Rise of the Rocket Girls

What begins as reckless backyard chemistry in Pasadena evolves into the foundation of planetary exploration. The story of the Jet Propulsion Laboratory (JPL) is ultimately about how experimentation, persistence, and diverse human talent transform rocketry from a fringe pursuit to a disciplined science that reaches the cosmos.

The risky birth of JPL

In the 1930s, the so-called Suicide Squad — Frank Malina, Jack Parsons, and Ed Forman — ignite both rockets and controversy at Caltech. Their accidental explosions and nitrogen dioxide spills became campus legends. Yet from those dangerous beginnings emerges a credible laboratory. With small grants — the first only $1,000 from the National Academy of Sciences — and the help of machinists and chemists, their hobby turns into a research enterprise. When the Army and later Aerojet Corporation join, the experiments move from Caltech’s garden plots to the Arroyo Seco canyon. An operation once characterized by improvisation gains structure, funding, and lasting direction.

The human computers who make rockets possible

Behind those roaring tests stand human computers — women like Barbara Canright, Macie Roberts, Melba Nead, and Sue Finley — whose calculations literally define what flies. They translate jittery data streams from gauges into specific impulse, thrust, and mass flow. Working with Friden calculators, slide rules, and battered WPA computation tables, they create the numerical backbone of propulsion science. They are the first link from observation to engineering truth, turning parabolas of smoke into data fit for military and scientific use.

Their diligence makes it possible for Jack Parsons’ famous solid propellants, like his “Jack’s cake,” to evolve from unsafe curiosities into reliable fuels. To compute one test, a computer might fill half a dozen notebooks and triple-check each value by different methods — prefiguring the redundancy that would later define rocket safety protocols. (Note: this meticulous verification process echoes practices later formalized in aerospace quality assurance.)

From handwritten logic to the first code

The step-by-step procedures written in those notebooks become the scaffolding for computer programs. Janez Lawson, one of the first African-American professionals at JPL, trains at IBM to convert hand-calculated procedures into instructions for room-sized electronic computers. These early conversions move JPL from analog tables toward a future of machine computation. Each woman becomes not only a mathematician but also a proto-programmer, foreshadowing the digital transformations that follow.

Social currents beneath scientific progress

As JPL grows into the 1940s and 1950s, its culture mirrors the contradictions of mid-century America. Building 11 houses an almost entirely female computing team. Their camaraderie — carpools, shared lunches, and handwritten slide-rule tips — creates a rare space of mutual reliance in a world that often viewed women as temporary workers. Yet beneath the sisterhood, institutional prejudice persists. Pregnancies force resignations; races and genders face interviews probing their “suitability.” The same society that depends on these women’s precision often undermines their permanence.

Still, out of those tensions grows resilience. The JPL community becomes an unlikely model of incremental inclusion. When Janez Lawson joins despite segregation, and later when Macie and Helen Ling mentor new generations through education and flexible hiring, JPL begins to subtly reshape what scientific workplaces can look like.

Cold War pressures and space race urgency

Political context soon asserts itself. During the McCarthy era, suspicions exile brilliant contributors such as Hsue-Shen Tsien while protecting German scientists like Wernher von Braun, revealing the uneven costs of loyalty politics. The launch of the Soviet Sputnik in 1957 jolts U.S. policy. Overnight, failed bureaucratic decisions give way to feverish authorization: JPL and von Braun are cleared to combine efforts, resulting in the January 1958 triumph of Explorer 1. You see the transformation — rockets moving from local experiments to geopolitical symbols, and human computers turning typed digits into national milestones.

The pattern that defines the book

Across decades, you watch the same rhythm repeat: trial and error lead to insight, politics reshapes opportunity, and mathematics — nearly always secondhand handwriting by women — silently powers the breakthrough. From amateur explosions in Pasadena to the quiet computation of escape velocities for interplanetary probes, JPL’s story is one of human persistence. It teaches that scientific revolutions are not about sudden genius but about hundreds of small verifications, countless cups of coffee, and the transformation of hand-drawn equations into machines speaking to planets.

As rocketry matures through the 1940s and 1950s, JPL learns its defining lessons through the Corporal and Bumper programs. These early missiles expose the physical, chemical, and structural laws that govern all later exploration.

From JATO to Corporal

Initial Jet-Assisted Takeoff (JATO) experiments bolt small rockets onto aircraft. When those tests halve takeoff distances, the Army sees practical value, funding formal programs. The Corporal and WAC Corporal missiles extend those principles: liquid propellants replace solids, and controlled guidance replaces strapped-on boosters. Early firings hit over 129,000 feet yet fail just as often; instability, oscillations, and structural cracks plague the tests.

Discovery through disaster

Each failure becomes an education in combustion physics. The Bumper WAC experiments — stacking a WAC Corporal atop a captured German V‑2 — culminate in 1949 when the upper stage surpasses 240 miles altitude, essentially touching space. These two-stage flights prove staging works and spark thinking about reentry heating and guidance, preconditions for satellites and lunar probes. (Note: Bumper’s design marks one of humanity’s first demonstrations of space-bound trajectories.)

Engineering intimacy: the star propellant

The Sergeant missile project refines solid propellants. A British-born idea — an internal five-pointed “star” grain — promises smooth thrust but repeatedly causes cracking and explosions. JPL’s practical adjustment, rounding the star’s points, teaches that geometry is as crucial as chemistry. A difference of a 13‑second burn time can define success or catastrophic failure.

From radio control to autonomy

Guidance moves from clumsy radio links to sophisticated inertial systems of gyroscopes and accelerometers. These developments evolve from the urgency of war but directly enable future space travel. The same computational logic governing missile control will later steer Voyager through planetary gravity fields. In each progression, the lesson holds: small procedural innovations accumulate into the capacity to aim beyond Earth itself.

By the mid‑1950s, JPL transitions from pencils to processors. Women who once computed with slide rules become coders shaping the logic of electronic machines. This shift from analog craft to digital reasoning defines the second act of the laboratory’s evolution.

Analog craftsmanship

Early computing tools — Friden machines, logarithmic tables, and French curves — demand artistry and patience. One mis-tabulated value can misfire a test motor. That culture of precision endures even as machines arrive. (Note: The human computers’ disciplined methods mirror pre-digital software engineering with explicit intermediate steps and redundancy checks.)

Room-sized machines and reluctant trust

The IBM 701 and 704 change everything. Costly and temperamental, they execute thousands of operations per second but break down unpredictably. Janez Lawson becomes one of the first trained operators, translating paper logic into coded punch cards. Her dual fluency — experimental data and electronic procedure — bridges generations of computation at JPL.

Programming as a new literacy

FORTRAN and keypunch machines turn human computing into software authorship. You write equations in notebooks, transcribe them into punched cards, and feed them to the compiler. One misplaced hole can destroy a deck of hundreds. Women like Helen Ling, Barbara Paulson, and Margie Behrens define workflows that become the first recognizable software pipelines in planetary science. They aren’t simply running machines — they are architecting algorithms that models of flight still rely on today.

From Cora to modern systems

The affectionately nicknamed IBM 1620 “Cora” and later the 7090/7094 bring higher capability to process telemetry and guidance data. Despite their quirks, they turn around results impossible by hand. When programming VICAR, the image processing system, these women pioneer the translation of analog signals into digital imagery — the computational heart of planetary science.

This period redefines what a computer is: not a person at a desk, but a collaboration between human insight and machine precision. In this hybrid practice, programming emerges as both art and analytics — a craft rooted in the mathematical patience that JPL’s women invented by necessity.

From the 1950s through the early 1960s, JPL evolves from a launch contractor to a planetary exploration hub. This expansion unfolds through a string of experiments — Jupiter‑C, Explorer, Pioneer, and Ranger — that transform rocketry into interplanetary science.

Jupiter‑C and the satellite revolution

Jupiter‑C combines stacked solid stages meticulously synchronized in spin rates up to 750 rpm. When its inert sandbag top stage achieves orbital velocity, engineers realize they already possess satellite capability. Bureaucratic caution delays that potential until Sputnik’s shock forces action, culminating in Explorer 1 — America’s first satellite. The number sequences logged by human computers confirm orbit, marking a triumph both technical and emotional.

Pioneer and Ranger lessons

Soon JPL pushes toward the moon. Pioneers 3 and 4 test deep-space tracking, with the latter becoming the first U.S. probe to reach solar orbit. Failures abound — upper stages misfire, guidance fails — but each mission yields data that refine the next. Ranger suffers six full losses before 1964’s success, proving that attitude control, shroud design, and software integration matter as much as chemistry.

Mariner’s victory and the rise of programming discipline

Mariner 1’s destruction over a missing code mark teaches the entire field that programming precision is life-or-death. Mariner 2’s subsequent success, guided by calculations and corrections from women programmers, makes history as the first interplanetary flyby, capturing Venusian data never before known. Each failure-to-success transition formalizes what JPL will call its “learning loop” — diagnose, redesign, retest, share.

These missions establish that interplanetary success arises not from luck but from iterative corrections across hundreds of systems, united by disciplined software and human computation.

Beyond building rockets, JPL builds communication infrastructure and data interpretation tools that make astronautics into astronomy. The Deep Space Network (DSN) and digital image processing redefine what science can extract from faint signals.

The global ear of exploration

The DSN — with massive antennas in California, Australia, and South Africa — enables continuous reception of spacecraft signals as the Earth rotates. Through this triad, whispers of telemetry from millions of miles away reach Pasadena. Sue Finley’s later work with Galileo exemplifies DSN ingenuity: when the spacecraft’s antenna fails to unfold, she writes code to link multiple ground dishes together, electronically imitating the missing structure.

From numbers to pictures

Analog waveforms become the planet portraits of modern science. When Mariner 4’s data arrive as numeric strings, engineers literally hand-color grid-paper to imagine Mars’s surface before digital transposition is possible. Margie Behrens and her team codify VICAR, which converts telemetry counts into pixel arrays, correcting distortions and turning voltage readings into recognizable landscapes. These processes foil data loss and inaugurate an age where planetary imaging depends on code as much as on lenses.

Together, DSN and digital imaging exemplify JPL’s philosophy: exploration is as much about communication fidelity as propulsion, requiring computation not just to fly but to see.

By the 1970s, JPL orchestrates unprecedented missions through mathematical ingenuity — particularly the mastery of gravity assist and enduring programming systems that outlast generations.

The art of gravitational choreography

Gravity assist leverages planetary motion as propulsion. Engineers like Sylvia Lundy and Roger Bourke calculate precise approach angles so Voyager can steal slivers of orbital momentum, slingshotting from Jupiter to Neptune. This grand tour window opens only once every 176 years, demanding timing precise to minutes. The strategy makes humanity’s farthest missions affordable, trading rocket fuel for celestial geometry.

Software as spacecraft skeleton

Voyager’s onboard computers hold only tens of kilobytes of memory, yet those lines of code still guide the probes. On Earth, Sue Finley and colleagues evolve HAL and FORTRAN codes, enabling complex mission autonomy and DSN synchronization. When Galileo’s high-gain antenna malfunctions, ground-based programming improvisations effectively rebuild functionality using signal-processing software — proof that code can substitute hardware.

Recognition and cultural change

Through Helen Ling’s mentorship, women advance from “computers” to titled engineers, reshaping career hierarchies. Training programs promote them into leadership across trajectory and imaging tasks. By the mid‑1970s, JPL mirrors societal transformation: beauty contests fade while technical recognition and authorship rise. (Note: This mirrors broader influences of second-wave feminism on U.S. scientific institutions.)

Legacy that endures

From mechanical calculators to microprocessors, from analog signals to pixel maps, the same hands — disciplined, methodical, creative — carry JPL’s missions forward. The programs they wrote decades ago continue to run billions of miles away, whispering back radio traces of interstellar space. Their rigor becomes immortal code: quiet, persistent, and infinitely reaching.