How Human Calculators Made Early Aerospace Missions Possible

The U.S. JPL (Jet Propulsion Laboratory) was founded long before it became NASA’s premier center for robotic exploration of the solar system – and even before the agency existed. In fact, JPL started as the test-bed for some of the earliest rocketry experiments. There were a number of factors that conspired to change JPL’s focus from rocketry to space exploration.

The space race and the resulting formation of NASA were two major factors. But also, with its growing expertise in launching rockets to new heights, JPL was anxious to take its experiments even farther. So in 1957, when the Soviet Union won the first leg of the space race by placing Sputnik, the first artificial satellite, into Earth orbit, JPL was called into action. A few months later, NASA launched the JPL-built Explorer 1, which became the first U.S. satellite.

One major contributor to early aerospace technology development was Alexander Kartveli. He was heavily involved with a 1960s-era Air Force project called "Aerospaceplane", to design and build an orbital logistics vehicle a decade before NASA attempted a similar concept, known as the Space Shuttle.The radical turboramjet-powered XF-103 was another Kartveli design, an attempt to produce a suitable engine to power the Mach 3 interceptor. Kartveli contributed significantly to the science of flight and the readiness of the US military, and was involved in designing and leading of various projects, which eventually included the A-10 Thunderbolt II.

Alexander Kartveli describes one of his an early space shuttle design

Alexander Kartveli describes one of his an early space shuttle design

Soon, the challenge was to land on the moon – and JPL was once again called to the task. Landing on another planetary body had never been accomplished so, understandably, it took a few tries to get things right. JPL’s first attempts at a moon landing with Rangers 1 through 6 all failed for various reasons.

Some of the spacecraft flew very near the moon only to miss it by a few hundred kilometers; others met their mark only to have onboard cameras fail. Ranger 7 was the first mission to successfully land on the moon and transmit data, capturing images 1,000-times better than those obtained by ground-based telescopes. It wasn’t a particularly soft landing; rather it was a purposeful crash landing, capturing images along the way. But everyone at JPL was thrilled to have hit their target and returned usable data. These data, and those collected by subsequent missions, made possible NASA’s later human missions to the moon.

How They Did It

What’s often not known is that all the early rocket experiments and later missions to the moon and beyond wouldn’t have been possible without a team at JPL known as the human “computers.” Most of these human computers were women who either had degrees in mathematics or were simply very good at mathematics. Over the course of time, these women not only performed hundreds of thousands of mathematical calculations crucial to the U.S. space program but also eventually became some of the first computer programmers at NASA.

In the early days of space exploration, the best mechanical computers were large (the size of a room) and not particularly powerful. Human capabilities were much more powerful for many tasks, including the rapid calculations needed for trajectory analysis and verification, as well as the graphing of data points on trajectories, which made a spacecraft’s path easy to see.

One of the human computers’ main tasks was computing the planned trajectories, or paths, for a spacecraft based on the vehicle weight, lift capacity of the rocket, and the orbital dynamics of the planets.

When a spacecraft is launched, it begins sending telemetry signals back to Earth. These signals tell engineers information about the spacecraft’s location and health. But this information isn’t perfectly straightforward. It arrives as a bunch of numbers that need to be combined in formulas along with other constantly changing parameters (such as velocity, vehicle mass and the effect of gravity from nearby bodies) in order to reveal the spacecraft’s actual location. Before there were computers (as we know them today) to do these calculations, human computers would feverishly calculate the exact location of the spacecraft as the telemetry came in and compare that to the planned trajectories. Their calculations would reveal whether the spacecraft was on target.

Human "computers" at JPL. Image source: NASA

Human "computers" at JPL. Image source: NASA

Doing the calculations required to get Explorer 1 into orbit was no small task. Calculating the trajectory for a Ranger crash landing or a Surveyor soft landing on the moon was even more challenging. Once humans were destined to be on board for the Apollo missions, the stakes were even higher. Fortunately, JPL had set the stage developing the techniques – and calculations – necessary to land a robotic spacecraft safely on the moon.

JPL's human computers didn't just help launch the U.S. space program; they also represented an important step forward for women. Demand for men and women who have a background in science, technology, engineering and mathematics (STEM) has expanded dramatically since the 1960’s as computer technology and exploration initiatives have combined to invent new and more complex problems to solve.

The Alexander Kartveli Foundation was formed to create awareness about the life and accomplishments of Alexander Kartveli. The Association has plans to open a learning center in Tbilisi, Georgia that will promote STEM educational programs and create a resource center for further research about Kartveli. The learning center will also house the various artifacts related to Kartveli collected over the years by the Association.