MIRRAS Miniature Resistive Regression and Ablation Sensor

ORBITAL TECHNOLOGIES
CORPORATION
MIRRAS
Miniature Resistive Regression
and Ablation Sensor
Small Business Leader
ORBITEC is a national leader in small business
innovations for the space industry, with over $90
million in government and industrial contracts
since its founding in 1988.
Mission Statement
To serve government and industry by developing
and demonstrating innovative technologies and
advanced products that enhance the quality of
human life and support mankind’s exploration of
the Universe.
MIRRAS is a low-cost, user-friendly,
and miniature sensor technology that
measures the instantaneous surface
regression in hybrid fuels, solid
propellants, and ablative materials.
500 lbf Hybrid Motor Assembly
Instrumented with MIRRAS Sensors
Subscale Universal Test Motor for Evaluation
of the MIRRAS Technology in Hybrid Fuels,
Solid Propellants, and Ablative Materials
Main Business Areas
• Advanced concepts and technology
development
• Space resource systems
• Space propulsion and propellant systems
• Space flight systems
• Human, animal, and plant habitation systems.
Company Background
Headquartered in Madison, WI, ORBITEC is
Wisconsin’s leader in space research, technology
and product development, working with the federal
small business innovation research and other
major technology development programs of the
nation. ORBITEC was awarded Wisconsin’s
Professional Service Business of the Year Award
(1995) and the Tibbitts Award (1996 and 1999)
from the SBA for outstanding work for the US
Government.
Contact Us
MIRRAS Sensor Package
ORBITAL TECHNOLOGIES CORPORATION
Space Center, 1212 Fourier Drive
Madison, WI 53717
Phone: (608) 827-5000; FAX: (608) 827-5050
www.orbitec.com
July 2006 ORBITAL TECHNOLOGIES CORPORATION

Miniature Resistive Regression and Ablation
Sensor (MIRRAS)
Advancements are continuously being sought in
hybrid fuels and oxidizers, solid propellants, and
ablative materials. The surface regression
characteristics of these materials need to be
determined as a function of key operational
parameters to establish their overall
performance and merit and to support overall
system design. A similar need exists for
propellant and material health monitoring.
ORBITEC has addressed these needs through
the development of a sensor that can accurately
measure instantaneous surface regression at a
fraction of the cost, size, and complexity of other
currently available methods. The resulting
instrument is called the Miniature Resistive
Regression and Ablation Sensor (MIRRAS).
This work was sponsored by the NASA/SSC
SBIR Program.
MIRRAS Capabilities/Features
• Provides highly accurate, instantaneous
surface regression and material thickness data
•
•
•
•
•
•
•
Applied and tested in hybrid fuels, solid
propellants, and ablative materials
Eliminates the need for specialized end user
training or calibration
Reduces implementation cost as compared
to ultrasonic, X-ray, and optical methods
Improves regression data quality and reliability
by measuring transients that often go undetected
Increases safety of operations
Reduces the number of required
developmental tests
Well suited for flight applications because of
small size and low mass.
MIRRAS Applications
• Materials and propellant regression rate
characterization
• Propulsion system design and development
• Health monitoring.
How Does MIRRAS Work?
The MIRRAS sensor is designed to be
embedded in the material of interest and
regresses along with it. During this process, the
resistance of the sensor is related to its
instantaneous length, allowing the instantaneous
thickness of the host material to be recorded.
The time derivative of these data reveals the
instantaneous surface regression rate as a
function of time.
Sensor Installation: Two sensor installation
approaches have been successfully developed.
The first is to directly cast sensors into the host
material. The second is to insert them after the
material has been formed or cured. Accurate
sensor positioning within the host material is
straightforward for most applications.
Sensor Design and Operation: MIRRAS is a
specialized resistor that has been designed to
meet the following requirements: (1) regresses
at the same rate as the host material; (2) does
not affect the regression of the host material or
adversely disrupt the process under study; (3)
exhibits a resistance that can be accurately
correlated to the instantaneous sensor length;
(4) does not require any end user calibration or
training; (5) is easy to install and operate; and
(6) is low cost.
Signal Conditioning: A multi-channel channel
signal conditioner has been developed. It
accommodates up to six sensors over a wide
range of sensor sizes and provides a voltage
signal related to the instantaneous sensor
length.
Data Transmission: The sensor signal is
transmitted from inside a high-pressure chamber
to the ambient environment on two leadwires
through a port in the side or top of the motor
case. Standard commercially available
feedthrough connectors produce a seal around
the wires. Another approach is to use a
miniature signal conditioner and data logger
installed inside the chamber, possibly embedded
in the motor case lining. The data logger would
record data during the test and could later be
retrieved for downloading. Alternatively, a
miniature transmitter could be used to send
sensor data to an external receiver in real time.
These two approaches eliminate the need to
produce any motor case penetrations and are
particularly well suited for flight-type motor
testing or onboard flight systems.
Sensor Output: The sensor provides localized
instantaneous material thickness and surface
regression rate data as a function of time.
Regression Rate (cm/s)
Ablative Thickness (cm)
0.14
0.13
0.12
0.11
0.1
0.09
0.08
0.07
2
1.8
1.6
1.4
1.2
1
0.8
0 5 10 15 20
Time (s)
Regression Rate vs. Time Measured
Using MIRRAS Technology in an
HTPB/GOX Hybrid Motor
Location #1
0.6
0 4 8 12 16
Time (s)
Location #2
MIRRAS Can Measure Local Material
Thickness as a Function of Time