Microscopic Radiator Flying on "Skin" of a NASA Spacecraft Set toLaunch March 14 (Forwarded)

Johns Hopkins University
Applied Physics Laboratory

Media Contacts:
Kristi Marren
Phone: 240-228-6268 or 443-778-6268

For Immediate Release: March 13, 2006

Microscopic Radiator Flying on "Skin" of a NASA Spacecraft Set to Launch
March 14

A small team of researchers from the Johns Hopkins University Applied
Physics Laboratory (APL) in Laurel, Md., in conjunction with NASA Goddard
Space Flight Center (GSFC), have developed a novel radiator so small its
components are only visible under a microscope. The temperature control
device, formally known as the "Variable Emittance (Vari-E) Coatings for
Thermal Control," is based on MicroElectroMechanical Systems (MEMS)
technology employing shutters so small that several abreast are smaller
than the width of a single human hair.

When NASA's Space Technology 5 (ST5) satellites launch tomorrow, one of
the three overhead projector-sized micro-satellites will be "wearing" this
device on its "skin" to demonstrate that MEMS-based technology can be used
to regulate the temperature of a satellite or one of its instruments.

"This is the first time a fully space-qualified device of this type has
ever been flown, and the first to be flown on the outside of a satellite,"
says Ann Darrin, APL's Vari-E program manager, who explained that the
devices underwent the same rigorous tests that all space products undergo
prior to launch. "It's also the first demonstration of MEMS technology
used to actively control temperature."

In a 4-inch square section atop one of the micro-satellites, tiny
comb-shaped motors powered by electrostatic charges open and close
microscopic shutters to regulate the temperature of that area of the
satellite. "When a satellite's in space, you need to keep its temperature
constant," says Darrin. "As we shrink the size of satellites and their
onboard systems, it becomes harder to regulate and maintain a constant
temperature. By putting these devices on the outside or 'skin' of a
satellite you can change its emissivity.

"When the satellite is facing the sun, for example, you could cool it by
closing our shutter doors and reflecting the heat," Darrin says. "Or if
you need to absorb more heat, the shutters would open."

The 4-inch square radiator contains 36 chips, each about the size of a
single key on a computer keyboard. Looking at a chip under a microscope,
one could see 72 shutter segments, each driven back and forth by six tiny
motors controlled from the electrostatic charge-based power source located
inside the satellite.

To protect the tiny devices from dust and condensation, which could hinder
their operation, the team developed a unique packaging solution. They
encased the devices in a "window" using a clear material known as CP-1, a
polymer rugged enough to sit on the outside of a satellite during
space-based operations, and more cost-effective than materials like single
crystal (clear, not blue jewelry quality) sapphire.

"Often people associate small with being frail," says Darrin. "But our
tiny shutters, which don't touch when they close, are exceptionally
strong, especially when operating in space where there's no gravity,
weight or resistance forces to wear or degrade moving parts."

According to Darrin, the very small, lightweight devices could shave off
numerous pounds from a microsat, resulting in smaller radiators, for
example, and making the overall micro-sat more efficient and
cost-effective.

APL is the principal investigator of the Variable Emittance devices, which
were fabricated by Sandia National Laboratories in Albuquerque, N.M.

The ST5 satellites, currently scheduled for launch from Vandenberg Air
Force Base, Calif., on March 14, will provide a platform for testing and
validating new technologies. For more information about the ST5 mission
and its onboard technologies being tested, visit
http://www.nasa.gov/mission_pages/st-5/main/index.html

The ST5 project, managed by NASA GSFC, is part of NASA's New Millennium
Program created to identify, develop, build and test innovative
technologies and concepts for infusion into future missions.

The Applied Physics Laboratory (APL) is a not for profit laboratory and
division of The Johns Hopkins University. APL conducts research and
development primarily for national security and for nondefense projects of
national and global significance. APL is located midway between Baltimore
and Washington, D.C., in Laurel, Md. For information, visit www.jhuapl.edu .

[NOTE: Images supporting this release are available at
http://www.jhuapl.edu/newscenter/pre...313_image1.asp ]