Tiny chip included in space shuttle experiment and shown against a penny contains 19 microthrusters, each of which acts like a rocket engine. Designed and built in a lab at The Aerospace Corporation, the thrusters could be used to orient a nanosatellite. (Photo by Pete Fuqua and Bill Hansen)

The experiment represents an evolution of research into micro- and nanotechnology begun in 1992 by senior scientists Drs. Henry Helvajian and Siegfried Janson and distinguished engineer Ernie Robinson.

First Systematic Testing
Conceived and created by The Aerospace Corporation, the experiment also represents the first systematic testing in space of MEMS, tiny electrically driven machines invisible to the naked eye but powerful and versatile enough to revolutionize space systems should they prove themselves in space. How they performed in launch, orbit and reentry conditions is the focus of the researchers.

Though MEMS have flown on selected flights, for example on the MightySat 1 mission of Dec. 1998, systematic testing of the sort conducted aboard the Columbia and scheduled for future flights has not been done. Thus, MEMS devices cannot be considered qualified for space use, particularly not for Department of Defense purposes.

Dr. David Sutton, a co-principal investigator of the experiment, said data from the 30 devices included in the experiment were downloaded onto a permanent medium within hours after shuttle touchdown on July 27. The devices had been anchored in a testbed in the Columbia's midsection during the flight.

Microgyros, Chemical Microsensors
Sutton, who is director of the Materials Processing and Evaluation Department, said data was being sorted, analyzed and provided to a number of organizations -- commercial, research and university -- which contributed microgyros, microaccelerometers, chemical microsensors and other micro- and nanodevices.

Data will be compared to see how MEMS with like characteristics performed, and how they all performed in flight compared with preflight tests in the labs. Also, MEMS data will be compared with data from sensors and instruments that the shuttle uses.

For example, readings for acceleration, attitude and roll will be compared. Comparisons also will be made for readings on humidity and carbon dioxide in the shuttle atmosphere. Astronauts took air samples near the air intake of the experiment testbed, which is about the size of a computer box.

Astronauts' Help Appreciated
"The interaction (of the experimenters and the astronauts) is wonderful on an experiment like this," said Sutton, who is co-principal investigator with Dr. Robert Smith, systems director of the company's NASA programs office at the Johnson Space Center in Houston. The Shuttle Upgrade Program at Johnson Space Center is the sponsor of the project.

Sutton said work on the experiment began in 1997 and that "it was ready in less than a year." It was scheduled for launch in the fall of 1998, but the mission was pushed back until July 23, 1999.

Another MEMS test mission, to the International Space Station, is planned for 2001. Next would be an operational test wherein a nanosatellite with MEMS aboard would be released from the space station, possibly with a mission to examine the station's exterior.

Cannon-Launched Satellite Swarms
MEMS hold great promise because of their low weight, low power requirements, low volume, and potentially low cost. Futuristic but possible concepts such as miniature cannon-launched satellites and swarms of tiny, intelligent and interactive spacecraft could be developed by packaging an assembly of MEMS, researchers at The Aerospace Corporation say.

The devices already have earned respect terrestrially. For example, they serve reliably as automotive air bag triggers, combustion control sensors, and ink-jet printer heads.

MEMS are the product of microelectronic fabrication, micromolding and advanced laser processing technologies.

The devices used in the Columbia experiment represent functions such as navigation and control, sensing, propulsion, computation, and thermal control that are required for spacecraft of any size.

Rocket Thrusters on a Chip
One of the devices, designed and fabricated at The Aerospace Corporation, comprises an array of 19 microthrusters which could be used to orient a nanosatellite. Each of the 19 cells represents a separate thruster like a solid rocket motor on a launch vehicle.

The microthruster research was funded by the Defense Advanced Research Projects Agency. TRW and Caltech are partners with The Aerospace Corporation on the project. Helvajian and Janson, both of the company's Center for Microtechnology, are the leading researchers in this area.

Pioneering Research
The Aerospace Corporation has been at the forefront of microengineering for space systems for nearly a decade.

In 1998 the company established the Center for Microtechnology, headed by principal director Seymour Feuerstein, to build on pioneering work by Helvajian -- author of the just-published book, "Microengineering Aerospace Systems" -- Janson, Robinson and others. More than 30 scientists at The Aerospace Corporation are involved in this area of research. The company also has organized two international conferences on integrated micro/nanotechnology for space systems to advocate and promote its advantages. The most recent was held in April 1999 in Pasadena.

Mass-Produced Satellites
Janson coined the term nanosatellite which has come into wide use. He conceived the first one-kilogram satellite and introduced the concept of mass production of nanosatellites using layered silicon wafers. These satellites would measure about four inches in diameter and about one inch high. They would weigh about one kilogram (2.2 pounds) or less. One advantage is the potential for huge reductions in the cost of satellite systems. Another is the possibility of exciting new missions with clusters of interactive satellites.

The radical new way of building and using spacecraft represented by the nanosatellite concept developed at The Aerospace Corporation was formally introduced in a paper, "The Concept of 'Nanosatellite' for Revolutionary Low Cost Space Systems," presented at the International Astronautical Federation Congress in Graz, Austria, in 1993, and further described in a series of reports by Janson, Helvajian and Robinson. These reports present the details on how to design, build, power and maneuver nanosatellites.

Nanosatellite technologies capable of use within five to ten years are now being explored by a number of national and international research organizations in addition to The Aerospace Corporation.