Here's how you fly the Vomit Comet: At 30,000 feet dive until the modified McDonnell Douglas DC-9 (C-9) hits 350 knots, pull the nose up 60 degrees — that's 1.8 Gs — until you reach 240 knots, then unload. Repeat 40 times and call it a day. The result: A whole 20 seconds of micro gravity for each parabolic arc, about 13 minutes of weightlessness. For two-thirds of the new passengers floating around untethered in the back the result will also be nausea, at least at first. When NASA retired the old Boeing KC-135 Comet and replaced it with the new C-9 in 2004, the space agency estimated that the ground crew had cleaned up nearly 300 gallons of spew. "They don't call it the Vomit Comet for nothing," says pilot Charles Justiz.
Justiz graduated from the Air Force Academy in 1974. "If you were at the top of the class you either went for fighters or instructing," he says. "To be honest I didn't know a thing about flying. I really wanted to understand the mechanics." Granting his wish, the Air Force made Justiz a test pilot at Eglin Air Force Base. In 1980 he joined NASA to train astronauts. Most of his 20,000 hours are in the Vomit Comet, but that's only where the fun begins. Justiz also instructs astronauts and mission specialists in cockpit resource management and space flight readiness training in the Northrop T-38 Talon. And he also trains shuttle pilots to land a Gulfstream GII configured to handle like the shuttle (which astronaut John Young described as descending like a safe with its door open). Like any airplane landing, the secret is energy control. So it's probably not all that secret. "You only have so much energy," Justiz says, "so you need to know how to get it back, how to lose it." The shuttle's approach speed is 300 knots, touchdown is 205 knots, and thanks to a few hundred landings with Justiz watching, most shuttle pilots hit that plus- or minus-3 knots, and within 300 feet of the touchdown point.
Despite winding down the shuttle program, Justiz is still logging time in the Vomit Comet. "We still have the space station up there that has to be supported," he says. "If you redesign something you want to test it on the Comet and find out the flaws." NASA always has some new pressure suit to inflate, some new assembly procedure to test. The space agency even installed a floor modeled on Mars' landscape to try out different types of Mars boots.
So, after thousands of hours flying the Vomit Comet, how much zero-G time does Justiz have? "I don't know," he says. "Maybe enough to fly a four-day mission. But I still get to come home at night."