Digital Micro-Propulsion Project

Project Title: "Microsatellite Propulsion and Attitude Control System"

Sponsored by:
Defense Advanced Research Projects Agency (DARPA)
Microsystems Technology Office (MTO)
Micro-Electro-Mechanical Systems (MEMS) Program
Clark T.-C. Nguyen, Ph.D., Program Manager
Digital Micro-Propulsion Prototype Chip (33k JPEG)
Digital Micro-Propulsion
Prototype Chip
TRW Logo
David H. Lewis, Ph.D., Program Manager
Space & Technology Group
Space & Technology Division
One Space Park
Redondo Beach, CA 90278, U.S.A.
Digital Micro-Propulsion Prototype Chip on a Penny (44k JPEG)
Aerospace Corp. Logo
The Aerospace Corporation
Siegfried W. Janson, Ph.D., Principal Investigator
Mechanics & Propulsion Department
Mechanics & Materials Technology Center
P.O. Box 92957
Los Angeles CA 90009-2957, U.S.A.
Caltech Logo
California Institute of Technology
Prof. Erik K. Antonsson, Ph.D., P.E., Principal Investigator
Engineering Design Research Laboratory
Department of Mechanical Engineering
Division of Engineering and Applied Science
1200 East California Blvd.
Pasadena, CA, 91125, U.S.A.
Engineering Design Research Laboratory Logo

Technology Review, October, 1999

October, 1999 Technology Review article
references the DARPA-funded TRW/Aerospace/Caltech MEMS Digital Micro-Propulsion project.
Page 82.

Scientific American, November, 1998

November, 1998 Scientific American article
describing the DARPA-funded TRW/Aerospace/Caltech MEMS Digital Micro-Propulsion project.
Pages 50-51.

Sensors & Actuators A: Physical, April, 2000

"Digital MicroPropulsion"
by D. Lewis, S. Janson, R. Cohen and E. Antonsson
Sensors and Actuators A: Physical, 2000, 80(2)
pages 143-154.
(774k PDF)


The DARPA-funded TRW/Aerospace/Caltech MEMS Digital Micro-Propulsion Program has two major goals. The first is to demonstrate several types of MEMS microthrusters, and to characterize their performance. The second goal is to fly MEMS microthrusters in space and verify their performance.

This Web site summarizes the concept and reports initial test results of the "Digital Propulsion" concept. Propulsion, station-keeping, and attitude control for micro-spacecraft (1 kg class) will require a compact and light-weight integrated system for controllably generating tiny amounts of impulse. To accomplish these goals, we adopted a novel approach to micro-propulsion that avoids tanks, fuel lines, and valves. In this concept, an array of small sealed plenums are constructed each with a rupturable diaphragm on one side. The plenums are loaded with a fuel or an inert substance in gas, liquid or solid form. In the case of a fuel, it is ignited and reacts to typically form a high-pressure, high-temperature fluid. In the case of an inert substance, it is heated to raise its pressure. Once the pressure exceeds the burst pressure of the diaphragm, the diaphragm ruptures, and an impulse is imparted as the fluid is expelled from the plenum. Thus, each plenum can deliver one "bit" of impulse. The size of the impulse is determined during fabrication by the size of the plenum and the fuel that is loaded into it. This approach eliminates valves (and valve leakage). It substitutes one-shot (and therefore consumable) individual thrusters for a multi-use conventional thruster and fuel tank (with a consumable fuel supply).

The application of MEMS technology to space systems offers new possibilities of increased orbit and station-keeping capabilities at potentially lower cost. Propulsion is one example of the application of MEMS technology to an essential satellite function.

There are several advantages to this design. These microthrusters have no moving parts, each engine has a low parts count (3 layers bonded together), no valves or lines or external tankage. The propulsion function can be combined with the satellite structure. The array of micro-thrusters is highly redundant. The array can be programmed to fire individual thrusters, several thrusters at once, or in controlled sequences. Since the dimensions of the individual rocket engines are under the designers' control, the creation of smaller and smaller "impulse bits" is straightforward. On the order of 106 thrusters can be fabricated on a wafer.

The current Digital Propulsion configuration is shown in here (8k GIF). As shown, it consists of a 3-layer sandwich. The top layer contains an array of thin diaphragms (0.5 micron thick silicon nitride, 190 or 290 or 390 microns square), and is shown here (14k GIF). The middle layer contains an array of through-holes (Schott FOTURAN® photosensitive glass, 1.5 mm thick, 300, 500, or 700 micron diameter holes) which are loaded with propellant, and is shown here (30k GIF). The bottom layer contains a matching array of polysilicon micro-resistors, and is shown here (37k GIF). The bottom two layers are bonded together, then fueled, then the top layer is bonded to complete the assembly. With a series of different sizes of plenum holes, diaphragms, and resistors, we have 90 different configurations that can be assembled. An assembled and mounted chip and is shown here (42k JPEG), and is shown on a penny here (44k JPEG).

Initial testing, using lead styphnate (5.6k GIF) as the propellant, has produced 0.1 milli-Newton-seconds of impulse and about 100 Watts (shown here (20k JPEG)), with the expectation that this can be increased by nearly a factor of 10 with more complete combustion of the fuel.

On this site are Presentation Slides and Images summarizing various aspects of our project, as well as Movies of thrusters firing in the laboratory. We welcome your comments.

David H. Lewis, Ph.D., Program Manager



  1. May 16, 2001:
  2. January, 2001: Helvagian, H., P.D. Fuqua, W.W. Hansen, and S. Janson, "Laser Microprocessing for Nanosatellite Microthruster Applications" Riken Review, (The Institute of Physical and Chemical Research), No. 32, Laser Precision Microfabrication (LPM2000), pages 57-63.
  3. April, 2000: "Digital MicroPropulsion" by D. Lewis, S. Janson, R. Cohen and E. Antonsson, Sensors and Actuators A: Physical, 2000, 80(2), pp. 143-154. (774k PDF)
  4. February, 2000: Hall, A., "Pint-Size Satellites Will Soon Be Doing Giant Jobs", Edited by Douglas Harbrecht, Business Week OnLine Daily Briefing, February 10, 2000.
  5. December, 1999: Aerospace Corporation Annual Report, Page 28, (39 kbytes PDF). Complete Annual Report, (1,648 kbytes PDF)
  6. December, 1999: Mirels, H., "Effect of Wall on Impulse of Solid Propellant Driven Millimeter-Scale Thrusters", AIAA Journal, Vol. 37, No. 12, December 1999, pp. 1617-1624.
  7. October, 1999: "La Micropropulsion s'adapte aux petits satellites" by Cécile Bonneau, L'Usine Nouvelle 21 October 1999, Page 79. (447 kbytes JPG)
  8. October, 1999: Reference in: "May the Micro Force by With You" by Ivan Amato, Technology Review, page 82. (131 kbytes HTML, JPEG, GIF)
  9. 1999: H. Helvajian and S. Janson, "Microengineering Space Systems," Chapter 2 in Microengineering for Aerospace Systems, ed. by H. Helvajian, ISBN 1-884989-03-9, Aerospace Press, El Segundo, CA, and AIAA, Reston, VA, 1999.
  10. 1999: S. Janson, H. Helvajian, and K. Breuer, "Micropropulsion Systems for Aircraft and Spacecraft," chapter 17 in Microengineering for Aerospace Systems, ed. by H. Helvajian, ISBN 1-884989-03-9, Aerospace Press, El Segundo, CA, and AIAA, Reston, VA, 1999.
  11. September, 1999: "Jet Engines Smaller Than a Penny Will Propel Satellites", by Mark Prigg, The Sunday Times (London), 5 September 1999, Page 3-12. (253 kbytes JPG) (371 kbytes PDF)
  12. September, 1999: S.W. Janson, "Mass-Producible Silicon Spacecraft for 21st Century Missions," paper 99-4458, AIAA, Space Technology Conference and Exposition, Albuerque, NM, Sept. 28-30, 1999.
  13. August, 1999: D. Sorid, "Micro-machines Herald Era of the Miniscule", Space.com, August 25, 1999.
  14. June, 1999: S.W. Janson, H. Helvajian, and K. Breuer, "MEMS, Microengineering and Aerospace Systems," AIAA paper 99-3802, 30th AIAA Fluid Dynamics Conference, Norfolk, VA, June 1999.
  15. June, 1999: J.E. Pollard, C.C. Chao, and S.W. Janson, "Populating and Maintaining Cluster Constellations in Low Earth Orbit," AIAA paper 99-2871, 35th AIAA/ASME/SAE/ASEE Joint Propulsion Conference, Los Angeles, CA, June 1999.
  16. May, 1999: "Pasadena Conference Focuses on Space Applications of Microtechnology", Micromachine Devices.
  17. April, 1999: P.Fuqua, S.W. Janson, W.W. Hansen, and H. Helvajian, "Fabrication of True 3D Microstructures in Glass/Ceramic Materials by Pulsed UV Laser Volumetric Exposure Techniques," Proceedings of the SPIE, Vol. 3618, "Laser Applications in Microelectronic and Optoelectronic Manufacturing IV," April 1999
  18. April, 1999: S.W. Janson, H. Helvajian, W.W. Hansen, and Lt. J. Lodmell, "Microthrusters for Nanosatellites," 2nd International Conference on Integrated MicroNanotechnology for Space Applications, Pasadena, CA, April 11-15, 1999, organized by The Aerospace Corporation.
  19. April, 1999: "Pocket Rocket" by Ben Iannotta, New Scientist, 10 April 1999, Vol. 162, No. 2181, page 38.
  20. January, 1999: "Digital MicroPropulsion", by D. Lewis, S. Janson, R. Cohen and E. Antonsson, IEEE MEMS'99 Meeting Oral Presentation, Paper published in the Conference Proceedings. (920 kbytes PDF)
  21. 1998: G.F. Carrier, F.E. Fendell, S.F. Fink IV, and R.D. McGregor, "Gaseous-Propellant Microthrusters, I. Completion of Burn Prior to Venting", Combust. Sci. and Tech., 1998, Vol. 140, pp. 169-195.
  22. 1998: G.F. Carrier, F.E. Fendell, and S.F. Fink IV, "Gaseous-Propellant Microthrusters, II. Venting Prior to Completion of Burn", Combust. Sci. and Tech., 1998, Vol. 140, pp. 197-223.
  23. November, 1998: "Little Bangs", by Gary Stix, Scientific American, pages 50-51. (8 kbytes HTML)
  24. October, 1998: Reference in: "MICROMACHINES: Fomenting a Revolution, in Miniature", by Ivan Amato, Science, 16 October, 1998; 282, pages 402-405. (in News Focus).
  25. October, 1998: Paper presented at: Formation Flying and Micro-Propulsion Workshop, sponsored by AFRL, Lancaster CA

Presentation Slides:


Movies of Recent Results:

DARPA/MTO/MEMS Logo (Updated May, 1999):

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Last Updated 2:33:54 PM PDT, Monday, July 15, 2002