NASA also instituted a second round of interviews, another change that helped ensure selection of the best candidates. Previously, 100–120 candidates were invited to JSC for a week of interviews, health assessments, briefings, and get-acquainted activities, and up to thirty-five candidates were selected from that number. Starting with the 2011 recruitment, NASA invited about fifty of those applicants back for second-round interviews and assessments before selecting ten to fifteen prospective astronauts for training.[24] The health and medical screenings became even more stringent than the NASA flight physical. All finalists had to undergo ultrasound and MRI (magnetic resonance imaging) examinations, in what was now called the “long-duration physical” focused on identifying any chronic or hidden issues, whether physical or mental, that might emerge as a problem in long-duration spaceflight. Examples are conditions that require ongoing medication (high blood pressure, thyroid disorders, depression, or bipolar disorder) or a congenital or incipient defect (such as an arteriovenous malformation or aneurysm) or tumors, kidney stones, or gallstones.

  From 2011 onward, and especially as NASA moved into the Artemis program with the goal of returning to the Moon to set the stage for future journeys to Mars, the desirable criteria for astronauts evolved to match the expected training and flight experiences. Recruitment and selection announcements outlined the five essential masteries now required of every new astronaut: operating and maintaining the International Space Station, spacewalks, complex robotics, operating a T-38 jet, and Russian language.[25] It was no longer optional, as it had been with a larger astronaut corps, to be certified in only some of those competencies. In addition, the new astronauts would need to become proficient in operating new spacecraft such as Orion, SpaceX, and Starliner, and training would include planetary science and geology fieldwork to inform surface activities on deep space destinations.

  The 2015 recruitment announcement that led to the 2017 astronaut class made clear the connection between NASA’s changing mission and the caliber of astronauts: “NASA’s mission, and what we need from the astronauts helping to carry it out, has evolved over the years. We want and need a diverse mix of individuals to ensure we have the best astronaut corps possible.”[26] Although some attributes had always been important—teamwork, for example—its meaning and practice changed somewhat from shuttle to space station to Artemis as missions became longer and more complex and, for Artemis, more distant. Crews would need to become even more skilled and autonomous the farther they ventured from mission control.

  The astronaut selection process is so important to NASA’s human spaceflight mission, and the astronauts are so important as the public face of NASA, that a tremendous amount of energy goes into finding, training, and cultivating talented individuals. The ideal astronaut is not a static concept; it evolves as the human spaceflight program and the operational culture of spacefaring evolve. This truism became evident in the astronaut recruitment and selection cycles from 2004 through 2021.

  The Class of 2004

  This recruitment cycle continued the practice of soliciting experienced jet pilots and mission specialist scientists and engineers. For the first time, application forms were available electronically online through the NASA Astronaut Selection Office website.[27] Also for the first time, teachers were invited to apply to join the regular astronaut corps as a new category, educator astronauts, eligible to be assigned to missions. They would share responsibilities with mission specialists, but their additional role was to conduct educational programming to connect with teachers and encourage students to study science and math. NASA Administrator Sean O’Keefe remarked that “the educator astronaut program will help us fulfill our mandate to inspire [the] next generation of explorers.”[28] More than 1,600 teachers applied, from whom NASA selected three, one of them a woman, Dorothy Metcalf-Lindenburger. NASA also selected two pilots and six mission specialists, only one of whom, Shannon Walker, was a woman. The fourteen-member class of 2004 also included three astronauts from Japan’s space agency, JAXA.

  Introduced by NASA at the Smithsonian’s National Air and Space Museum rather than the Johnson Space Center as usual, the 2004 astronaut class was presented as “the next generation of explorers” who would help develop the next generation vehicle and “lead us through the next steps in the new exploration vision.”[29] This astronaut class was the last to train for space shuttle missions.[30]

  Dorothy Marie Metcalf-Lindenburger

  Dorothy Metcalf-Lindenburger was one of three teachers selected in 2004 to train as regular mission specialists within the astronaut corps. This position was unlike that of the first teacher in space, Christa McAuliffe, who trained briefly as a guest spaceflight participant for a single specific mission but was not a NASA astronaut. The daughter of science and math teachers and a geology major with fieldwork experience, Dottie taught high school earth science and astronomy for five years and coached the Science Olympiad and cross-country running. She was an Academic All-American in cross country and track during her college years.

  Metcalf-Lindenburger was the first astronaut to have attended Space Camp at the US Space and Rocket Center in Huntsville, Alabama. That experience in 1990, when she was fourteen, and the wonders revealed by the Hubble Space Telescope, launched at the same time, inspired her to want to work at NASA, whether as an astronaut or in some other position.[31] After being selected as a candidate she stayed at NASA for ten years, during which she flew on a shuttle mission and commanded a NEEMO mission. She also had assignments in the ISS and station operations branches of the Astronaut Office and worked as a Cape Crusader for the final three space shuttle missions in 2011.

  Her fifteen-day shuttle mission, STS-131 (2010), resupplied the International Space Station. The crew delivered more than thirteen tons of supplies and equipment and returned with more than three tons of hardware, science results, and trash. Metcalf-Lindenburger served as shuttle flight engineer, assisting the commander and pilot during launch, entry, and return. She also operated the shuttle remote manipulator system arm and supported all three spacewalks as the choreographer and backup EVA crewmember.

  Two other women, NASA’s Stephanie Wilson and Japan’s Naoko Yamazaki, were on this flight, the last one to include three women, the last one with a seven-person crew, and the last one to include any rookies on their first mission. The three women shared duties operating the robotic arm to inspect the vehicle’s surfaces for any signs of damage, support three spacewalks by the men on board, and transfer cargo between the shuttle and space station. When the shuttle docked with the ISS, where Tracy Caldwell Dyson was a resident crewmember, four women were in space together for the first time.

  In 2012, Metcalf-Lindenburger welcomed her assignment to command the twelve-day NEEMO-16 mission as an opportunity for leadership and responsibility.[32] Its focus was a simulated exploration of a near-Earth asteroid, then being considered as a possible NASA mission. The aquanauts tested techniques and protocols for such a remote mission, and they operated with a communication time delay keyed to the longer distance of interplanetary spaceflight. Because communication delays will be a significant factor in a Mars mission, crews will be forced to be more autonomous in responding to problems.

  For fun while at JSC, Metcalf-Lindenburger was a lead singer with the all-astronaut rock band Max-Q, which performs at NASA and astronaut events, weddings, and parties, mostly in the Houston area. Composition of the group changes as astronauts are available to perform.

  After leaving NASA in 2014, Metcalf-Lindenburger moved to Washington State, where her family could pursue their enthusiasm for outdoor activities. She also earned a master’s degree in applied geosciences and joined an environmental consulting firm. She remains active as a public speaker, serves on nonprofit boards such as the Challenger Center and the Museum of Flight in Seattle, and supports other organizations to advance STEM and STEAM education. She looks back at her astronaut years with humility and gratitude for the opportunity: “I was not perfect, but I did a very good job.”[33]

  Flights: 1 on space shuttle • 42nd US woman astronaut in space • 53rd woman worldwide • Time in space: 15 days, 2 hours (362 hours)

  Shannon Walker

  Shannon Walker has accumulated a number of astronaut “firsts” in her career, and it hasn’t ended yet. She is the first astronaut born, bred, and educated in Houston, home of NASA’s Johnson Space Center and the astronaut corps. She is the first astronaut to have earned her bachelor’s, master’s, and doctoral degrees from Houston’s Rice University. A physicist, she was the first woman to launch into space from US soil since the space shuttles were retired. When SpaceX was ready to transport crews, Walker and crew were launched from Kennedy Space Center on its first operational flight in late 2020, after nine years of NASA’s dependence on Russia for rides to and from orbit.

  Walker grew up with NASA and astronauts in the background of her daily life. She was four years old when Americans landed on the Moon, and her parents took her outside to gaze up, telling her that people were up there. She thought it “sounded like the best thing ever” and decided to go to the Moon someday, too.[34] As a member of the Artemis team, she may indeed have a chance.

  Walker applied five times in ten years and when selected as an astronaut had accumulated so much relevant experience that she was hardly a novice.[35] Upon graduating college in 1987, she worked at JSC with NASA’s space operations contractor, Rockwell, as a robotics flight controller for space shuttle missions. She took a three-year break for graduate school in space physics and returned to JSC in 1995, this time as a NASA employee working on development of robotic systems and general problem resolution for International Space Station missions. She then moved to Moscow for a year to work with the Russian Space Agency and its teams on avionics and ISS problem solving, basically ensuring that hardware and software provided by each of the partner agencies worked together seamlessly. When she returned to JSC, she moved into technical leadership roles for ISS operations and engineering until her selection in 2004 as an astronaut candidate. Her assignments after basic astronaut training included ISS crew support and CAPCOM for both shuttle and ISS missions.

  Shannon Walker wearing the Russian Sokol suit, ready for her Soyuz launch to the ISS, 2010. NASA

  After training as a backup crewmember for two ISS expeditions, Walker flew her first mission to the space station as Soyuz pilot and as an Expedition 24/25 crewmember in 2010. During this time, the ISS broke the record previously held by the Russian space station Mir for longest continuously occupied facility in space. The crew also celebrated the tenth anniversary of a continuous human presence in space on ISS.

  Ten years later, Walker was assigned to her second mission as a crewmember on the first operational flight of the SpaceX Crew Dragon spacecraft (SpaceX Crew-1) as part of NASA’s Commercial Crew Program. This flight made her part of ISS Expedition 64/65 in 2020/2021, with Kate Rubins also aboard for the Expedition 64 segment. This expedition occurred during the height of the worldwide coronavirus pandemic, which forced the crew to take strict precautions against exposure to the virus and do much of their training remotely. Walker served briefly as commander of Expedition 65, the third woman to be in charge, but her tenure was the shortest, only eleven days before her departure.[36] On both ISS missions, Walker was fully engaged with the scientific research program and station operations.

  Between the two space station expeditions, Walker commanded NASA’s NEEMO-15, a two-week underwater mission to simulate exploration on the surface of an asteroid. The aquanaut team tested ways to anchor a spacecraft, equipment, and spacewalkers without the aid of gravity, which is negligible on small asteroids. They also evaluated strategies for using instruments and moving around to collect data.

  Upon returning from space, Walker served as chief of at least three branches in the Astronaut Office, supervisor for the 2021 astronaut class, and deputy chief of the Astronaut Office. As she awaits her next assignment, she has inspired two unusual honors. SpaceX named one of its Dragon support vessels Shannon in her honor, and the Houston Public Library named a new branch near her childhood home the Dr. Shannon Walker Neighborhood Library.[37]

  Flights: 2 on International Space Station, via Soyuz and SpaceX • 43rd US woman astronaut in space • 55th woman worldwide • Time in space: 330 days, 13 hours (7,933 hours)

  The Class of 2009

  The 2007 announcement for applications was the first to indicate that long-duration stays on the International Space Station and missions to the Moon were possible.[38] There was no mention of the space shuttle, nor any mention of pilots or mission specialists, although educators were still encouraged to apply. This was the first recruitment to implement the updated skills and experience criteria that were developed under Ellen Ochoa’s leadership since 2003 for long stays on the ISS and expeditions to the Moon and beyond.

  Along with the standard press release announcement, NASA issued a companion “Help Wanted: Astronauts” ad on its website announcing that “NASA HAS SPACE FOR YOU!”[39] Mimicking the lingo of military recruitment posters with “America needs YOU at the frontiers of space and technology!,” it called for “a few men and women who want to fulfill their dreams and be a part of the next generation of explorers.” This ad spelled out the scope of technical training and duties astronauts must master for ISS expeditions in preparation for missions to the Moon in the Constellation program.

  More than 3,500 applications arrived, from which NASA selected nine new astronaut candidates.[40] The 2009 class included three women: Serena Auñón, Jeanette Epps, and Kathleen Rubins. Five international astronauts, two from Canada and three from Japan, brought the class size to fourteen. This class signaled the transition from spaceflight on the shuttle to future exploration of space, with preparation on the International Space Station.

  Serena Marie Auñón-Chancellor

  Serena Auñón, later Auñón-Chancellor, first worked with NASA as a flight surgeon before selection as an astronaut candidate. After earning a bachelor’s degree in electrical engineering, she graduated from medical school in 2001 and then completed residencies in internal medicine and aerospace medicine and a master of public health degree. From 2006 to 2009, as a NASA flight surgeon, she was involved in medical activities for the Astronaut Office and flight crews and supported crews training in Russia. She also practiced medicine at a free clinic. Her published research focuses on astronauts’ exposure to radiation.

  As part of her astronaut training, Auñón-Chancellor participated in specialized exploration training on a two-month Antarctic Search for Meteorites (ANSMET) expedition and on two underwater NEEMO missions during which she operated a submersible and worked as an aquanaut. She then was a flight engineer on International Space Station Expedition 56/57, traveling via Soyuz and staying for 197 days, to become the first Hispanic woman resident on the space station. During that time, she and crewmates installed a new life sciences glovebox for expanded research in a sealed work area and worked on experiments in other disciplines. Since returning, she has been a management astronaut working in the CAPCOM branch and handling medical issues for the ISS operations branch of the Astronaut Office. She also took a part-time university position as an associate professor of clinical medicine working with residents in internal medicine and was on duty in a hospital during the peak of the COVID pandemic.[41]

  At some point, Auñón-Chancellor or NASA and the media ceased using the accents in Auñón, her Cuban American father’s surname, and the pronunciation shown on her official biography fact sheet is anglicized as ON-un.[42] She is an avid amateur radio operator who enjoyed making calls from the space station. A Colorado native, she enjoys hiking in the mountains, and since living in Galveston, Texas, during her medical training, jet-skiing along the coast.

  Auñón-Chancellor has noted a connection between engineering and medicine: “Both require that you examine problems from all angles and reason through multiple solutions.” [43] Of her career thus far, Auñón-Chancellor says, “The decisions I made in my professional career were not toward a specific goal but because I loved what I was doing at the time.” [44] Those decisions led her directly into the post-shuttle era of space exploration.

  Flights: 1 on International Space Station via Soyuz • 45th US woman astronaut in space • 61st woman worldwide • Time in space: 196 days, 17 hours (4,721 hours)

  Jeanette Jo Epps

  A physicist and aerospace engineer, Jeanette Epps worked in engineering research for ten years before she applied to be an astronaut. Her graduate studies focused on uses of shape-memory alloys, or “smart materials.” She then went to Ford Motor Company’s scientific research laboratory as a research engineer investigating applications of those materials in the automative industry, earning a patent for her work. From Ford she was recruited into the Central Intelligence Agency as a technical analyst to “reverse engineer” technology assets of US adversaries.[45]

  Epps had long considered being an astronaut but humbly doubted whether NASA would select her. However, her admiration of Sally Ride, Guy Bluford, and Mae Jemison, and the encouragement of her astronaut friend Leland Melvin, finally persuaded her. At age thirty-eight, she decided it was “now or never” and had to try. To her amazement but no one’s surprise, she was selected on her first application.