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Vision for Microtechnology Space Missions 23

that serves to free up precious spacecraft resources. For example, the mass
savings afforded by using the MEMS-based ISC could be allocated for additional
propellant or, likewise, the power savings could potentially be directly applied to
the mission payload. These are some of the advantages afforded by using MEMS
technology.

2.2.5 MICROTHRUSTERS
Over the past several years MEMS catalytic monopropellant microthruster research
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and development has been conducted at NASA’s GSFC. MEMS-based propulsion
systems have the potential to enable missions that require micropropulsive maneu-
vers for formation flying and precision pointing of micro-, nano-, or pico-sized
satellites. Current propulsion technology cannot meet the minimum thrust require-
ments (10–1000 mN) or impulse-bit requirements (1–1000 mN sec), or satisfy the
3
severely limited system mass (<0.1 kg), volume (<1cm ), and power constraints
(<1 W). When compared to other proposed micropropulsion concepts, MEMS
catalytic monopropellant thrusters show the promise of the combined advantages
of high specific density, low system power and volume, large range of thrust levels,
repeatable thrust vectors, and simplicity of integration. Overall, this approach offers
an attractive technology solution to provide scalable micro-Newton level micro-
thrusters. This particular MEMS microthruster design utilizes hydrogen peroxide as
the propellant and the targeted thrust level range is between 10 and 500 mN with
impulse bits between 1 and 1000 mN sec and a specific impulse (I sp ) greater than
110 sec.
A prototype MEMS microthruster hardware has been fabricated as seen in
Figure 2.8, using GSFC’s detector development laboratory (DDL) facilities and
equipment. Individual MEMS fabricated reaction chambers are approximately 3.0
2.5 2.0 mm. Thrust chambers are etched in a 0.5 mm silicon substrate and the
vapor is deposited with silver using a catalyst mask.

2.2.6 OTHER EXAMPLES OF SPACE MEMS DEVELOPMENTS

The small sampling of space MEMS developments given earlier can be categorized
as some very significant technological steps toward the ultimate goal of routine and
systematic infusion of this technology in future space platforms. Clearly NASA
researchers have identified several areas where MEMS technology will substan-
tially improve the performance and functionality of the future spacecraft. NASA is
currently investing at an increasing rate in a number of different MEMS technology
areas. A review of the NASA Technology Inventory shows that in fiscal year 2003
there were a total of 111 distinct MEMS-based technology development tasks being
funded by NASA. Relative to GFY02 where 77 MEMS-based technology tasks
were cataloged in the NASA Technology Inventory, this is over a 40% increase in
MEMS tasks. It is almost a 90% increase relative to GFY01 where 59 MEMS R&D
tasks were identified. The MEMS technologies included in the NASA inventory
are:

© 2006 by Taylor & Francis Group, LLC