Katherine Johnson, who died last Monday aged 101, was the human "computer" charged with calculating the paths of the flights that sent Americans into space and - eventually - put Neil Armstrong on the Moon.
At the Langley Research Center in Hampton, Virginia, she was one of a team of young female mathematicians who performed the time-consuming calculations that determined a spacecraft's orbit trajectory.
The centre was run by the National Advisory Committee for Aeronautics (Naca), the precursor to Nasa.
In the days before sophisticated computer programmes, these human "computers" relied on such basic tools as slide rules and graph paper to crunch their data.
Many, Katherine Johnson included, were black women, hired in the wake of Franklin Roosevelt's executive order prohibiting racial discrimination in the national defence industry.
In 1958, the same year that Naca became Nasa, Katherine Johnson secured a promotion to the administration's all-white, all-male Space Task Force, which was gearing up to launch the first American citizen, Alan Shepard, into orbit.
The calculations for this mission, Katherine Johnson recalled, were "Easy… it was just a matter of shooting him up and having him come back down."
She went on to plot the trajectory for John Glenn's complete orbit around the Earth in 1962. Glenn had asked for her personally, as he doubted the ability of Nasa's enormous, newly purchased mechanical computer to do the job. As a further reassurance, Katherine Johnson also produced navigational charts for astronauts to use in the event of a systems failure.
By the time of the Apollo mission to the Moon, in 1969, Katherine Johnson's job was to calculate the trajectories that would put a craft into lunar orbit, drop a lander safely on to the Moon's surface, and return the mission to Earth.
On the day of the landing itself she was attending a meeting in Pennsylvania, and watched the event on television - along with half a billion people around the world. Nasa later presented her with a souvenir flag that had returned from the Moon with Neil Armstrong and his crew. Later still, aged 97, she received the Presidential Medal of Freedom, America's highest civilian honour, from Barack Obama.
The youngest of four children, she was born Katherine Coleman on August 26, 1918 in White Sulphur Springs, West Virginia. Her father Joshua held various jobs as a lumberjack and farm hand, while her mother Joylette had worked as a teacher.
Though Joshua had received no formal schooling past the age of 12, he could solve mathematical problems at great speed and was determined that all his children should benefit from a college education.
Early on, it was apparent that Katherine's gift with numbers surpassed even her father's. She was enrolled at high school aged 10; four years later she started at West Virginia State College, where she took every mathematics course available. She graduated in 1937 and worked for a time as a teacher in Marion, Virginia.
It was not until 1952 that she learnt of opportunities for black female mathematicians at Langley Research Center, where she was initially put to work analysing the data from the black boxes of crashed aircraft.
In 1953 she and a colleague were "loaned out" from the computing pool to assist with calculation in Naca's flight research division - the nucleus of the American space programme. The loan became a permanent position on the Space Task Force.
In all, Katherine Johnson co-wrote 26 scientific papers during the 1960s and 1970s, several which established key principles for successful manned flights.
She retired in 1986, after 33 years of service, with three Nasa special achievement awards to her name.
Despite these accolades, the extent of Katherine Johnson's role was scarcely acknowledged by the mainstream media during her professional career. Only one New York paper covered her story after Alan Shepard's return to Earth (under the heading "Negro Math Expert Helped Launch US Spaceman").
It was not until her ninth decade, when footage of her various talks on the role of women in science began to garner notice online, that her celebrity came to extend beyond Nasa. Annie Leibovitz photographed her for Vanity Fair, while the BBC included her in its 2016 list of the 100 most inspiring women worldwide. In 2017 Hidden Figures, a film celebrating the achievements of Katherine Johnson and her fellow Naca mathematicians Dorothy Vaughn and Mary Jackson, was released to considerable attention.
Katherine Johnson's first husband was James Francis Goble, whom she married in 1939. They had three children. He died of a brain tumour in 1956 and she married, secondly, Lt-Col James Johnson, a Korean War veteran.