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Right now the only way you can hitch a ride into space is at the top of a powerful rocket that gets destroyed during the trip. Maneuvering is severely limited by the spacecraft's fuel supplies once you're in orbit. And spacecraft traveling to distant planets such as Mars -- or even just hopping to the Moon -- mostly coast along on a preset course that can be altered only slightly. To make matters worse, it's frightfully expensive: It costs $10,000 to put just one pound of payload into orbit. For a human of average weight, the cost would be about $1.6 million, not counting food and beverage.
But NASA wants to slash the price to $1,000 a pound. It has recently tested some novel concepts for getting to space -- and getting around once you're there. NASA is developing air-breathing engines and others equipped with down-home spark plugs that would chug into orbit like the family buggy. It is also working on electrical-powered thrusters that could speed astronauts to Mars in a mere three months and high-tech balloons that will float tons of instruments to the edge of the earth's atmosphere and stay aloft for months -- or even years.
A long-term goal at NASA, spearheaded by a program called Pathfinder, has been to develop reusable space-planes that could fly into orbit and return to earth safely. In late May, for example, Boeing Co. delivered an 85% prototype of a space-plane, called the X-40A, to NASA's Dryden Flight Research Center at Edwards, Calif., where it will be tested and ultimately ferried into orbit on a space shuttle for space testing in 2002. If tests succeed, an unmanned armada of these new craft soon will be used to transport cargo into orbit.
LIKE RIDING FIRECRACKERS.
But X-40A and its relatives still rely on conventional rocket technology from the 1950s. Already in line is another concept: Call it the "rocket for the common man," which is fueled by atmospheric oxygen for most of its journey into space. NASA's Marshall Space Flight Center in Huntsville, Ala., and its industry partner, Rocketdyne of Canoga Park, Calif., http://www.boeing.com/space/rdyne/, recently completed the first hour of testing on an air-breathing rocket.
Known as a "rocket-based, combined-cycle engine," the spacecraft gets its initial takeoff power from specially designed "air-augmented" rockets, which, as do automotive turbochargers, boost performance about 15% beyond that of conventional rockets. When the vehicle's velocity reaches twice the speed of sound, the rockets are turned off and the engine relies on oxygen in the atmosphere to burn hydrogen fuel. At about 10 times the speed of sound, the engine converts to a conventional rocket to thrust it into orbit. Because they are designed to take off and land at airport runways -- and be ready to fly again within days -- NASA says they could "make space transportation safe, reliable, and affordable for ordinary people.
"The rocket scientists at Marshall have another trick up their sleeves, called the pulse-detonation rocket engine, which went into early, small-scale testing in April. While today's astronauts face the equivalent of sitting on a bomb and waiting for the ride to start, pulse detonation will use small explosions, set off by a spark plug, to give them a ride more like roosting on a chain of Chinese firecrackers. Like automobile engines, pulse-detonation rocket engines operate by injecting fuel and oxidizer into cylinders and igniting the mixture. The explosive pressure of the detonation pushes the exhaust out the open end of the cylinder, providing thrust to the vehicle.
HIGH-TECH BALLOONS.
Once in orbit, there's another problem -- getting where you want to go. The answer may be another developmental propulsion system, with the tongue-twisting name of Variable Specific Impulse Magneto-Plasma Rocket (VASIMR). These engines use a source of electricity -- probably nuclear -- to create a superheated gas of ions, known as plasma. The plasma, made from stored hydrogen, is trapped and controlled by powerful superconducting magnets and ejected from the engine, pushing the spacecraft forward in the depths of space -- but with a controllable thrust rather like the transmission in a car.
NASA's Johnson Space Center in Houston, which just signed a development agreement with Technology Applications Inc. in Butte, Mont., http://www.mse-ta.com/aea/pde.htm, hopes these engines will be operational in the next decade. According to NASA, the VASIMR could cut the travel time to Mars in half -- minimizing future astronauts' exposure to space radiation and lessening the ill health effects of time spent in weightlessness.
Indeed, the idea is that on a mission to Mars, such a rocket would continuously accelerate through the first half of its voyage, then reverse its direction to slow the spacecraft during the second half. The flight could take slightly more than three months. A conventional chemical rocket would take seven to eight months to reach its objective and involve long periods of drifting and limited control en route.
Nearer to home, the VASIMRs could be used to provide a new level of mobility to space vehicles, satellites, and even space stations. "The VASIMR provides a power-rich, fast-propulsion architecture," says Franklin Chang-Diaz, a NASA astronaut who heads the program and began working on the plasma rocket in 1979.
Closer to the ground, NASA has the idea of eliminating rockets altogether to put heavy payloads, such as weather monitors, earth-sensing instruments, telescopes, and communications gear, into low-earth orbit on the cheap. It is testing high-tech balloons that will soar to the very edge of the atmosphere and stay aloft for extended periods. Their payloads can be floated back to the earth on parachutes, only to be lofted again.
POLYMER SANDWICH.
On June 13, NASA's Goddard Space Flight Center's Wallops Flight Facility, in Wallops Island, Va., successfully completed a 30-hour test flight of a prototype Ultra Long-Duration Balloon (ULDB), which was launched from Ft. Sumner, N.M. The scientific balloon's pumpkin-shaped design is a distant cousin to the first balloons created by two French brothers, Joseph and Etienne Montgolfier, who discovered in 1783 that filling a bag with hot air would cause it to rise. But unlike conventional balloons, which vent gas to compensate for heating and cooling by the sun, the ULDB is completely sealed. The key is a lightweight polyethylene skin, about the thickness of plastic food wrap, developed by Raven Industries of Sioux Falls, S.D. The polymer sandwich is strong enough to maintain pressure differences, secure enough to resist leaking, durable enough to withstand prolonged ultraviolet radiation in the high atmosphere, and tough enough to survive high winds and fast-flying dust particles.
In a recent test, a one-tenth scale balloon bore a 1,660-pound payload to an altitude of more than 16 miles. The first full-scale model, scheduled to be launched from New Zealand in December 2001 is scheduled to truck a scientific package weighing 3,500 pounds to an altitude of 21 miles -- three to four times higher than passenger planes and above 99% of the atmosphere. The behemoth balloon, when fully inflated, would barely fit inside a football stadium.
If NASA's efforts pan out, its varied menu of new technology could give a new boost to humanity's exploration and commercial exploitation of space. And they might spark a new generation of "Uppies," who will blast off in their Boeing SUVs (space utility vehicles) for a weekend of fast action at the Casino in the Sky.
Copyright 2000 , by The McGraw-Hill Companies Inc. All rights reserved.
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