Ten years from now, the solar system could be teeming with pint-sized space probes, each no larger than a baseball. That’s the claim of William Tang, of Nasa’s Jet Propulsion Laboratory (JPL), speaking last week at the 1998 Institute of Electrical and Electronics Engineers Aerospace Conference in Colorado.
Tang works on micro-electro- mechanical systems, or Mems, and their application to space flight. Mems are tiny motors and sensors, made using photolithography — the same technique used to etch microchips on to wafers of silicon.
JPL has already built a miniature gyroscope and a micro rocket thruster, both no bigger than a coin. And they are now developing miniature science instruments for measuring seismic activity and atmospheric humidity, as well as a micro mass spectrometer for identifying gases.
“Theoretically, a Mems spacecraft containing the essential functions of propulsion, navigation, power generation, communications, and one or two science instruments can be as small as a baseball,” he says, adding that components could one day be as small as a millionth of a millimetre.
Mems technology has already been adopted in other areas. Hair-thin silicon motion sensors are now used in the deployment mechanism of driver’s airbags in cars. And military researchers are investigating the possibility of dust-sized Mems containing infrared sensors, which float in the air above a battlefield, monitoring enemy movements.
“The technology is moving at an incredible pace,” says Robert Yates, head of the Mems unit at the University of Sheffield. There now exist aircraft measuring 10cm, controlled by active skins containing Mems devices.
The next step – Mems equipment for use in space – will be flight-tested later this year on the United States defence department’s Space Technology Research Vehicle 2 orbital mission. And a Mems gyroscope, developed by JPL and due for completion in June, is to be used in the prototypes for the Nasa-sponsored Lockheed Martin X-33 reusable launch vehicle -planned to replace the space shuttle in 2005.
Miniature spacecraft are a far cry from the pomp of the Apollo programme. But they will be the next step in Nasa’s drive towards quicker, sleeker, more cost-effective space flight. The Cassini mission to Saturn was Nasa’s last “great” space mission, costing $1,5-billion. By comparison, Mars Pathfinder cost just $150-million. Mems devices could lead to savings by factors of several thousand.
It could mean a whole new approach to exploring the solar system. “One can imagine a mother ship going into deep space, which launches a constellation of these tiny baseball-sized spacecraft to do exploration,” says Tang. “This type of space mission could be achieved in the next five to 10 years.”
Frank Tipler of Tulane University, New Orleans, believes that lightweight Mems devices may take space exploration beyond the confines of the Milky Way. Investigating the theoretical limits of space flight, Tipler examined whether it is possible to send a rocket from Earth to explore the other side of the universe. “Only if the payload were very small – total mass 100g or less – would this be feasible,” he says.
Mems technology should have no problem making spacecraft this light. “This work is an exceedingly important step in the development of robotic spaceflight,” adds Tipler.