On this page
Mary Golda Ross worked on the part of the space age you cannot see: the mathematics that decides where a spacecraft goes and when it has to leave.
Who was Mary Golda Ross?
According to the Smithsonian's National Air and Space Museum, Ross was born in 1908 in Park Hill, Oklahoma, near the Cherokee Nation's capital, Tahlequah. Her great-great-grandfather was John Ross, Principal Chief of the Cherokee Nation. She earned a mathematics degree in 1928, taught maths and science in public schools, and completed a master's in mathematics by 1938.
She qualified as a registered professional engineer in 1949, and the museum calls her the first known Native American woman engineer.
What did Mary Golda Ross do at Lockheed?
Lockheed hired Ross as a mathematician, and she worked on the P-38 Lightning fighter plane, according to NASA. The US National Park Service gives 1942 as the year she was hired. It also says she was one of 40 founding members of Lockheed's secret Skunk Works in 1952, and NASA says she was the only woman on that original team.
At Lockheed Missiles and Space Company, Ross worked on the submarine-launched Polaris missile and on the Agena launch vehicle, which carried military, intelligence and civilian payloads to space (Smithsonian). In 1958 she appeared on the TV quiz show What's My Line?, and she stumped the panel (NASA).
She retired in 1973. Through the Society of Women Engineers, she lectured in classrooms and funded scholarships. Her advice, as quoted by the Smithsonian: "the world is so technical, if you plan to work in it, a math background will let you go farther and faster." The US Mint's 2019 Native American $1 coin shows her writing calculations as an Atlas-Agena rocket lifts off (collectSPACE).
How do you plan a flight to Mars or Venus?
Ross contributed to Volume 3 of NASA's Space Flight Handbooks (1963), the planetary flight handbook. According to its NASA Technical Reports Server record, it was written at Lockheed Missiles and Space Company for NASA's Marshall Space Flight Center as "a series of maps, graphs, and tables" for scheduling round-trip missions to Mars and Venus between 1965 and 1999. Part 2 tabulates outbound trajectories, with trip times that vary in 10-day steps.
The simplest such path is a Hohmann transfer: half an ellipse that touches Earth's orbit at one end and the target planet's orbit at the other. NASA's Basics of Space Flight explains that a spacecraft speeds up along Earth's direction of motion to reach Mars, and slows down to fall inwards to Venus.
You can work out the trip time with Class 11 gravitation. NASA's planetary fact sheet gives mean distances from the Sun of 149.6 million km for Earth, 228.0 million km for Mars and 108.2 million km for Venus. In astronomical units (AU, Earth's distance = 1), that puts Mars at 1.524 AU and Venus at 0.723 AU.
Find the ellipse. It stretches from Earth's orbit to Mars's orbit, so its semi-major axis is a = (1 + 1.524) / 2 = 1.262 AU.
Use Kepler's third law. With T in years and a in AU, T squared = a cubed, so one full lap takes 1.262 to the power 1.5 = 1.418 years.
Halve it. The spacecraft flies only from one end to the other: 0.709 years, about 259 days.
Repeat for Venus: a = 0.862 AU, a full lap takes 0.800 years, so the trip takes about 146 days.
The hard part is timing: the planet must reach the far end of the ellipse with the spacecraft. NASA notes Mars launch opportunities come about every 25 months, and Venus opportunities about every 19 months. Tables like those in Ross's handbook let designers weigh launch date against trip time without redoing the arithmetic. For why the Sun sits at a focus of each ellipse, see our explainer on Kepler's first law and the Sun at the focus.
What can a student learn from Mary Golda Ross?
The calculation above uses only algebra, an ellipse and Kepler's laws, all part of school physics. Try this plan on any orbit problem:
Draw it first: the Sun, both orbits and the half-ellipse between them.
Write down what is fixed (the radii) and what you need (the semi-major axis, then the time).
Work one example by hand before you reach for a formula sheet.
Change one input, such as a planet at 2 AU, and predict whether the trip gets longer before you calculate.
If ellipses and foci are hard to picture, the Fermi Simulation Lab has interactive simulations for ideas that are easier to see than to read. If Kepler's laws are shaky, the Fermi Concept Library gives each physics concept its own lesson.
For India's side of this story, read how Ritu Karidhal planned Mangalyaan's path to Mars and about A. Lalitha, India's first woman engineer.
