Page 367 - MEMS and Microstructures in Aerospace Applications

Osiander / MEMS and microstructures in Aerospace applications DK3181_c016 Final Proof page 360 1.9.2005 12:56pm

360 MEMS and Microstructures in Aerospace Applications

. De-rating system (allowing safe margins within a well-defined SOA [2x’s
where possible operating margins])
. Material identification and utilization logs (MIUL)
. Stress screening, qualification, and acceptance testing requirements
. FMEA
. Life cycle environment profile (defined more fully in the following section)
In addition, required documentation for submission should include all of the
appropriate traceability records.

16.5 ENVIRONMENTAL TEST
At the assembly, subsystem, and system level, temperature cycling and vibration are
often used in combination with a vacuum as the predominant test screens. Other
screens that are used at these levels of assembly include low- and high-temperature
burn-in, power cycling, shock, and electrical screening. Stress screening can dramat-
ically benefit the system at various hardware assembly levels. Part and component
screening can remove defects in a system prior to higher assembly level testing. At the
subsystem level, screens can remove an additional percent of the remaining defects
before system testing. It is important to identify defects at the lowest possible level of
assembly in order to have the greatest impact on cost savings and timeliness. Parts
screening and qualification test requirements must (1) remove defects at the earliest
possible time in a system build cycle and (2) assure the parts will be able to fully
perform in the required environment. For a good overview of component-level
screening requirements, see the General Environmental Verifications Specification
11
for STS and ELV Payloads, Subsystems, and Components (GEVS-SE document) or
MIL-STD-1540 Test Requirements for Vehicles.

16.5.1 SAMPLE ENVIRONMENTAL COMPONENT TEST REQUIREMENTS
An example of a GEVS-SE based set of test requirements for a specific mission is
shown below. The ‘‘Component Test Requirements And Guidelines’’ ST5-495-007
used on the New Millennium Program (NMP) Space Technology 5 Project (ST5) is
GEVS-SE based. Some of the examples illustrate a tailoring of the GEVS-SE based
on mission specific requirements. The ST5 project is a mission utilizing a three-
spacecraft constellation, where integrated on each vehicle is a suite of science
validation instruments and new spacecraft technologies. Through flight validation
of these technologies, ST5 will reduce the risks for future development of nano-
satellites and constellation missions. One of the technologies to be demonstrated is
the variable emissivity (Vari E) experiment using a MEMS-based approach. The
following defines the verification and test process for all Vari E devices. Designed for
a technology demonstration, this MEMS-based experiment is defined as a nonmis-
sion critical component. Critical components are components that have a direct effect
on the spacecraft health and safety. Nonflight critical components are components
that do not have a direct effect on the spacecraft health and safety. Both critical and

© 2006 by Taylor & Francis Group, LLC