[Editors] MIT rocket aims to cut spacecraft costs

[Elizabeth Thomson]

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New MIT rocket aims for cheaper nudges in space
--Plasma thruster is small, runs on inexpensive gases
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For Immediate Release
MONDAY, FEB. 23, 2009

Contact: Elizabeth A. Thomson, MIT News Office
E: thomson at mit.edu, T: 617-258-5402

Photo and Video Available

CAMBRIDGE, Mass.--Satellites orbiting the Earth must occasionally be  
nudged to stay on the correct path. MIT scientists are developing a  
new rocket that could make this and other spacecraft maneuvers much  
less costly, a consideration of growing importance as more private  
companies start working in space.

The new system, called the Mini-Helicon Plasma Thruster, is much  
smaller than other rockets of its kind and runs on gases that are much  
less expensive than conventional propellants. As a result, it could  
slash fuel consumption by 10 times that of conventional systems used  
for the same applications, said Oleg Batishchev, a principal research  
scientist in the Department of Aeronautics and Astronautics and leader  
of the work.

The propulsion systems currently used for maintaining a satellite’s  
orbit, pushing a spacecraft from one orbit to another, and otherwise  
maneuvering in space rely on chemical reactions that occur within the  
fuel, releasing energy that ultimately propels the object.

Although such systems have brought humans to the moon and are  
regularly used in a variety of other applications, they have  
limitations. For example, chemical rockets are expensive largely due  
to the amount of fuel they use.

As a result, engineers have been developing alternative, non-chemical  
rockets. In these, an external source of electrical energy is used to  
accelerate the propellant that provides the thrust for moving a craft  
through space.

Such non-chemical rockets have been successfully used by NASA and the  
European Space Agency in missions including NASA’s Deep Space 1, which  
involved the flyby of a comet and asteroid.

But the field is still relatively new, and these advanced rockets are  
one focus of the MIT Space Propulsion Laboratory (SPL). “The Mini- 
Helicon is one exciting example of the sorts of thrusters one can  
devise using external electrical energy instead of the locked-in  
chemical energy. Others we in the SPL work on include Hall thrusters  
and Electrospray thrusters. This area tends to attract students with a  
strong physics background, because it sits at the intersection of  
physics and engineering, with ample room for invention,” said Manuel  
Martinez-Sanchez, director of the SPL and a professor in the  
Department of Aeronautics and Astronautics.

The Mini-Helicon is the first rocket to run on nitrogen, the most  
abundant gas in our atmosphere.

It was conceived through work with former astronaut Franklin Chang- 
Diaz ScD ’77 on a much larger, more powerful system developed by Chang- 
Diaz. Batishchev’s team did a theoretical analysis showing that the  
first of three parts of the larger rocket could potentially be used  
alone for different applications.

The idea “was that a rocket based on the first stage [of Chang-Diaz’s  
system] could be small and simple, for more economical applications,”  
said Batishchev, who noted that the team’s prototype would fit in a  
large shoe box.

Since then, 12 MIT students have worked on the Mini-Helicon, resulting  
in one PhD and four masters’ theses to date. Batishchev notes,  
however, that it could be years before the technology can be used  
commercially, in part due to certification policies through NASA and  
other agencies.

The Mini-Helicon has three general parts: a quartz tube wrapped by a  
coiled antenna, with magnets surrounding both. The gas of interest is  
pumped into the quartz tube, where radio frequency power transmitted  
to the gas from the antenna turns the gas into a plasma, or  
electrically charged gas.

The magnets not only help produce the plasma, but also confine, guide,  
and accelerate it through the system. “The plasma beam exhausted from  
the tube is what gives us the thrust to propel the rocket,” Batishchev  
said.

He noted that the exhaust velocity from the new rocket is some 10  
times higher than the velocity from the average chemical rocket, so  
much less propellant is needed.

Work continues. Batishchev notes that last summer, for fun, his team  
built a plasma rocket based on a glass bottle (a stand-in for the  
quartz tube) and an aluminum can (the radio-frequency antenna), both  
of which previously held soft drinks. It worked. “This shows that this  
is a robust, simple design. So in principal, an even simpler design  
could be developed,” he said.

This work was funded by the Air Force Research Laboratory.

--END--

Written by Elizabeth A. Thomson, MIT News Office
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