Rise of the Rocket Girls

by Nathalia Holt

  But achieving a short runway launch with a trim Ercoupe was a relatively minor accomplishment. The army needed to lift a fourteen-thousand-pound bomber into the air. In one month, Barby filled more than twenty notebooks with rows of neatly printed numbers. Each column represented a value from the experiment, plugged into lines of exquisitely complex equations. One of the key computations Barby was responsible for was the thrust-to-weight ratio, an equation that allowed the group to compare the performance of the engines under different conditions. She repeated the calculation many times, sliding the numbers into the equation with the ease of slipping on a pair of shoes. It was all building to one singular achievement.

  It took just a year for the JPL rockets to boost the Douglas A-20A bomber into the air. They experimentally fired the JATO units on the heavy bomber forty-four times, the rockets needing only minor fixes. The project was a success. For the second time, Barby Canright’s face beamed with pride as she stood next to the bomber. It was time to take the work out of the lab and bring the technology into production. Frank and von Kármán set up a company, Aerojet, to manufacture rockets while they continued their research in the Arroyo Seco.

  Money and success brought support for the ragtag group, and they made the California canyon their permanent home. All JPL needed now was more employees. Barby was excited when Frank told her he was hiring two more computers, a man and a woman, Freeman Kincaid and Melba Nead. Until then, Barby and Frank’s secretary had been the only two women at the institute. Barby, who didn’t spend much time with the secretary, had felt the lack of female companionship.

  Melba, on the other hand, was overwhelmed. Attending her first party at Jack and Helen Parsons’ house, she felt shy among the group of people she barely knew. Perhaps sensing her reticence, an older gentleman came up to her. “I’m von Kármán,” he said pleasantly, extending a hand. Melba took it, awed to meet the director of the lab. The intimate feel of the gathering soon swayed her. She mixed among the engineers and her fellow computers and began to feel at ease.

  One of those computers was leaving. Barby’s husband was promoted to engineer. It was what Richard had always hoped for. Although Barby’s experience was similar to his, she was not promoted and hadn’t expected to be. It was simply one of the limits of being female. Although she loved her work, with Richard’s promotion and subsequent added income, she was thinking about starting a family.

  While they considered having children, Richard was launching something new at the lab. He was going to look at the performance of their rockets underwater. In preparation, the group dug a channel into the dirt near the test pits and filled it with water. The engineers sank their engines into the ditch, the water creeping into the engine and up the fuel line. The motor was only nine inches deep, yet it still looked hopelessly submerged to Barby. JPL was trying to develop what they called a hydrobomb. While it was essentially a torpedo, they didn’t dare call it that. Only the navy was allowed to develop torpedoes. Richard and his team fired the engines, expecting them to sputter and die. Instead they worked just fine underwater. In no time at all Richard was leaving the channel behind and moving to a nearby lake where the motors could be submerged six feet deep. He’d bring back the data to his wife, excited for her analysis.

  Not long after Richard’s promotion, JPL hired two more women, Virginia Prettyman and Macie Roberts, rounding out the computer room to a team of five: four women and one man. The new recruits didn’t seem promising at first. Virginia and Macie, or Ginny and Bobby, as they soon became known, had never heard of a computer before. They answered the want ad with little idea of what they were getting themselves into. Despite the newcomers’ naïveté, the computers immediately became good friends. They spent every day working together, sweating over their calculations, observing experiments in the test pits, and chatting with the engineers. And since their houses were practically next door to one another in Pasadena, they often ate dinner and relaxed together in the evenings.

  Most of the employees drove to the lab, occasionally carpooling. Freeman and Melba preferred the streetcar. They got off at Ventura Street, a stop that looked like a desolate canyon with a road running through it, then walked across a rickety bridge over the dry streambed to get to the office. At the site, there were only a few structures: an old barn, two small laboratories, a shop for liquid propellant, two hydraulic presses to shape the metal, and Building 11. Building 11 was the engineering building, and it sat right next to the test pits, which made up Buildings 5 through 7 and 10, although they were little more than shacks covering the pits in the ground where the rockets were fired.

  Building 11 was small but brand-new, with a conference room, a darkroom, and freshly painted offices for the engineers and computers. One side of the computer room was framed in windows, filling the space with California sunshine. Each of the computers had her or his own wooden desk, and when the sun hit them, they turned a golden hue.

  The room was never quiet. Between their large electric calculator, slide rules, and the general hum of conversation, the five computers made a lot of noise. But nothing was as loud as the noise from the test pits. It was so shocking that it often caused them to jump. Things only got worse when the field team decided to add a warning sound. For this, one of the mechanics pulled the cable of a Ford truck horn. The horn went “Aruugah!,” making employees jump almost as high as when they heard the explosions themselves. Neither noise was popular with residents whose newly built homes were within earshot.

  For a little quiet, Melba sometimes walked down the hall. She would chat pleasantly with Frank’s secretary, Dorothy Lewis, and then proceed into his small office to discuss data. Frank, all of twenty-nine years old, had just taken over the role as acting director of JPL.

  Von Kármán left the lab in 1944 to launch the air force’s Scientific Advisory Group. His decision to leave set off a scuffle over the JPL directorship. Clark Millikan, professor of aeronautics at Caltech, was aching to take the reins of the fledgling institute. Despite Millikan’s years of experience, von Kármán preferred to turn over the lab to his former student, who, although relatively untried, made up for it with his zeal for research.

  It must have been strange for Barby to watch Frank grow up in front of her eyes, moving from student to professor in a short period. By necessity he had to be serious now, at least most of the time. He still pulled pranks around the lab, but mostly late at night, when he had the grounds to himself. It was a rocky transition from carefree member of the Suicide Squad to leader of a major research institute. One day, Barby and the other computers at JPL watched with disbelief as Frank harshly disciplined one of the engineers.

  Whiling away time between JATO tests in Muroc, California, today Edwards Air Force base, Walter Powell was playing with a toy airplane. Frank was curt with him: “Put away the toy, Walt. It’s not a playground.” Walter was furious. For the first few years their work had always had an element of play. Now things were changing. When Frank went back to his office, Walter couldn’t stop thinking about his rebuke. If Frank didn’t take him seriously, he would make him listen. He grabbed a hatchet and stood outside Frank’s office, holding it over his head. Letting out a yell, he brought the blade against the closed door. Once, twice, three times.

  Through the shredded wood of his office door, Frank could make out Walter’s face, red with anger, and began to scream for help. A few men came running. They tried talking to Walter, but he was shaking with anger. One of the engineers was holding a pair of scissors and had an idea. He walked over to Walter and cut off his necktie. The hallway fell silent. Then laughter began to percolate through the group. Soon even Frank was laughing. Walter didn’t laugh, but he dropped the hatchet. He was incredibly embarrassed. For a month, it was all anyone at the institute could talk about. Barby and Melba would act out the final dramatic scene, Barby playfully chasing Melba with a pair of scissors. It was a long time before Walter would wear a necktie to work again.

  To avoid future hatchet jobs,
Frank personally did all the hiring. He was careful to build a dedicated staff as the institution expanded. After establishing the lab in the desolate canyon, he wanted to make sure the small group worked well together. Given their long hours, they had to be more than just co-workers to each other—they needed to resemble a family.

  The computer room worked as seamlessly as a machine, notebooks passed from desk to desk as the five colleagues spent their days transforming raw numbers into meaningful data. Their prize possession was a single Friden calculator. It looked nothing like the modern, sleek devices we’re used to today that can perform hundreds of functions and sit in the palm of our hand. Instead, the calculator was the size of a bread box and heavy. When they first received the Friden, Barby was excited to be in command of a machine that so few people knew how to use. It was the latest technology and much faster than a slide rule, though it could only add, subtract, multiply, and divide. It was a dull gray and looked like a typewriter, but instead of letters, the keyboard held rows of repeating numbers, from 0 to 9. Advertisements for the calculator boasted that with a “flick of the key” the Friden could “automatically transfer products from dials to keyboard.” Only once the numbers were typed into each individual column could the “fully automatic” calculations begin.

  Advertisement for Friden calculators

  The calculator dispensed a small piece of paper showing the equation and its solution at the top of the machine, like a sheet of paper in a typewriter. Looking at the complex contraption now, it’s hard to believe that it was able to perform only simple functions. Of course these simple functions were just the tip of the iceberg—Barby and the other computers had to do everything else by hand. Their fingers became rough with calluses from gripping a pencil eight hours a day.

  Barby was no longer calculating how many rockets were needed to lift a bomber into the sky. With that project completed, the group turned back to trying to pierce the edges of space. They had to find a way to propel a rocket to an altitude higher than that achieved by a simple helium-filled balloon. To devise the perfect motor, the engineers and computers had to solve four equations describing the relationship between the motor’s physical properties and their rates of change. As the group worked together, it became clear from their calculations that they would need to focus on propellants.

  Melba, Macie, Virginia, Freeman, and Barby were responsible for calculating the potential of rocket propellants. Macie, perhaps because she was twenty years older than her fellow computers and obsessed with using precise terminology, would get annoyed if someone mistakenly called a rocket propellant “fuel.” She had come to engineering late in life, after working as an auditor for the Internal Revenue Service, and so had taken her lessons in rocket science to heart. In her strict and proper way she would gently remind the transgressor that a propellant is not composed of fuel alone. It also includes an oxidizer, an element such as oxygen that is able to accept an electron, thus setting in motion a powerful oxidation-reduction reaction, often called a redox reaction. These reactions, in which electrons are transferred, create energy whether they occur in a rocket engine or in a cell in the human body.

  Fuels can’t burn without an oxidizer like oxygen. Oxygen’s powerful pull on electrons, those tiny particles with a negative charge, is needed for the fuel to combust. This is important, because if rockets were eventually to travel to space, where there is no oxygen, they would have to carry their own oxidizer.

  Virginia and Barby sat outside eating their lunch one day. Virginia was complimenting Barby’s new hairstyle: “The short bangs are so cute. You look just like Bette Davis.” Barby thanked her, running a finger through her new stylish bangs and carefully patting the tapered hair curling in at the nape of her neck. That day she was feeling especially pretty in a bright white shirtdress cinched tight at the waist and white pumps. They were taking a picture of everyone who worked at the lab, and she wanted to look her best. The white was a mild act of defiance for Barby, her stand against the dust that whipped around the canyon.

  As they talked about hairstyles, Barby brought the conversation back to the propellants they discussed in the computer room.

  “I hear Jack has an idea for a new one,” she said, recalling her conversation with Richard the night before. “You’re not going to believe what it’s made of—asphalt.”

  Virginia shook her head. “That sounds like Jack,” she said.

  As crazy as it sounded to use the heavy asphalt that paved roads, no one knew what would best make rockets fly, so everything was fair game. At JPL, the team tested a wide range of solid, liquid, and gas options. They loaded the fuel and oxidizers into rocket motors that were housed in the test pits in a dirt field. These were directly adjacent to a handful of permanent buildings and the row of tar-paper shacks that made up the lab. Then they fired them.

  Gauges on the motors measured how fast the exhaust gas left the rocket motor and how the mass of the propellant changed over the course of the test. Technicians took pictures of the gauges after every test and brought the film to the darkroom in Building 11. In the darkroom, Barby, Melba, Macie, Virginia, and Freeman hovered over the photos of the gauges in the dim light and carefully recorded the data on blue graph paper. They’d bring their notebooks back to the computer room and begin work.

  By measuring how quickly the exhaust left the rocket engine, the computers could analyze how much force was generated from each experiment. From the raw data, they calculated by hand the thrust (the force propelling the rocket forward), the rate of combustion, and the velocity (the combined speed and direction). After noting these values in their brown notebooks, they plugged them into the Friden calculator and triple-checked them with a slide rule. Melba preferred the simple, straightforward nature of the slide rule. It looked like a ruler, but by placing the pointer at one number and sliding the middle section of the ruler into the proper position, they could use it for multiplication, division, square roots, and even trigonometry. It took Melba years to feel as comfortable with the Friden as she did with her slide rule.

  The calculation the engineers and computers were most interested in was the specific impulse, the change in force that accumulates as a rocket uses fuel. Specific impulse indicates roughly how much momentum builds up as the propellant is being thrown out the back of the rocket. The faster the propellant is thrown, the faster the rocket can travel. Having a high specific impulse means less fuel is needed to go farther. This calculation is the simplest way to compare the effectiveness of different propellants. It took four different equations for the computers to get to the specific-impulse equation. They had to compute thrust and velocity first. They would then plug these numbers into a formula that calculated the thrust per unit mass flow of each propellant.

  These calculations could not be done quickly, since they were all done by hand. It took only seconds for a rocket engine to be fired, but analyzing that one experiment could take a week or more for the human computers. Notebooks quickly accumulated, often six to eight of them for each experiment. Barby liked to stack them on her desk, forming a wall of paper. As the notebooks piled up, so did her feeling of accomplishment. Then, at the end of the experiment, after the final report was written up, she’d clear the notebooks off her desk.

  On a mild autumn morning, Barby and Macie were eager to begin analyzing the first experiments using asphalt as a base in the rocket fuel. The computers had been whispering about it for months. Only part of the gossip was about the fuel itself. No one had ever tested asphalt before, it was true, but the engineer who thought it up was also a curiosity.

  Barby had been friends with Jack and his wife, Helen, from the early days of the Suicide Squad. Jack was brilliant, but also eccentric. It wasn’t until he met Frank that his genius began to shine. He was always coming up with quirky solutions to their engineering challenges.

  His engineering designs weren’t the only unusual thing about him. Jack and Helen were often gossiped about at work. Jack talked about science ficti
on stories as if they were real, and he had separated from Helen after joining a bizarre, cultlike religion. Although Jack was by far JPL’s most peculiar employee, they were thankful to have his rocket-fuel genius.

  The new propellant that Barby and Macie were excited about was a unique mixture of liquefied asphalt with a potassium perchlorate oxidizer. The computers still had to figure out what proportions of fuel and oxidizer were needed to work in a rocket. The best mixture, they calculated, was 70 percent Texaco No. 18 asphalt combined with 30 percent Union Oil lubricating oil. The technicians liquefied the asphalt-oil combination by heating it to 275 degrees Fahrenheit and then added crushed potassium perchlorate. The propellant was mixed and allowed to cool, becoming a solid round block, a cake of rocket-blasting power. They called it Jack’s cake.

  The technicians and engineers packed the black powder cake tightly inside the combustion chamber of an engine lying at the bottom of one of the test pits. The engine looked like a dirty, rolled-up newspaper. A clay nozzle lay at one end, connecting the propellant with the igniter. On the other end of the engine lay the charge, which emitted a smoke trail, so they could follow the exhaust as it flew down the test pit. The engine, anchored in the test pit, was under intense pressure, and when it was ignited, the ground shook. Seconds later the exhaust hit the hillside, and huge clouds of white smoke made of potassium chloride, a by-product of the propellant, rose from the pit.

  The computers collected their data from the gauges on the engine and then began to calculate. Their goal was a lofty one: they were trying to find a propellant that could deliver a thrust of 1,000 pounds over the course of ten to thirty seconds. No powder rocket had ever accomplished such a feat. At JPL they weren’t sure it was even possible. Most of the tests of black-powder propellant ended in explosions. The seals of the engine failed or the charges cracked and the whole thing burst into flames. Jack’s cake, however, was different.