Rocket scientist aims to relaunch propulsion technology
2010-10-20 04:00:00.0
Posted By Daniel Terdiman
The time has come to jettison the traditional chemical rocket propulsion system and move to one powered by beamed microwaves, say a group of researchers.
For decades, even as rockets have gotten lighter and more powerful, the basic system for putting them in space hasn't changed. A combustion chamber is loaded with propellants, which are put through a chemical reaction, causing hot gases to accelerate and be ejected through a nozzle at very high velocity, which in turn, provides momentum to the rocket's engine.
But a team led by 25-year-old CalTech Ph.D. student Dmitriy Tseliakhovich thinks that the time has come for a new rocket propulsion paradigm, one that requires no chemical explosions, which could cut the cost of putting payloads in space by a factor of ten or more, and which could dramatically reduce the environmental impact of a launch.
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"What we propose," said Tseliakhovich, who is the founder of Escape Dynamics, a start-up devoted to solving the problem, "is, let's get rid of producing energy on board the launch vehicle and delivery energy by way of microwave beams."
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Essentially, the idea is that microwaves beamed from the ground would heat hydrogen, which would then flow through a heat exchanger and out through the rocket's nozzle. This system would allow for a single-stage launch vehicle that would be both reusable, and highly reliable, Tseliakhovich said.
One of the major advantages of a beamed microwave external propulsion system, said Kevin Parkin, the deputy director of the Mission Design Center at NASA's Ames Research Center in Mountain View, Calif., is that it can bypass some of the typical constraints of a traditional propulsion engine.
According to Parkin, who is an Escape Dynamics adviser and who wrote his own Ph.D. thesis on microwave thermal propulsion, a beamed energy propulsion system is capable of producing 2.5 times as much thrust as a traditional chemical-based system. He said that the standard system tops out at an energetic reaction of 16 megajoules per kilogram, while the beamed energy approach can reach 40 megajoules per kilogram.
"So you get a higher performance out of the rocket by sending the same amount of mass out the back," Parkin said. "So that translates to a rocket with a bigger payload."
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"Until five years ago," said Tseliakhovich, "we could not produce enough output of the microwave power. We did not have efficient enough gyrotrons."
Today, however, it's possible to produce more than a megawatt of energy per gyrotron, Tseliakhovich said, speaking of devices that, according to Wikipedia, are "high-powered vacuum tubes which emit millimeter-wave beams by bunching electrons with cyclotron motion in a strong magnetic field."
And Parkin said his own research demonstrated five years ago that it was possible to heat hydrogen to high enough temperatures using microwaves to create high-performance propulsion.
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....NASA is already looking into the technology, Parkin said, pointing to a research project under way at the U.S. space agency's Glenn Research Center in Cleveland.
For his part, Tseliakhovich said he believes it will be technologically possible to build a prototype beamed microwave infrastructure and launch vehicle in as little as seven years, though he admits that the psychological shift required to back such an effort might take longer. That's particularly true, he said, because sending such a rocket into space would require enough land to build a functional beamed microwave array and the support of a government interested in the technology.
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