Aerospace & Defense Technology - December 2024 - 12

Data Acquisition
A data delay module can be used to store data for later transmission during telemetry blackouts. (Image:
Curtiss Wright Defense Solutions)
Space COTS is a good example of how additional
testing can confirm whether off-the-shelf hardware
can meet harsh environmental conditions.
(Image: Curtiss Wright Defense Solutions)
that are part of the hypersonic platforms).
In this case, the COTS data
acquisition units need to be capable of
supporting various bus types, e.g., serial
interfaces, Ethernet, MIL-STD-1553,
IEEE-1394, and ARINC-429.
The modularity of COTS data acquisition
products enables hypersonic platform
developers and integrators to construct
specific combinations of data
acquisition solutions for the different
stages of the launch platforms.
Flight tests, especially hypersonic
flight tests, are expensive. Therefore, end
users and integrators typically overcompensate
by increasing the number of
measurements and specifying the environmental
survivability to a much higher
level than what is needed, resulting in
increased flight test package cost and
schedule demands. This result is more
pronounced if the end user is using a
custom FTI solution that has a fixed
number of measurements. As programs
mature, the required measurements will
likely change, presenting complexity,
qualification, and size, weight, and
power challenges.
These challenges can be quickly
addressed by ruggedizing existing
12
COTS FTI products to the hypersonic
environments, thereby preserving
their modularity and leveraging their
prior qualification pedigree.
Hypersonic Telemetry
After the data has been acquired, it
must be transferred, or telemetered, over
an RF link in real time. Some of the physics
of the hypersonic environment pose
unique challenges to this RF telemetry.
For example, the disassociation and ionization
of the air can result in an unpredictable
RF channel. Also, because multistage
platforms will encounter stage
separation events, the plasma created
behind it will result in a blackout period.
How does reliable flight test data get
delivered to the ground stations during
these blackout periods? One of the solutions
that has been tested and proven for
delivering reliable flight test data to
ground stations is to acquire the data,
store a certain amount, and then rebroadcast
it later along with real-time data.
A data delay module allows a suitable
delay time to be programmed, subject to
any limitations due to the amount of
memory available. Another approach is
to request a rebroadcast of data from an
onboard recorder using an uplink, or a
command signal sent from the ground
to the air. The last solution is to recover
the recorder's media cartridge post-mission
for data analysis. This relies on the
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platform being intact on recovery or the
storage media being crash-protected.
Link Margin and the Doppler Shift
One challenge for hypersonic flight
test telemetry is the increased down
range distance. Since the distances
may be between 4,000 and 12,000 kilometers,
a single line-of-sight RF link
will not have the link margin to maintain
reliable telemetry. One way to
increase the link margin is to use forward
error correction schemes, such as

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Aerospace & Defense Technology - December 2024

Table of Contents for the Digital Edition of Aerospace & Defense Technology - December 2024