Bathtub In The Sky
IF THINGS GO AS PLANNED , in 1999 the unmanned Lockheed-Martin X-33 rocket, the forerunner of America’s next generation of spaceships, will blast off from Edwards Air Force Base in California and soar up more than fifty miles before gliding unpowered to a soft runway landing. The Los Angeles Times calls it “among the most revolutionary concepts in rocket science in decades,” and Gary Payton of NASA says Lockheed’s design was “the most daring and innovative” of all those proposed. Despite these ebullient claims, however, the contours of the X-33 are far from innovative. Decades ago American engineers conceived and demonstrated the audacious idea of a “lifting body,” a clunky bathtub that could glide unpowered from deep space to land gently and precisely on an ordinary airport runway.
The first to propose this curious notion were the engineers Alfred J. Eggers and H. Julian Allen, at the Ames Research Center in Mountain View, California. In 1951, while working on intercontinental missiles, Alien realized that giving a missile a blunt tip would cause a detached bow shock to form, creating a cushion of air that would protect it from the heat of re-entry. Eggers then figured out that reshaping Alien’s missile tip into a tapered half-cylinder would give the rocket enough lift to let it glide through the air unpowered.
An engineer named Robert Dale Reed worked at NASA’s Flight Research Center (or FRC, later Dryden Flight Research Center) at Edwards. In his spare time Reed built model airplanes. He heard about Alien and Eggers’s work, and in February 1962 he built a wingless two-foot model based on their findings. Reed towed his creation airborne using a larger radio-controlled model plane and landed the little glider while his wife took 8-mm movies. Then, with film in hand and the test pilot Milt Thompson willing to get involved, Reed pitched the concept of a full-scale manned prototype to Paul Bikle, the director of the FRC.
Bikle approved Reed’s proposal, though he knew NASA would not authorize a full development program. The agency had great doubts about Eggers’s lifting-body concept and would soon cancel its own somewhat similar Dyna-Soar program, forsaking controlled runway landings for space- craft in favor of simpler ocean splashdowns. Bikle kept the project in-house, giving Reed’s craft the nondescript name of M2-F1. In just over a year, for less than $30,000, a twenty-foot prototype was built from a tubular steel frame and a plywood shell, with landing gear cannibalized from a Cessna 150. For its first ground tows the FRC engineers used a modified, stripped-down Pontiac convertible, painted military yellow lest anyone think they were using government funds to build souped-up racing cars.
More than four hundred times this unusual tow vehicle pulled the bathtubshaped glider across a dry lakebed in Nevada while engineers refined its design. As the government hot rod zoomed to 120 miles per hour, M2-F1 was lifted from six inches to twenty feet off the ground and released so that Thompson could guide it to a soft landing. By August 1963 they felt confident enough to take the bathtub more than 12,000 feet into the air, where it was dropped from a C-47 transport plane for Thompson to pilot neatly to the lakebed’s marked runway. “Watching that ship dive and then gently glide to earth was probably the most exciting moment of my life,” Reed remembers.
Over the next ten years a number of larger, heavier versions were developed and flown, including the rocketpowered X-24A and the HL-IO, both of which bear a striking resemblance to the X-33. The space shuttle was redesigned on the basis of these test flights.
While the lifting body may look as if it could never fly, its demonstrated ability to take a heavy, unpowered spacecraft moving at many times the speed of sound and guide it safely and precisely to a runway has become one of the essentials of aerospace design. The spaceships of the future will therefore resemble not the sleek, pointed jets of Buck Rogers but that original American bathtub in the sky.