For decades, Franklin has good-naturedly tolerated what he calls “the giggle factor.” Going to Mars? With a plasma engine? He doesn’t take the puzzled looks personally. He’s used to it. The suggestion that Franklin is impractical has dogged him for most of his life. After all, how many Costa Rican children graduate from high school, knowing little English, and ask their parents to send them to the United States so they can become astronauts? It’s a story that most in his circle have heard by now. In 1968, on a cold and damp August morning in Escazú, eighteen-year-old Franklin rose early to catch a flight. Not all of his family could fit into their three-person Peugeot pickup truck, but his mom wasn’t keen on goodbyes anyway. Franklin’s sister held his baby brother on her lap, and his father, the son of a Chinese immigrant, gripped the wheel. In Franklin’s pocket, he carried $50 and a one-way ticket to Hartford, Connecticut. He’d arranged to move in with his aunt, uncle, and seven cousins in a three-bedroom apartment. He’d managed to memorize just a few phrases, like “Hello, my name is Franklin” and “Where is the school?” When his relatives picked him up at the airport, he swung his bag into their car and told them he was moving to the U.S. to become an astronaut. His family encouraged him, of course, and yet who could be surprised when he struggled those first few months? Though he’d already gotten his diploma in Costa Rica, he decided that a senior year at a U.S. high school would help him get into an American college, and rather than suffer through the recommended English-language-learner’s courses, he requested entry into Hartford High’s senior class—complete immersion into a regular classroom. Sitting in his English class those initial weeks gave him plenty of time to reevaluate his ambition. He was attempting to read and respond to Dickens and Shakespeare when he could barely ask how to catch a bus, and by the end of the first quarter, he’d failed all his classes. Only a few months in, though, his grades started to improve, eventually putting him near the top of his class, and before graduation, his homeroom teacher asked him to meet some local scouts from the University of Connecticut. As he describes in his autobiography, Dream’s Journey, he arrived at the interview in his usual coat and tie, carrying a load of books on rocketry and orbital mechanics. (Most days he smoked a pipe, a habit that caused some kids to mistake him for a teacher.) He must have seemed the nerdiest of nerds, a stock character out of the movies. When the curious scouts asked Franklin about his books, he wasn’t sure if he should tell the truth. “I want to be an astronaut and rocket scientist, and that is why I came to this country,” he finally confessed. The scouts had found their ideal candidate. Franklin entered UConn that fall, and though he was still struggling with English, he managed to absorb even the most advanced scientific concepts. He plunged headlong into experimental research in atomic physics, and he became interested in plasma. His research “was not only fascinating,” he wrote in his memoir, “it was just plain cool.” After UConn, he worked on his doctorate at the Massachusetts Institute of Technology, where he began to study the limitations of the modern chemical engine: it required too much fuel, it was too heavy, and it could never reach deep space. Franklin also saw the need for something faster, and he figured that if he could meld that vision with actual experience in spaceflight, he could invent a solution. By 1977, married with a young child, he was finishing his thesis, and his career was ascendant. He submitted his application to the Astronaut Selection Program. Months later, when he got a stock rejection letter from NASA, he was devastated. He reminded himself that he rarely succeeded on the first try, but he still sank into a depression. He started avoiding newspaper stories about NASA’s growing shuttle program. To make matters worse, he and his wife split up. At one point, as he was barreling down the highway on his motorcycle, he fantasized about getting into a wreck. Would Franklin accept a position in the upcoming class of astronauts? “Yes,” he mumbled, trying to find his voice. “Yes.” He found some solace in his work. He joined the Flight Dynamics and Control Division at MIT’s Draper Laboratory, where he began experimenting with ways to control plasma’s exhaust velocity and thrust. This was the stuff of Star Trek (naturally, his favorite show). What he realized was: when a ship needed more thrust—say, to escape a gravitational field or push itself out of orbit—a driver could spend more fuel; once the ship broke away from the gravitational field, the driver could shift gears to spend less fuel and continue accelerating. For Franklin, this notion was thrilling. Two years passed, and he thought he had made peace with his NASA rejection. Then one day he spotted a tall, sandy-haired man in a blue flight suit walking down a hallway of Draper labs. Franklin recognized him right away as Jack Lousma, a space shuttle astronaut. After exchanging a quick nod with Lousma, Franklin returned to his desk wondering if he should give NASA another shot. He’d gained valuable research experience since his rejection, he’d reasoned, and he’d also become a U.S. citizen. In October 1979, when NASA announced its plans to accept a class of nineteen astronauts into its program, he filled out the application, sealed the envelope, and sent it off to Houston. Seven months later, he received a call from Johnson Space Center’s director of flight operations, George Abbey. Initially thinking the call was a prank, Franklin, then thirty years old, paused and searched for some clue that one of his Draper colleagues was teasing him. Who knew that he wanted to fly in space? Was the caller stifling a laugh? Only when Abbey grew impatient did Franklin grasp what was happening. Would Franklin accept a position in the upcoming class of astronauts? “Yes,” he mumbled, trying to find his voice. “Yes.”

Franklin on an Endeavor space shuttle mission, in 2002. Courtesy of Franklin Chang Díaz Franklin (far right) on a Discovery mission, in 1998. Courtesy of NASA/Newsmakers Left: Franklin on an Endeavor space shuttle mission, in 2002. Courtesy of Franklin Chang Díaz Right: Franklin (far right) on a Discovery mission, in 1998. Courtesy of NASA/Newsmakers

When Franklin landed in Houston, the astronaut culture at the JSC still seemed torn from the pages of The Right Stuff. Published around the same time as his arrival, the book famously captured the charisma and machismo of early NASA test pilots, and plenty of the pilots in Franklin’s class came from a military tradition. He met guys like David Hilmers, a Marine who’d go on to fly four space shuttle missions, and David Leestma, a Navy test pilot who’d fly three. Although Franklin no longer wore the suit and tie (and he’d quit the pipe), he was a different breed. He was at the forefront of a sea change emphasizing research at the agency. It even prompted a new entry in the astronaut training syllabus: “scientific and technical proficiency training,” meaning incoming scientists would continue to pursue their areas of expertise. But Franklin was no slouch as a pilot either. He eventually flew seven space shuttle missions and tied the record for most spaceflights with Jerry L. Ross. He logged more than 1,600 hours in space, including three spacewalks that totaled 19 hours and 31 minutes. Franklin was impressed with NASA’s newfound emphasis on recruiting scientists into the astronaut program, but he was surprised by ways that the agency was slow to change. When it came to Mars travel, many of his colleagues adamantly stuck to concepts they’d relied on to get to the moon. “Going to Mars is a leap in orders of magnitude and complexity,” Franklin says. “NASA had fallen asleep or was enamored with the beauty of the Apollo program, because it was a wonderful thing, but it was a chapter that had to be closed, and we needed to open a new chapter that was different. That transition was not happening.” In 1981, NASA officials gave Franklin the okay to start a small research program at the JSC. But at meetings, in conferences, even in small talk, he could always sense skepticism about his plans for a plasma-propelled engine. And when doubt entered the room, resources found the exit. The major U.S. propulsion centers certainly didn’t share his interest in high-power plasma: the Jet Propulsion Laboratory, in California, and the Glenn Research Center, in Ohio, continued to fund research into low-ion engines and their sibling, Hall thrusters; the Marshall Space Flight Center, in Alabama, focused on chemical propulsion. The hesitation wasn’t entirely rooted in an unfamiliarity with plasma. It was also based on anxiety—and it wasn’t unfounded. The engine he was proposing would require considerable power. Solar energy would be sufficient in cislunar space—the expanse between the Earth and the moon. But any flight beyond the moon (farther away from the sun’s rays) would require a nuclear reactor. That specification tended to provoke groans. “ ‘Nuclear power’ was almost a swear word,” Franklin says. “And still is. There’s a lot of taboos about nuclear power, but I have pointed out for years that without nuclear space power, we are not going to go far in space. No way.” To allay fears, Franklin often mentioned the U.S.S. Nautilus, the first nuclear submarine, built in 1955. The nuclear navy had a stellar record, he’d tell skeptics, and the ship was so well-shielded that passengers were exposed to more radiation just walking down the street than they were inside the submarine. (Even now, some researchers are uneasy. Jason Crusan, the director of NASA’s Advanced Exploration Systems division, allows that putting a nuclear reactor aboard a spaceship would not be all that different from installing one in a submarine, “except that you’re strapping it to a rocket, flying it through the atmosphere, and getting it into space, which could make some people who don’t understand the technology nervous.”) It is there, in that nondescript warehouse, that the future of planetary flight may be changed forever. Franklin says some colleagues capitalized on the fear and the uncertainty to undermine his work. The sabotage took many forms. Hastily assembled review panels critiqued his research and didn’t allow him to provide a rebuttal. Once, after a board temporarily shut down his lab, other researchers tried to poach his machinery for parts. Colleagues complained that he was working on a “dangerous nuclear device” and that he didn’t have enough oversight. But perhaps the most brazen example: in 2002, Franklin had just blasted off on the space shuttle and was on his way to the International Space Station when a review board locked his team out of his laboratory and temporarily canceled its contract. Decades of fighting for funding had finally taken a toll, and his frustration had peaked. “You’re just one more mouth to feed, and they don’t want to see you there,” Franklin says with a shrug. “That’s the law of the land.” But who else would pay for him to work on plasma besides the government? As it turned out, plenty of people. By 2004, the private space industry had grown, and a crop of new billionaires—the kinds of entrepreneurs who’d struck it rich because of their own unorthodox ideas—were eyeballing Franklin’s work. One day Elon Musk visited him at the JSC’s lab, the Advanced Space Propulsion Laboratory. Later, Franklin chatted with one of the backers of the Ansari X Prize, a $10 million award for the first private company to successfully launch a reusable manned spacecraft twice within a two-week period. The more people he spoke with, the more seriously Franklin began to consider if he too should go private. After all, the ASPL was starved for funding anyway. The officials holding the purse strings at the time seemed to think that plasma was technology for the distant future. “And I kind of felt like, ‘We have to do it now in order to have it for the future,’ ” Franklin says. “That attitude was, to me, too narrow. Too slow. I needed to move on, to move fast.” By year’s end, he’d decided to shift his laboratory out from under NASA’s guardianship and, with its blessing, create his own company. His old NASA boss, George Abbey, whom Franklin had brought on as a board member, coined the name: Ad Astra, Latin for “to the stars.” With his second wife’s approval, Franklin pulled his family’s entire liquid savings out of the bank: $50,000. Next, he found a 24,000-square-foot warehouse near the JSC and began rolling a convoy of equipment there, past a series of chain restaurants and auto parts shops. Then Franklin left the agency he’d dreamed of joining as a boy and bet on himself.

Franklin at the Ad Astra offices in December 2017.