A "space plane" has been science-fiction fantasy since the days of the Flash Gordon movie serials comic strip of the 1930s. It's a vehicle that can take off from Earth, fly into space, return through the atmosphere, land, refuel and take off again.
Throughout the history of space exploration, reality has lagged behind that dream. When rockets blast off, they drop spent boosters or stages or both.By the time the crew of a manned spacecraft lands, only a fraction of the original vehicle remains - the space shuttle, which needs extensive refurbishment between missions and must be bolted to a huge assembly of stages and boosters before it's launched again.
But the dream of a space plane is becoming reality, and Utah has at least two major roles to play in the adventure. The space plane is the VentureStar, the first reusable orbiter, with commercial development slated to begin in the year 2000. This state is deeply involved both in it and the X-33, the half-size demonstrator model.
The VentureStar is envisioned as the vehicle that finally opens space to economic use and exploration.
"The big drive is to reduce the cost of launching items into orbit," said Dan Dumbacher, the NASA deputy program manager for the X-33, based in Palmdale, Calif. "Right now, the shuttle costs a little bit under $10,000 a pound to get something to orbit. What we're trying to do is to get the technology in place so that commercial companies could . . . get the cost down to $1,000 a pound." That's low enough to vastly improve access to space.
Last year NASA signed a partnership agreement with aerospace powerhouse Lockheed Martin to develop the X-33. The space agency budgeted $941 million for the project; Lockheed Martin, budgeted up to $220 million. Only one X-33 is to be built.
The X-33 should make its first flight by the middle of 1999, with at least 15 test flights through by the end of that year. Construction of the VentureStar is to begin in 2000.
Both the X-33 and the VentureStar will launch in a vertical position and land on a runway like an airplane. Remarkably, each will be shaped like a gigantic wedge, slightly wider than it is long. The space planes will have stubby wings and relatively small tails.
"The typical aircraft has a large wing that helps the lift, to carry the weight in the air," said Hussein Youssef, head of X-33 science for Lockheed Martin's Skunk Works in Palmdale. "In a lifting body (like the space plane), the body is so huge that you don't need that much of a wing to provide lift."
The X-33 and its successor will be powered by a revolutionary new engine called a linear aerospike, which uses liquid hydrogen and liquid oxygen for fuel. No linear aerospike has ever flown on a large craft.
"We're preparing to do tests on the SR-71," the famous Blackbird spy plane built by Lockheed. Late next year, a half-size version of the X-33 will be attached to a Blackbird, which will fly with the model on top. Then the model will be fired to test the aerospike engine.
The test will reach speeds of around 2,500 mph and an altitude of 70,000 feet. They are needed because the aerospike is such an unusual device.
A conventional rocket engine has a bell-shape nozzle that is the same shape and size throughout the flight. But any nozzle configuration works best at only one altitude, where the shape is perfectly keyed to the atmospheric conditions. Engineers compromise, designing nozzles that do as well as possible for all different pressures.
The aerospike sports two lines of thrusters that the exhaust gas pours from during flight. The gas flow automatically adjusts to the atmospheric conditions. Result: The thrust is correct for whatever altitude the space plane is flying, even for operations beyond the atmosphere.
While VentureStar is seen as an ideal vehicle to deliver material to the International Space Station, the X-33 test vehicle will not go into orbit.
Still, X-33 will be a large vehicle, 67 feet long by 668 feet wide, carrying 211,000 pounds of fuel. It will be capable of flying as high as 50 miles above Earth and as fast 11,000 mph.
It will burn liquid hydrogen, which will combine with liquid oxygen. This is the most environmentally benign fuel, according to NASA, because the byproduct released is simply water.
Inside a fabrication plant operated by Alliant Techsystems (the former Hercules Inc.) at the Clearfield Freeport Center, a sophisticated new machine has been spinning fuel tanks for the X-33, much as a spider spins a web. The tanks are made of fiber composite material, as are the shuttle's booster.
If you were to wrap kite twine around a stick, you'd get a ball or cylinder of twine. If the X-33 fuel tanks were perfectly cylindrical, that would be fine. But they're not. The two engines are made of four sections, each about 22 feet long by 10 feet across. They are not identical, and each is shaped something like half a peanut shell.
To wind composite material into a peanutty shape, the moving head of the machine places sticky strands of fiber on a mandrel (a model form) mounted on a spindle. As the head moves, the spindle rotates. Both motions are computer controlled.
The head "lays down a band of fiber that's approximately three inches wide," said Mark Messick, Alliant's program manager for the X-33. The fibers must be precisely aligned, with the right number of strands oriented properly. Hydrogen is the tiniest atom, so the composite must be tightly wound to keep hydrogen from leaking out.
Late in May, the Alliant crew finished the skin of the first lobe, or section of tank. "It's really exciting once that first part comes out, and it went well," Messick said. "It kind of energizes you."
Also energizing Alliant is the fact that Lockheed Martin recently awarded them a contract to also build the hydrogen tanks for the VentureStar. The X-33 contract is worth $39 million while the VentureStar project adds around $160 million. Each contract is for a year and a half to two years.
According to a draft environmental impact statement to be released by the end of this month, X-33 test flights will be launched from Edwards Air Force Base, Calif. Up to seven landings are slated for Michael Army Air Field on Dugway Proving Ground, located in Utah's western desert.
Dugway is an excellent site for mid-range tests, said Rebecca McCaleb, director of environmental engineering at Marshall Space Flight Center, Huntsville, Ala. Other landing sites are two runways in California, for short hops, and alternatives in Montana or Washington for long-range tests.
Does Dugway have any drawbacks? "We haven't found any," McCaleb said.
The X-33 will hurtle in empty, having burned all its fuel in the first two or three minutes of flight, somewhere near the California-Nevada border. But it will be gliding so swiftly that it will create two loud sonic booms as it approaches, like "a double clap of thunder," she said.
When the X-33 spirals in for the first time above Utah, slowing as it prepares to land, the sight should be a thrilling peek into the future of spaceflight. Gliding above sagebrush and dry rugged peaks, it will no longer be fantasy: It will be a real space plane.
Speed: 11,000 mph (mach 15+)
Altitude: 50 miles
Fuel: liquid hydrogen and oxygen (211,000 pound capacity)
Nozzles: Bell, Aerospike
An aerospike nozzle is designed to adjust its performance to different altitudes, unlike a bell nozzle that performs best at one specific altitude.
The X-33 is a half-scale, unmanned version of the VentureStar.
The primary structure is made of a graphite composite. The outer surface may be made of ceramics (similar to the shuttle) and metallic materials.
...........Current shuttle VentureStar X-33
Size: 184 by 78 feet 127 by 128 feet 67 by 68 feet
Cargo bay: 15 by 60 feet 15 by 45 feet 5 by 10 feet
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