Aerospace & Defense Technology - August 2024 - 10

Microelectronics
Silicon Sensing began discussing Space
Forge's ambitions for the ForgeStar program
in a meeting at one of the first events
following the Covid pandemic in 2021 -
Space-Comm Expo in Farnborough, U.K..
These early discussions with Andrew
Bacon, founder of Space Forge, and his
team lead to more detailed technical meetings
as the potential of micro electro-mechanical
systems (MEMS) technology for
this challenging project was realized.
Traditionally MEMS technology had
been perceived as compact and
extremely reliable and rugged - but
not able to offer the highest levels of
precision performance seen in competitive
technologies such as larger, heavier
fiber optic gyro (FOG)-based sensors
and systems. MEMS inertial sensors
and systems have typically been used in
industrial-grade applications, but
recent advances have seen several companies
in this field, including Silicon
Sensing, bring products to market that
can deliver far more precise 'tactical-grade'
levels of performance.
Across many market sectors, including
space, there are persistent imperatives
to both extend operational
endurance and to shrink platform size,
impacting available space, weight, and
power. In this environment the latest
performance levels of these compact,
low power consuming, MEMS products
means there is an immense, and
ever growing, range of applications
across extraordinarily diverse sectors.
Space, including LEO satellites such as
the ForgeStar program, is one of many
sectors that MEMS products can be
used in.
In Space Forge's ForgeStar program,
A computer generated image of the ForgeStar solar array satellite that is currently in development.
(Image: Space Forge)
the challenge is not simply motion sensing
or platform stabilization. Instead, an
ultra-precise MEMS-based accelerometer,
the CAS291, will be used for the first
time to measure the level of microgravity
inside the LEO satellite. The data will be
used to assess the impact of microgravity
on the effective manufacture, in the
ultra-vacuum conditions of space, of
advanced materials such as alloys, proteins
and semiconductors.
In LEO applications such as the
A terrestrial made semiconductor (background) vs space-made (foreground). (Image: Space Forge)
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ForgeStar program, space, weight, and
power are critical constraints, given
the compact size of the CubeSat which
will require lower power, highly sensitive
accelerometers to accurately measure
low gravitat ional forces. The
CAS291 is supplied as a small (10.4 ×
6.7 × 2.7 mm), surface-mounted package
in both flat and orthogonal variations,
enabling acceleration to be measured
on all required axis. It is able to
measure linear acceleration by using a
silicon MEMS detector, forming an
orthogonal pair of sprung masses. Each
mass provides the moving plate of a
variable capacitor formed by an array
of interlaced 'fingers'. When linear
acceleration occurs, it results in a
change of capacitance which is measured
by demodulation of the square
wave excitation. This structure yields a
robust design, enabling the CAS accelerometer
series to measure a wide range
of gravitational forces ranging from
±0.85g to ±96g.
Aerospace & Defense Technology, August 2024

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Aerospace & Defense Technology - August 2024

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