From: Mark Ciotola (mciotola@seds.lpl.arizona.edu)
Date: Sat Jan 29 2000 - 11:51:48 MST
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* SEDS-discuss : Discussion of Anything SEDS or Space-Related *
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The University of Michigan
News and Information Services
Contact: Karl Leif Bates
Phone: (734) 647-7088
E-mail: batesk@umich.edu
News Release: January 25, 2000 (23)
Student-built satellite to hang by a thread
ANN ARBOR -- A team of engineering students from the University of
Michigan has designed and built an entire satellite for an upcoming NASA
mission.
Weighing in at only 50 pounds and about the size of a small microwave oven,
the box-like satellite is named Icarus [http://aoss.engin.umich.edu/icarus/]
after the Greek legend of the man who flew too close to the sun, melted his
wax-covered wings, and plunged into the Aegean sea. If everything goes right,
the painstakingly hand-built satellite will meet a similar fate, burning up in
the Earth's atmosphere a week or two after its mission begins sometime in
the fall 2000.
Though student teams at Michigan have flown experiment packages on the
space shuttle and participated in building sub-systems of satellites before,
the Icarus project will be the first entirely student-built U-M satellite to be
flown by NASA.
"It was made to function as an autonomous satellite," said student project
manager Jane Ohlweiler, a master's degree student in space systems
engineering -- or satellite-making. The package's primary function is to act
as a weight to pull a 9-mile-long string called a tether out from a spool on
a spent Delta II rocket booster. If everything works as designed, Icarus will
end up sailing along at the end of this tether like an orbital plumb bob. "First
and foremost, we're a dead weight at the end of the tether," Ohlweiler
acknowledges.
But rather than making the box a mere lump of mass, the students have
covered Icarus with solar cells and crammed it full of instruments that
will gather data on the tether's motion and position and then beam that
information down to listening stations around the Earth. The finished
satellite will be a rectangular box about 18 inches long and a foot high, and
all of it -- the aluminum box, the instruments inside it, the complex network
of wiring, and even the circuit boards that make it work -- were designed,
built and tested entirely by the student team.
"Our mission is to prove that we can do this," said B.T. Cesul, a senior in
chemical engineering and assistant manager of the project. "And we're
helping NASA prove the smaller, faster, cheaper model."
Icarus is part of a larger mission in which Brian Gilchrist, associate professor
of electrical engineering and computer science and associate professor of
atmospheric, oceanic and space sciences, is participating called ProSEDS,
the Propulsive Small Expendable Deployer System. The primary mission of
the Delta II rocket launch will be to lift a Global Positioning System satellite
into orbit sometime this fall. Once that is done, ProSEDS will get to work.
Icarus, the spool of tether, and an array of instruments to gauge the
experiment's success will be mounted on the side of the rocket's
second-stage booster.
Normally, a spent booster like this would take as much as a year and a half
to tumble into reentry and burn up, but ProSEDS aims to bring it down in 21
days or less. Gilchrist and his colleagues who have been studying varying
uses for space tethers think the fuel-free source of thrust created by a
15-kilometer kite string could be a boon to satellite operators. Though
nobody anticipated this problem in the go-go years of the 1960s and 1970s,
space has become a fairly hazardous place to fly, with thousands of bits of
dead spacecraft and spare parts zinging around. A cost-effective way to
quickly deorbit spent payloads, pull big things like space stations into higher
orbit, or even to do mundane tasks like taking out a space station's trash,
would be a great improvement. For example, if tethers were used to help
keep the new International Space Station aloft for 10 years, the savings
over conventional fuels would be about $2 billion, NASA estimates.
As the ProSEDS project took shape, it was Gilchrist's idea to hand over the
entire "endmass" project to students. "It's small enough in scale that
students can really handle everything," Gilchrist said. Icarus started as
a class project in September 1998, and the completed package will be
delivered to the Marshall Space Flight Center in Huntsville, Ala., by March
1, 2000. Marshall has provided about $230,000 for the project and the U-M
has put in another $70,000. NASA officials are visiting the Michigan campus
on Jan. 26 to view the finished product.
Icarus also represents the latest in a new trend in engineering education
being pursued at Michigan -- student team projects. Tackling authentic
engineering problems and working in an interdisciplinary team helps prepare
students for the way engineering is currently being practiced in the real
world. "It's the kind of thing you don't learn in the classroom," said
Ohlweiler, sitting shoulder to shoulder with her teammates in a cramped
office plastered with posters from U.S. and Russian space missions. Nearly
100 students from six different engineering disciplines have been
involved. "We've had everybody from freshmen to Ph.D.s participating and
doing things they never thought they'd get a chance to do," Ohlweiler
said.
NASA's move toward smaller, cheaper missions also opens up a world of new
learning experiences for students interested in learning about space systems
design, said Lennard Fisk, chair of U-M Department of Atmospheric, Oceanic
and Space Sciences. "It used to be that rockets were the only option for
hardware training, but this new generation of small satellites opens up all
kinds of opportunities."
* * * * * * * * * * * * * * *
HOW IT WORKS
At 250 miles of altitude, the drag created by the tether isn't from air
resistance, it's from the Earth's magnetic field. The first 5 kilometers of
the tether are a conductive wire that captures passing electrons and sends
them streaming toward the Delta II rocket booster. The interaction between
that electrical current and the Earth's magnetosphere results in a sort of
drag that slows the rocket stage down and makes it start to fall. The tether
also generates about 100 watts of electricity that can recharge the
experiment's batteries and keep its instruments running. Icarus is powered
by some space-grade C batteries and solar panels.
WHY USE TETHERS?
Tether propulsion should work near any planet with a magnetic field, including
Jupiter. And it wouldn't be just for taking things down. This fuel-free source
of thrust could also be used to lift satellites and space stations into a higher
orbit. One proposal envisions a fleet of tether-powered tug boats in space that
would lift satellites up to higher orbits after they've been carried aloft by
rockets. That's what NASA terms a "low-recurring-cost space asset" or a
good deal.
# # # # #
EDITORS: For further information, contact
* Prof. Brian Gilchrist, (734) 763-6230, gilchrst@umich.edu
* U-M Icarus Project Office, (734) 936-0511, icarus-m@umich.edu
* June Malone, NASA/Marshall Space Flight Center, (256) 544-7061,
june.malone@msfc.nasa.gov
Downloadable images are available at
http://www.engin.umich.edu/news/imagebank/
---
Andrew Yee
ayee@nova.astro.utoronto.ca
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