A New Book Shows How Project Gemini Led to the Glory of Apollo

Gemini astronauts risked their lives to prove that spacewalking was possible.

In his latest book, Gemini: Stepping Stone to the Moon, the Untold Story, Jeffrey Kluger uncovers the pioneering brilliance that was Project Gemini. Spanning 10 two-man missions during a 20-month period that began in 1965 and ended the following year, Gemini was the bridge between NASA’s Project Mercury and the Apollo moon missions. Gemini more than once imperiled the lives of its astronauts in orbit, but they and the engineers assigned to the program persevered, and they were rewarded by the plucky demonstration of spacecraft rendezvous and extra-vehicular activity. Kluger, who is editor at large at Time and co-author of Lost Moon: The Perilous Voyage of Apollo 13, was recently interviewed by Air & Space Quarterly senior editor Diane Tedeschi.

Is Project Gemini underappreciated? 

Gemini has indeed been underappreciated by history. It was during the Mercury program that Americans first traveled in space, and the astronauts who flew those missions—the likes of John Glenn, Al Shepard, Gus Grissom—became national heroes. During the Apollo program, we first sent astronauts moonward, and the various missions—piloted by Neil Armstrong, Jim Lovell, Buzz Aldrin and others—were global events. The Gemini mission, when we launched two-man ships on Earth orbital missions, was very much the middle child, elided over in many historical accounts. But it was in Gemini that we mastered the skills we’d need to go to the moon—rendezvous and docking in space, walking in space, conducting long-duration missions of up to two weeks. Without Gemini there’d have been no Apollo.

How did NASA pronounce Gemini?

NASA pronounced Gemini as GEM-in-ee, with a long “e” instead of a long “i” at the end. It started among a handful at the agency and ultimately became sort of a shibboleth among everyone there—a way of exhibiting your membership in a rare fraternity.

How badly did Lyndon Johnson want to win the space race? Even more than President Kennedy?

That’s a good question. It was Kennedy who set Americans on the path to the moon and, as with other initiatives from his presidency, including the Civil Rights Act and the Voting Rights Act, Johnson saw seeing them through to completion as a way of honoring the martyred president’s legacy. From about 1966 on, however, as LBJ got the country deeper and deeper into Vietnam, his focus shifted. Ultimately, it was Richard Nixon, who had been in office for only six months in July of 1969 who was at the helm when Apollo 11 stuck the first moon landing.

Reading your book, I was struck by how dangerous the spacewalks were: fogged-up visors, difficulty navigating via the tether, physical exhaustion, etc. Could NASA have done a better job anticipating some of these difficulties?

I don’t think NASA reckoned with the physics of spacewalking until astronauts actually tried it. The same was true with the Soviets, who achieved the first spacewalk. The closest astronauts could come to rehearsing walking in space was practicing maneuvering during intermittent 20-second episodes of zero-gravity in a NASA aircraft flying parabolic loops. That was poor practice for the real deal. Both the American and Soviet space agencies could only learn by doing. The fact that we had it mastered by the end of Gemini is one more achievement of the program.

Were the Gemini spacewalks riskier than walking on the moon during Apollo?

Another good question. The answer is yes and no. Yes, because once the astronauts were on the moon, they were in a gravity field—one-sixth gravity, yes, but gravity all the same. Walking—or bunny-hopping, which was the easiest way to get around—is a lot more familiar than floating. But the ‘no’ piece comes from the fact that the Apollo astronauts were dependent upon a portable life support system which, if it failed, would have killed them in seconds. Spacewalking astronauts were connected by a tether that provided them oxygen, electricity, and communications—a somewhat more secure life support system.

The uncontrolled spacecraft spin that almost led to the deaths of Armstrong and Dave Scott during Gemini 8 is shocking. How clutch was Armstrong in saving the mission?

Armstrong was a maestro. Facing vertigo and the risk of unconsciousness, he shut down the maneuvering system that was causing the spin, powered up a backup system designed only for reentry, and feathered the thrusters until he stopped the out-of-control rotation. Even additional seconds of the roll they were experiencing could have cost him and Scott their lives.

The pairing of Armstrong and Aldrin to be the first to walk on the moon is interesting. With Armstrong, NASA was getting someone who could function calmly in dire situations. And in MIT-educated Aldrin, they were getting a genius in orbital mechanics. Perhaps their complementary strengths are why they were chosen for Apollo 11?

I can’t argue with that. But, remember, Apollo 11 may have been the first moon landing, but had the mission not succeeded, that historical distinction could have gone to Apollo 12, 13, 14, and beyond. NASA was prepared for any of the Apollos to be the first, so all of the crews were chosen with care.

What can you tell me about the speech  President Nixon had prepared in case Armstrong and Aldrin didn’t make it off the surface of the moon during Apollo 11?

It was written by New York Times columnist and presidential speechwriter William Safire (in a memo to White House chief of staff H.R. Haldeman) and kept at hand in case it was needed. The opening line is beautiful and chilling: “Fate has ordained that the men who went to the moon to explore in peace will stay on the moon to rest in peace.”

How did the loss of his colleagues in the Apollo 1 fire affect the usually gregarious Wally Schirra?

Wally became unforgiving about even the tiniest lapses in the redesign and manufacture of the original Apollo spacecraft that claimed the lives of the Apollo 1 crew. I interviewed him once or twice and he told me that on at least one occasion he said to the [North American Rockwell] engineers on the factory floor “You roasted my friends in that thing. You’re not going to roast me.” He was equally cantankerous while in space in command of the Apollo 7 mission.

Did Donn Eisele and Walter Cunningham pay a price for their insubordination during Apollo 7, when they frequently ignored requests from mission control?

They did. They were both permanently grounded. That spelled the end of the space careers of two men who would easily have been tapped for a later lunar mission. [NASA flight director Chris] Kraft told me that he left the door open a crack for Eisele, telling him that if he could prove himself, he might fly again. But he never did.

Except for Apollo 13, would it be accurate to say that Gemini endangered more astronauts than either Mercury or Apollo?

I’d say not. First of all, there’s the Apollo 1 fire to consider too. Also, every lunar mission was an order of magnitude more complex than the Gemini missions—and with additional complexity comes additional danger. The fact that Apollo largely dodged those bullets didn’t mean they weren’t whizzing by all the time.

What did the Gemini program accomplish?

Every rendezvous and docking, every spacewalk, every long duration mission attempted today is a legacy of—and a gift from—Gemini. It was the training ground for complex space flight.

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Diane Tedeschi is Air & Space Quarterly's senior editor.

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This article, originally titled "The Legacy of Gemini," is from the Spring 2026 issue of Air & Space Quarterly, the National Air and Space Museum's signature magazine that explores topics in aviation and space, from the earliest moments of flight to today. Explore the full issue.

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Diane Tedeschi | Read More

Diane Tedeschi is a senior editor at Air & Space Quarterly.