According to Escape Dynamics, “the key operational components of the microwave beam power launch system are a ground-based microwave array and an engine based on the heat exchange between the hydrogen propellant and the incoming microwave radiation. Hydrogen heating is achieved with the heat exchanger, which heats the propellant to a temperature above 2,000 [degrees Kelvin], which is necessary for efficient operation of the engine.”
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.”
And what that means, Parkin added, is that a rocket launched under this paradigm could have more of its mass devoted to structural integrity, a key component in getting to a reusable launch vehicle that requires being inspected only once over 100 flights or so. “It’s more akin to an airliner than a rocket,” he explained.
“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.”
Tseliakhovich said he believes it will be technologically possible to build a prototype beamed microwave infrastructure and launch vehicle in as little as seven year