November 4, 2011
If Dr. Laxminarayan Raja has his way, the same kinds of devices that light up our laptop screens and the fluorescent bulbs in our classrooms will propel our rockets as well.
"In science fiction movies, you see this nice luminous jet plume that comes out the back of space ships," Dr. Raja said. "That's a plasma propulsion device." And plasma propulsion could increase the efficiency of our flight vehicles several fold if the same energy that illuminates our plasma televisions can be harnessed to drive rocket fuel.
So Dr. Raja's research focuses on understanding what's going on within this fourth state of matter that comprises more than 90 percent of our universe.
"My specialty is understanding what's going on within the plasma: what kind of temperatures you get in the plasma for a certain amount of power you put in and what kind of densities of charged particles such as ions or electrons you get from the device," Raja said. "And once you have that, how do you manipulate the charged particles using electric and magnetic fields to produce thrust?"
Using computational modeling, Raja is working toward a future where deep space mission vehicles use ion thrusters and small satellites rely on ever more efficient micropropulsion devices.
"All of these satellites' lifetimes are invariably determined by how much propellant fuel they can carry, which in turn means if the fuel is consumed within a month, the satellite's lifetime is only a month," Raja said. "If we can come up with a propulsion device that is twice as efficient, or four times as efficient, it directly impacts the lifetime of the satellite."
Raja said that plasma exists all around us already, such as the atmospheric plasma of Aurora Borealis that so frequently disrupts telecommunications.
"If we understood the nature of plasma better, we could design telecommunications infrastructure to avoid the influence of the atmospheric plasma." Although this type of research is not where Raja focuses his own energy, the problems presented by the Northern Lights reveal how broadly applicable our improved knowledge of plasmas might be.
"My research is specifically to come up with new models, methods and computational algorithms to solve these problems," Raja said.
Instead of using models that require days or weeks to solve on a computer, Raja wants to find more efficient computing algorithms for plasma models, which can be run on extremely fast supercomputers, such as Ranger at the Texas Advanced Computing Center.
Raja said he has always been interested in plasma research since his days as a PhD candidate in Mechanical Engineering at UT in the early and mid-1990s. After finishing his doctorate in 1996, he moved from working on high density plasma research to looking into lower temperature plasmas. He said a unique feature of these lower temperature plasmas is that they are not hot to the touch despite the high temperature of the electrons - unlike a dense, high temperature plasma like our sun.
One project Raja is working on aims to use plasmas for aerodynamic flow control without the need for moving surfaces. In other words, instead of an aircraft that requires all those moving parts on the wings to direct airflow, an aircraft with the ability to generate plasma discharges on its surface could better manipulate the flow, especially for hypersonic vehicles.
"It would basically significantly reduce complexity of these flying bodies and it would be an enabling feature for aerodynamic flight of very high speed vehicles, like Mach 5 and higher," Raja said. "Controlling the flow field fast enough around a high speed moving vehicle is very difficult. You have to be able to adjust extremely quickly. Plasmas will respond in microseconds and can be switched on and off."
But the ability to create plasma-generating flight vehicles or plasma propulsion requires a better understanding of how plasma behaves and how those properties can be manipulated. As Raja works on developing efficient methods for investigating these properties and modeling plasmas, we take one step closer to building those plasma propulsion science fiction spaceships that have occupied our imagination for so many years.
