On March 23, 1965, the first crewed flight of Project Gemini orbited the Earth three times. Over the course of the next nine Gemini flights, NASA scientists and astronauts developed and tested the technology and skills needed for a successful moon landing.
NASA’s second human spaceflight program, Gemini, lasted between 1965 and 1966 and bridged the Mercury and Apollo projects. In the twelve Gemini flights, ten crewed and two uncrewed, NASA made extraordinary progress in its spaceflight capability that culminated with the lunar landings of the Apollo program. Most importantly, Gemini demonstrated the endurance of humans and equipment needed for the extended periods required for a Moon landing.
Top of mind for NASA was to ensure the health and safety of its crews, who tested the limits of what humans are capable of in space. Biomedical sensors tracked the stress of space flight on the body. Heart rate, blood pressure, breathing, and body temperature data was collected and transmitted to Earth, where NASA medical experts could identify problems and find solutions in real time.
Space suits and helmets protected astronauts inside and outside of spacecraft during NASA’s first spacewalks. Three lens visors went on the helmets used by astronauts training for the Gemini missions. When in use, the visors attached to the helmet to offer visual, thermal, and micrometeorite protection. The "fish bowl" shape of the lens shield allowed astronauts to see clearly and turn their head more easily inside the space suit.
During Gemini, NASA also invented the fuel cell, which used the chemical reaction of liquid oxygen and liquid hydrogen to generate electricity. Fuel cells provided enough power and water for astronauts to break the human spaceflight endurance record.
Gemini missions established the technology that enable astronauts to meet and dock with other spacecraft while in flight and honed their skills at reentering Earth’s atmosphere and safely land. The hand rotational controller was pioneered on these missions. The controller used engine thrust to adjust attitude, the orientation of the spacecraft's nose. It relied on new fly-by-wire technology that communicated the pilot's maneuvers through a flight control computer to help eliminate errors. Prior to the technology, maneuvers were done manually.
In addition to the ingenuity, scientific achievement, and vitally important decisions made during Gemini, the program also produced some funny moments. The most unexpected being a contraband corned beef sandwich smuggled aboard Gemini III. Instead of sticking to the carefully prepared meal approved by NASA, which consisted of items like cubed food covered in a layer of gel, astronaut John Young hid the sandwich in his spacesuit and shared some with his crewmate while in orbit. The mess of crumbs created by the sandwich didn’t result in serious problems for the spacecraft but NASA administrators were not amused. The House Appropriations Committee went so far as to hold a meeting to investigate. Young, who went on to have a long and illustrious career piloting and commanding four different spacecraft, said of the incident, “it was a thought, anyway…not a very good one.”