February 23rd, 2007
A five-gear space rocket engine
Georgia Tech researchers have had a brilliant idea. Rocket engines used today to launch satellites run at maximum exhaust velocity until they reach orbit. For a car, this would be analog to stay all the time in first gear. So they have designed a new space rocket which works as it has a five-gear transmission system. This space engine uses 40 percent less fuel than current ones by running on solar power while in space and by fine-tuning exhaust velocity. But as it was designed with funds from the U.S. Air Force, military applications will be ready before civilian ones.
This technology has been developed by a team led by Mitchell Walker, an assistant professor in the Aerospace Engineering Department and leader of the High-Power Electric Propulsion Laboratory.
Before going further, below is a diagram showing how this new rocket engine "uses a novel electric and magnetic field design that helps better control the exhaust particles. Ground control units can then exercise this control remotely to conserve fuel" (Credit: Mitchell Walker's team, Georgia Tech). Here is a link to a larger version.
Here is how this new engine could pave the way "for deep space missions, lower launch costs and more payload in orbit."
The efficient satellite engine uses up to 40 percent less fuel by running on solar power while in space and by fine-tuning exhaust velocity. Satellites using the Georgia Tech engine to blast off can carry more payload thanks to the mass freed up by the smaller amount of fuel needed for the trip into orbit. Or, if engineers wanted to use the reduced fuel load another way, the satellite could be launched more cheaply by using a smaller launch vehicle.
And here is how the engine will shift from first to fifth gear.
The new Georgia Tech engine allows ground control units to adjust the engine’s operating gear based on the immediate propulsive need of the satellite. The engine operates in first gear to maximize acceleration during orbit transfers and then shifts to fifth gear once in the desired orbit. This allows the engine to burn at full capacity only during key moments and conserve fuel.
Finally, as Walker's lab doesn't contain many details about this military-funded project, here are some tidbits of information on how the engine works.
The Georgia Tech engine operates with an efficient ion propulsion system. Xenon (a noble gas) atoms are injected into the discharge chamber. The atoms are ionized, (electrons are stripped from their outer shell), which forms xenon ions. The light electrons are constrained by the magnetic field while the heavy ions are accelerated out into space by an electric field, propelling the satellite to high speeds.
Sources: Georgia Institute of Technology news release, via The Engineer Online, UK, February 22, 2007; and various other websites
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