seems very likely that The Right Stuff screenwriters picked up on a call Mercury Control made to Glenn soon after his Atlas booster burned out and was jettisoned: “You have a go, at least seven orbits.” As Rick Booth has detailed, that was based on a quick computer calculation NASA’s Goddard Space Flight Center in Greenbelt, Maryland, made on its giant mainframe—one of NASA’s only computers at the time. 

The call, which was made on all four Mercury orbital missions, indicated the spacecraft would stay up for at least seven trips around the Earth.

Mercury capsules were inserted into very low orbits—not much over a hundred miles. They were thus subject to drag created by the Earth’s extreme outer atmosphere. This was an advantage, because if the capsule’s retrorockets failed, it might reenter on its own in a day or two. 

But in the short run, Mercury Control and the astronaut wanted to be sure that he wasn’t going to come down much sooner than expected, perhaps in a remote ocean or jungle. If the spacecraft wasn’t in a viable orbit at all, he would have to quickly fire the retrorockets to land in the Atlantic. 

Did Any Mercury Astronaut Orbit Earth More Than Seven Times?

Only one Mercury flight went more than seven circuits: Gordon Cooper’s 22 orbit mission lasting a day and a half in May 1963. He landed in the Pacific off Hawaii. So did Wally Schirra after his six orbits in October 1962. Earlier, in May 1962, Scott Carpenter had repeated Glenn’s three orbits.

We would do well to remember Glenn’s historic trip as it was—and not the Hollywood version of it.