Perseverance is also key. Mike Foreman, 55, a solidly built former Navy pilot and veteran of two shuttle missions, applied eight times before he was accepted in 1998. “I guess they finally got tired of seeing my name,” he says.

Planes, Pools, and VR
The dozen or so applicants per class who make the cut—referred to within NASA as Ascans (short for “astronaut candidates” and pronounced to generate a smirk)—undergo two and a half years of intensive training before earning the title of astronaut. Training has changed a lot in the 50 years since Glenn was strapped into a giant centrifuge to experience the devastating g-forces of spaceflight. Today’s regimen is less physically demanding (the centrifuge was mothballed in 1999 due to cost) but considerably more intellectually rigorous, high-tech, and global in scope.

Much of the training is carried out with sophisticated simulations inside the Virtual Reality Laboratory, a two-room space cluttered with computer monitors, electronic gear, and a poster from the Clint Eastwood movie Space Cowboys. Elaborate headsets suspended from the ceiling with pulleys and wires immerse the trainees in a digital illusion of floating alongside the space station while Earth slowly rotates below. The simulations model the station down to the handrails, struts, and patterns of shadows and sunlight playing across the solar arrays. Using glove-mounted controls, the candidates practice space walking and extravehicular repair skills. “This is the only place we can fit the entire station,” says Dave Homan, a former lab manager.

Ascans receive plenty of real-world training, too. They fly in supersonic, two-seat T-38N jets to practice making high-speed, high-stakes decisions. Then they dive into the 6.2-million-gallon pool known as the Neutral Buoyancy Lab. The astronauts spend six-hour sessions underwater, getting used to the feel of zero gravity. “It’s very demanding mentally and physically,” astronaut and doctor Kjell Lindgren says. “You have to learn to be very efficient to keep from duplicating tasks and to conserve energy.”

The candidates also spend weeks at a stretch overseas, training in countries, like Japan and Russia, that are partners on the International Space Station. In fact, today American astronauts are required to learn Russian, the language of their former cold war rivals. After all, they need to be able to talk to their counterparts giving them a lift on the Soyuz.

Is It Time to Go to Space Yet?
As I toured the Johnson facilities, it was easy at first to forget that NASA’s manned space program is in such flux. Then I entered the Space Vehicle Mockup Facility, a brightly lit, hangarlike building filled with full-scale models of space station modules and the cockpit of the Soyuz. In the corner I caught a glimpse of the space shuttle mockup being dismantled and readied for shipment to the Museum of Flight in Seattle. The daily routine within the Johnson Space Center may seem normal, but it is headed for certain change now that NASA’s only space vehicle, which transported 852 people over 30 years, is out of service.

Even during the shuttle era, astronauts often waited years after basic training to be assigned a trip into space. Simple math suggests those waits will get longer. NASA used to fly several seven-person shuttle crews each year but has purchased just 12 round-trip seats through 2016 on Russia’s Soyuz spacecraft. Once assigned to a specific mission, the lucky dozen who will fill those seats spend an additional two years training, much of it in Russia with their crewmates.

The 56 active astronauts are well aware of the unsettling possibility that all this training will be for nothing. NASA’s funding is perpetually under threat, and its goals change with each presidential administration. Johnson’s staff has been cut significantly since the scrapping of the shuttle.

Still, there is reason to buy into NASA’s optimism that astronauts will get more real-world experience soon. In May the private company SpaceX successfully launched its unmanned Dragon capsule to the space station. If its next 12 contracted missions go well, the vehicle could start carrying passengers (some employed by SpaceX, others by NASA) into low Earth orbit by 2015. The timetable for NASA’s longer-term projects is more handwavy—the Obama administration talks vaguely about missions to an asteroid around 2025 and Mars around 2030—but the agency is working on a well-defined program, called the Space Launch System, to develop powerful rockets for interplanetary travel, whatever the destination.

For now, astronauts like Foreman and Metcalf-Lindenburger remain confident that their daredevil flights and six-hour swims will lead to inspiring space adventures—that NASA's drift is a temporary lull. “I think the future is bright for the space program,” Foreman insists. “We’re on the right path. It’s just a question of what steps we’ll take.”